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原 Android8.0 Audio系统之AudioPolicy

热度：22   发布时间：2023-12-22 12:49:32.0
原

Android8.0 Audio系统之AudioPolicy

2018年08月14日 11:43:43 SherlockCharlie 阅读数：1184 
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<article class="baidu_pl"><div id="article_content" class="article_content clearfix csdn-tracking-statistics" data-pid="blog" data-mod="popu_307" data-dsm="post"><div class="article-copyright"><svg class="icon" title="CSDN认证原创" aria-hidden="true" style="width:53px; height: 18px; vertical-align: -4px;"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#CSDN_Cert"></use></svg>版权声明：未经本人同意，不得转载					https://blog.csdn.net/u013928208/article/details/81660347				</div><link rel="stylesheet" href="https://csdnimg.cn/release/phoenix/template/css/ck_htmledit_views-f57960eb32.css"><div id="content_views" class="markdown_views prism-atom-one-dark"><!-- flowchart 箭头图标 勿删 --><svg xmlns="http://www.w3.org/2000/svg" style="display: none;"><path stroke-linecap="round" d="M5,0 0,2.5 5,5z" id="raphael-marker-block" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0);"></path></svg><p>上一篇我们跟踪分析了AudioFlinger，它是Audio系统的核心，但是AudioFlinger却不能脱离AudioPolicy工作。AudioPolicy模块承载着音频切换，音轨路由的重要工作，没有它，音频输出将乱套。在分析AudioFlinger的时候我们稍微涉及了AudioPolicyService，现在我们重新来看它。在Android7.0中Audio代理部分被组成独立的模块。<br>

这里写图片描述

void AudioPolicyService::onFirstRef()
{
    {
    ......// class AudioPolicyClient : public AudioPolicyClientInterfacemAudioPolicyClient = new AudioPolicyClient(this);mAudioPolicyManager = createAudioPolicyManager(mAudioPolicyClient); //创建Audio管理}
}

  

  
    
   
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头文件 AudioPolicyClientInterface 位于 AudioPolicyInterface.h文件中


extern "C" AudioPolicyInterface* createAudioPolicyManager(AudioPolicyClientInterface *clientInterface)
{
    return new AudioPolicyManager(clientInterface);
}

extern “C” void destroyAudioPolicyManager(AudioPolicyInterface *interface)
{
delete interface;
}

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对于AudioPolicyClientImpl.cpp实现了 AudioPolicyClient，直接与AudioFlinger交互。对于AudioPolicyIntefaceImpl实现了AudioPolicyInterface直接与AudioPolicyManager交互，

AudioPolicyManager::AudioPolicyManager(AudioPolicyClientInterface *clientInterface):
#ifdef AUDIO_POLICY_TESTThread(false),
#endif //AUDIO_POLICY_TESTmLimitRingtoneVolume(false), mLastVoiceVolume(-1.0f),mA2dpSuspended(false),mAudioPortGeneration(1),mBeaconMuteRefCount(0),mBeaconPlayingRefCount(0),mBeaconMuted(false),mTtsOutputAvailable(false),mMasterMono(false),mMusicEffectOutput(AUDIO_IO_HANDLE_NONE)
{
    mpClientInterface = clientInterface;bool speakerDrcEnabled = false;//解析 xml Audio策略，路由
#ifdef USE_XML_AUDIO_POLICY_CONFmVolumeCurves = new VolumeCurvesCollection();AudioPolicyConfig config(mHwModules, mAvailableOutputDevices, mAvailableInputDevices,mDefaultOutputDevice, speakerDrcEnabled,static_cast<VolumeCurvesCollection *>(mVolumeCurves));if (deserializeAudioPolicyXmlConfig(config) != NO_ERROR) {
    
#elsemVolumeCurves = new StreamDescriptorCollection();AudioPolicyConfig config(mHwModules, mAvailableOutputDevices, mAvailableInputDevices,mDefaultOutputDevice, speakerDrcEnabled);if ((ConfigParsingUtils::loadConfig(AUDIO_POLICY_VENDOR_CONFIG_FILE, config) != NO_ERROR) &&(ConfigParsingUtils::loadConfig(AUDIO_POLICY_CONFIG_FILE, config) != NO_ERROR)) {
    
#endifALOGE("could not load audio policy configuration file, setting defaults");config.setDefault();}// must be done after reading the policy (since conditionned by Speaker Drc Enabling)mVolumeCurves->initializeVolumeCurves(speakerDrcEnabled);

<span class="token comment">// Once policy config has been parsed, retrieve an instance of the engine and initialize it</span>
<span class="token comment">//代理引擎</span>
audio_policy<span class="token punctuation">:</span><span class="token punctuation">:</span>EngineInstance <span class="token operator">*</span>engineInstance <span class="token operator">=</span> audio_policy<span class="token punctuation">:</span><span class="token punctuation">:</span>EngineInstance<span class="token punctuation">:</span><span class="token punctuation">:</span><span class="token function">getInstance</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>engineInstance<span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token function">ALOGE</span><span class="token punctuation">(</span><span class="token string">"%s:  Could not get an instance of policy engine"</span><span class="token punctuation">,</span> __FUNCTION__<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">return</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token comment">// Retrieve the Policy Manager Interface</span>
mEngine <span class="token operator">=</span> engineInstance<span class="token operator">-&gt;</span>queryInterface<span class="token operator">&lt;</span>AudioPolicyManagerInterface<span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//获取引擎</span>
mEngine<span class="token operator">-&gt;</span><span class="token function">setObserver</span><span class="token punctuation">(</span>this<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//设为观察者</span>
status_t status <span class="token operator">=</span> mEngine<span class="token operator">-&gt;</span><span class="token function">initCheck</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//初始</span>
<span class="token punctuation">(</span><span class="token keyword">void</span><span class="token punctuation">)</span> status<span class="token punctuation">;</span>
<span class="token comment">// mAvailableOutputDevices and mAvailableInputDevices now contain all attached devices</span>
<span class="token comment">// open all output streams needed to access attached devices</span>
audio_devices_t outputDeviceTypes <span class="token operator">=</span> mAvailableOutputDevices<span class="token punctuation">.</span><span class="token function">types</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
audio_devices_t inputDeviceTypes <span class="token operator">=</span> mAvailableInputDevices<span class="token punctuation">.</span><span class="token function">types</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">&amp;</span> <span class="token operator">~</span>AUDIO_DEVICE_BIT_IN<span class="token punctuation">;</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span>size_t i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> mHwModules<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token comment">//调用ClientInterface加载Audio模块，ClientInterface将调用AudioFlinger的loadHwModule</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mHandle <span class="token operator">=</span> mpClientInterface<span class="token operator">-&gt;</span><span class="token function">loadHwModule</span><span class="token punctuation">(</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mHandle <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token function">ALOGW</span><span class="token punctuation">(</span><span class="token string">"could not open HW module %s"</span><span class="token punctuation">,</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token comment">//查找输出模块设备</span><span class="token keyword">for</span> <span class="token punctuation">(</span>size_t j <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> j <span class="token operator">&lt;</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mOutputProfiles<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> j<span class="token operator">++</span><span class="token punctuation">)</span><span class="token punctuation">{</span><span class="token keyword">const</span> sp<span class="token operator">&lt;</span>IOProfile<span class="token operator">&gt;</span> outProfile <span class="token operator">=</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mOutputProfiles<span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>outProfile<span class="token operator">-&gt;</span><span class="token function">hasSupportedDevices</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token function">ALOGW</span><span class="token punctuation">(</span><span class="token string">"Output profile contains no device on module %s"</span><span class="token punctuation">,</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>outProfile<span class="token operator">-&gt;</span><span class="token function">getFlags</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">&amp;</span> AUDIO_OUTPUT_FLAG_TTS<span class="token punctuation">)</span> <span class="token operator">!=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>mTtsOutputAvailable <span class="token operator">=</span> true<span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>outProfile<span class="token operator">-&gt;</span><span class="token function">getFlags</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">&amp;</span> AUDIO_OUTPUT_FLAG_DIRECT<span class="token punctuation">)</span> <span class="token operator">!=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span>audio_devices_t profileType <span class="token operator">=</span> outProfile<span class="token operator">-&gt;</span><span class="token function">getSupportedDevicesType</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>profileType <span class="token operator">&amp;</span> mDefaultOutputDevice<span class="token operator">-&gt;</span><span class="token function">type</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator">!=</span> AUDIO_DEVICE_NONE<span class="token punctuation">)</span> <span class="token punctuation">{</span>profileType <span class="token operator">=</span> mDefaultOutputDevice<span class="token operator">-&gt;</span><span class="token function">type</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>profileType <span class="token operator">=</span> outProfile<span class="token operator">-&gt;</span><span class="token function">getSupportedDeviceForType</span><span class="token punctuation">(</span>outputDeviceTypes<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>profileType <span class="token operator">&amp;</span> outputDeviceTypes<span class="token punctuation">)</span> <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span>sp<span class="token operator">&lt;</span>SwAudioOutputDescriptor<span class="token operator">&gt;</span> outputDesc <span class="token operator">=</span> new <span class="token function">SwAudioOutputDescriptor</span><span class="token punctuation">(</span>outProfile<span class="token punctuation">,</span>mpClientInterface<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">const</span> DeviceVector <span class="token operator">&amp;</span>supportedDevices <span class="token operator">=</span> outProfile<span class="token operator">-&gt;</span><span class="token function">getSupportedDevices</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">const</span> DeviceVector <span class="token operator">&amp;</span>devicesForType <span class="token operator">=</span> supportedDevices<span class="token punctuation">.</span><span class="token function">getDevicesFromType</span><span class="token punctuation">(</span>profileType<span class="token punctuation">)</span><span class="token punctuation">;</span>String8 address <span class="token operator">=</span> devicesForType<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">&gt;</span> <span class="token number">0</span> <span class="token operator">?</span> devicesForType<span class="token punctuation">.</span><span class="token function">itemAt</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token operator">-&gt;</span>mAddress<span class="token punctuation">:</span> <span class="token function">String8</span><span class="token punctuation">(</span><span class="token string">""</span><span class="token punctuation">)</span><span class="token punctuation">;</span>outputDesc<span class="token operator">-&gt;</span>mDevice <span class="token operator">=</span> profileType<span class="token punctuation">;</span>audio_config_t config <span class="token operator">=</span> AUDIO_CONFIG_INITIALIZER<span class="token punctuation">;</span>config<span class="token punctuation">.</span>sample_rate <span class="token operator">=</span> outputDesc<span class="token operator">-&gt;</span>mSamplingRate<span class="token punctuation">;</span>config<span class="token punctuation">.</span>channel_mask <span class="token operator">=</span> outputDesc<span class="token operator">-&gt;</span>mChannelMask<span class="token punctuation">;</span>config<span class="token punctuation">.</span>format <span class="token operator">=</span> outputDesc<span class="token operator">-&gt;</span>mFormat<span class="token punctuation">;</span>audio_io_handle_t output <span class="token operator">=</span> AUDIO_IO_HANDLE_NONE<span class="token punctuation">;</span><span class="token comment">//熟悉的openOutput</span>status_t status <span class="token operator">=</span> mpClientInterface<span class="token operator">-&gt;</span><span class="token function">openOutput</span><span class="token punctuation">(</span>outProfile<span class="token operator">-&gt;</span><span class="token function">getModuleHandle</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token operator">&amp;</span>output<span class="token punctuation">,</span><span class="token operator">&amp;</span>config<span class="token punctuation">,</span><span class="token operator">&amp;</span>outputDesc<span class="token operator">-&gt;</span>mDevice<span class="token punctuation">,</span>address<span class="token punctuation">,</span><span class="token operator">&amp;</span>outputDesc<span class="token operator">-&gt;</span>mLatency<span class="token punctuation">,</span>outputDesc<span class="token operator">-&gt;</span>mFlags<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span>status <span class="token operator">!=</span> NO_ERROR<span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token function">ALOGW</span><span class="token punctuation">(</span><span class="token string">"Cannot open output stream for device %08x on hw module %s"</span><span class="token punctuation">,</span>outputDesc<span class="token operator">-&gt;</span>mDevice<span class="token punctuation">,</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>outputDesc<span class="token operator">-&gt;</span>mSamplingRate <span class="token operator">=</span> config<span class="token punctuation">.</span>sample_rate<span class="token punctuation">;</span>outputDesc<span class="token operator">-&gt;</span>mChannelMask <span class="token operator">=</span> config<span class="token punctuation">.</span>channel_mask<span class="token punctuation">;</span>outputDesc<span class="token operator">-&gt;</span>mFormat <span class="token operator">=</span> config<span class="token punctuation">.</span>format<span class="token punctuation">;</span><span class="token keyword">for</span> <span class="token punctuation">(</span>size_t k <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> k  <span class="token operator">&lt;</span> supportedDevices<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> k<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>ssize_t index <span class="token operator">=</span> mAvailableOutputDevices<span class="token punctuation">.</span><span class="token function">indexOf</span><span class="token punctuation">(</span>supportedDevices<span class="token punctuation">[</span>k<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">// give a valid ID to an attached device once confirmed it is reachable</span><span class="token keyword">if</span> <span class="token punctuation">(</span>index <span class="token operator">&gt;=</span> <span class="token number">0</span> <span class="token operator">&amp;&amp;</span> <span class="token operator">!</span>mAvailableOutputDevices<span class="token punctuation">[</span>index<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">isAttached</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>mAvailableOutputDevices<span class="token punctuation">[</span>index<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">attach</span><span class="token punctuation">(</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token keyword">if</span> <span class="token punctuation">(</span>mPrimaryOutput <span class="token operator">==</span> <span class="token number">0</span> <span class="token operator">&amp;&amp;</span>outProfile<span class="token operator">-&gt;</span><span class="token function">getFlags</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">&amp;</span> AUDIO_OUTPUT_FLAG_PRIMARY<span class="token punctuation">)</span> <span class="token punctuation">{</span>mPrimaryOutput <span class="token operator">=</span> outputDesc<span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token function">addOutput</span><span class="token punctuation">(</span>output<span class="token punctuation">,</span> outputDesc<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token function">setOutputDevice</span><span class="token punctuation">(</span>outputDesc<span class="token punctuation">,</span>outputDesc<span class="token operator">-&gt;</span>mDevice<span class="token punctuation">,</span>true<span class="token punctuation">,</span><span class="token number">0</span><span class="token punctuation">,</span><span class="token constant">NULL</span><span class="token punctuation">,</span>address<span class="token punctuation">.</span><span class="token function">string</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token comment">//遍历输入Audio设备</span><span class="token keyword">for</span> <span class="token punctuation">(</span>size_t j <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> j <span class="token operator">&lt;</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mInputProfiles<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> j<span class="token operator">++</span><span class="token punctuation">)</span><span class="token punctuation">{</span><span class="token keyword">const</span> sp<span class="token operator">&lt;</span>IOProfile<span class="token operator">&gt;</span> inProfile <span class="token operator">=</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mInputProfiles<span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>inProfile<span class="token operator">-&gt;</span><span class="token function">hasSupportedDevices</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token function">ALOGW</span><span class="token punctuation">(</span><span class="token string">"Input profile contains no device on module %s"</span><span class="token punctuation">,</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token comment">// chose first device present in profile's SupportedDevices also part of</span><span class="token comment">// inputDeviceTypes</span>audio_devices_t profileType <span class="token operator">=</span> inProfile<span class="token operator">-&gt;</span><span class="token function">getSupportedDeviceForType</span><span class="token punctuation">(</span>inputDeviceTypes<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>profileType <span class="token operator">&amp;</span> inputDeviceTypes<span class="token punctuation">)</span> <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span>sp<span class="token operator">&lt;</span>AudioInputDescriptor<span class="token operator">&gt;</span> inputDesc <span class="token operator">=</span>new <span class="token function">AudioInputDescriptor</span><span class="token punctuation">(</span>inProfile<span class="token punctuation">)</span><span class="token punctuation">;</span>inputDesc<span class="token operator">-&gt;</span>mDevice <span class="token operator">=</span> profileType<span class="token punctuation">;</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>audio_config_t config <span class="token operator">=</span> AUDIO_CONFIG_INITIALIZER<span class="token punctuation">;</span>config<span class="token punctuation">.</span>sample_rate <span class="token operator">=</span> inputDesc<span class="token operator">-&gt;</span>mSamplingRate<span class="token punctuation">;</span>config<span class="token punctuation">.</span>channel_mask <span class="token operator">=</span> inputDesc<span class="token operator">-&gt;</span>mChannelMask<span class="token punctuation">;</span>config<span class="token punctuation">.</span>format <span class="token operator">=</span> inputDesc<span class="token operator">-&gt;</span>mFormat<span class="token punctuation">;</span>audio_io_handle_t input <span class="token operator">=</span> AUDIO_IO_HANDLE_NONE<span class="token punctuation">;</span>status_t status <span class="token operator">=</span> mpClientInterface<span class="token operator">-&gt;</span><span class="token function">openInput</span><span class="token punctuation">(</span>inProfile<span class="token operator">-&gt;</span><span class="token function">getModuleHandle</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token operator">&amp;</span>input<span class="token punctuation">,</span><span class="token operator">&amp;</span>config<span class="token punctuation">,</span><span class="token operator">&amp;</span>inputDesc<span class="token operator">-&gt;</span>mDevice<span class="token punctuation">,</span>address<span class="token punctuation">,</span>AUDIO_SOURCE_MIC<span class="token punctuation">,</span>AUDIO_INPUT_FLAG_NONE<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span>status <span class="token operator">==</span> NO_ERROR<span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">const</span> DeviceVector <span class="token operator">&amp;</span>supportedDevices <span class="token operator">=</span> inProfile<span class="token operator">-&gt;</span><span class="token function">getSupportedDevices</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">for</span> <span class="token punctuation">(</span>size_t k <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> k  <span class="token operator">&lt;</span> supportedDevices<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> k<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>ssize_t index <span class="token operator">=</span>  mAvailableInputDevices<span class="token punctuation">.</span><span class="token function">indexOf</span><span class="token punctuation">(</span>supportedDevices<span class="token punctuation">[</span>k<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">// give a valid ID to an attached device once confirmed it is reachable</span><span class="token keyword">if</span> <span class="token punctuation">(</span>index <span class="token operator">&gt;=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>sp<span class="token operator">&lt;</span>DeviceDescriptor<span class="token operator">&gt;</span> devDesc <span class="token operator">=</span> mAvailableInputDevices<span class="token punctuation">[</span>index<span class="token punctuation">]</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>devDesc<span class="token operator">-&gt;</span><span class="token function">isAttached</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>devDesc<span class="token operator">-&gt;</span><span class="token function">attach</span><span class="token punctuation">(</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>devDesc<span class="token operator">-&gt;</span><span class="token function">importAudioPort</span><span class="token punctuation">(</span>inProfile<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token punctuation">}</span>mpClientInterface<span class="token operator">-&gt;</span><span class="token function">closeInput</span><span class="token punctuation">(</span>input<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token comment">// make sure all attached devices have been allocated a unique ID</span>
<span class="token comment">//遍历输入输出设备，由路由引擎设置各设备的连接状态</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span>size_t i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i  <span class="token operator">&lt;</span> mAvailableOutputDevices<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>mAvailableOutputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">isAttached</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>mAvailableOutputDevices<span class="token punctuation">.</span><span class="token function">remove</span><span class="token punctuation">(</span>mAvailableOutputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token comment">// The device is now validated and can be appended to the available devices of the engine</span>mEngine<span class="token operator">-&gt;</span><span class="token function">setDeviceConnectionState</span><span class="token punctuation">(</span>mAvailableOutputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">,</span>AUDIO_POLICY_DEVICE_STATE_AVAILABLE<span class="token punctuation">)</span><span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span>size_t i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i  <span class="token operator">&lt;</span> mAvailableInputDevices<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>mAvailableInputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">isAttached</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">;</span>mAvailableInputDevices<span class="token punctuation">.</span><span class="token function">remove</span><span class="token punctuation">(</span>mAvailableInputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token comment">// The device is now validated and can be appended to the available devices of the engine</span>mEngine<span class="token operator">-&gt;</span><span class="token function">setDeviceConnectionState</span><span class="token punctuation">(</span>mAvailableInputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">,</span>AUDIO_POLICY_DEVICE_STATE_AVAILABLE<span class="token punctuation">)</span><span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token function">updateDevicesAndOutputs</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

}

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可以看到AudioPolicyManager通过解析Audio配置文件，加载各输入输出音频Module，然后遍历各输入输出设备，找出稳定的设备后，由路由引擎设置各设备的连接状态。在分析AudioFlinger的时候走过 mpClientInterface->openOutput()函数

sp<AudioFlinger::ThreadBase> AudioFlinger::openOutput_l(.....)
{
    //找到Device, 这个函数很重要，稍后分析AudioHwDevice *outHwDev = findSuitableHwDev_l(module, devices);//音频流输出到硬件设备AudioStreamOut *outputStream = NULL;status_t status = outHwDev->openOutputStream(&outputStream,*output,devices,flags,config,address.string());

mHardwareStatus <span class="token operator">=</span> AUDIO_HW_IDLE<span class="token punctuation">;</span>
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在 createTrack_l()的时候，会去根据流类型来获取路由策略

    uint32_t strategy = AudioSystem::getStrategyForStream(streamType);for (size_t i = 0; i < mTracks.size(); ++i) {
    sp<Track> t = mTracks[i];if (t != 0 && t->isExternalTrack()) {
    //获取路由策略uint32_t actual = AudioSystem::getStrategyForStream(t->streamType());if (sessionId == t->sessionId() && strategy != actual) {
    ALOGE("createTrack_l() mismatched strategy; expected %u but found %u",strategy, actual);lStatus = BAD_VALUE;goto Exit;}}}

  

  
    
   
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调用 Audio代理服务的 getStrategyForStream

uint32_t AudioSystem::getStrategyForStream(audio_stream_type_t stream)
{
    const sp<IAudioPolicyService>& aps = AudioSystem::get_audio_policy_service();if (aps == 0) return 0;return aps->getStrategyForStream(stream);
}

  

  
    
   
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具体的实现在AudioPolicyInterfaceImpl.cpp文件中
\frameworks\av\services\audiopolicy\service\AudioPolicyInterfaceImpl.cpp

uint32_t AudioPolicyService::getStrategyForStream(audio_stream_type_t stream)
{
    if (uint32_t(stream) >= AUDIO_STREAM_PUBLIC_CNT) {
    return 0;}if (mAudioPolicyManager == NULL) {
    return 0;}return mAudioPolicyManager->getStrategyForStream(stream);
}

  

  
    
   
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uint32_t AudioPolicyManager::getStrategyForStream(audio_stream_type_t stream) {
    return (uint32_t)getStrategy(stream);
}

  

  
    
   
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routing_strategy AudioPolicyManager::getStrategy(audio_stream_type_t stream) const
{
    ALOG_ASSERT(stream != AUDIO_STREAM_PATCH,"getStrategy() called for AUDIO_STREAM_PATCH");return mEngine->getStrategyForStream(stream);
}
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在文件 frameworks\av\services\audiopolicy\managerdefault\AudioPolicyManager.h 中 AudioPolicyManagerInterface *mEngine; 位于frameworks\av\services\audiopolicy\engine\interface\AudioPolicyManagerInterface.h，在frameworks\av\services\audiopolicy\enginedefault\src\Engine.h文件中被实现如下

  /// Interface membersclass ManagerInterfaceImpl : public AudioPolicyManagerInterface{
    public:explicit ManagerInterfaceImpl(Engine *policyEngine): mPolicyEngine(policyEngine) {
    }

    <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>virtual routing_strategy <span class="token function">getStrategyForStream</span><span class="token punctuation">(</span>audio_stream_type_t stream<span class="token punctuation">)</span><span class="token punctuation">{</span><span class="token keyword">return</span> mPolicyEngine<span class="token operator">-&gt;</span><span class="token function">getStrategyForStream</span><span class="token punctuation">(</span>stream<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
private<span class="token punctuation">:</span>Engine <span class="token operator">*</span>mPolicyEngine<span class="token punctuation">;</span>
<span class="token punctuation">}</span> mManagerInterface<span class="token punctuation">;</span>
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最终将调用Engine.cpp的getStrategyForStream查询音频路由策略

routing_strategy Engine::getStrategyForStream(audio_stream_type_t stream)
{
    // stream to strategy mappingswitch (stream) {
    case AUDIO_STREAM_VOICE_CALL:case AUDIO_STREAM_BLUETOOTH_SCO:return STRATEGY_PHONE;case AUDIO_STREAM_RING:case AUDIO_STREAM_ALARM:return STRATEGY_SONIFICATION;case AUDIO_STREAM_NOTIFICATION:return STRATEGY_SONIFICATION_RESPECTFUL;case AUDIO_STREAM_DTMF:return STRATEGY_DTMF;default:ALOGE("unknown stream type %d", stream);case AUDIO_STREAM_SYSTEM:// NOTE: SYSTEM stream uses MEDIA strategy because muting music and switching outputs// while key clicks are played produces a poor resultcase AUDIO_STREAM_MUSIC:return STRATEGY_MEDIA;case AUDIO_STREAM_ENFORCED_AUDIBLE:return STRATEGY_ENFORCED_AUDIBLE;case AUDIO_STREAM_TTS:return STRATEGY_TRANSMITTED_THROUGH_SPEAKER;case AUDIO_STREAM_ACCESSIBILITY:return STRATEGY_ACCESSIBILITY;case AUDIO_STREAM_REROUTING:return STRATEGY_REROUTING;}
}

  

  
    
   
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在AudioPolicyService.h文件中定义了如下函数，用来处理设备改变时调整路由策略

virtual status_t handleDeviceConfigChange(audio_devices_t device,const char *device_address,const char *device_name);

  

  
    
   
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至此音频代理路由部分暂到这，目前所看到的只是一小部分，随着Android系统的日益复杂，Audio会变得越来越庞大；
不过万变不离其宗，只要大体架构上不做大改动，也是很容易分析的，下一篇我们来看Audio系统的硬件抽象层。

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</article>
原

Android8.0 Audio系统之AudioPolicy

2018年08月14日 11:43:43 SherlockCharlie 阅读数：1184 
																														</div><div class="operating"></div></div></div>
</div>
<article class="baidu_pl"><div id="article_content" class="article_content clearfix csdn-tracking-statistics" data-pid="blog" data-mod="popu_307" data-dsm="post"><div class="article-copyright"><svg class="icon" title="CSDN认证原创" aria-hidden="true" style="width:53px; height: 18px; vertical-align: -4px;"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#CSDN_Cert"></use></svg>版权声明：未经本人同意，不得转载					https://blog.csdn.net/u013928208/article/details/81660347				</div><link rel="stylesheet" href="https://csdnimg.cn/release/phoenix/template/css/ck_htmledit_views-f57960eb32.css"><div id="content_views" class="markdown_views prism-atom-one-dark"><!-- flowchart 箭头图标 勿删 --><svg xmlns="http://www.w3.org/2000/svg" style="display: none;"><path stroke-linecap="round" d="M5,0 0,2.5 5,5z" id="raphael-marker-block" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0);"></path></svg><p>上一篇我们跟踪分析了AudioFlinger，它是Audio系统的核心，但是AudioFlinger却不能脱离AudioPolicy工作。AudioPolicy模块承载着音频切换，音轨路由的重要工作，没有它，音频输出将乱套。在分析AudioFlinger的时候我们稍微涉及了AudioPolicyService，现在我们重新来看它。在Android7.0中Audio代理部分被组成独立的模块。<br>

这里写图片描述

void AudioPolicyService::onFirstRef()
{
    {
    ......// class AudioPolicyClient : public AudioPolicyClientInterfacemAudioPolicyClient = new AudioPolicyClient(this);mAudioPolicyManager = createAudioPolicyManager(mAudioPolicyClient); //创建Audio管理}
}

  

  
    
   
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头文件 AudioPolicyClientInterface 位于 AudioPolicyInterface.h文件中


extern "C" AudioPolicyInterface* createAudioPolicyManager(AudioPolicyClientInterface *clientInterface)
{
    return new AudioPolicyManager(clientInterface);
}

extern “C” void destroyAudioPolicyManager(AudioPolicyInterface *interface)
{
delete interface;
}

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对于AudioPolicyClientImpl.cpp实现了 AudioPolicyClient，直接与AudioFlinger交互。对于AudioPolicyIntefaceImpl实现了AudioPolicyInterface直接与AudioPolicyManager交互，

AudioPolicyManager::AudioPolicyManager(AudioPolicyClientInterface *clientInterface):
#ifdef AUDIO_POLICY_TESTThread(false),
#endif //AUDIO_POLICY_TESTmLimitRingtoneVolume(false), mLastVoiceVolume(-1.0f),mA2dpSuspended(false),mAudioPortGeneration(1),mBeaconMuteRefCount(0),mBeaconPlayingRefCount(0),mBeaconMuted(false),mTtsOutputAvailable(false),mMasterMono(false),mMusicEffectOutput(AUDIO_IO_HANDLE_NONE)
{
    mpClientInterface = clientInterface;bool speakerDrcEnabled = false;//解析 xml Audio策略，路由
#ifdef USE_XML_AUDIO_POLICY_CONFmVolumeCurves = new VolumeCurvesCollection();AudioPolicyConfig config(mHwModules, mAvailableOutputDevices, mAvailableInputDevices,mDefaultOutputDevice, speakerDrcEnabled,static_cast<VolumeCurvesCollection *>(mVolumeCurves));if (deserializeAudioPolicyXmlConfig(config) != NO_ERROR) {
    
#elsemVolumeCurves = new StreamDescriptorCollection();AudioPolicyConfig config(mHwModules, mAvailableOutputDevices, mAvailableInputDevices,mDefaultOutputDevice, speakerDrcEnabled);if ((ConfigParsingUtils::loadConfig(AUDIO_POLICY_VENDOR_CONFIG_FILE, config) != NO_ERROR) &&(ConfigParsingUtils::loadConfig(AUDIO_POLICY_CONFIG_FILE, config) != NO_ERROR)) {
    
#endifALOGE("could not load audio policy configuration file, setting defaults");config.setDefault();}// must be done after reading the policy (since conditionned by Speaker Drc Enabling)mVolumeCurves->initializeVolumeCurves(speakerDrcEnabled);

<span class="token comment">// Once policy config has been parsed, retrieve an instance of the engine and initialize it</span>
<span class="token comment">//代理引擎</span>
audio_policy<span class="token punctuation">:</span><span class="token punctuation">:</span>EngineInstance <span class="token operator">*</span>engineInstance <span class="token operator">=</span> audio_policy<span class="token punctuation">:</span><span class="token punctuation">:</span>EngineInstance<span class="token punctuation">:</span><span class="token punctuation">:</span><span class="token function">getInstance</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>engineInstance<span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token function">ALOGE</span><span class="token punctuation">(</span><span class="token string">"%s:  Could not get an instance of policy engine"</span><span class="token punctuation">,</span> __FUNCTION__<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">return</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token comment">// Retrieve the Policy Manager Interface</span>
mEngine <span class="token operator">=</span> engineInstance<span class="token operator">-&gt;</span>queryInterface<span class="token operator">&lt;</span>AudioPolicyManagerInterface<span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//获取引擎</span>
mEngine<span class="token operator">-&gt;</span><span class="token function">setObserver</span><span class="token punctuation">(</span>this<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//设为观察者</span>
status_t status <span class="token operator">=</span> mEngine<span class="token operator">-&gt;</span><span class="token function">initCheck</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//初始</span>
<span class="token punctuation">(</span><span class="token keyword">void</span><span class="token punctuation">)</span> status<span class="token punctuation">;</span>
<span class="token comment">// mAvailableOutputDevices and mAvailableInputDevices now contain all attached devices</span>
<span class="token comment">// open all output streams needed to access attached devices</span>
audio_devices_t outputDeviceTypes <span class="token operator">=</span> mAvailableOutputDevices<span class="token punctuation">.</span><span class="token function">types</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
audio_devices_t inputDeviceTypes <span class="token operator">=</span> mAvailableInputDevices<span class="token punctuation">.</span><span class="token function">types</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">&amp;</span> <span class="token operator">~</span>AUDIO_DEVICE_BIT_IN<span class="token punctuation">;</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span>size_t i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> mHwModules<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token comment">//调用ClientInterface加载Audio模块，ClientInterface将调用AudioFlinger的loadHwModule</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mHandle <span class="token operator">=</span> mpClientInterface<span class="token operator">-&gt;</span><span class="token function">loadHwModule</span><span class="token punctuation">(</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mHandle <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token function">ALOGW</span><span class="token punctuation">(</span><span class="token string">"could not open HW module %s"</span><span class="token punctuation">,</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token comment">//查找输出模块设备</span><span class="token keyword">for</span> <span class="token punctuation">(</span>size_t j <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> j <span class="token operator">&lt;</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mOutputProfiles<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> j<span class="token operator">++</span><span class="token punctuation">)</span><span class="token punctuation">{</span><span class="token keyword">const</span> sp<span class="token operator">&lt;</span>IOProfile<span class="token operator">&gt;</span> outProfile <span class="token operator">=</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mOutputProfiles<span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>outProfile<span class="token operator">-&gt;</span><span class="token function">hasSupportedDevices</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token function">ALOGW</span><span class="token punctuation">(</span><span class="token string">"Output profile contains no device on module %s"</span><span class="token punctuation">,</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>outProfile<span class="token operator">-&gt;</span><span class="token function">getFlags</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">&amp;</span> AUDIO_OUTPUT_FLAG_TTS<span class="token punctuation">)</span> <span class="token operator">!=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>mTtsOutputAvailable <span class="token operator">=</span> true<span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>outProfile<span class="token operator">-&gt;</span><span class="token function">getFlags</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">&amp;</span> AUDIO_OUTPUT_FLAG_DIRECT<span class="token punctuation">)</span> <span class="token operator">!=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span>audio_devices_t profileType <span class="token operator">=</span> outProfile<span class="token operator">-&gt;</span><span class="token function">getSupportedDevicesType</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>profileType <span class="token operator">&amp;</span> mDefaultOutputDevice<span class="token operator">-&gt;</span><span class="token function">type</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator">!=</span> AUDIO_DEVICE_NONE<span class="token punctuation">)</span> <span class="token punctuation">{</span>profileType <span class="token operator">=</span> mDefaultOutputDevice<span class="token operator">-&gt;</span><span class="token function">type</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>profileType <span class="token operator">=</span> outProfile<span class="token operator">-&gt;</span><span class="token function">getSupportedDeviceForType</span><span class="token punctuation">(</span>outputDeviceTypes<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>profileType <span class="token operator">&amp;</span> outputDeviceTypes<span class="token punctuation">)</span> <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span>sp<span class="token operator">&lt;</span>SwAudioOutputDescriptor<span class="token operator">&gt;</span> outputDesc <span class="token operator">=</span> new <span class="token function">SwAudioOutputDescriptor</span><span class="token punctuation">(</span>outProfile<span class="token punctuation">,</span>mpClientInterface<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">const</span> DeviceVector <span class="token operator">&amp;</span>supportedDevices <span class="token operator">=</span> outProfile<span class="token operator">-&gt;</span><span class="token function">getSupportedDevices</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">const</span> DeviceVector <span class="token operator">&amp;</span>devicesForType <span class="token operator">=</span> supportedDevices<span class="token punctuation">.</span><span class="token function">getDevicesFromType</span><span class="token punctuation">(</span>profileType<span class="token punctuation">)</span><span class="token punctuation">;</span>String8 address <span class="token operator">=</span> devicesForType<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">&gt;</span> <span class="token number">0</span> <span class="token operator">?</span> devicesForType<span class="token punctuation">.</span><span class="token function">itemAt</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token operator">-&gt;</span>mAddress<span class="token punctuation">:</span> <span class="token function">String8</span><span class="token punctuation">(</span><span class="token string">""</span><span class="token punctuation">)</span><span class="token punctuation">;</span>outputDesc<span class="token operator">-&gt;</span>mDevice <span class="token operator">=</span> profileType<span class="token punctuation">;</span>audio_config_t config <span class="token operator">=</span> AUDIO_CONFIG_INITIALIZER<span class="token punctuation">;</span>config<span class="token punctuation">.</span>sample_rate <span class="token operator">=</span> outputDesc<span class="token operator">-&gt;</span>mSamplingRate<span class="token punctuation">;</span>config<span class="token punctuation">.</span>channel_mask <span class="token operator">=</span> outputDesc<span class="token operator">-&gt;</span>mChannelMask<span class="token punctuation">;</span>config<span class="token punctuation">.</span>format <span class="token operator">=</span> outputDesc<span class="token operator">-&gt;</span>mFormat<span class="token punctuation">;</span>audio_io_handle_t output <span class="token operator">=</span> AUDIO_IO_HANDLE_NONE<span class="token punctuation">;</span><span class="token comment">//熟悉的openOutput</span>status_t status <span class="token operator">=</span> mpClientInterface<span class="token operator">-&gt;</span><span class="token function">openOutput</span><span class="token punctuation">(</span>outProfile<span class="token operator">-&gt;</span><span class="token function">getModuleHandle</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token operator">&amp;</span>output<span class="token punctuation">,</span><span class="token operator">&amp;</span>config<span class="token punctuation">,</span><span class="token operator">&amp;</span>outputDesc<span class="token operator">-&gt;</span>mDevice<span class="token punctuation">,</span>address<span class="token punctuation">,</span><span class="token operator">&amp;</span>outputDesc<span class="token operator">-&gt;</span>mLatency<span class="token punctuation">,</span>outputDesc<span class="token operator">-&gt;</span>mFlags<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span>status <span class="token operator">!=</span> NO_ERROR<span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token function">ALOGW</span><span class="token punctuation">(</span><span class="token string">"Cannot open output stream for device %08x on hw module %s"</span><span class="token punctuation">,</span>outputDesc<span class="token operator">-&gt;</span>mDevice<span class="token punctuation">,</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>outputDesc<span class="token operator">-&gt;</span>mSamplingRate <span class="token operator">=</span> config<span class="token punctuation">.</span>sample_rate<span class="token punctuation">;</span>outputDesc<span class="token operator">-&gt;</span>mChannelMask <span class="token operator">=</span> config<span class="token punctuation">.</span>channel_mask<span class="token punctuation">;</span>outputDesc<span class="token operator">-&gt;</span>mFormat <span class="token operator">=</span> config<span class="token punctuation">.</span>format<span class="token punctuation">;</span><span class="token keyword">for</span> <span class="token punctuation">(</span>size_t k <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> k  <span class="token operator">&lt;</span> supportedDevices<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> k<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>ssize_t index <span class="token operator">=</span> mAvailableOutputDevices<span class="token punctuation">.</span><span class="token function">indexOf</span><span class="token punctuation">(</span>supportedDevices<span class="token punctuation">[</span>k<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">// give a valid ID to an attached device once confirmed it is reachable</span><span class="token keyword">if</span> <span class="token punctuation">(</span>index <span class="token operator">&gt;=</span> <span class="token number">0</span> <span class="token operator">&amp;&amp;</span> <span class="token operator">!</span>mAvailableOutputDevices<span class="token punctuation">[</span>index<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">isAttached</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>mAvailableOutputDevices<span class="token punctuation">[</span>index<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">attach</span><span class="token punctuation">(</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token keyword">if</span> <span class="token punctuation">(</span>mPrimaryOutput <span class="token operator">==</span> <span class="token number">0</span> <span class="token operator">&amp;&amp;</span>outProfile<span class="token operator">-&gt;</span><span class="token function">getFlags</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">&amp;</span> AUDIO_OUTPUT_FLAG_PRIMARY<span class="token punctuation">)</span> <span class="token punctuation">{</span>mPrimaryOutput <span class="token operator">=</span> outputDesc<span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token function">addOutput</span><span class="token punctuation">(</span>output<span class="token punctuation">,</span> outputDesc<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token function">setOutputDevice</span><span class="token punctuation">(</span>outputDesc<span class="token punctuation">,</span>outputDesc<span class="token operator">-&gt;</span>mDevice<span class="token punctuation">,</span>true<span class="token punctuation">,</span><span class="token number">0</span><span class="token punctuation">,</span><span class="token constant">NULL</span><span class="token punctuation">,</span>address<span class="token punctuation">.</span><span class="token function">string</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token comment">//遍历输入Audio设备</span><span class="token keyword">for</span> <span class="token punctuation">(</span>size_t j <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> j <span class="token operator">&lt;</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mInputProfiles<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> j<span class="token operator">++</span><span class="token punctuation">)</span><span class="token punctuation">{</span><span class="token keyword">const</span> sp<span class="token operator">&lt;</span>IOProfile<span class="token operator">&gt;</span> inProfile <span class="token operator">=</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mInputProfiles<span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>inProfile<span class="token operator">-&gt;</span><span class="token function">hasSupportedDevices</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token function">ALOGW</span><span class="token punctuation">(</span><span class="token string">"Input profile contains no device on module %s"</span><span class="token punctuation">,</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token comment">// chose first device present in profile's SupportedDevices also part of</span><span class="token comment">// inputDeviceTypes</span>audio_devices_t profileType <span class="token operator">=</span> inProfile<span class="token operator">-&gt;</span><span class="token function">getSupportedDeviceForType</span><span class="token punctuation">(</span>inputDeviceTypes<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>profileType <span class="token operator">&amp;</span> inputDeviceTypes<span class="token punctuation">)</span> <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span>sp<span class="token operator">&lt;</span>AudioInputDescriptor<span class="token operator">&gt;</span> inputDesc <span class="token operator">=</span>new <span class="token function">AudioInputDescriptor</span><span class="token punctuation">(</span>inProfile<span class="token punctuation">)</span><span class="token punctuation">;</span>inputDesc<span class="token operator">-&gt;</span>mDevice <span class="token operator">=</span> profileType<span class="token punctuation">;</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>audio_config_t config <span class="token operator">=</span> AUDIO_CONFIG_INITIALIZER<span class="token punctuation">;</span>config<span class="token punctuation">.</span>sample_rate <span class="token operator">=</span> inputDesc<span class="token operator">-&gt;</span>mSamplingRate<span class="token punctuation">;</span>config<span class="token punctuation">.</span>channel_mask <span class="token operator">=</span> inputDesc<span class="token operator">-&gt;</span>mChannelMask<span class="token punctuation">;</span>config<span class="token punctuation">.</span>format <span class="token operator">=</span> inputDesc<span class="token operator">-&gt;</span>mFormat<span class="token punctuation">;</span>audio_io_handle_t input <span class="token operator">=</span> AUDIO_IO_HANDLE_NONE<span class="token punctuation">;</span>status_t status <span class="token operator">=</span> mpClientInterface<span class="token operator">-&gt;</span><span class="token function">openInput</span><span class="token punctuation">(</span>inProfile<span class="token operator">-&gt;</span><span class="token function">getModuleHandle</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token operator">&amp;</span>input<span class="token punctuation">,</span><span class="token operator">&amp;</span>config<span class="token punctuation">,</span><span class="token operator">&amp;</span>inputDesc<span class="token operator">-&gt;</span>mDevice<span class="token punctuation">,</span>address<span class="token punctuation">,</span>AUDIO_SOURCE_MIC<span class="token punctuation">,</span>AUDIO_INPUT_FLAG_NONE<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span>status <span class="token operator">==</span> NO_ERROR<span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">const</span> DeviceVector <span class="token operator">&amp;</span>supportedDevices <span class="token operator">=</span> inProfile<span class="token operator">-&gt;</span><span class="token function">getSupportedDevices</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">for</span> <span class="token punctuation">(</span>size_t k <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> k  <span class="token operator">&lt;</span> supportedDevices<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> k<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>ssize_t index <span class="token operator">=</span>  mAvailableInputDevices<span class="token punctuation">.</span><span class="token function">indexOf</span><span class="token punctuation">(</span>supportedDevices<span class="token punctuation">[</span>k<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">// give a valid ID to an attached device once confirmed it is reachable</span><span class="token keyword">if</span> <span class="token punctuation">(</span>index <span class="token operator">&gt;=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>sp<span class="token operator">&lt;</span>DeviceDescriptor<span class="token operator">&gt;</span> devDesc <span class="token operator">=</span> mAvailableInputDevices<span class="token punctuation">[</span>index<span class="token punctuation">]</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>devDesc<span class="token operator">-&gt;</span><span class="token function">isAttached</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>devDesc<span class="token operator">-&gt;</span><span class="token function">attach</span><span class="token punctuation">(</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>devDesc<span class="token operator">-&gt;</span><span class="token function">importAudioPort</span><span class="token punctuation">(</span>inProfile<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token punctuation">}</span>mpClientInterface<span class="token operator">-&gt;</span><span class="token function">closeInput</span><span class="token punctuation">(</span>input<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token comment">// make sure all attached devices have been allocated a unique ID</span>
<span class="token comment">//遍历输入输出设备，由路由引擎设置各设备的连接状态</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span>size_t i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i  <span class="token operator">&lt;</span> mAvailableOutputDevices<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>mAvailableOutputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">isAttached</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>mAvailableOutputDevices<span class="token punctuation">.</span><span class="token function">remove</span><span class="token punctuation">(</span>mAvailableOutputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token comment">// The device is now validated and can be appended to the available devices of the engine</span>mEngine<span class="token operator">-&gt;</span><span class="token function">setDeviceConnectionState</span><span class="token punctuation">(</span>mAvailableOutputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">,</span>AUDIO_POLICY_DEVICE_STATE_AVAILABLE<span class="token punctuation">)</span><span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span>size_t i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i  <span class="token operator">&lt;</span> mAvailableInputDevices<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>mAvailableInputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">isAttached</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">;</span>mAvailableInputDevices<span class="token punctuation">.</span><span class="token function">remove</span><span class="token punctuation">(</span>mAvailableInputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token comment">// The device is now validated and can be appended to the available devices of the engine</span>mEngine<span class="token operator">-&gt;</span><span class="token function">setDeviceConnectionState</span><span class="token punctuation">(</span>mAvailableInputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">,</span>AUDIO_POLICY_DEVICE_STATE_AVAILABLE<span class="token punctuation">)</span><span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token function">updateDevicesAndOutputs</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

}

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可以看到AudioPolicyManager通过解析Audio配置文件，加载各输入输出音频Module，然后遍历各输入输出设备，找出稳定的设备后，由路由引擎设置各设备的连接状态。在分析AudioFlinger的时候走过 mpClientInterface->openOutput()函数

sp<AudioFlinger::ThreadBase> AudioFlinger::openOutput_l(.....)
{
    //找到Device, 这个函数很重要，稍后分析AudioHwDevice *outHwDev = findSuitableHwDev_l(module, devices);//音频流输出到硬件设备AudioStreamOut *outputStream = NULL;status_t status = outHwDev->openOutputStream(&outputStream,*output,devices,flags,config,address.string());

mHardwareStatus <span class="token operator">=</span> AUDIO_HW_IDLE<span class="token punctuation">;</span>
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在 createTrack_l()的时候，会去根据流类型来获取路由策略

    uint32_t strategy = AudioSystem::getStrategyForStream(streamType);for (size_t i = 0; i < mTracks.size(); ++i) {
    sp<Track> t = mTracks[i];if (t != 0 && t->isExternalTrack()) {
    //获取路由策略uint32_t actual = AudioSystem::getStrategyForStream(t->streamType());if (sessionId == t->sessionId() && strategy != actual) {
    ALOGE("createTrack_l() mismatched strategy; expected %u but found %u",strategy, actual);lStatus = BAD_VALUE;goto Exit;}}}

  

  
    
   
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调用 Audio代理服务的 getStrategyForStream

uint32_t AudioSystem::getStrategyForStream(audio_stream_type_t stream)
{
    const sp<IAudioPolicyService>& aps = AudioSystem::get_audio_policy_service();if (aps == 0) return 0;return aps->getStrategyForStream(stream);
}

  

  
    
   
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具体的实现在AudioPolicyInterfaceImpl.cpp文件中
\frameworks\av\services\audiopolicy\service\AudioPolicyInterfaceImpl.cpp

uint32_t AudioPolicyService::getStrategyForStream(audio_stream_type_t stream)
{
    if (uint32_t(stream) >= AUDIO_STREAM_PUBLIC_CNT) {
    return 0;}if (mAudioPolicyManager == NULL) {
    return 0;}return mAudioPolicyManager->getStrategyForStream(stream);
}

  

  
    
   
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uint32_t AudioPolicyManager::getStrategyForStream(audio_stream_type_t stream) {
    return (uint32_t)getStrategy(stream);
}

  

  
    
   
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routing_strategy AudioPolicyManager::getStrategy(audio_stream_type_t stream) const
{
    ALOG_ASSERT(stream != AUDIO_STREAM_PATCH,"getStrategy() called for AUDIO_STREAM_PATCH");return mEngine->getStrategyForStream(stream);
}
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在文件 frameworks\av\services\audiopolicy\managerdefault\AudioPolicyManager.h 中 AudioPolicyManagerInterface *mEngine; 位于frameworks\av\services\audiopolicy\engine\interface\AudioPolicyManagerInterface.h，在frameworks\av\services\audiopolicy\enginedefault\src\Engine.h文件中被实现如下

  /// Interface membersclass ManagerInterfaceImpl : public AudioPolicyManagerInterface{
    public:explicit ManagerInterfaceImpl(Engine *policyEngine): mPolicyEngine(policyEngine) {
    }

    <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>virtual routing_strategy <span class="token function">getStrategyForStream</span><span class="token punctuation">(</span>audio_stream_type_t stream<span class="token punctuation">)</span><span class="token punctuation">{</span><span class="token keyword">return</span> mPolicyEngine<span class="token operator">-&gt;</span><span class="token function">getStrategyForStream</span><span class="token punctuation">(</span>stream<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
private<span class="token punctuation">:</span>Engine <span class="token operator">*</span>mPolicyEngine<span class="token punctuation">;</span>
<span class="token punctuation">}</span> mManagerInterface<span class="token punctuation">;</span>
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最终将调用Engine.cpp的getStrategyForStream查询音频路由策略

routing_strategy Engine::getStrategyForStream(audio_stream_type_t stream)
{
    // stream to strategy mappingswitch (stream) {
    case AUDIO_STREAM_VOICE_CALL:case AUDIO_STREAM_BLUETOOTH_SCO:return STRATEGY_PHONE;case AUDIO_STREAM_RING:case AUDIO_STREAM_ALARM:return STRATEGY_SONIFICATION;case AUDIO_STREAM_NOTIFICATION:return STRATEGY_SONIFICATION_RESPECTFUL;case AUDIO_STREAM_DTMF:return STRATEGY_DTMF;default:ALOGE("unknown stream type %d", stream);case AUDIO_STREAM_SYSTEM:// NOTE: SYSTEM stream uses MEDIA strategy because muting music and switching outputs// while key clicks are played produces a poor resultcase AUDIO_STREAM_MUSIC:return STRATEGY_MEDIA;case AUDIO_STREAM_ENFORCED_AUDIBLE:return STRATEGY_ENFORCED_AUDIBLE;case AUDIO_STREAM_TTS:return STRATEGY_TRANSMITTED_THROUGH_SPEAKER;case AUDIO_STREAM_ACCESSIBILITY:return STRATEGY_ACCESSIBILITY;case AUDIO_STREAM_REROUTING:return STRATEGY_REROUTING;}
}

  

  
    
   
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在AudioPolicyService.h文件中定义了如下函数，用来处理设备改变时调整路由策略

virtual status_t handleDeviceConfigChange(audio_devices_t device,const char *device_address,const char *device_name);

  

  
    
   
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至此音频代理路由部分暂到这，目前所看到的只是一小部分，随着Android系统的日益复杂，Audio会变得越来越庞大；
不过万变不离其宗，只要大体架构上不做大改动，也是很容易分析的，下一篇我们来看Audio系统的硬件抽象层。

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</article>
原

Android8.0 Audio系统之AudioPolicy

2018年08月14日 11:43:43 SherlockCharlie 阅读数：1184 
																														</div><div class="operating"></div></div></div>
</div>
<article class="baidu_pl"><div id="article_content" class="article_content clearfix csdn-tracking-statistics" data-pid="blog" data-mod="popu_307" data-dsm="post"><div class="article-copyright"><svg class="icon" title="CSDN认证原创" aria-hidden="true" style="width:53px; height: 18px; vertical-align: -4px;"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#CSDN_Cert"></use></svg>版权声明：未经本人同意，不得转载					https://blog.csdn.net/u013928208/article/details/81660347				</div><link rel="stylesheet" href="https://csdnimg.cn/release/phoenix/template/css/ck_htmledit_views-f57960eb32.css"><div id="content_views" class="markdown_views prism-atom-one-dark"><!-- flowchart 箭头图标 勿删 --><svg xmlns="http://www.w3.org/2000/svg" style="display: none;"><path stroke-linecap="round" d="M5,0 0,2.5 5,5z" id="raphael-marker-block" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0);"></path></svg><p>上一篇我们跟踪分析了AudioFlinger，它是Audio系统的核心，但是AudioFlinger却不能脱离AudioPolicy工作。AudioPolicy模块承载着音频切换，音轨路由的重要工作，没有它，音频输出将乱套。在分析AudioFlinger的时候我们稍微涉及了AudioPolicyService，现在我们重新来看它。在Android7.0中Audio代理部分被组成独立的模块。<br>

这里写图片描述

void AudioPolicyService::onFirstRef()
{
    {
    ......// class AudioPolicyClient : public AudioPolicyClientInterfacemAudioPolicyClient = new AudioPolicyClient(this);mAudioPolicyManager = createAudioPolicyManager(mAudioPolicyClient); //创建Audio管理}
}

  

  
    
   
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头文件 AudioPolicyClientInterface 位于 AudioPolicyInterface.h文件中


extern "C" AudioPolicyInterface* createAudioPolicyManager(AudioPolicyClientInterface *clientInterface)
{
    return new AudioPolicyManager(clientInterface);
}

extern “C” void destroyAudioPolicyManager(AudioPolicyInterface *interface)
{
delete interface;
}

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对于AudioPolicyClientImpl.cpp实现了 AudioPolicyClient，直接与AudioFlinger交互。对于AudioPolicyIntefaceImpl实现了AudioPolicyInterface直接与AudioPolicyManager交互，

AudioPolicyManager::AudioPolicyManager(AudioPolicyClientInterface *clientInterface):
#ifdef AUDIO_POLICY_TESTThread(false),
#endif //AUDIO_POLICY_TESTmLimitRingtoneVolume(false), mLastVoiceVolume(-1.0f),mA2dpSuspended(false),mAudioPortGeneration(1),mBeaconMuteRefCount(0),mBeaconPlayingRefCount(0),mBeaconMuted(false),mTtsOutputAvailable(false),mMasterMono(false),mMusicEffectOutput(AUDIO_IO_HANDLE_NONE)
{
    mpClientInterface = clientInterface;bool speakerDrcEnabled = false;//解析 xml Audio策略，路由
#ifdef USE_XML_AUDIO_POLICY_CONFmVolumeCurves = new VolumeCurvesCollection();AudioPolicyConfig config(mHwModules, mAvailableOutputDevices, mAvailableInputDevices,mDefaultOutputDevice, speakerDrcEnabled,static_cast<VolumeCurvesCollection *>(mVolumeCurves));if (deserializeAudioPolicyXmlConfig(config) != NO_ERROR) {
    
#elsemVolumeCurves = new StreamDescriptorCollection();AudioPolicyConfig config(mHwModules, mAvailableOutputDevices, mAvailableInputDevices,mDefaultOutputDevice, speakerDrcEnabled);if ((ConfigParsingUtils::loadConfig(AUDIO_POLICY_VENDOR_CONFIG_FILE, config) != NO_ERROR) &&(ConfigParsingUtils::loadConfig(AUDIO_POLICY_CONFIG_FILE, config) != NO_ERROR)) {
    
#endifALOGE("could not load audio policy configuration file, setting defaults");config.setDefault();}// must be done after reading the policy (since conditionned by Speaker Drc Enabling)mVolumeCurves->initializeVolumeCurves(speakerDrcEnabled);

<span class="token comment">// Once policy config has been parsed, retrieve an instance of the engine and initialize it</span>
<span class="token comment">//代理引擎</span>
audio_policy<span class="token punctuation">:</span><span class="token punctuation">:</span>EngineInstance <span class="token operator">*</span>engineInstance <span class="token operator">=</span> audio_policy<span class="token punctuation">:</span><span class="token punctuation">:</span>EngineInstance<span class="token punctuation">:</span><span class="token punctuation">:</span><span class="token function">getInstance</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>engineInstance<span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token function">ALOGE</span><span class="token punctuation">(</span><span class="token string">"%s:  Could not get an instance of policy engine"</span><span class="token punctuation">,</span> __FUNCTION__<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">return</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token comment">// Retrieve the Policy Manager Interface</span>
mEngine <span class="token operator">=</span> engineInstance<span class="token operator">-&gt;</span>queryInterface<span class="token operator">&lt;</span>AudioPolicyManagerInterface<span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//获取引擎</span>
mEngine<span class="token operator">-&gt;</span><span class="token function">setObserver</span><span class="token punctuation">(</span>this<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//设为观察者</span>
status_t status <span class="token operator">=</span> mEngine<span class="token operator">-&gt;</span><span class="token function">initCheck</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//初始</span>
<span class="token punctuation">(</span><span class="token keyword">void</span><span class="token punctuation">)</span> status<span class="token punctuation">;</span>
<span class="token comment">// mAvailableOutputDevices and mAvailableInputDevices now contain all attached devices</span>
<span class="token comment">// open all output streams needed to access attached devices</span>
audio_devices_t outputDeviceTypes <span class="token operator">=</span> mAvailableOutputDevices<span class="token punctuation">.</span><span class="token function">types</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
audio_devices_t inputDeviceTypes <span class="token operator">=</span> mAvailableInputDevices<span class="token punctuation">.</span><span class="token function">types</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">&amp;</span> <span class="token operator">~</span>AUDIO_DEVICE_BIT_IN<span class="token punctuation">;</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span>size_t i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> mHwModules<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token comment">//调用ClientInterface加载Audio模块，ClientInterface将调用AudioFlinger的loadHwModule</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mHandle <span class="token operator">=</span> mpClientInterface<span class="token operator">-&gt;</span><span class="token function">loadHwModule</span><span class="token punctuation">(</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mHandle <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token function">ALOGW</span><span class="token punctuation">(</span><span class="token string">"could not open HW module %s"</span><span class="token punctuation">,</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token comment">//查找输出模块设备</span><span class="token keyword">for</span> <span class="token punctuation">(</span>size_t j <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> j <span class="token operator">&lt;</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mOutputProfiles<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> j<span class="token operator">++</span><span class="token punctuation">)</span><span class="token punctuation">{</span><span class="token keyword">const</span> sp<span class="token operator">&lt;</span>IOProfile<span class="token operator">&gt;</span> outProfile <span class="token operator">=</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mOutputProfiles<span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>outProfile<span class="token operator">-&gt;</span><span class="token function">hasSupportedDevices</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token function">ALOGW</span><span class="token punctuation">(</span><span class="token string">"Output profile contains no device on module %s"</span><span class="token punctuation">,</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>outProfile<span class="token operator">-&gt;</span><span class="token function">getFlags</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">&amp;</span> AUDIO_OUTPUT_FLAG_TTS<span class="token punctuation">)</span> <span class="token operator">!=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>mTtsOutputAvailable <span class="token operator">=</span> true<span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>outProfile<span class="token operator">-&gt;</span><span class="token function">getFlags</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">&amp;</span> AUDIO_OUTPUT_FLAG_DIRECT<span class="token punctuation">)</span> <span class="token operator">!=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span>audio_devices_t profileType <span class="token operator">=</span> outProfile<span class="token operator">-&gt;</span><span class="token function">getSupportedDevicesType</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>profileType <span class="token operator">&amp;</span> mDefaultOutputDevice<span class="token operator">-&gt;</span><span class="token function">type</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator">!=</span> AUDIO_DEVICE_NONE<span class="token punctuation">)</span> <span class="token punctuation">{</span>profileType <span class="token operator">=</span> mDefaultOutputDevice<span class="token operator">-&gt;</span><span class="token function">type</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>profileType <span class="token operator">=</span> outProfile<span class="token operator">-&gt;</span><span class="token function">getSupportedDeviceForType</span><span class="token punctuation">(</span>outputDeviceTypes<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>profileType <span class="token operator">&amp;</span> outputDeviceTypes<span class="token punctuation">)</span> <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span>sp<span class="token operator">&lt;</span>SwAudioOutputDescriptor<span class="token operator">&gt;</span> outputDesc <span class="token operator">=</span> new <span class="token function">SwAudioOutputDescriptor</span><span class="token punctuation">(</span>outProfile<span class="token punctuation">,</span>mpClientInterface<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">const</span> DeviceVector <span class="token operator">&amp;</span>supportedDevices <span class="token operator">=</span> outProfile<span class="token operator">-&gt;</span><span class="token function">getSupportedDevices</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">const</span> DeviceVector <span class="token operator">&amp;</span>devicesForType <span class="token operator">=</span> supportedDevices<span class="token punctuation">.</span><span class="token function">getDevicesFromType</span><span class="token punctuation">(</span>profileType<span class="token punctuation">)</span><span class="token punctuation">;</span>String8 address <span class="token operator">=</span> devicesForType<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">&gt;</span> <span class="token number">0</span> <span class="token operator">?</span> devicesForType<span class="token punctuation">.</span><span class="token function">itemAt</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token operator">-&gt;</span>mAddress<span class="token punctuation">:</span> <span class="token function">String8</span><span class="token punctuation">(</span><span class="token string">""</span><span class="token punctuation">)</span><span class="token punctuation">;</span>outputDesc<span class="token operator">-&gt;</span>mDevice <span class="token operator">=</span> profileType<span class="token punctuation">;</span>audio_config_t config <span class="token operator">=</span> AUDIO_CONFIG_INITIALIZER<span class="token punctuation">;</span>config<span class="token punctuation">.</span>sample_rate <span class="token operator">=</span> outputDesc<span class="token operator">-&gt;</span>mSamplingRate<span class="token punctuation">;</span>config<span class="token punctuation">.</span>channel_mask <span class="token operator">=</span> outputDesc<span class="token operator">-&gt;</span>mChannelMask<span class="token punctuation">;</span>config<span class="token punctuation">.</span>format <span class="token operator">=</span> outputDesc<span class="token operator">-&gt;</span>mFormat<span class="token punctuation">;</span>audio_io_handle_t output <span class="token operator">=</span> AUDIO_IO_HANDLE_NONE<span class="token punctuation">;</span><span class="token comment">//熟悉的openOutput</span>status_t status <span class="token operator">=</span> mpClientInterface<span class="token operator">-&gt;</span><span class="token function">openOutput</span><span class="token punctuation">(</span>outProfile<span class="token operator">-&gt;</span><span class="token function">getModuleHandle</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token operator">&amp;</span>output<span class="token punctuation">,</span><span class="token operator">&amp;</span>config<span class="token punctuation">,</span><span class="token operator">&amp;</span>outputDesc<span class="token operator">-&gt;</span>mDevice<span class="token punctuation">,</span>address<span class="token punctuation">,</span><span class="token operator">&amp;</span>outputDesc<span class="token operator">-&gt;</span>mLatency<span class="token punctuation">,</span>outputDesc<span class="token operator">-&gt;</span>mFlags<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span>status <span class="token operator">!=</span> NO_ERROR<span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token function">ALOGW</span><span class="token punctuation">(</span><span class="token string">"Cannot open output stream for device %08x on hw module %s"</span><span class="token punctuation">,</span>outputDesc<span class="token operator">-&gt;</span>mDevice<span class="token punctuation">,</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>outputDesc<span class="token operator">-&gt;</span>mSamplingRate <span class="token operator">=</span> config<span class="token punctuation">.</span>sample_rate<span class="token punctuation">;</span>outputDesc<span class="token operator">-&gt;</span>mChannelMask <span class="token operator">=</span> config<span class="token punctuation">.</span>channel_mask<span class="token punctuation">;</span>outputDesc<span class="token operator">-&gt;</span>mFormat <span class="token operator">=</span> config<span class="token punctuation">.</span>format<span class="token punctuation">;</span><span class="token keyword">for</span> <span class="token punctuation">(</span>size_t k <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> k  <span class="token operator">&lt;</span> supportedDevices<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> k<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>ssize_t index <span class="token operator">=</span> mAvailableOutputDevices<span class="token punctuation">.</span><span class="token function">indexOf</span><span class="token punctuation">(</span>supportedDevices<span class="token punctuation">[</span>k<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">// give a valid ID to an attached device once confirmed it is reachable</span><span class="token keyword">if</span> <span class="token punctuation">(</span>index <span class="token operator">&gt;=</span> <span class="token number">0</span> <span class="token operator">&amp;&amp;</span> <span class="token operator">!</span>mAvailableOutputDevices<span class="token punctuation">[</span>index<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">isAttached</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>mAvailableOutputDevices<span class="token punctuation">[</span>index<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">attach</span><span class="token punctuation">(</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token keyword">if</span> <span class="token punctuation">(</span>mPrimaryOutput <span class="token operator">==</span> <span class="token number">0</span> <span class="token operator">&amp;&amp;</span>outProfile<span class="token operator">-&gt;</span><span class="token function">getFlags</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">&amp;</span> AUDIO_OUTPUT_FLAG_PRIMARY<span class="token punctuation">)</span> <span class="token punctuation">{</span>mPrimaryOutput <span class="token operator">=</span> outputDesc<span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token function">addOutput</span><span class="token punctuation">(</span>output<span class="token punctuation">,</span> outputDesc<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token function">setOutputDevice</span><span class="token punctuation">(</span>outputDesc<span class="token punctuation">,</span>outputDesc<span class="token operator">-&gt;</span>mDevice<span class="token punctuation">,</span>true<span class="token punctuation">,</span><span class="token number">0</span><span class="token punctuation">,</span><span class="token constant">NULL</span><span class="token punctuation">,</span>address<span class="token punctuation">.</span><span class="token function">string</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token comment">//遍历输入Audio设备</span><span class="token keyword">for</span> <span class="token punctuation">(</span>size_t j <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> j <span class="token operator">&lt;</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mInputProfiles<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> j<span class="token operator">++</span><span class="token punctuation">)</span><span class="token punctuation">{</span><span class="token keyword">const</span> sp<span class="token operator">&lt;</span>IOProfile<span class="token operator">&gt;</span> inProfile <span class="token operator">=</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span>mInputProfiles<span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>inProfile<span class="token operator">-&gt;</span><span class="token function">hasSupportedDevices</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token function">ALOGW</span><span class="token punctuation">(</span><span class="token string">"Input profile contains no device on module %s"</span><span class="token punctuation">,</span> mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token comment">// chose first device present in profile's SupportedDevices also part of</span><span class="token comment">// inputDeviceTypes</span>audio_devices_t profileType <span class="token operator">=</span> inProfile<span class="token operator">-&gt;</span><span class="token function">getSupportedDeviceForType</span><span class="token punctuation">(</span>inputDeviceTypes<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>profileType <span class="token operator">&amp;</span> inputDeviceTypes<span class="token punctuation">)</span> <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span>sp<span class="token operator">&lt;</span>AudioInputDescriptor<span class="token operator">&gt;</span> inputDesc <span class="token operator">=</span>new <span class="token function">AudioInputDescriptor</span><span class="token punctuation">(</span>inProfile<span class="token punctuation">)</span><span class="token punctuation">;</span>inputDesc<span class="token operator">-&gt;</span>mDevice <span class="token operator">=</span> profileType<span class="token punctuation">;</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>audio_config_t config <span class="token operator">=</span> AUDIO_CONFIG_INITIALIZER<span class="token punctuation">;</span>config<span class="token punctuation">.</span>sample_rate <span class="token operator">=</span> inputDesc<span class="token operator">-&gt;</span>mSamplingRate<span class="token punctuation">;</span>config<span class="token punctuation">.</span>channel_mask <span class="token operator">=</span> inputDesc<span class="token operator">-&gt;</span>mChannelMask<span class="token punctuation">;</span>config<span class="token punctuation">.</span>format <span class="token operator">=</span> inputDesc<span class="token operator">-&gt;</span>mFormat<span class="token punctuation">;</span>audio_io_handle_t input <span class="token operator">=</span> AUDIO_IO_HANDLE_NONE<span class="token punctuation">;</span>status_t status <span class="token operator">=</span> mpClientInterface<span class="token operator">-&gt;</span><span class="token function">openInput</span><span class="token punctuation">(</span>inProfile<span class="token operator">-&gt;</span><span class="token function">getModuleHandle</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token operator">&amp;</span>input<span class="token punctuation">,</span><span class="token operator">&amp;</span>config<span class="token punctuation">,</span><span class="token operator">&amp;</span>inputDesc<span class="token operator">-&gt;</span>mDevice<span class="token punctuation">,</span>address<span class="token punctuation">,</span>AUDIO_SOURCE_MIC<span class="token punctuation">,</span>AUDIO_INPUT_FLAG_NONE<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span>status <span class="token operator">==</span> NO_ERROR<span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">const</span> DeviceVector <span class="token operator">&amp;</span>supportedDevices <span class="token operator">=</span> inProfile<span class="token operator">-&gt;</span><span class="token function">getSupportedDevices</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">for</span> <span class="token punctuation">(</span>size_t k <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> k  <span class="token operator">&lt;</span> supportedDevices<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> k<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>ssize_t index <span class="token operator">=</span>  mAvailableInputDevices<span class="token punctuation">.</span><span class="token function">indexOf</span><span class="token punctuation">(</span>supportedDevices<span class="token punctuation">[</span>k<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">// give a valid ID to an attached device once confirmed it is reachable</span><span class="token keyword">if</span> <span class="token punctuation">(</span>index <span class="token operator">&gt;=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>sp<span class="token operator">&lt;</span>DeviceDescriptor<span class="token operator">&gt;</span> devDesc <span class="token operator">=</span> mAvailableInputDevices<span class="token punctuation">[</span>index<span class="token punctuation">]</span><span class="token punctuation">;</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>devDesc<span class="token operator">-&gt;</span><span class="token function">isAttached</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>devDesc<span class="token operator">-&gt;</span><span class="token function">attach</span><span class="token punctuation">(</span>mHwModules<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>devDesc<span class="token operator">-&gt;</span><span class="token function">importAudioPort</span><span class="token punctuation">(</span>inProfile<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token punctuation">}</span>mpClientInterface<span class="token operator">-&gt;</span><span class="token function">closeInput</span><span class="token punctuation">(</span>input<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token comment">// make sure all attached devices have been allocated a unique ID</span>
<span class="token comment">//遍历输入输出设备，由路由引擎设置各设备的连接状态</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span>size_t i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i  <span class="token operator">&lt;</span> mAvailableOutputDevices<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>mAvailableOutputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">isAttached</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>mAvailableOutputDevices<span class="token punctuation">.</span><span class="token function">remove</span><span class="token punctuation">(</span>mAvailableOutputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token comment">// The device is now validated and can be appended to the available devices of the engine</span>mEngine<span class="token operator">-&gt;</span><span class="token function">setDeviceConnectionState</span><span class="token punctuation">(</span>mAvailableOutputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">,</span>AUDIO_POLICY_DEVICE_STATE_AVAILABLE<span class="token punctuation">)</span><span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span>size_t i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i  <span class="token operator">&lt;</span> mAvailableInputDevices<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>mAvailableInputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token operator">-&gt;</span><span class="token function">isAttached</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">;</span>mAvailableInputDevices<span class="token punctuation">.</span><span class="token function">remove</span><span class="token punctuation">(</span>mAvailableInputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">continue</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token comment">// The device is now validated and can be appended to the available devices of the engine</span>mEngine<span class="token operator">-&gt;</span><span class="token function">setDeviceConnectionState</span><span class="token punctuation">(</span>mAvailableInputDevices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">,</span>AUDIO_POLICY_DEVICE_STATE_AVAILABLE<span class="token punctuation">)</span><span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token function">updateDevicesAndOutputs</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

}

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可以看到AudioPolicyManager通过解析Audio配置文件，加载各输入输出音频Module，然后遍历各输入输出设备，找出稳定的设备后，由路由引擎设置各设备的连接状态。在分析AudioFlinger的时候走过 mpClientInterface->openOutput()函数

sp<AudioFlinger::ThreadBase> AudioFlinger::openOutput_l(.....)
{
    //找到Device, 这个函数很重要，稍后分析AudioHwDevice *outHwDev = findSuitableHwDev_l(module, devices);//音频流输出到硬件设备AudioStreamOut *outputStream = NULL;status_t status = outHwDev->openOutputStream(&outputStream,*output,devices,flags,config,address.string());

mHardwareStatus <span class="token operator">=</span> AUDIO_HW_IDLE<span class="token punctuation">;</span>
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在 createTrack_l()的时候，会去根据流类型来获取路由策略

    uint32_t strategy = AudioSystem::getStrategyForStream(streamType);for (size_t i = 0; i < mTracks.size(); ++i) {
    sp<Track> t = mTracks[i];if (t != 0 && t->isExternalTrack()) {
    //获取路由策略uint32_t actual = AudioSystem::getStrategyForStream(t->streamType());if (sessionId == t->sessionId() && strategy != actual) {
    ALOGE("createTrack_l() mismatched strategy; expected %u but found %u",strategy, actual);lStatus = BAD_VALUE;goto Exit;}}}

  

  
    
   
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调用 Audio代理服务的 getStrategyForStream

uint32_t AudioSystem::getStrategyForStream(audio_stream_type_t stream)
{
    const sp<IAudioPolicyService>& aps = AudioSystem::get_audio_policy_service();if (aps == 0) return 0;return aps->getStrategyForStream(stream);
}

  

  
    
   
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具体的实现在AudioPolicyInterfaceImpl.cpp文件中
\frameworks\av\services\audiopolicy\service\AudioPolicyInterfaceImpl.cpp

uint32_t AudioPolicyService::getStrategyForStream(audio_stream_type_t stream)
{
    if (uint32_t(stream) >= AUDIO_STREAM_PUBLIC_CNT) {
    return 0;}if (mAudioPolicyManager == NULL) {
    return 0;}return mAudioPolicyManager->getStrategyForStream(stream);
}

  

  
    
   
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uint32_t AudioPolicyManager::getStrategyForStream(audio_stream_type_t stream) {
    return (uint32_t)getStrategy(stream);
}

  

  
    
   
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routing_strategy AudioPolicyManager::getStrategy(audio_stream_type_t stream) const
{
    ALOG_ASSERT(stream != AUDIO_STREAM_PATCH,"getStrategy() called for AUDIO_STREAM_PATCH");return mEngine->getStrategyForStream(stream);
}
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在文件 frameworks\av\services\audiopolicy\managerdefault\AudioPolicyManager.h 中 AudioPolicyManagerInterface *mEngine; 位于frameworks\av\services\audiopolicy\engine\interface\AudioPolicyManagerInterface.h，在frameworks\av\services\audiopolicy\enginedefault\src\Engine.h文件中被实现如下

  /// Interface membersclass ManagerInterfaceImpl : public AudioPolicyManagerInterface{
    public:explicit ManagerInterfaceImpl(Engine *policyEngine): mPolicyEngine(policyEngine) {
    }

    <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>virtual routing_strategy <span class="token function">getStrategyForStream</span><span class="token punctuation">(</span>audio_stream_type_t stream<span class="token punctuation">)</span><span class="token punctuation">{</span><span class="token keyword">return</span> mPolicyEngine<span class="token operator">-&gt;</span><span class="token function">getStrategyForStream</span><span class="token punctuation">(</span>stream<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token punctuation">}</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
private<span class="token punctuation">:</span>Engine <span clas
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