编程步骤：
1.指定使用最新的ALSA API
#define ALSA_PCM_NEW_HW_PARAMS_API
2.包含头文件
#include <alsa/asoundlib.h>
3.定义变量
snd_pcm_t *handle; //调用snd_pcm_open打开PCM设备返回的文件句柄，后续的操作都使用是、这个句柄操作这个PCM设备
snd_pcm_hw_params_t *params; //设置流的硬件参数
snd_pcm_uframes_t frames; //snd_pcm_uframes_t其实是unsigned long类型
4.打开PCM设备
使用snd_pcm_open函数
/* Open PCM device for playback */
rc = snd_pcm_open(&handle, "defalut", SND_PCM_STREAM_PLAYBACK, 0);
if (rc < 0)
{
printf("unable to open pcm device\n");
return -1;
}
函数原型：
int snd_pcm_open(snd_pcm_t **pcm, const char *name, snd_pcm_stream_t stream, int mode);
参数说明：
pcm：即第三步声明的变量handle，用来接收返回的PCM文件句柄
name：可以是hw:0,0，或plughw:0,0
stream：可以是SND_PCM_STREAM_PLAYBACK //Playback stream
或SND_PCM_STREAM_CAPTURE //Capture stream
mode：暂时不明白是什么意思
5.分配一个硬件参数对象
/* Allocate a hardware parameters object */
snd_pcm_hw_params_alloca(¶ms);
6.向对象填充默认值
/* Fill it in with default values. */
snd_pcm_hw_params_any(handle, params);
7.设置所需的硬件参数
7.1.设置交错模式
/* Interleaved mode */
snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
可以设置的模式如下：
7.2.设置格式
/* Signed 16-bit little-endian format */
snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE);
7.3设置通道
/* Two channels (stero) */
snd_pcm_hw_params_set_channels(handle, params, 2);
7.4设置采用率
/* 44100 bits/second sampling rate */
val = 44100;
snd_pcm_hw_params_set_rate_near(handle, params, &val, &dir);
8.将上面设置的参数传给驱动，只有经过这步，上面设置的参数才有效
/* Write the parameters to the dirver */
rc = snd_pcm_hw_params(handle, params);
if (rc < 0) {
printf("unable to set hw parameters: %s\n", snd_strerror(rc));
exit(1);
}
9.获取存储采用数据buffer的大小
int dir;
snd_pcm_hw_params_get_period_size(params, &frames, &dir);
size = frames * 4;
buffer = (char *)malloc(size);
获取period time时间
snd_pcm_hw_params_get_period_time(params, &val, &dir);
10.将数据读入buffer
rc = read(0, buffer, size);
11.将buffer数据写入PCM设备
rc = snd_pcm_writei(handle, buffer, frames);
if (rc == -EPIPE) {
printf("underrun occured\n");
}
else if (rc < 0) {
printf("error from writei: %s\n", snd_strerror(rc));
}
12.将handle冲刷干净，关闭流，释放buffer
snd_pcm_drain(handle);
snd_pcm_close(handle);
free(buffer);
以下是通过alsa-lib播放wav文件的代码
/*
*作者：韦访
*CSDN:https://blog.csdn.net/rookie_wei
**/
#define ALSA_PCM_NEW_HW_PARAMS_API#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <alsa/asoundlib.h>#define u32 unsigned int
#define u8 unsigned char
#define u16 unsigned short#pragma pack(push)
#pragma pack(1) //1字节对齐typedef struct {u32 dwSize;u16 wFormatTag;u16 wChannels;u32 dwSamplesPerSec;u32 dwAvgBytesPerSec;u16 wBlockAlign;u16 wBitsPerSample;
} WAVEFORMAT;typedef struct {u8 RiffID [4];u32 RiffSize;u8 WaveID[4];u8 FmtID[4];u32 FmtSize;u16 wFormatTag;u16 nChannels;u32 nSamplesPerSec; /*采样频率*/u32 nAvgBytesPerSec; /*每秒所需字节数*/u16 nBlockAlign; /*数据块对齐单位,每个采样需要的字节数*/u16 wBitsPerSample;/*每个采样需要的bit数*/u8 DataID[4];u32 nDataBytes;
} WAVE_HEADER;#pragma pack(pop) /* 恢复先前的pack设置 */WAVE_HEADER g_wave_header;
snd_pcm_t *gp_handle; //调用snd_pcm_open打开PCM设备返回的文件句柄，后续的操作都使用是、这个句柄操作这个PCM设备
snd_pcm_hw_params_t *gp_params; //设置流的硬件参数
snd_pcm_uframes_t g_frames; //snd_pcm_uframes_t其实是unsigned long类型
char *gp_buffer;
u32 g_bufsize;FILE * open_and_print_file_params(char *file_name)
{FILE * fp = fopen(file_name, "r");if (fp == NULL){printf("can't open wav file\n");return NULL;}memset(&g_wave_header, 0, sizeof(g_wave_header));fread(&g_wave_header, 1, sizeof(g_wave_header), fp);printf("RiffID:%c%c%c%c\n", g_wave_header.RiffID[0], g_wave_header.RiffID[1], g_wave_header.RiffID[2], g_wave_header.RiffID[3]);printf("RiffSize:%d\n", g_wave_header.RiffSize);printf("WaveID:%c%c%c%c\n", g_wave_header.WaveID[0], g_wave_header.WaveID[1], g_wave_header.WaveID[2], g_wave_header.WaveID[3]);printf("FmtID:%c%c%c%c\n", g_wave_header.FmtID[0], g_wave_header.FmtID[1], g_wave_header.FmtID[2], g_wave_header.FmtID[3]);printf("FmtSize:%d\n", g_wave_header.FmtSize);printf("wFormatTag:%d\n", g_wave_header.wFormatTag);printf("nChannels:%d\n", g_wave_header.nChannels);printf("nSamplesPerSec:%d\n", g_wave_header.nSamplesPerSec);printf("nAvgBytesPerSec:%d\n", g_wave_header.nAvgBytesPerSec);printf("nBlockAlign:%d\n", g_wave_header.nBlockAlign);printf("wBitsPerSample:%d\n", g_wave_header.wBitsPerSample);printf("DataID:%c%c%c%c\n", g_wave_header.DataID[0], g_wave_header.DataID[1], g_wave_header.DataID[2], g_wave_header.DataID[3]);printf("nDataBytes:%d\n", g_wave_header.nDataBytes);return fp;
}int set_hardware_params()
{int rc;/* Open PCM device for playback */ rc = snd_pcm_open(&gp_handle, "hw:0,0", SND_PCM_STREAM_PLAYBACK, 0); if (rc < 0) { printf("unable to open pcm device\n"); return -1; } /* Allocate a hardware parameters object */ snd_pcm_hw_params_alloca(&gp_params); /* Fill it in with default values. */ rc = snd_pcm_hw_params_any(gp_handle, gp_params);if (rc < 0) { printf("unable to Fill it in with default values.\n"); goto err1; }/* Interleaved mode */ rc = snd_pcm_hw_params_set_access(gp_handle, gp_params, SND_PCM_ACCESS_RW_INTERLEAVED);if (rc < 0) { printf("unable to Interleaved mode.\n"); goto err1; }snd_pcm_format_t format;if (8 == g_wave_header.FmtSize){format = SND_PCM_FORMAT_U8;}else if (16 == g_wave_header.FmtSize){format = SND_PCM_FORMAT_S16_LE;}else if (24 == g_wave_header.FmtSize){format = SND_PCM_FORMAT_U24_LE;}else if (32 == g_wave_header.FmtSize){format = SND_PCM_FORMAT_U32_LE;}else{printf("SND_PCM_FORMAT_UNKNOWN.\n"); format = SND_PCM_FORMAT_UNKNOWN;goto err1; }/* set format */ rc = snd_pcm_hw_params_set_format(gp_handle, gp_params, format);if (rc < 0) { printf("unable to set format.\n"); goto err1; }/* set channels (stero) */ snd_pcm_hw_params_set_channels(gp_handle, gp_params, g_wave_header.nChannels);if (rc < 0) { printf("unable to set channels (stero).\n"); goto err1; }/* set sampling rate */ u32 dir, rate = g_wave_header.nSamplesPerSec; rc = snd_pcm_hw_params_set_rate_near(gp_handle, gp_params, &rate, &dir); if (rc < 0) { printf("unable to set sampling rate.\n"); goto err1; } /* Write the parameters to the dirver */ rc = snd_pcm_hw_params(gp_handle, gp_params); if (rc < 0) { printf("unable to set hw parameters: %s\n", snd_strerror(rc)); goto err1; } snd_pcm_hw_params_get_period_size(gp_params, &g_frames, &dir);g_bufsize = g_frames * 4;gp_buffer = (u8 *)malloc(g_bufsize);if (gp_buffer == NULL){printf("malloc failed\n");goto err1; }return 0;err1:snd_pcm_close(gp_handle);return -1;
}int main(int argc, char *argv[])
{if (argc < 2){printf("usage: %s filename.wav\n", argv[0]);return -1;}FILE * fp = open_and_print_file_params(argv[1]);int fd = open(argv[1], O_RDONLY);if (fp == NULL){printf("open_and_print_file_params error\n");return -1;}int ret = set_hardware_params();if (ret < 0){printf("set_hardware_params error\n");return -1;}size_t rc;while (1){rc = fread(gp_buffer, g_bufsize, 1, fp);if (rc <1){break;}ret = snd_pcm_writei(gp_handle, gp_buffer, g_frames); if (ret == -EPIPE) { printf("underrun occured\n"); break; } else if (ret < 0) { printf("error from writei: %s\n", snd_strerror(ret)); break;} }snd_pcm_drain(gp_handle); snd_pcm_close(gp_handle); free(gp_buffer); fclose(fp);return 0;
}编译命令：
gcc wavplayer.c -o wavplayer -lasound -ldl -lm