ffmpeg 在mac os x 编译完成后，在项目中导入 （.a）文件后出现一下错误：
Undefined symbols for architecture i386:
"_CGAffineTransformMakeRotation", referenced from:
-[iFrameExtractorAppDelegate applicationDidFinishLaunching:] in iFrameExtractorAppDelegate.o
"_av_register_all", referenced from:
-[VideoFrameExtractor initWithVideo:] in VideoFrameExtractor.o
"_av_open_input_file", referenced from:
-[VideoFrameExtractor initWithVideo:] in VideoFrameExtractor.o
"_av_find_stream_info", referenced from:
-[VideoFrameExtractor initWithVideo:] in VideoFrameExtractor.o
"_avcodec_find_decoder", referenced from:
-[VideoFrameExtractor initWithVideo:] in VideoFrameExtractor.o
"_avcodec_open", referenced from:
-[VideoFrameExtractor initWithVideo:] in VideoFrameExtractor.o
"_avcodec_alloc_frame", referenced from:
-[VideoFrameExtractor initWithVideo:] in VideoFrameExtractor.o
"_avpicture_free", referenced from:
-[VideoFrameExtractor setupScaler] in VideoFrameExtractor.o
-[VideoFrameExtractor dealloc] in VideoFrameExtractor.o
"_sws_freeContext", referenced from:
-[VideoFrameExtractor setupScaler] in VideoFrameExtractor.o
-[VideoFrameExtractor dealloc] in VideoFrameExtractor.o
"_avpicture_alloc", referenced from:
-[VideoFrameExtractor setupScaler] in VideoFrameExtractor.o
"_sws_getContext", referenced from:
-[VideoFrameExtractor setupScaler] in VideoFrameExtractor.o
"_avformat_seek_file", referenced from:
-[VideoFrameExtractor seekTime:] in VideoFrameExtractor.o
"_avcodec_flush_buffers", referenced from:
-[VideoFrameExtractor seekTime:] in VideoFrameExtractor.o
"_av_free", referenced from:
-[VideoFrameExtractor dealloc] in VideoFrameExtractor.o
"_avcodec_close", referenced from:
-[VideoFrameExtractor dealloc] in VideoFrameExtractor.o
"_av_close_input_file", referenced from:
-[VideoFrameExtractor dealloc] in VideoFrameExtractor.o
"_avcodec_decode_video2", referenced from:
-[VideoFrameExtractor stepFrame] in VideoFrameExtractor.o
"_av_free_packet", referenced from:
-[VideoFrameExtractor stepFrame] in VideoFrameExtractor.o
"_av_read_frame", referenced from:
-[VideoFrameExtractor stepFrame] in VideoFrameExtractor.o
"_sws_scale", referenced from:
-[VideoFrameExtractor convertFrameToRGB] in VideoFrameExtractor.o
"_CGDataProviderCreateWithCFData", referenced from:
-[VideoFrameExtractor imageFromAVPicture:width:height:] in VideoFrameExtractor.o
"_CGColorSpaceCreateDeviceRGB", referenced from:
-[VideoFrameExtractor imageFromAVPicture:width:height:] in VideoFrameExtractor.o
"_CGImageCreate", referenced from:
-[VideoFrameExtractor imageFromAVPicture:width:height:] in VideoFrameExtractor.o
"_CGColorSpaceRelease", referenced from:
-[VideoFrameExtractor imageFromAVPicture:width:height:] in VideoFrameExtractor.o
"_CGImageRelease", referenced from:
-[VideoFrameExtractor imageFromAVPicture:width:height:] in VideoFrameExtractor.o
"_CGDataProviderRelease", referenced from:
-[VideoFrameExtractor imageFromAVPicture:width:height:] in VideoFrameExtractor.o
ld: symbol(s) not found for architecture i386