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audioffmpeglibavcodeclibavlibavformat

How can I determine if a codec / container combination is compatible with FFmpeg?

I'm looking at re-muxing some containers holding audio and video such that I extract the best, first audio stream, and store it in a new container where e.g. only the audio stream is present.

The output context for FFmpeg is created like so:

AVFormatContext* output_context = NULL;
avformat_alloc_output_context2( &output_context, NULL, "mp4", NULL );

I have a shortlist of acceptable outputs, e.g. MP4, M4A, etc … essentially those that are readable by Apple's Audio File Services:

kAudioFileAIFFType              = 'AIFF',
kAudioFileAIFCType              = 'AIFC',
kAudioFileWAVEType              = 'WAVE',
kAudioFileSoundDesigner2Type    = 'Sd2f',
kAudioFileNextType              = 'NeXT',
kAudioFileMP3Type               = 'MPG3',   // mpeg layer 3
kAudioFileMP2Type               = 'MPG2',   // mpeg layer 2
kAudioFileMP1Type               = 'MPG1',   // mpeg layer 1
kAudioFileAC3Type               = 'ac-3',
kAudioFileAAC_ADTSType          = 'adts',
kAudioFileMPEG4Type             = 'mp4f',
kAudioFileM4AType               = 'm4af',
kAudioFileM4BType               = 'm4bf',
kAudioFileCAFType               = 'caff',
kAudioFile3GPType               = '3gpp',
kAudioFile3GP2Type              = '3gp2',
kAudioFileAMRType               = 'amrf'

My question is this : is there an easy API in FFmpeg that can be leveraged to choose a compatible output container given the codec the audio stream is in?

Solution

  • For each individual muxer, there is usually a codec tag writing function.That function will check against a list in another source file or work through a switch statement in the same. There is no central roster or container-matching utility function. Your best bet is to identify the codec id in libavcodec/allcodecs.c and then grep in libavformat/ for that ID, particularly within files suffixed with enc e.g. matroskaenc.c.