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Reputation: 1187

FFmpeg's AAC ("libfaac") Codec Options?

For AAC ("libfaac") audio encoder, how can I specify the "MPEG Version" to either "MPEG-4" or "MPEG-2" through FFmpeg's command?

Upvotes: 0

Views: 4634

Answers (1)

slhck
slhck

Reputation: 38652

When using libfaac, FFmpeg hard-codes the MPEG version to MPEG-4. You can observe this in libfaac.c, line 118.

faac_cfg->mpegVersion = MPEG4;

If you want to change it, you will have download the FFmpeg source, modify this line to use MPEG2 instead, and recompile FFmpeg with the appropriate configuration (including --enable-libfaac). This works and produces a playable file, however you'll obviously have to use a bitstream filter to create a valid bitstream for MPEG-4 containers now:

ffmpeg -i in.wav -c:a libfaac -absf aac_adtstoasc out.m4a

If instead you use the FAAC API directly, you can of course change this parameter as you wish.

Ideally, one would submit a patch for FFmpeg to include a new option which allows you to set this manually, but given that MPEG-4 was chosen as a hardcoded default I don't see a compelling reason to implement this.

Upvotes: 1

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