[FFmpeg-user] map_channel with H264/AAC input question

Tim Nicholson nichot20 at yahoo.com
Wed Feb 29 12:37:36 CET 2012

On 29/02/12 07:46, Robert Reinhardt wrote:
> I have an H264/AAC video with an audio program that has two channels (left/right), and I'd like to separate these channels into discrete program tracks (left channel as mono to one track, right channel as mono to another track). I was hoping the map_channel option would work without needing to reencode the audio, but I can only seem to get this type of channel mapping by using avfilter / pan option, which reencodes the audio to pcm_s16le first, and then encode back to AAC.

ISTR that AAC will encode stereo in a kind of M/S mode rather than A/B for
efficiency purposes. Therefore it is unlikely that you will be able to avoid a

> Many thanks in advance for any suggestions.
> Best,
> Robert


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