[FFmpeg-user] .avi audio question

Carl Eugen Hoyos cehoyos at ag.or.at
Wed Jan 18 04:00:59 CET 2012

Rick C. <rickcorteza <at> gmail.com> writes:

> When creating an .avi I know that using mp3 audio codec can only give 2
> channels.

That is correct.
(There is MPEG surround and multichannel MPEG but both are not supported by
FFmpeg and both are not widely supported at all.)

> And I know if the source video has let's say 6 channels that the conversion 
> can sometimes fail.

Could you elaborate? I don't think downmixing to stereo fails (anymore).

> So what is the common alternative to use instead of mp3?  I was thinking
> either aac or ac3?

Both are possible, aac in avi is unusual, multichannel ac-3 has the disadvantage
that while it works with WMP (because FFmpeg conforms to Microsoft's avi
specification), there have been rumours that some (famous) open source media
players expects multichannel ac-3 audio to not confirm to the specification and
playback therefore fails. (Works fine with MPlayer.)

> I thought aac actually but I had a problem getting the sound
> to play back with VLC even using -vtag DX50, so I thought I'd ask.

The "v"tag part of this sentence makes no sense at all with respect to audio.

Carl Eugen

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