[FFmpeg-devel] Channel layouts for aac encoding/decoding and vorbis decoding

Nicolas George nicolas.george
Mon Aug 10 23:05:07 CEST 2009

Le tridi 23 thermidor, an CCXVII, Andreas ?man a ?crit?:
> I agree but I think that is better addressed with the use of planar (ie.
> non-interleaved) audio. Than a transcoding from one codec to another
> with ffmpeg would not require any reordering at all (just some pointer
> swizzling). And output to Alsa, PulseAudio, whatever would just require
> one interleaving step (just as you mention)

As far as I know, most libraries and hardware work with interleaved content,
and non-interleaved streams do not travel well through FIFOs. Therefore, I
think that working with non-interleaved channels would but add more
complexity to the problem.

> Having said that I still think the use of a coherent channel order for
> interleaved audio was (and still is) a good intermediate step.

That is precisely what I do not agree with (is this sentence even correct

For lavc native encoders and decoders, I guess the choice of the channel
layout is neutral, and therefore adopting always the same is a good idea.

But for the other places:
- wrapper for external libraries,
- data to/from libavdevice,
- uncompressed interleaved formats,
adopting the native layout of the library/device/format seems more logical
and efficient, provided the data is correctly tagged to allow
automatic conversion if needed.


  Nicolas George
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