[FFmpeg-devel] [RFC] Channel layouts

Måns Rullgård mans
Sun Sep 7 17:00:24 CEST 2008

Andreas ?man <andreas at lonelycoder.com> writes:

> M?ns Rullg?rd wrote:
>> Don't forget that the channel layout must specify not only which
>> components are present, but also their order.  Currently lavc tells
>> you neither, making it practically useless for multi-channel audio.
> The idea is that the order is the same as the CHANNEL_LAYOUT bits.
> I.e. LEFT must be the first channel if it exists, then RIGHT, etc.
> Still, this would only be mandatory for codecs (and formats) that
> specifies channel_layout.
> This is IMHO no more strange than that PIX_FMT_YUV always have
> the planes in Y,U,V order. From an application perspective i find
> this much more convenient. There might be more work in the decoders
> though. Still, with float_to_int16_interleave() (that all of the
> "popular" multi-channel codecs currently use (AC3, DTS and AAC))
> this is just a matter of swizzling a few pointers at setup time.

Using the same order for all codecs makes sense.  At the moment,
however, the each decoder outputs channels in a different, and
undocumented, order.

M?ns Rullg?rd
mans at mansr.com

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