[Ffmpeg-devel] channel ordering and downmixing

Michael Niedermayer michaelni
Tue Apr 10 01:28:43 CEST 2007


On Mon, Apr 09, 2007 at 05:58:45PM -0400, Justin Ruggles wrote:
> Andreas ?man wrote:
> > Hi,
> > 
> > Justin Ruggles wrote:
> > 
> > 
> >>Decoding:
> >>If required, the decoder sets AVCodecContext->channel_layout to the
> >>channel layout of the input audio stream.  If downmixing is done in the
> >>decoder (current situation), the final downmixed channel layout is
> >>considered the input layout.
> > 
> > 
> > It would be nice, at least for interactive applications, to be able
> > to retrieve the original channel layout, for presentation purposes.
> > But perhaps the long term idea is that no codec should perform its own
> > downmixing? Either way, I suggest that we add an additional pointer
> > AVCodecContext->original_channel_layout (or something) that is never
> > messed with by any (codec internal) downmixers at all.
> The downmixing will indeed be moved out of the decoders.  I was just
> pointing out how the new channel layout scheme would fit into the
> existing downmixing scheme.  Downmixing outside of the decoders is the
> next step once channel layout/reordering is complete.

downmixing outside the decoders is needed yes, but downmixing support
inside the decoders cannot be removed as it often is faster to downmix
inside the decoder ...


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The educated differ from the uneducated as much as the living from the
dead. -- Aristotle 
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