[FFmpeg-devel] [RFC] Channel layouts
Fri Aug 29 16:13:42 CEST 2008
Peter Ross wrote:
> This patch adds the notion of channel layouts to libavcodec.
> Summary of new concepts:
> * Channel IDs: We give each speaker a notional bit index.
> e.g. CHANNEL_FRONT_LEFT=0, CHANNEL_FRONT_RIGHT=1, CHANNEL_BACK_CENTER=9
> * Channel Layout: An ORing together of Channel IDs.
> e.g. ((1<<CHANNEL_FRONT_LEFT)|(1<<CHANNEL_FRONT_RIGHT))
> The resulting layout is identical to the dwChannelMask value found in
> WAVEFORMATEXTENSIBLE. A channel layout of zero implies 'no statement'.
> * Chanels are stored with the FFmpeg 'samples' array according to ID order
> e.g. left comes before right.
> * Encoders will indicate their supported channel layouts in AVCodec, in the
> same way we do for pixel and sample formats.
> -- Peter
> (A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)
We also need to add a parameter to request the decoded channelmask. For
example dca have 2 4 channel layouts. Without a requested channelmask it
would only be possible to get 1 layout.
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