[FFmpeg-devel] [PATCH 001/244] Add a new channel layout API

[Nicolas George]

Anton Khirnov (12020-01-13):
> You still did not say which filters those are, why do they need to
> create streams with duplicate channels, or for that matter how they can
> even do so when the current API does not support it.

The one that comes to mind immediately is amerge, which is meant to be
used in conjunction with pan to perform arbitrary mix between different
audio streams. It was here significantly before the fork introduced
amix, and had features that are not available there.

With the current code, when the layouts overlap, it resorts to declaring
an unknown layout and relying on channel order after printing a warning.
But the natural way of doing it is to have repeated channels:

	[sfx][music][cmt]amerge=3 ;
	pan=5.1 | FC<FC.sfx+FC.cmt |
	          FL<FL.sfx+FL.music |
	          FR<FR.sfx+FR.music |
	          BL<BL.sfx |
	          BR<BR.sfx |
	          LF<LF.sfx

Any new channel layout API must contain provisions to handle this
pattern.

Regards,

-- 
  Nicolas George
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