[libav-api] Packed RGB formats missing from libav

wm4 nfxjfg at googlemail.com
Fri Sep 4 19:34:31 CEST 2015


On Fri, 4 Sep 2015 02:42:29 +0200
Luca Barbato <lu_zero at gentoo.org> wrote:

> On 03/09/15 17:28, Patric Schmitz wrote:
> > So, how would I go from here?
> 
> Check for their presence and do not add them in the case.
> 
> > Does libav use other identifiers for those formats which I could use,
> > and which are present in libav as well as ffmpeg? What's the specific
> > reason those formats are not supported?
> 
> Those formats are a shorthand for "RGBA with A ignored so is fine to
> leave it as 0", used to avoid fitting the alpha channel with 255 in
> formats that do not really support alpha...

They also signal whether the decoder output includes an alpha channel
or not. With FFmpeg you know from the pixel format, with Libav you
have to guess. I've brought this up before.

> Some of our users usually do complain whenever a new pixel format is
> added (it is a reason why I'm still halfway adding CFA (such as Bayer)
> support as codec), so we keep the number of pixel formats down to the
> bare minimum.

That's not true. You also have formats like AV_PIX_FMT_YUVA422P9BE,
which almost never happen in real life, and which are significantly
less useful than the RGB0 formats would be.

> > Maybe they make no sense whatsoever and should be dropped from the
> > software I'm building?
> 
> Probably.
> 
> lu
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