[FFmpeg-devel] [RFC] Exporting the alpha mode from decoders

wm4 nfxjfg at googlemail.com
Fri Feb 6 13:48:07 CET 2015

On Fri, 6 Feb 2015 12:10:59 +0000 (UTC)
Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:

> wm4 <nfxjfg <at> googlemail.com> writes:
> > > I will fix this later if nobody beats me.
> > 
> > How do you intend to beat this?
> Setting it to 0RGB32 instead of RGB32.
> Unrelated to your API suggestion, this is a 
> bug in FFmpeg that we should fix.
> > Explicitly writing the alpha component?
> > (I was assuming this was a no-go.)
> We do this in many cases but it is not 
> necessary in this case.
> Concerning your API suggestion, the pix_fmt 
> should always tell you if there is a useful 
> transparency layer or not. If this is not 
> done correctly in some cases, I would like 
> to fix them.

The pixfmt docs seems to imply that the extra component must be set to
0 if a RGB0 format is used. Camtasia puts random stuff.

What about AV_PIX_FMT_RGB555? It's documented as having 1 alpha bit,
though it doesn't have the alpha pixfmt flag set. Fix the docs? Or
introduce RGB05551?

There is no AV_PIX_FMT_RGB064. Is it guaranteed that there is no 64 bit
format with padding? If one ever exists, is it guaranteed that a 0
variant will be added?

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