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

[Michael Niedermayer]

On Fri, Feb 06, 2015 at 01:48:07PM +0100, wm4 wrote:
> 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?

if such pixfmt would be needed it should be added

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

it is not once nor twice but times without number that the same ideas make
their appearance in the world. -- Aristotle
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