[FFmpeg-devel] [PATCHv2 3/4] avutil/pixdesc: add AV_PIX_FMT_FLAG_ALPHA to AV_PIX_FMT_PAL8

[wm4]

On Sun, 22 Apr 2018 13:24:11 +0200 (CEST)
Marton Balint <cus at passwd.hu> wrote:

> On Fri, 20 Apr 2018, wm4 wrote:
> 
> > On Thu, 19 Apr 2018 23:25:03 +0200
> > Marton Balint <cus at passwd.hu> wrote:
> >  
> >> Signed-off-by: Marton Balint <cus at passwd.hu>
> >> ---
> >>  doc/APIchanges            | 3 +++
> >>  libavutil/pixdesc.c       | 3 +--
> >>  libavutil/pixdesc.h       | 8 ++------
> >>  libavutil/tests/pixdesc.c | 4 ----
> >>  libavutil/version.h       | 2 +-
> >>  5 files changed, 7 insertions(+), 13 deletions(-)
> >> 
> >> diff --git a/doc/APIchanges b/doc/APIchanges
> >> index 4f6ac2a031..d9b457e080 100644
> >> --- a/doc/APIchanges
> >> +++ b/doc/APIchanges
> >> @@ -15,6 +15,9 @@ libavutil:     2017-10-21
> >>
> >>  API changes, most recent first:
> >> 
> >> +2018-04-xx - xxxxxxxxxx - lavu 56.16.100 - pixdesc.h
> >> +  Add AV_PIX_FMT_FLAG_ALPHA to AV_PIX_FMT_PAL8.
> >> +  
> 
> [..]
> 
> >
> > Probably fine. While I like it, we also have to be careful about the
> > consequences. Does it change FATE or the results of that pixfmt choosing
> > function, avcodec_find_best_pix_fmt_of_list()?  
> 
> Fate passes. I am not sure about avcodec_find_best_pix_fmt_of_list(), but 
> since pixdesc_has_alpha() in avutil/pixdesc.c already considered PAL8 as a 
> format with alpha, I don't think it changes.

Oh, interesting point. So this whole discussion is moot anyway, since
it always suggested RGBA when converting PAL8 to a non-paletted RGB
format?

> > Are there any formats
> > that decode to PAL8, but write garbage to the alpha component of the
> > palette?  
> 
> If there are, then those should be fixed. The damage was already done when 
> it was decided to consider PAL8 a format with alpha, so in some cases 
> garbage was already used...

Agreed.