On Sun, 22 Apr 2018, wm4 wrote:
On Sun, 22 Apr 2018 13:24:11 +0200 (CEST)
Marton Balint <c...@passwd.hu> wrote:
On Fri, 20 Apr 2018, wm4 wrote:
> On Thu, 19 Apr 2018 23:25:03 +0200
> Marton Balint <c...@passwd.hu> wrote:
>
>> Signed-off-by: Marton Balint <c...@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?
Only if has_alpha was true when the user called
avcodec_find_best_pix_fmt_of_list() or av_find_best_pix_fmt_of_2().
For avfiltergraph format negotiation or for ffmpeg.c automatic codec pixel
format selection, pal8 was not considered as a format with alpha
(nb_components % 2 == 0 check was used), so they called
av_find_best_pix_fmt_of_2() with has_alpha=false, therefore alpha loss was
not penalized. A subsequent patch takes care of that.
Regards,
Marton
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
