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

[Marton Balint]

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.

> 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...

Regards,
Marton