[FFmpeg-devel] [PATCH] Make decoding alpha optional for some codecs.

[Robert Krüger]

On Thu, Sep 19, 2013 at 11:32 AM, Mark Himsley <mark.himsley at gmail.com> wrote:
> On 18 September 2013 13:04, Robert Krüger <krueger at lesspain.de> wrote:
>
>> and basically every video player. E.g. quicktime displays full
>> transparency in Prores4444 as black and so does FCP.
>
> You have to decode the alpha to use the alpha mask any picture content
> which is under transparent regions.
>
> You cannot display the video correctly without multiplying the alpha
> with the video content - unless the alpha is 100% across the whole
> picture, which you don't know until you've decoded the alpha..

You are right. Thanks for correcting this statement before it made
others screw up their video players ;-). That, of course, makes the
feature a lot less valuable for my use cases as the picture would
really mislead the user in any other cases but those with 100% alpha.