[FFmpeg-devel] [PATCH 2/3] lavc/assenc: set AV_CODEC_CAP_SINGLE_SUB_RECT

Ridley Combs rcombs at rcombs.me
Tue Feb 21 10:12:53 EET 2023

> On Feb 21, 2023, at 01:48, Nicolas George <george at nsup.org> wrote:
> rcombs (12023-02-20):
>> This already gave garbled output when multiple rects were present,
>> so this is simply documenting an existing requirement.
>> ---
>> libavcodec/assenc.c | 2 ++
>> 1 file changed, 2 insertions(+)
> NAK: the code has provisions for multiple rectangles, if you enforce a
> single rectangle you need to remove the code that is now useless.

Fair enough, if we're fine with breaking the existing case further. Should I simply drop rectangles after a first, or return an error?

> But I do not think pushing the issue onto the applications is a good way
> to fix the problem. Or even pushing the issue onto the framework, since
> the framework does not know the specifics. Better fix the code in ASS
> that handles multiple rectangles than inventing yet another annoying
> flag. A single frame can be encoded into multiple packets, so that
> should not be hard.

This is only true for audio/video encoders; subtitle encoders still use a different API, which does not have M:N support. There's some long-ongoing work to change that, but for now, this seems like the only way to deal with this case before that API overhaul.

> Regards,
> -- 
>  Nicolas George
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