[FFmpeg-devel] [PATCH v16 08/16] fftools/ffmpeg: Replace sub2video with subtitle frame filtering

[Andreas Rheinhardt]

Soft Works:
> 
> 
>> -----Original Message-----
>> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of Anton
>> Khirnov
>> Sent: Saturday, November 27, 2021 10:04 AM
>> To: FFmpeg development discussions and patches <ffmpeg-devel at ffmpeg.org>
>> Subject: Re: [FFmpeg-devel] [PATCH v16 08/16] fftools/ffmpeg: Replace
>> sub2video with subtitle frame filtering
>>
>> Quoting Soft Works (2021-11-27 08:18:37)
>>>> -----Original Message-----
>>>> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of Andreas
>>>> Rheinhardt
>>>> Sent: Friday, November 26, 2021 2:02 PM
>>>> To: ffmpeg-devel at ffmpeg.org
>>>> Subject: Re: [FFmpeg-devel] [PATCH v16 08/16] fftools/ffmpeg: Replace
>>>> sub2video with subtitle frame filtering
>>>
>>>> Furthermore, missing check.
>>>> (Maybe ass subtitle based codecs should set AVCodecContext.width and
>>>> height based upon this play_res_x/y?
>>>
>>> Breaks the decoder API.
>>
>> Why? I'd think width/height are currently unused for subtitles, so you
>> can repurpose them without breaking anything.
> 
> It breaks the API because every decoder would be required to do this, and
> would need to be changed.
> 

1. If by "every decoder" you mean every decoder in lavc, then this does
not mean that this would be an API break; it just means that it would be
more work.
2. Why would "every decoder" need to be changed? We do not need to
promise to set these fields all the time; we should not even set these
fields all the time, but only if there is really something meaningful to
report (e.g. I don't consider this default value (where does this number
even come from?) meaningful).

- Andreas