[FFmpeg-devel] [PATCH v16 01/16] global: Prepare AVFrame for subtitle handling

[Andreas Rheinhardt]

Anton Khirnov:
> Quoting Andreas Rheinhardt (2021-11-27 10:06:35)
>> Anton Khirnov:
>>>
>>> Not sure whether this was asked already - why do we need this new
>>> function? Seems to me you can accomplish the same thing by just adding
>>> the type field to AVFrame. Then
>>> - if type is AVMEDIA_TYPE_SUBTITLE -> allocate a subtitle
>>> - if type is AVMEDIA_TYPE_{VIDEO,AUDIO} -> allocate video/audio
>>> - otherwise detect video/audio as we do now
>>>
>>
>> https://ffmpeg.org/pipermail/ffmpeg-devel/2021-September/285185.html
> 
> So IIUC the only concern is that a user might "manually" unref the frame
> without calling av_frame_unref(). I would say that this is already
> illegal, because we can (and did) add new allocated objects to AVFrame
> that would break things if you just kept them from one frame to the
> other (especially of a different type), e.g. hw_frames_ctx.
> 

And how is a user then supposed to know which modifications of an
AVFrame are legal or not? I think the onus is on us not to break user
apps and not on the user to behave in such a way that it is compatible
with all possible future additions to AVFrames (which would be
impossible anyway).

- Andreas