[FFmpeg-devel] [PATCH v2 00/11] fix broken CC detection and ffprobe fields (cover letter)

[Marton Balint]

On Wed, 27 Nov 2024, Marth64 wrote:

> As it stands today, ffprobe has two stream-level fields (closed_captions and film_grain)
> that do not work. Their value is always 0 because ffprobe cannot access the internal
> codec properties in the stream context when it is setting up its internal streams.
>
> Additionally, avformat/dump used to successfully print about the presence of
> Closed Captions (EIA-608/CEA-708) and the presence of film grain. This does
> not work either anymore, because avformat_find_stream_info() does not copy
> them in the skeleton context it uses after calling codec_close().
>
> To clarify: the aforementioned features/code are broken.
>
> So, to the user, Closed Caption detection as a feature is broken, and ffprobe
> and the dump is essentially having two fields that do not work.
>
> This patchset aims to fix the issue by:
> (1) Adding a video stream disposition, AV_DISPOSITION_CAPTIONS_EIA608 that
>    can be set in avformat_find_stream_info(), and using it to express
>    the presence of Closed Captions (EIA-608/CEA-708)

Manually mapping between different codec properties and stream 
dispositions seems ugly, and I am not sure if we should even use the 
disposition field for something like this.

I suggest you try adding the "properties" attribute to AVCodecParameters, 
because as far as I see it is very similar to profile or level. Can you 
see if that works? If it does, we might even promote the FF_CODEC_PROPERTY 
flags to AV_CODEC_PROPERTY so they will become properly public.

Thanks,
Marton


> (2) Removing the broken fields from ffprobe entirely, since it cannot access
>    the underlying data and in v1 of this set the concept of providing this
>    access to private fields was rejected (rightfully so)
> (3) Copying the stream properties in avformat_find_stream_info() so that
>    the dump function (which is internal to lavf) can print the presence of
>    the film grain properties now
>
> View the diff on GitHub:
> https://github.com/FFmpeg/FFmpeg/compare/master...Marth64x:FFmpeg:fix_cc
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