[FFmpeg-devel] [PATCH v2 2/3] libavcodec: add a new AV_CODEC_EXPORT_DATA_FILM_GRAIN flag and option

[Lynne]

Nov 16, 2020, 15:56 by ffmpeg at haasn.xyz:

> In terms of an API user needing this functionality, the way I see it
> working is that presence of the side-data will imply that it still needs
> to be applied, with the side data being removed the moment grain
> actually is applied. So that means that decoders applying film grain
> must never export this side data, and decoders not applying film grain
> must always export this side data.
>
> A decoder both applying grain and exporting the side data is
> nonsensical, and would only result in double-grain-application. In terms
> of the capability checking, I don't need you to tell me whether or not
> the decoder can apply/export side data or not, rather, I need to tell
> *you* whether or not I can apply film grain myself. This is what I
> understand AV_CODEC_EXPORT_DATA_FILM_GRAIN to be. Whether or not it's
> actually exported when that flag is present is irrelevant to me, all I'm
> trying to do is signaling that I'd prefer film grain to be exported
> rather than applied.
>

Yup, that's my idea of how this should work as well.
Maybe even analyzers should want to skip applying film grain in a majority
of cases or apply it independently. So I still think of having an export
flag control the decoder behavior is acceptable in this case.