[FFmpeg-devel] [PATCH] avcodec/h264_sei: fix H.274 film grain parsing

[Niklas Haas]

On Mon, 02 Aug 2021 08:49:49 -0300 James Almer <jamrial at gmail.com> wrote:
> On 8/2/2021 7:36 AM, Niklas Haas wrote:
> > From: Niklas Haas <git at haasn.dev>
> > 
> > The current code has a number of issues:
> > 1. The fg_model_id is specified in H.274 as u(2), not u(8)
> 
> Yes, good catch.
> 
> > 2. This SEI has no ue(v) "repetition period", but a u(1) persistence flag
> 
> This one however isn't. ITU-T H.264 has an ue value with a range 
> 0..16384 called film_grain_characteristics_repetition_period in the SEI 
> message that was replaced by the u(1) persistence flag in H.265, which 
> was then adopted by H.274. Everything else in the spec is exactly the 
> same otherwise, including how it's applied.
> 
> film_grain_characteristics_repetition_period == 0 means the the film 
> grain described by the SEI applies only to the current decoded picture. 
> Non zero means it persists.

Ah, I see. I was looking at H.274, how confusing for them to have
changed it like that. I'll send a new patch.