[vlc-devel] [PATCH 2/7] picture_pool: add the video format requested when waiting for a picture

[Rémi Denis-Courmont]

Le maanantaina 9. marraskuuta 2020, 10.04.49 EET Steve Lhomme a écrit :
> On 2020-11-06 18:00, Rémi Denis-Courmont wrote:
> > Le perjantaina 6. marraskuuta 2020, 16.42.09 EET Steve Lhomme a écrit :
> >> In push mode it's convenient to keep the same pool of buffers when only
> >> small changes to the video format occur.
> > 
> > This makes no sense to me. In push mode, the allocator is also the format
> > controller. It is free to switch pool if it needs to, or if it is simpler,
> > or to keep the same pool.
> 
> Yes, except 99% of the code doesn't do that (nvdec being a rare
> exception). The pool is invisible to the decoder, it is handled in
> decoder_helpers.c.
> 
> The good news is that it makes easier to change this for 99% of the usage.

The bad news is that it fails to cover 50% of cases, opaque surface formats, 
whereby generic core code cannot know if two picture formats have compatible 
picture buffers. This API makes no sense to me regardless of whether 99% of 
codecs still depend on the old pull-model API.

In fact, in opaque surface formats, the effective pool, of picture contexts or 
whatever underlying opaque surface handles, is very much visible to the codec 
and not visible to the core.

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