[vlc-devel] [PATCH 3/3] snapshot: fix copy of opaque pictures

[Rémi Denis-Courmont]

Le maanantaina 5. kesäkuuta 2017, 18.19.13 EEST Thomas Guillem a écrit :
> On Mon, Jun 5, 2017, at 18:10, Rémi Denis-Courmont wrote:
> > Le maanantaina 5. kesäkuuta 2017, 19.02.22 EEST Rémi Denis-Courmont a
> > 
> > écrit :
> > > Stating the obvious here, but the patch does not do what the commit
> > > title
> > > implies.
> > > 
> > > AFAICT, there are essentially only two way to handle copying of pictures
> > > with an opaque context: the very obvious but very slow way and the
> > > rather
> > > obvious and very fast way. And that means either adding a copy callback
> > > (slow), or replacing the destroy callback with a pair hold/release
> > > callbacks.
> > 
> > (The "correct" way is to perform a shallow copy of the context. A pure
> > reference counter would interfere with context changes in VDPAU filters.)
> 
> This means that the same context will be used simultaneously by the
> video output and by a video filter (via the video converter needed for
> the image encoder).
> 
> This will create issues with some hardwares.

No. The picture context has always had reference counting internally. It just 
was never exposed to the core.

In other words, a back-end without reference counting can´t use the picture 
context trick. And it has always been but a trick to make up for the lack of 
converter, filter and splitter pools.

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