[vlc-devel] [PATCH 1/5] vout: update the format after filters

Rémi Denis-Courmont remi at remlab.net
Tue Oct 20 18:32:33 CEST 2020

Le tiistaina 20. lokakuuta 2020, 18.06.53 EEST Romain Vimont a écrit :
> On Tue, Oct 20, 2020 at 05:02:58PM +0300, Rémi Denis-Courmont wrote:
> > Hi,
> > 
> > We have already covered this in (audio and) video-related IRL discussions
> > and concluded every time that the current system is the least bad.
> Hmmm, I'm not sure (especially in discussions about push).

In the pure ultimate push model, filters are created from upstream to 
downstream, and the output is created last, supplied with the output format of 
the filter chain. When the filter chain is changed, all downstream elements 
(filters if any, and output) are destroyed and recreated. Visual glitches are 
no longer a concern because the video window is preserved. A potential 
optimisation is to reuse the output if only ratii and/or size change.

But as was pointed out at the workshop, and as Steve already pointed out 
again, if you need to change the pixel format, you need to go through the 
display capability modules to re-apply priorities and fallback chroma search.

Of course, this only makes sense whence filters are created before output.

> OpenGL filters accept "any" input format (the OpenGL interop takes care
> of the import) and always produce RGBA pictures.

As you know, there are other display modules than OpenGL at stake.

And even OpenGL is essentially legacy nowadays.


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