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

Steve Lhomme robux4 at ycbcr.xyz
Wed Oct 21 07:49:59 CEST 2020

On 2020-10-20 18:32, Rémi Denis-Courmont wrote:
> 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

I don't think this model can ever happen. There will always be 
differences between what the last (automatic+user) filter produces and 
what a display module can accept. The "osys->converters" will always 
need to be there (called p_final_conv_static in the transcoder). In this 
case the converter doesn't push an output format but is forced to use 
one. So, at least converters, would need to work in a non-push way.

> 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.
> -- 
> 雷米‧德尼-库尔蒙
> http://www.remlab.net/
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