[vlc-devel] [PATCH v2 21/22] opengl: document filters implementation

[Rémi Denis-Courmont]

Le torstaina 2. heinäkuuta 2020, 19.21.02 EEST Alexandre Janniaux a écrit :
> Hi,
> 
> The point that I explained in previous patchset is exactly
> that it can very easily be exposed as a filter_t by exposing
> a video fliter capability wrapping an instantiation of
> opengl{filters=MODULE_STRING},

No. Video filters don't have access to their output, and their output is not 
even necessarily a display plugin. You can't simply "wrap" them.

And then filters (or VLC in general) can't do introspection nor reflection, so 
they can't simply "pass on" arbitrary parameters.

(...)
> Since years, the OpenGL doesn't handle the input format,
> glconv modules did and glinterop are doing it now. Here the
> hardware-accelerated filter will be the video filter "opengl"
> but not necessarily "opengl filter" modules directly.

... because it never had to, because it never had filters. "Since years", VDPAU 
(and probably some other opaque formats) have had filters operating on, well, 
opaque formats - with the conversion from CPU bitmaps handled by conversion 
filters.

This is not exactly a ground-breaking discovery. Laurent already was 
considering how to map OpenGL and DX filters when designing the "new" video 
output - like a decode. Conclusion was that you can either do it like VDPAU 
does now, or through a combination of video format and VOUT_CHANGE control. 
The later obviously does not scale up.

-- 
Реми Дёни-Курмон
http://www.remlab.net/