Composite several frames into one

[cicero]

Wed, 20 Dec 2017 09:49:06, Nicolas Dufresne:

> It still need improvement, like more optimization and thread support. Its
> no different then videomixer in this regard. One trick is to set the
> background to black, that helps. You can also do multiple composition in
> order to use multiple threads.

I see. Well setting background to black and scaling via separate videoscale
elements improved performance a lot, thank you. However, it's still far behind
glvideomixer. I would also prefer to mix frames on GPU since my app is already
quite CPU intensive. Thanks for the link, I will try this patch and see if I can
provide any help.