[winswitch] Xpra Protocol Streaming Changes Or Video

Antoine Martin antoine at nagafix.co.uk
Tue Apr 16 18:42:34 BST 2019

On 17/04/2019 00:20, Kaloyan Manev via shifter-users wrote:
> Hello guys,
> I've been reading that Xpra server is only sending data about the changes
> that happened on the screen therefore it should skip a lot of unnecessary
> packets.
It does.

> If that's true how does it utilize the h.264, VP8 and VP9? They
> are all video codecs.
Yes. Xpra uses all sorts of tricks to figure out when it is appropriate
to use a video codec rather than a picture codec.

> I a bit confused because the encoders' main idea is to encode one full
> frame at the beginning and then keep encoding only what has to change in
> order to get to the next frame.
The problem is that an application may update many different areas of a
window, and not all of those areas are suitable for video compression.
So in the end, your screen updates will arrive as a mixture of all sorts
of codecs.
The best way to visualize this is to enable paint debugging, see
XPRA_OPENGL_PAINT_BOX=1 in this ticket:


> I will be grateful if someone could explain this. Thanks in advance!
> Regards,
> Kalyan Manev
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