[Development] Qt/Quick and VNC [ was: damage tracking ... ]

Giuseppe D'Angelo giuseppe.dangelo at kdab.com
Sat Jun 4 23:20:55 CEST 2022

Il 04/06/22 19:59, Uwe Rathmann ha scritto:
>> [ Giuseppe D'Angelo wrote: ]
>> Properly signalling damage areas has a lot
>> of interesting use cases, from compositors to efficiently enable
>> remoting solutions (frame streaming/VNC/etc.).
> Well, Qt/Quick is usually for modern user interfaces with smooth state
> transitions, what means you have to deal with a lot of fullscreen
> operations like fading in/out of pages etc. that have to run at 60fps.
> While limiting update regions to the damage areas is of course often an
> improvement - it is is no game changer as you also have the use cases
> above. IMHO the solution to the problem can only be: using image
> compression formats like JPEG or even better H.264.

I'd tend to agree; for some of our customers we indeed used H.264 
encoding using VDPAU/VAAPI.

However, for lower end embedded platforms lacking HW video encoders (but 
still with a GPU), we had to do CPU encoding of the changes and having 
damage areas helps tremendously.

Also, some low-end GPUs don't even have fast framebuffer clears; I 
strongly suspect that scissoring and clearing/redrawing only the damaged 
areas would help them a lot.

My 2 c,
Giuseppe D'Angelo | giuseppe.dangelo at kdab.com | Senior Software Engineer
KDAB (France) S.A.S., a KDAB Group company
Tel. France +33 (0)4 90 84 08 53, http://www.kdab.com
KDAB - The Qt, C++ and OpenGL Experts
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