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Re: [Qemu-devel] Reducing X communication bandwidth
From: |
Julian Seward |
Subject: |
Re: [Qemu-devel] Reducing X communication bandwidth |
Date: |
Sun, 11 Jul 2004 12:22:02 +0100 |
User-agent: |
KMail/1.6.2 |
On Sunday 11 July 2004 10:53, Johannes Schindelin wrote:
> Hi,
>
> On Sat, 10 Jul 2004, Julian Seward wrote:
> > The attached patch against sdl.c fixes this. It keeps a shadow
> > copy of video memory. When a request arrives at sdl_update()
> > to redraw an area, the area is compared against the shadow copy,
> > and only the parts that have really changed are passed to
> > SDL_UpdateRect(). The comparison is done at a granularity of
> > 32x32 chunks of pixels.
>
> Why does this remind me of VNC? In fact, that kind of application is the
> exact reason I started my VNC patch. It could also be useful as a Windows
> 98 Terminal Server...
Exactly -- I got the idea from VNC. First I noticed that using qemu
just as a remote X client gave appalling performance *but* when you
run it on a remote VNC server and connect with vncviewer, the results
is quite usable. That immediately suggests that vnc found a lot of
redundant screen updates and did not bother to send them over the
network, and at that point I started hacking :-)
J