[mythtv-users] Any advice on cooling down my backend

Don Lewis dl-mythtv at catspoiler.org
Sat Sep 20 00:39:05 UTC 2008


On 19 Sep, Yan Seiner wrote:

> Last time I looked at the VNC code, it required video hardware.  It works
> by reading the video buffer.  No video card, no video buffer, no VNC.
> 
> There is a dummy video buffer built into the kernel but it is quite
> literally a black hole; it only shows black.
> 
> This is as of a couple of years ago, so perhaps VNC implements some sort
> of virtual buffer, although that would require a huge rewrite of libvnc,
> or the kernel has implemented a functioning virtual buffer, which would be
> much easier to do.  Or perhaps an aspiring kernel driver guru could hack
> one up.  I've been told that it would be easy but clearly it's over my
> head; a kernel hacker I am not.

When you start a VNC session with either the RealVNC or TightVNC
vncserver scripts, a virtual X11 server (X11vnc) is started.  It plays
the same role as the Xorg server does for normal X11 sessions.  Just
like Xorg, the clients receive keyboard and mouse inputs from Xvnc via
the X11 socket, and send drawing commands to Xvnc via the X11 socket.
Whereas Xorg contains various drivers that interact with the frame
buffer hardware to draw things on the screen, Xvnc just updates the
contents of its internal frame buffer.

I suspect that Xvnc is more efficient than X11VNC because it can keep
track of which pixels on the screen are being changed, whereas X11VNC
probably needs to repeatedly scrape the screen contents and look for
changes.
 



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