Re: [Qemu-devel] [PATCH] Add JPEG encoding to VNC server

[Jamie Lokier]

Alexander Graf wrote:
> While this might sound like it renders the whole implementation useless, it
> does make sense to implement it nevertheless. I have some ideas to implement
> progressive encodings for video.
> 
> So when we'd detect that one region is updated a lot in a short
> about of time with content that zlib can't really handle well, we'd
> just send a really low quality JPEG first and then send the update
> after a timer if the region wasn't updated within that timeframe.

Detecting video regions may also be possible if virtual video overlay
hardware can be offered.  It would probably require a special guest
driver.  virtio-video :-) Then again the trend, if you believe in the
<video> element demos in web browsers, is likely towards OpenGL-driven
video frame rendering because it's more versatile.

Sending JPEG quality first and a lossless update after is an
interesting idea, even for non-video.  On a slow link, seeing boxes
and buttons appear quickly might be quicker to click through a GUI, as
you can see where to click even if the text and decorations are a bit
fuzzy for a moment.  Especially if you already know what to expect.

Is it possible to use any of the lossless or "near-lossless" JPEG
encodings, and would that be any more efficient than VNC's usual
lossless encoding?

-- Jamie