[Theora-dev] Theora camera/fast computers

Ralph Giles giles at xiph.org
Tue Mar 22 17:39:05 PST 2005

On Tue, Mar 22, 2005 at 05:14:39PM -0700, Andrey Filippov wrote:

> What exactly effects did you notice about the noise? Maybe there are some
> bugs?

The noise level (including the chroma subsampling artifacts) is pretty 
high, but doesn't change between frames in the static parts of the 
scene. That, the resolution, and watching it at 7 fps, gives it a really 
interesting 'frozen in time' feeling.

> This will come. Currently when there is no restriction to the frame rate
> placed (in a web interface when the frame rate input field is blank or 0)
> systems tries to run sensor as fast as possible. With the default sensor
> clock of 48MHz and required "margins" around the used window of
> (1280+4)*(1024+4) it all results to that frame rate. It is possible to
> program the sensor clock and also change "virtual frame" of the sensor by
> adding invisible rows and/or columns.

So it just works out that way? Interesting. How fast can the sensor go? 
And can you bin the pixels to read out the full frame at lower 

> What about dual-CPU systems? Is it possible to load them properly? What
> about Intel - do they have any advantages? I'm trying to build a demo
> system that could handle the stream even if it will be rather expensive -
> I don't think I have much choice here.

Well, that's not existing software. IF you bought a dual 3 GHz Xeon, AND 
Ruik gets a good speedup with the idct, AND some simple paralellization 
scheme works, THEN you might hit 30 fps by mid April. I guess you'll get 
to find out!

I'd experiment with paralellization first to see what scales the best. 
Off the top of my head you could try: serial stream decode but parallel 
frame reconstruction (best for smp) or entirely parallel decode dropping 
anything outside the crop (might work on a cluster of mac minis).

> I'm trying to be able to demonstrate the camera at it's best :-). BTW, I
> made a clip of the falling water droplets on a narrow frame of 1280x64
> pixels at 360fps.

Cool! Put that one online. :)


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