[AG-TECH] Re: AG video node using berkley mjpeg work

Bob Riddle bdr at internet2.edu
Thu Nov 15 07:18:20 CST 2001


I'm using v5.1.6 - is there a "better" version I should get?  I'm
guessing I'll need to use CVS & pull down & build the code.

Andrew Swan wrote:
> 
> Bob Riddle writes:
> > If I set the mjpeg capture rate greater than 10 mbps the display machine
> > never saw the mjpeg stream.  I don't understand why this is true.
> 
> we've done a fair amount of work recently on the mjpeg decode
> and render path.  the problems that we've been working on are
> mostly in the handling of large jpeg images (i.e., the images
> in a high bandwidth stream).  you didn't mention which version
> of mash you were running although i'd be interested to hear if
> you saw any improvement with the latest version from the mash
> cvs repository.
> 
> it could be that the frames are simply too large for the
> static sized buffers in the jpeg reassembly code -- you can
> check this by clicking on "info..." next to the thumbnail in
> the main vic window, then choosing "decoder stats" and looking
> a the "huge frame" statistic.  again though, our changes from
> the last few weeks should address many of these problems.
> 
> > On the Display machine (Win2K), when I expanded the mjpeg vic window,
> > the reported frame rate dropped from 30 fps to about 15-17 fps.  The
> > data rate reported also dropped from 10 mbps to about 6-7 mbps.
> > However, the picture was great looking.  I checked the CPU with task
> > manager & one processor was tapped out completely.  My belief is if I
> > had a faster processor, I could have sustained higher frame rates.
> 
> yeah, openmash (and i suspect all the other vics since they come
> from a common source base) doesn't degrade well when the display
> machine cannot decode and render all the video that's being
> received.  your socket buffers just overflow while the cpu is
> hopelessly grinding away at jpeg decoding.  that's why the
> reported bandwidth and frame rate drop.
> 
> -Andrew



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