[Spice-devel] libjpeg performance

[Alexander Larsson]

On Mon, 2010-04-12 at 20:57 +0200, Alexander Larsson wrote:
> I did some simple testing of the new mjpeg encoder.
> Showing the youtube "will it blend - ipad" video i got quite better
> compression (24k per frame average as opposed to 35k before), but the
> code used a bit more cpu (9.8 msec per frame where it was 4.2 before). I
> made a simple change in the libjpeg code to make it a bit faster, but we
> might still be able to tweak this a bit in favour of performance rather
> than compression if thats what we want.

I just tried http://libjpeg-turbo.virtualgl.org/ which is a drop in
replacement for libjpeg, and it bumped our performance to ~2.7 msec per
frame (i.e. 55% faster than ffmpeg), while still keeping the better
compression (of course the compression can be tuned by changing the
quality setting). 

By using libjpeg-turbo specific extensions (JCS_EXT_XBGR) we can get
even better performance since we can avoid a type conversion. Didn't try
this though.

-- 
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 Alexander Larsson                                            Red Hat, Inc 
       alexl at redhat.com            alexander.larsson at gmail.com 
He's a maverick white trash cowboy haunted by an iconic dead American 
confidante She's a psychotic mute barmaid living homeless in New York's 
sewers. They fight crime!