[PD] lowering gem camera capture CPU overhead

[Anders Friberg]

Hi Ico,
I've run into exactly the same problem. Most probably it is the decoding 
of the firewire signal that eats the cpu cycles. The dv format (same as 
firewire) is compressed into a 29 Mbits/sec stream (see e.g. 
http://www.adamwilt.com/DV-FAQ-tech.html#DVformats) that needs to be 
unpacked before processing in GEM (or any other video software). My 
solution is to use analog video cameras with a capture card.  In this 
way I am able to use four simultaneous cameras using less than half of 
the cpu power on a standard winpc with pentium 4, 3GHz. I don't need 
much picture quality so I got really cheap surveillance CCD cameras 
costing less than 50 euro each connected to a four-input capture card 
(about 190 euro). Another great thing is that your are not limited in 
cable length as with firewire. Another solution would be to find a 
firewire capture card with built-in decoder (I guess there are such 
cards out there).
/Anders

Ivica Ico Bukvic wrote:
> Hi all,
>
> I've been trying to shave off precious cycles off the FW camera input 
> capture. The problem is that vanilla capture of a FW camera feed 
> (NTSC) already introduces 50+% of CPU overhead on an AMD64 3000+. I 
> have experimented with lowered gem frame value, but anything below 20 
> seems to jagged.
>
> So, here are the questions:
>
> What is the cause of such a high capture overhead?
>
> Is there a way to minimize such overhead beyond just optimizing code 
> for sse and other similar methods, plus the aforesaid frame option for 
> the gem object?
>
> Many thanks!
>
> Best wishes,
>
> Ico
> ------------------------------------------------------------------------
>
> _______________________________________________
> PD-list at iem.at mailing list
> UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
>   


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.puredata.info/pipermail/pd-list/attachments/20070318/d95b6813/attachment.htm>