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Hi Ico,<br>
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.
<a class="moz-txt-link-freetext" href="http://www.adamwilt.com/DV-FAQ-tech.html#DVformats">http://www.adamwilt.com/DV-FAQ-tech.html#DVformats</a>) 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).<br>
/Anders<br>
<br>
Ivica Ico Bukvic wrote:
<blockquote
cite="mid7cc710c20703171956v2b6b173eu573e0e5c2bf4184e@mail.gmail.com"
type="cite">Hi all,<br>
<br>
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.
<br>
<br>
So, here are the questions:<br>
<br>
What is the cause of such a high capture overhead?<br>
<br>
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?
<br>
<br>
Many thanks!<br>
<br>
Best wishes,<br>
<br>
Ico<br>
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