usb or 1394 uses less CPU?

Eno Kasal_ · Post by **Eno Kasal_** » Fri Sep 05, 2003 15:37

Can anyone tell me about their experiences between the two methods. I was thinking of dedicating a resolume box as a "video mixer" with 3 video inputs but I would obvisouly have to worry about CPU utilization. I ask because i thought I read elsewhere on this forum that usb video cap devices are cpu hogs.

Thanks

Eno Kasal_ · Post by **Eno Kasal_** » Sat Sep 06, 2003 00:11

oh, i forgot to mention for all those interested... I have a Lifeview tv tuner card which can be found very cheap these days. Uses pretty much 0 cpu overhead for its overlay and the resolume effects look good - so it should be possible to use 3 of these cards with resolume and have a very usable video mixer with effects in a super low-end box (it just sucks to eat up all those slots).

This is why I'm so curious about firewire or usb as a video input. Thanks

Don Bloomfield_ · Post by **Don Bloomfield_** » Sat Sep 06, 2003 04:27

I'm working on a similar project. Using my laptop (P4 1.8GHz 256 DDR, rgb out at 640x480) I'm mixing feeds from both firewire and usb1.1 webcams.

The output looks nice, but its worth noting the usb cameras don't have a huge light tolerance. The firewires don't really either, (nightmodes become important), but they handle it better without the grainy (albeit artistic) look of the usb webcams.

I actually quite like the look of the grainy video overlayed (especially using Difference) over a nice shot from a fixed firewire, or vice versa.

Have fun,

Don
Have a great day

martijn -- eyesupply_ · Post by **martijn -- eyesupply_** » Sat Sep 06, 2003 11:15

this grainy look does not have anything to do with using USB or firewire. It's all about the quality of the cam you're using. If you use a cam (firewire or usb) with high quality (sensitive) CCD (3) than the picture will be much better... Those cam's are more expensive ofcourse...
Martijn

Eno Kasal_ · Post by **Eno Kasal_** » Sat Sep 06, 2003 14:19

I think thats what he meant actually...

anyway, i usually have a camera on stage (which is well lit if I'm lucky or if there is a live act) and run that with coax (use a DA for long runs), I've had good luck with a cheap wireless video "rabbit" type device too.

So the question still remains, am I going to get hit with cpu utilization more on usb or firewire? my Lifeview tvtuner doesn't seem to hit the cpu at all.

Thanks. Eno

Don Bloomfield_ · Post by **Don Bloomfield_** » Sun Sep 07, 2003 05:07

yep, that was the implication of using usb=grainy.

Are you making a firewire cable from the coax? I've been trying to find some info i saw once on doing this...

I did some experimentation last night, and found another advantage of dvcam-firewire over webcam-usb. The usb takes approx. 3 seconds to initialise a connection when I select it, during which time all video in resolume freezes. The firewire pauses for maybe 3 frames... This would seem to be a major decision factor, as this is the biggest delay i've seen. I get around this by just having one usb webcam in the lowest slot, and not deactivating it, just lowering alpha if neccessary. The other two slots give me fades between a few firewire cameras and any flash animations.

Have a good one, Don