[PD] video latency with webcams

[John Harrison]

This may be slightly off-topic. We have 4 Logitech Pro 4000 webcams 
processed through PiDiP on ubuntu 6.04. There is a latency (less than 1 
second?) between the live action and the video as shown by the webcams. 
The number of webcams connected doesn't affect the latency. The latency 
is not cause by  PiDiP since the same latency is present when using the 
webcams with any application, such as VLC.

My experience with webcams is basically limited to just this Linux 
system with these webcams. Is this latency normal? Is it avoidable? 
Would I experience this latency on any OS and with all webcams and 
distros? Is the USB2 part of it i.e. would there be less latency with 
firewire? Would a patched real-time kernel make any difference, or are 
the differences from patched kernels mostly about sound? Is the latency 
coming from the webcam itself, video for Linux, or the pwc driver for 
the webcam?

Related: I have been under the impression that running realtime-lsm and 
realtime scheduling for JACK would pretty much minimize the latency for 
sound. However, I've been wondering if a patched kernel would have 
further benefits. If anybody has advice for me on this, I'd appreciate it.

Thanks,

-John