Several Webcams on One Machine
A problem with several webcams is USB bandwidth. By default, we couldn't attach more than one webcam to a single USB host.
We could tweak the webcam driver, so that it doesn't claim too much of USB.
modprobe uvcvideo quirks=128
echo 128 > /sys/module/uvcvideo/parameters/quirks
Note that the greater resolution you want, the less webcams you will be able to connect! I could attach three webcams to one host with width=426:height=320 (fps is unknown). (We used this http://www.logitech.com/ru-ru/webcam-communications/webcams webcam).
If a PC has several distinct USB hosts, webcams could be attached to different ones.
This page http://patchwork.linuxtv.org/patch/4530/ suggests that the number of cameras can be improved further by patching the kernel driver.
Here's a script I used for testing:
#!/bin/bash # Run with cmdline to pass to the driver # Use something like width=75:height=48:noaudio for i in /dev/video*; do mplayer tv:// -tv device=$i:$1 & sleep 1 done wait %1 %2 %3