Hi i think compossed video is very DIFICULT process signals sync, video levels and speed process
Other option is use usb web cam
I think cypress makes some..check it out, cypress uC which support USB.
PIC, AVR may not have enough processing power speed to dowhat you want with elegance
YOU MAYBE RUN PIC TO 300 MHZ TO PROCESS ALL DIGITAL SIGNALS, IS NO POSSIBLE TODAY
Before you get involved with any type of data transmition, check the bandwidth
(eg 320x240 x30fps = 2.3Mb/sec or about 2250kbps just for video
maybe this help to you some idea:
http://www.circuitcellar.com/avr2004/Second.htmlhttp://www.embeddedrelated.com/usenet/embedded/show/34134-1.phpmcucam2
http://www.cs.cmu.edu/~cmucam/http://www.jrobot.net/http://home.teleport.ch/idobson/ using bascom avr
http://home.teleport.ch/idobson/projects/UDP-webcam.htmhttp://home.teleport.ch/idobson/start_e.htmhttp://www.nslu2-linux.org/wiki/THE AUDIO IS NO PROBLEM
BEST REGARDS.