4 channel real time capture

[agarbino]

Hello,

I'm trying to record 4 video streams real time on a mobile platform.
The off-the-shelf solution would be to use a couple of Hauppauge
PVR500 cards (USD 150 each), and use a motherboard with 2 PCI slots.
However, I want to build a standalone encoder/compression device that
would grab the video/audio stream, encode it, and output it in a
~1-2Mbits/s stream via USB (for example) to a small form-factor PC (eg
mini-ITX). This would also allow channels to be added/removed
independently.

There are USB plug in analog capture devices as well as USB hardware
encoders (eg using H.264); what I want to do is basically combine the
two onto one device.

Possible approaches would be to use an encoding chip (eg CX23416)
managed by a 16bit AVR/PIC, or have a Blackfin/ARM/AVR32 do the
encoding/compression/streaming (TI makes the DaVinci chips, which are ~
$10, would this be the best solution?
http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=dsp&...
).

Any suggestions on how to get this done/possible cost?? This is a
personal use project, so I would just need the design/a prototype.

Thanks!
Alex