libuvc can be used to capture from these devices: https://github.com/ktossell/libuvc
You can get cheap off-brand UVC USB grabbers, or you can get higher quality gear, like the AJA U-TAP:
https://www.aja.com/en/products/u-tap
Admittedly though I haven't seen anything that comes close to £45 :-)
Depending on your project, it might be worthwhile using GStreamer instead of tying yourself to a specific driver like libuvc. There's a lot you can do with just GStreamer's command-line tools -- for some examples see the first 5 minutes of my talk[1] -- and if you need more you can drop down into C or Python, though admittedly the learning curve is fairly high.
[1]: http://www.youtube.com/watch?v=Fdn2LxxM7wA&list=SPSIUOFhnxEi...
https://www.amazon.com/Magewell-HDMI-USB-Capture-Dongle/dp/B...
Can do lossless capture with extremely low latency, which is pretty nice - it's good enough that I've been able to play console video games on it directly instead of plugging into a TV.
all solutions so far cost well over what most people paid for their computers or TVs.
there was pro composite capture under 200 for a long time. and cobsumer ones for 30ish. and thats dealing with analog. hdmi without DRM should produce even cheapers devices, but yeah, everyone has to embrace DRM to name it hdmi
Was that $300~$400 worth the time needed to reverse engineer the cheaper solution? It's all about tradeoffs really. At least it's open source so other people can use it now without the time involved. Also if you need to read in from 5 ~ 10 cameras, the cost can grow very quickly.
Here's a device that looks a lot like the Magewell USB 3 UVC HDMI grabber for $118 (with free shipping):
http://www.aliexpress.com/item/Free-Shipping-XI100D-UVC-USB3...
Not really. HDMI capture devices actually can't "embrace" DRM; no (legitimate) HDMI capture device is permitted to decode HDCP at all since that would defeat the point of HDCP.
HDMI capture devices are expensive because it really is difficult-- 1080p is a lot of bytes per second to decode, reencode, and record to permanent storage.
These are slightly more niche products too, so you don't get the economy of scale you would with something like an ARM SoC.
Also these UVC grabber deal in uncompressed video, so they are more expensive but produce a far higher quality capture.
The £45 Cat5 grabber is performing some pretty heavy compression to fit the HD video signal down a 100 Mbit Ethernet connection.