Digital and Analog over cat5
 

So, I've been wanting to connect my TV to my computer via cables so I can watch video from the computer on said tv. This is the plan, tell me if you think it'll work.

I have your typical 8 wire(4 pair) cat5 cable already running from the computer to the entertainment center for the internet but since the 100Mb connection to the router only requires 4 wires(orange pair and green pair) I'm left with an extra 2 pair of wires blue and brown.

I want to run the composite video feed through the brown pair and connect the data lines from a USB sound card to the other two(I'll put a 5v ac adaptor to power the device).

Now, here is the question. Will the digital signals interfere with the analog signal to a point that I end up with a dirty video signal? The cable is a good 20 foot long. The other, more expensive, option is to run data lines to an external USB sound card and video card. Then I only need one pair and a hub. But, again, it's more than I want to spend on this project.

The external sound card was only $2.50 shipped. I'm eager to hear the sound quality out of it(how much noise it has) since it would make for a VERY cheap and easy external DAC.

Normally you need to impedance match the cables, some discussion here..
https://www.avsforum.com/avs-vb/showthread.php?t=711031

but suck it and see. If it is no good, then it's probably cheaper to run coax and speaker wire for that distance rather than get the right baluns or amplifiers.

Perhaps I've missed something, but wouldn't there be the option to run a separate shielded cable to do the same work as the two pairs you were going to use? If you don't want to run prefab A/V cables, Cat6 is pretty nice.

Yeah, I'd have to buy the shielded cable but i've read of analog signals going just fine over shielded cat5. I just wasn't sure about the digital and analog sharing a cable like that though. If I'm gonna do that, I might as well buy a 25 foot svideo cable and run it along with the cat5 under the metal door sill.

Sooo, guess what I did? I bought a 25 foot S-video cable(it's way thicker than I'd expected) and am going to splice into the cat5 for the external sound card only. I'll have everything default to the internal sound card except for media player classic.

Winner!