I used to feed composite-video to my PC's graphics-card, and the audio to Line-in via a hacked SCART adapter. This was a pain with regard to switching inputs behind my PC, especially as the current video outputs audio in mono, and I had to bridge connectors with a paperclip to feed both L & R channels. This is pictured on the introduction.
As I've got a lot of bits from old stereos, TV's Videos, I had everything I needed to make a switching box / vision-mixer, so it was about time that I did.
(I use AV to mean Audio/Video)
Step 1: Parts
From an old stereo I removed (with much difficulty) an input selector switch bank. Pushing one of these switches releases any others that are engaged, so you only have one "on" at a time.
Out of a McDonnel Douglas P-LAN node, some wire.
From my kitchen, an empty mustard tin.
From a laser toner cartridge, some heavy black plastic sheet.
From I can't remember what, screws
Step 2: Assembly - 1
Step 3: Assembly - 2
The device was then tested - you don't want to cram it into the box and then find out that it's faulty.
A few bits of insulation were added with some glue, just in case things moved in the final assembly.
Notice in the images that there's more length of wire between the switches and the sockets than is needed: this is to help in fitting both inside the tin.
The sockets were mounted in the tin with screws, then the switches. Notice how the length of wire allowed me to do this.
The screw closest to the yellow-lid clamps that lid in place.
Step 4: The Finished Box
Excepting the clip of the box it's self, the video sequence is unedited, and it switches pretty well - the only glitch being due to a slow press I think. This was not designed for vision-mixing, but it does the job rather well regardless.
Note that as two switches are redundant, pressing either disengages all AV feeds (that is I have two "off" switches). The original buttons did not suit the application, and I couldn't find anything else this week.