I have a DVD player, a VHS video, and a mini-DV video camera. I record off the mini-DV to my PC, I'm also recording VHS to digital in a similar way. Sometimes I take audio-video from the DVD to the PC.

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 TVs / Videos I unsoldered the AV sockets.
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
Solder.

Also used:
Drill.
Dremel-a-like
Knife
Scissors
Paint
Glue
File
Tweezers
Sandpaper

Step 2: Assembly - 1

I drilled holes in the tin to accommodate the switches and sockets, which involved drilling, reaming, and destroying a few Dremel-a-like bits (the tin is tougher than the abrasive bits). Painting was just a simple spray-job. The pieces were thought out first, then added in steps.

Step 3: Assembly - 2

Once I'd got the holes and layout, I punched holes in a sheet of heavy plastic to match the holes in the tin. Having forced the AV sockets through these holes they were held in the right place for soldering together, with a bit of useful flexibility. In such a tight space you need the wiring well organised, and you can't solder it up inside the tin. See the diagrams for a schematic and wiring layout, the ground connections are not shown, but all GND terminals were connected together with a single length of bare stranded wire.

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

I hooked-up the three inputs: DVD, VCR & MiniDV camera to the box, set each to "play" and flipped through the switches while recording (Windows Movie Maker).
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.