The Raspberry Pi A, and Raspberry Pi B both had a composite video out, on an composite video plug (RCA), the new model B+ uses a 4-pole socket which carries both audio and video signals. This style of connector is sometimes referred to as “TRRS”, which stands for “Tip-Ring-Ring-Sleeve”.
The pin out for the Raspberry Pi B+ is Video(Yellow), Ground (Black), Right Audio (Red), Left Audio (White).
The Pin out for a standard AV in is however not the same! and the one for my projector (I can’t say if it is for all equipment) is Ground, Right Audio, Left Audio, Video.
The ones I picked up from Amazon are quite hard to solder, and in the process I wrote two of them off. as such I am on the look out for a better supplier.
I have an idea for a project for my cheap projector. its raiting plate suggests it needs a maximum of 2 Amp at 12 VDC, and with a USB out (as you can see on the right) I can daisy chain it to a Raspberry Pi, meaning I only need to feed it 12 V.