My SVideo to composite adapter is just a svideo adapter connected to 2 of the pins instead of 4. Since the video signal is the same and just the chroma/luminance is split up. I am not sure if this will work with all devices. My adapter came with the matrox video card.
Just checked and it seems, thats how it is made... and here I thought I had been ripped off

, The adapter uses just a small cap which I guess hides in the wire joint.
http://www.epanorama.net/circuits/svideo2cvideo.html