s-video cable and quicktime

Hi,

This is a very basic question, does s-video carry audio signal? I have a Canopus ADV analog to DV converter, it has two options for input, one is RCA, another one is S-Video, if I use a RCA cable, and capture the video with Quicktime, it has audio. but if I use S-Video cable alone, video has no audio, is this normal?
Thanks,