Forgot to mention - the Video Processor/Audio Mixer is a Videotech VEC1030. It has 1xVideo and 3xStereo Audio inputs, each with its own Slider control. 1xVideo Out and 1xStereo Audio Out.
Video and Audio from Proc'r go to Video In on PC Video card and Line-in on Sound card. Line-in on Sound card has a one-to-two adapter plug to accommodate audio from Proc'r and from Line out on HiFi.