There is something I still don't understand. Why do file sizes vary enormously when I capture from different sources? For instance, if I capture a one hour file from a VCR (VHS), using 5 Mbits and 720x480 I get a file of around 2,250 Gb. Now, if I capture with exactly the same settings but this time from a S-video source (like satellite TV), I get a file of only 1 Gb. Why??
Is it something to do with resolution differences? What resolution should I use when capturing from a standard VHS?

Thanks for any hints!

Greetings!
Marcos.