When burning a season of a TV show like Seinfeld, which is around 500+ minutes on 4 discs plus around 13 hours of special features, can i fit a disc onto a regular blank disc or do i have to burn it onto a dual layer?
Its your choice, you can do one or the other. If you put a season of Seinfeld on a 4.7Gb DVD expect to lose quality, or you can spend more on dual layer 8.5Gb DVDs and get the entire disc or at least most of it on the media.
I would imagine those 4 discs are DL. You could try compressing them to fit on 2 or 3 DL discs but I would recommend using dvd rb pro with CCE or procoder in order to get descent video quality. I don't think you would be happy with the results from using a transcoding program.
