What is the maximum length of programming
that can fit on a DVD (4.7 GB)?
Can the duration be lengthened by lowering the quality of the video, or is
quality fixed by the DVD player?
Most DVDs will hold about 4 hours of quality video, but anything more
than that that compromises the quality of the video. The method of doing this involves changing the video size and bit rate
at which it is saved.
Here is an excellent site that really goes into detail of how to get
more video on a DVD: