to movie_rebel_82, who brought this thread up after 6 months:
Things are not as simple as garbage in = garbage out.
An old analog tape may have poor quality, but if this is all we have we try to preserve it the best we can.
Digitalizing it and compressing it to fit a DVD with a lossive algorithm such as mpeg2 further adds artifacts and reduces even more the quality.
The fact that a source has poor quality does not mean that a transfer that can perform better picture qualities given better sources will fully preserve the quality of a poor source.
so in conclusion, your equation should be:
garbage in --- lossive algorithm---> garbage with more artifacts out