Mpeg2 degraded due to rendering question

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

If I loaded an mpeg2 video into a video editor and created some
transitions between scenes. Would the whole mpeg2 video need to be
rendered or just the parts where transitions take place.
My concern is that if the mpeg2 is rendered again then it's likely to
be more degraded resulting in poor quality video.

My other question is can mpeg and avi files be loaded into a video
editor such as media studio pro so the timeline has a mixture of both
mpeg2 and avi files?
If this is possible then can I render only the avi parts of the video
or will the whole video need to be rendered?

Regards Brian