Creative Sound Blaster Audigy 2 ZS User Manual page 32

When significant editing is done, a project whose underlying video files are DV
may better preserve video quality than one whose underlying videos were
captured in MPEG. To appreciate this, imagine a compressed frame of video you
have captured, upon which you would like to overlay a title. In order to render
such a frame for output to a DVD, the original frame needs to be decompressed
from its stored form (MPEG or DV) into raw video, the graphics of the title need to
be composited or blended with the graphics of the frame, then it needs to be
recompressed (this whole operation actually takes place during the render phase).
Each compression and decompression operation introduces a slight loss of quality.
Full Image Raw Video
Video is
decompressed
for editing
In the case of an MPEG frame, it will be decompressed using data from nearby
frames due to MPEG's inter-frame encoding technique. DV frames are complete
within themselves, using the same compression technique that the JPEG format
uses to compress still images, resulting in less quality loss and imposing a lesser
burden on the CPU.
Full Image Raw Video
with added title
Your DVD
Title
Planning Your DVD Project 5-5
Your DVD
Title
Video is
recompressed
for burning
onto DVD