10 Why not just scale up what you're doing with MPEG I? (MPEG-video)
Description
This article is from the MPEG FAQ, by Frank Gadegast phade@cs.tu-berlin.de with numerous contributions by others.
10 Why not just scale up what you're doing with MPEG I? (MPEG-video)
The main difficulty is the interlacing. The simplest way to extend
MPEG I to interlaced material is to put the fields together into
frames (720x486x30/s). This results in bad motion artifacts that
stem from the fact that moving objects are in different places
in the two fields, and so don't line up in the frames. Compressing
and decompressing without taking that into account somehow tends to
muddle the objects in the two different fields.
The other thing you might try is to code the even and odd field
streams separately. This avoids the motion artifacts, but as you
might imagine, doesn't get very good compression since you are not
using the redundancy between the even and odd fields where there
is not much motion (which is typically most of image).
Or you can code it as a single stream of fields. Or you can
interpolate lines. Or, etc. etc. There are many things you can
try, and the point of MPEG II is to figure out what works well.
MPEG II is not limited to consider only derivations of MPEG I.
There were several non-MPEG I-like schemes in the competition in
November, and some aspects of those algorithms may or may not
make it into the final standard for entertainment video compression.
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