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Thorsten Froehlich <tho### [at] trfde> wrote:
> hence, it is not absolutely correct to say
> MEPG-4 is "more developed" than MEPG-2, it is simply better targeted for a
> different application domain.
I see.
I have to admit I don't know too much about MPEG-2 and how it differs
from MPEG-1.
However, from my experience I can say that MPEG-4 differs from MPEG-1
by an enormous amount. Some important differences I know of:
- In MPEG-1 the types of frames are fixed to a certain pattern
(eg. IBBBPBBBPBBB) regardless of the movie contents. In MPEG-4
keyframes can be located anywhere (and are usually located at
places where they are most needed, ie. where the image changes
a lot).
- In MPEG-1 the image is divided into fixed-sizes squares which are
compressed in a similar way as JPEG. In MPEG-4 the image is divided
into completely free-shaped parts.
- The MPEG-1 format supports only a very limited amount of frame rates
(I really don't understand why). In MPEG-4 it's completely free.
- AFAIK the quality of MPEG-1 is highly dependant on the resolution
of the video. That is, a larger resolution needs a larger bitrate
to preserve the same image quality. In MPEG-4, however, image
resolution is irrelevant: Video resolution doesn't matter, you
can always compress to the same bitrate and get about the same
image quality. In fact, if you use a larger resolution, the image
quality will increase, not decrease, at the same bitrate (this is
from empirical experience; I don't have any technical proof of this).
- A 200 Megs MPEG-1 will compress to something like 50 Megs MPEG-4
with no important decrease in image quality. (Again, by empirical
experience.)
In the same way, if you try to make an MPEG-1 with the same file size
as the MPEG-4, the image (and sound) quality will be highly degraded.
--
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -
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