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 -

Post a reply to this message