Why are DVDShrink and Rejig so fast ?

[DaisyF]

When I copy one of my DVD to a DVD-R I use DVDShrink or Rejig. Since the file format (mpeg2) isn't changed it's fast.

Why ?

When you have avi (video in xvid = the best) and encode it with TmpgEnc or CCE and want to keep some quality it takes a bit longer before you have your mpeg2-files.

It's my impression that what cce does is very different from what dvdshrink does, that it doesn't even compare.

DVDShrink or Rejig shrink content to 70% of its original size very very very fast... Do they just chop bits off ? Is it because of some very complicated aspect of the intra-frame-thingy that it is so quick ? Is this then called transcoding which is faster than encoding which is in general slower ?

D F

I love thingies. The workings of svcd2dvd-mpeg is another example of very fast "transcoding".

[killingspree]

jup you pretty much got your answeres in your post:

dvdshrink does transcoding, which is much much faster than reencoding! the quality is better when using CCE though - but for the normal john doe user, dvdshrink surely does suffice! honestly i do not know about the exact technical specs behind the transcoding process!

CCE (re)encodes the content - it doesn't care if the previous movie was mpeg2 or anything else, so the process takes much longer! in addition you have much more configurability! you can add filters while frameserving - even reencode from NTSC to PAL or vice versa. all of this is not possible when transcoding!

svcd2dvdmpeg does a completely different job! it utilizes the fact that svcds are already mpeg2 video, fools the dvd authoring app/dvd player into believing this is a dvd standard compliant video (which actually it isn't), creates the necessary dvd structure and does not change the actual video data one bit! naturally this process is much faster too, as you actually only do the authoring steps, but no real encoding!

hth
steVe

[DaisyF]

Thanks for the comment killingspree. I was really curious.

I found something if someone else is interested.

Just now I was reading the rebuilder.txt of DvdRebuilder. It states :


BACKGROUND:

Over the course of the past couple of years DVD ripping techniques have changed
dramatically. Newer "one click" programs have made backing up a DVD a fairly
simple process... but there is a significant trade-off. The quality that can
be attained by even the best of these programs is poor in comparison to original
techniques that used Cinemacraft Encoder, TMPEGENC, or other top-notch encoders.
The reason is simple. When using one of these encoders the picture is rebuilt
from scratch and optimized for the resulting bitrate. One-touch transcoders
usually drop DCT coefficients or change quantization info in order to lower the
bitrate. This can result in pixelation and poor overall picture.

But, man, they sure are convenient.



This stuff keeps getting more and more interesting.