Nothing will do a better job than CCE
Not true. A few tidbits from the Doom 9 forums:
[i]German magazine c't tested all the "one-click" copiers against CCE in the 11/2003 issue.
For movie-only (5MBit/sec) and complete copy (3.8MBit/sec), each using 3pass VBR, CCE results were slightly worse those of DVDShrink (1.03), InstantCopy (7.01.119) and CloneDVD (ElBy Beta 1) but better than those of DVD2One/9to5 DVD Ripper and DVDXcopy Xpress.
Transcoding may fail for too high compression levels, but can show impressive results for low or medium compression.
Not necessarily so. Even though most movies are originally encoded using CCE, it is not easy to duplicate a good studio encode.
The reason is tweaking, inserting I frames at specific frames, altering the bitrate to suit the content, etc. A good transcoder will take advantage of all that tweaking, and reduce the bitrate proportionately. And, of course, transcoders never change the GOP structure, or pulldown flags, and they can retain Pan/Scan offsets and Closed Captioning.
If CCE would get the uncompressed stream as input, it would of course produce always better or at least equal results compared to a good transcoder.
Then again, compressing an image which was already compressed by removing the higher spatial frequencies is a less ideal scenario. Removing the higher coefficients of the discrete cosinus transformation used by JPEG/MPEG creates the typical "ghost image" artifacts on sharp edges. These are caused by the missing higher coefficients which would normally extinguish the oscillation.
When recompressing this, the encoder will try to reproduce the edge including the artifacts. When transcoding, just some more coefficients are deleted. It is obvious that the latter approach not only creates less data but also a higher image quality.
This works fine for medium compressin ratios. However at some point only removing coefficients will create too many block artefacts. Then it would me wiser to recalculate the motion vetors and/or insert/delete I-frames at the right position and so on. That's were an encoder wins over a transcoder.
But for compression ratios of about 30-40% or less, I would bet on the transcoder. Please note that some of the current one click transcoders use pretty simple algorithms.
I've made similar discoveries and found clear instances where transcoders beat encoders (yes even CCE). What I find strange is peoples unwillingness to accept this. (Can you say group preassure).
We might not have it yet but certainly theoretically it should be obvious that transcoders could do a better job than any encoder since the main effort in finding quantifier and motion vector values is allready done!
The extra work that is done by an encoder as compared to a trancoder is roughly: IDCT to RGB/YUV to DCT. The last step is hardly bijective (1:1), in fact this is the very heart of the encoding and the main reason for encoders having a difference in quality (and price). It can in short be done in an astronomical amount of ways and only one is optimal (if you think CCE can do a better encoding than the uncompressed stream that is fed to it...think again). [/i]
With a source of only 4.8 any of the transcoders should work well. Compressing 8G with CCE will not produce better results than compressing 5G with CCE, but 8G compressed with CCE will produce much better results than DVD Shrink will with 8G. My favorite transcoder for most jobs (I'm a movie only fan) is InstantCopy 8, although twitchy for some, it's vid quality will always beat Shrink et al. Rebuilder/CCE gets the nod for the very long movies, those pushing the 2 1/2 hour+ mark.