Compression-question [DVD Skrink VS CCE]

[Anonymus]

Hi Everybody!

I have a question. When you shrink a DVD to fit a DVD-5, you can use DVD Shrink and that´ll take about 20 minutes or so. How come that's so fast compared to for example DVD ReBuilder (CCE). What's the difference in compression?

I'm a newbie so please explain it like I was 5 years old. That would be nice

Greetings! // KvejkarN

[MOVIEGEEK]

DVDShrink,Nero Recode,etc=Transcode
CCE,TMPGEnc,etc=Encode
Transcoding eliminates repeated P or B frames in the GOP(Group Of Pictures),encoding doesn't eliminate any frames and produces better quality when compressing >20%.Compressing a GOP is more CPU intensive than eliminating frames.

[RickTheRed]

Anonymus,

Have you heard: " Longer is better?".
The answer lies above.

Humm, not sure it is for a 5 years old.

[ZippyP.]

CCE (or any encoder) will completely rewrite every frame of the video at the new lower bitrate that is required to effectively reduce the overall size. Quality will suffer if the bitrate falls too low.

A transcoder will scan through blocks of the video (GOP's) and look for any extra bits that it can discard, hopefully without hurting the video too much. The more it discards the worse the video will appear.

As already stated, transcoding is fast but it does not compare quality-wise to a true encoder at higher compression levels .

[skebenin]

A point of clarification: trancoders do not remove any frames. Compressed domain transcoders increase video compression by increasing the quantization in each frame. Pushed too far, quantization results in poor video quality (but this is true of encoders too).

The most recent round of trancoder improvements have put them within a stone's throw of the best encoders. For myself, at reasonable compression levels I can't see a difference, and at unreasonable levels they both produce unacceptable results. There is probably some narrow margin of compression (which varies from one DVD to the next) where an encoder will produce acceptable results while a transcoder will not, but I don't consider it worth my time to find out. If a transcode turns out unacceptable, 9 times out of 10 an encode will be unaceptable too, and I'm not willing to encode the 9 bad ones to find the 1 that's okay.

Just my opinion on the matter. If you're a purist, spend the time and encode all of your backups.

[Gurm]

Well there are those that find that 20% is an unacceptable amount of transcoding.

For those people, re-encoding is viable.

Or, for example, I like to do half-D1 on the extras to make even more room for the movie - something that I need a tool like DVD-Rebuilder for.