compression ratio and number of passes

[MarioGarcia]

Hello, I have a silly question here
what's the maximum compression that can be applied to a disc in order to get a very good quality, also what do you recommend concerning the number of passes of cce?
can you give me some ideas please.
thank you.
Mario

[jdobbs]

The first part of your question is very difficult to answer. The level of compression that will result in good quality depends heavily upon the source you are planning to compress.

For example, you may have a fairly simple DVD that contains a 90 minute movie and a few minor extras that were all encoded at a very high average bitrate and therefore takes a lot of space on the original disc. You might be able to compress that one to 30% of its original size and not even be able to tell it was compressed.

On the other end of the spectrum you may encounter a 4 hours of source material on a DVD that is loaded with extras. It may be encoded at a bitrate that barely makes the mark on the original... and attempting to compress it and keep decent quality is very difficult.

Luckily when using a high quality encoder like CCE, QuEnc (FFMPEG), or HC -- you will find that there are very few DVDs that can't be reencoded at a level of quality that is barely if at all distinguishable from the original. No matter what -- you can always feel assured that it is the best it can be in the space of a DVD-5.

As for passes. Everyone has an opinion on that one. My opinion: Two is enough for most material. Three is good for hard-to-compress. The effect of 4+ passes is barely if noticable at all. But many people who run DVD-RB in batch mode figure "It's running overnight, and I'm sleeping, so why not just do as many passes as will get done in that time?"

[MarioGarcia]

you told me that a movie that the prepare phase gave a 23.3% compression or reduction, you said it would result with not very good quality picture.
so what does that mean. 50%, 20% all those figures preceded by the %
I though the better the figure was close to 0 the better, but that doesn't seem to be that way.
i have a movie with 46% 4 passes, and i don't like the quality.

[TheSeeker]

if it says %46 percent then that means that the resulting dvd will be %46 percent of the original size. WHich means that Lower percentages are bad. You want the percentage from the prepare phase to be as high as possible. But what really matters are the bitrates that the dvd is being encoded at. Just take a look at the High/Low/Avg. bitrates and decide from that how many passes to do.

[jdobbs]

Originally posted by MarioGarcia
you told me that a movie that the prepare phase gave a 23.3% compression or reduction, you said it would result with not very good quality picture.
so what does that mean. 50%, 20% all those figures preceded by the %
I though the better the figure was close to 0 the better, but that doesn't seem to be that way.
i have a movie with 46% 4 passes, and i don't like the quality. I did? Hmm... in most cases that would be true. The only time I've ever seen numbers that low was when there was ILVU material that wouldn't compress. That will be fixed in future Pro versions.

But that's what I'm trying to tell you. 46% of what? The complexity and size of source is the determining factor, not necessarily the percentage.

[MarioGarcia]

I got this log,
I want to know what does that mean:
[quote]
[23:44:02] Phase I, PREPARATION started.
- VTS_01: 2,439,413 sectors.
-- Scanning and writing .D2V file
-- Processed 133,611 frames.
-- Building .AVS and .ECL files
- VTS_02: 594,784 sectors.
-- Scanning and writing .D2V file
-- Processed 44,530 frames.
-- Building .AVS and .ECL files
- VTS_03: 453,065 sectors.
-- Scanning and writing .D2V file
-- Processed 34,240 frames.
-- Building .AVS and .ECL files
- VTS_04: 184,239 sectors.
-- Scanning and writing .D2V file
-- Processed 14,910 frames.
-- Building .AVS and .ECL files
- VTS_05: 74,543 sectors.
-- Scanning and writing .D2V file
-- Processed 5,674 frames.
-- Building .AVS and .ECL files
- Reduction Level for DVD-5: 48.7%
- Overall Bitrate : 2,726Kbs
- Space for Video : 3,100,416KB
- HIGH/LOW/AVERAGE Cell Bitrates: 3,344/410/2,726 Kbs
[23:51:40] Phase I, PREPARATION completed in 7 minutes[/qoute]
also how many passes do you advice me to do?
do you have any range in the High/low/average? I a range to choose two passes and a range to choose three or more.

[edeus]

This may sound stupid but I really want to double check:

If i am getting as an example:
Reduction Level for DVD-5: 73.5%
Overall Bitrate: 3539Kbs
Space for Video: 4,022,704KB
Movie improvement from extra reductino = 18.5%

Does this mean my final reduction level is 73.5+18.5 = 92% of original source quality?

Target bitrate isnt as important though as it is movie type dependant?

Thanks!

[jdobbs]

The numbers can't be related directly to quality. The 73.5% means that after the removing audio streams, etc. the output size of the video will be reduced to 73.5% of it's original size.

Then, within the space set aside for video, you've used extra reduction. By doing so you've reallocated enough space to increase the amount given to the main movie by 18.5% --- which is quite a bit.

As for how that relates to quality -- that depends upon the source and can't be determined directly from these numbers. It isn't unusual at all to reduce to 73% using CCE and be at very close to 100% of the original quality. Quality, though, is a very subjective measurement.

The IMPORTANT fact is that you are getting the BEST quality that can fit on a DVD-5. In that I am very confident.

[TheSeeker]

@MarioGarcia

For that particular case I would run (1+1) maybe (1+2) passes, but I would also use rb opt to apply a kvcd notch or maybe the bach1 custom quanti mat. to it. I honestly almost never do more than (1+1) passes. Just seems like it isnt really needed.

[artoor]

As far as I am concerned for me is not important to have Reduction Level for DVD-5: 70% I can have even 30% if below will be HIGH/LOW/AVERAGE Cell Bitrates: (...)/(...)/4,410 Kbs. It seems that AVG is the most important factor... Am I right??

[TheSeeker]

yea for the most part the avg. bitrate is the most important thing you should take note of.

[gizzin]

Usually from what I can tell in encoding with CCE is that anything with a average of 3000kb or more will yield high quality encodes almost indisgiusable against the original. I've also seen encodes with 2500kb-3000kb that are really good quality too. As for the amount of passes I like to do 6 just to make sure everything is at the best it can be. What is recommended is that you use 4-5 (it's very rare you can tell the difference with the 5th pass). This is all a opinion though use at your own will.