Number of passes

[tomaste]

I'm pretty new to CCE encoding, and DVD-RB has allowed me to venture into the process with little to no pain! I most likely would have never even tried it without this tool.

Now that I've done some backups, and had tremendous success, I'm looking at some settings I can adjust. The first one is the CCE "number of passes"

I've been reading a lot of threads about this, and I found this one (from RB)in particular to be helpful:

And a few words about the number of passes for a multipass VBR encode in CCE-SP. The CCE-SP 2.50 manual says:

Image quality slightly improves each time encoding is repeated, but quality improvement reaches its limit at 3 ~ 4 times of encoding

and you can trust it on that even for the later versions. Remember that in multipass VBR mode you have a fixed average bitrate and all that CCE-SP can do is try to find an optimal distribution of the available bits between easy and difficult to encode scenes. More passes will not make up more bitrate from air. You are free to use up to 9 passes, but, and this is strictly IMHO, anything more than 3 passes is just a waste of time at any given bitrate. 2 passes will be enough most of the time.

My question is, due to the way RB counts passes, if time was of no concern, should I set the number of passes to 4 or 5 according to the CCE manual?

[insanescape]

According to the manual and RB, setting it to 4 or 5 passes in RB would be the 3 or 4 passes CCE is talking about (it's easy to see when you're encoding.. it'll say pass 1/3, 2/3, 3/3 for the m2v if you set it to 4 in the RB options)

[tomaste]

Ok, thats what I'd guessed. Thanks for the clarification. Sounds like setting it to 5 will have little return, but the highest possible quality.

Thanks again!

[Joergen]

I'm very critical of quality but I always do 3 passes (2 in CCE tongue). I'd rather remove a 70MB trailer (of another movie I've already seen or dont care of) or an even bigger 2.0 or commentary track or even the other subtitle languages (around 20-50MB usually) and gain that extra quality than wait several more hours for more passes.

Plus due to the segmented nature that DVD-RB does the encodes, CCE is unable to take more and more bitrate from the entire length of the movie with each pass so I'd suspect several passes is futile.

[tomaste]

Originally posted by Joergen
...Plus due to the segmented nature that DVD-RB does the encodes, CCE is unable to take more and more bitrate from the entire length of the movie with each pass so I'd suspect several passes is futile.

I guess I dont understand the "segmented nature" part of this. Most likely because I've never done a CCE encode outside of DVD-RB. Thanks for the insight anyway.

[insanescape]

I think by segmented nature they mean that it breaks it up into many parts (chapters?).. It does x passes on chunk 1, finishes, then does x passes on chunk 2.

which means that it only has x amount of minutes to analyze again instead of the entire movie.

So, for example, let's say you had an hourlong movie broken up into 6 10-minute parts. Each would be encoded separately, so the vbr process can't look back at part 1 and say "Ahh, let's take a few bits from minute 8 and put them in minute 13" because minute 8 and minute 13 are in separate encoding pieces. Make sense?

[tomaste]

Originally posted by insanescape
I think by segmented nature they mean that it breaks it up into many parts (chapters?).. It does x passes on chunk 1, finishes, then does x passes on chunk 2.

which means that it only has x amount of minutes to analyze again instead of the entire movie.

So, for example, let's say you had an hourlong movie broken up into 6 10-minute parts. Each would be encoded separately, so the vbr process can't look back at part 1 and say "Ahh, let's take a few bits from minute 8 and put them in minute 13" because minute 8 and minute 13 are in separate encoding pieces. Make sense?

Yes, it does now. Thanks for the clarification! Is this segmentation in RB done purposefully, and in the long run, does it lower the quality of the backup over doing a backup via another method (such as "big3")

[Joergen]

The Dynamic Bit Allocation makes up for some of it, as it uses the original studio-mastered VBR data for allocating bits to each segment.

And, most of the time dvd-rb creates segments 100-300MB in size so there is quite a length of data to analyze. Thirdly, the end-credits segment usually would use alot of bitrate in a full-movie encode, so in the segmented method they probably do not get super-bitrates due to the constraint of the segment.

It's all theory though and imho if you lose some quality (that is unnoticeable) compared to the big3 you gain it ten fold in time saved (especially with RBFarm) thanks to DVD-RB automatic restructuring of the disc and mental health :)

[insanescape]

Yeah, I'll gladly take a fractionable difference in quality, while still being noticeably better than a transcode (all I've bothered to do until RB), and keeping such ease of use.

[Joergen]

I just did a movie that was 7.8GB in size and about half extras and half movie. The results were again amazing.

And I forgot to mention, compared to big3, DVD-RB maintains the original structure of the video aswell so you dont get nasty errors from encoding something progressive only to see one scene is interlaced, or deinterlacing stuff wrongly etc. That is one of the many "firsts" of dvd-rb in the encoding scene.

[tomaste]

Fantastic. Re-confirms that I probably would never be able to figure out the "old" way of doing it.

Thanks again Jdobbs.