General DVD shrink enquiry

[mpawsey]

I have been getting on with DVD Shrink for a while now, for anything that doesn't need much shrinkage, and for re-authoring. One thing ws bothering me though.

In general I use it for anything that needs to be shrunk by 70% or higher, otherwise I use DVD RB. If a film is only, say, 90 minutes long, but is on a DVD 9, it will obviously need a lot of shrinkage. But if it is this short, surely it doesn't really *need* to be this big, and you should be able to shrink it a lot without much loss of quality.

I hope this makes sense, and input would be appreciated.

I am interested to know when people use DVD Shrink, and when they go for a longer, higher quality option.

[sweetness]

i'll use dvdshrink at 80% and higher.
there are many reasons why your disc is so big. audio(dts and LPCM are big files), a lot of extras or large motion menus. have you tried applying mixed compression on the titles?

[fewtch]

I'll use DVDShrink down to as low as 70% (main movie) and 50% (extras), but then again I have a regular 25 inch interlaced TV set.

Actually though, I think 70% is acceptable to my eyes even on my progressive scan PC monitor, as long as deep analysis and AEC (usually "smooth" at that level) is used. Into the 80's and up is always preferable, of course. Depends how bad I want to keep the extras, and how low on discs I'm getting ;). But in general, I find DVDShrink artifacts much less troubling to my eyes than XviD or DivX backups, even at higher compression levels. Other than in rare circumstances, IMO re-encoding is just too much time & hassle.

P.S. I'm puzzled too about how some shorter (~90 min or less) movies can get over 7GB in size, even without that many soundtracks. Possibly created CBR at near the max allowable DVD bitrate. You're right, these shouldn't need to be so big and so more compression could be used with less perceived quality loss. The type of DVD it's on (DVD-5 or DVD-9) is basically irrelevant though... there are many reasons why studios choose one or the other format other than length of the main movie.

[blutach]

@mpawsey - you have touched on the correct interpreation here. It is not the compression ratio but the bitrate devoted to the video which matters. See here (http://forum.digital-digest.com/showthread.php?s=&threadid=45129).

@fewtch - yes, such a short movie could be "superbit" (though it is unlikely to be encoded at a CBR) and necessitate a DVD-9, or it could have both WS and FS versions on the disk.

Regards

[sweetness]

Originally posted by blutach
It is not the compression ratio but the bitrate devoted to the video which matters.
blutach that's very interesting. never look at it in that way. i'll keep that in mind.thanks for the info.

[nwg]

It is the bitrate that is important rather than the compression ratio.

When I have a DVD that needs a lot of compression. I do a DVD with Shrink and make a ISO. I then mount the ISO using Nero Imagedrive. I can then use DVD Bitrate Viewer on the DVD to get the avergae Bitrate. It saves having to burn a DVD.

I just done Motorcycle Diaries and it had 40% compression (60% in Shrink). The Bitrate viewer program give an average bitrate of nearly 5Mb/sec which to me is still high.

[MackemX]

I stuck to 75% as a general rule but normally I would do a quick reauthoringcrop to see what it turns out like first before processing the whole thing

[cannew]

Depends upon the purpose of the copy. Just to watch and not a great movie, I'd go as low as 70% compression. If it's a movie to be kept and you want a good backup I rarely go below 85%. For great movies use 100% and if necessary split into 2 disks with the re-author feature of Shrink.

Many thanks to DVD Shrink for giving us this product!!!!!!

[Surf]

I would like to add my 2 bits....

I have been backing up oldie movies pressed in 1997-1999. Came across a 1hr55min movie with 6700mb!!! By the time I'm done with tailoring and running through with Recode(or DVDshrink) the compression 60-65%. But but but the end result is still great considering I'm watching in hi-def. Star Wars' for instance, are all in the mid 8mbps rate.

Like my bud bud blutach sez, it's all in the bitrate, with a twist.

[blutach]

@nwg - As I'm sure you're aware, IfoEdit has a very easy to use bitrate calculator. There are also other sites with more advanced calculators, but the IfoEdit one should be just fine.

5Mb/sec would be more than just fine!

@surf - 8mb/sec "after shrinking" for a 2 hour movie wouldn't fit on a DVD-5. Be lucky to squeeze it onto a DL, bud :)

Again folks, the % is irrelevant. I can start with 8Mb/sec and compress it by 40% (on average) to 4.8Mb and this would still, on average, be better than a 5Mb/sec compressed by just 10% (although, in this example, the differences would be unnoticeable.

Regards

[nwg]

Originally posted by blutach
@nwg - As I'm sure you're aware, IfoEdit has a very easy to use bitrate calculator. There are also other sites with more advanced calculators, but the IfoEdit one should be just fine.

Regards


I am aware of it, although I keep forgeting to use it. As I have been creating ISO's and burning a lot more with Decrypter. I sometimes put the DVD in bitrate viewer first. I like seeing the graph. :)

[dragongodz]

Again folks, the % is irrelevant. I can start with 8Mb/sec and compress it by 40% (on average) to 4.8Mb and this would still, on average, be better than a 5Mb/sec compressed by just 10% (although, in this example, the differences would be unnoticeable.
% is not irrelevant but instead needs to be taken in context of the original bitrate. so really its the whole that needs considering and not any 1 part. ;)
yes the end results should be both good and hard to tell any real difference, however to say 8Mb/s reduced would on average be better i have to disagree. AEC will certainly help reduce/limit error propagation but the smaller changes to the 5Mb/s should mean that the chances of major errors should be very small anyway with less frames generally touched by more than a tiny amount(I and P frames more importantly). so less MBs changed to sub optimal MVs etc.
as you said though in general the differences in the 2 cases given should be ,again in general, unnoticable. :D

[blutach]

@dragongodz - agreed. Irrelevant is too strong a word (although it was qualified by "on average") and my comment should be subject to how the important frames, such as I-frames are affected.

Regards mate

(PS Go pies in 2005!)

[Surf]

I have been in agreement with you blu.;)

All I wanted to point out is that merely by basing one's backup strategy on the percentage is a tad mis-leading. My 115min with 6700mb is a poifect example. DVDshrink/Recode will report 60-65%. One should never based it strictly on that percentage info. The end result of the example got me high 4mbps rate which is quite tolerable even in hi-def boob tube. :p

(edit typos)

[dragongodz]

All I wanted to point out is that merely by basing one's backup strategy on the percentage is a tad mis-leading.
One should never based it strictly on that percentage info.
basing it on just any 1 thing is wrong. the whole has to be considered, such as footage type, original bitrate and effect on what frames reduction percentage will have etc etc etc. so basically we seem to all generally agree. :)

(PS Go pies in 2005!)
HAHAHA i wish. :D

[blutach]

@surf - yup. Except, out where dragongodz and I come from a boob tube has a meaning that is not only associated with watching TV!

@dragongodz - we can but hope (sigh)

Regards

[mpawsey]

Thanks for all the info, it has been interesting to read.

I think generally now I will be taking the film length into consideration just as much as the compression, as a short film (say 90-100 minutes), if on a DVD9, should surely be able to be compressed heavily without too much loss

[fewtch]

Originally posted by mpawsey
I think generally now I will be taking the film length into consideration just as much as the compression, as a short film (say 90-100 minutes), if on a DVD9, should surely be able to be compressed heavily without too much loss
As long as it's the movie itself (and not the menus & extras) taking up most of the room on the DVD-9.

You really need to take everything into consideration. If there are too many factors, then the simple (but slower) solution: Shrink the movie to a HD folder, and view it with a software DVD player -- then let your eyes decide. :)