DVD has ONLY 5.1 Audio?

[ROCKwithRESPECT]

I'm trying to backup the Indiana Jones trilogy. I'm using DVD Shrink. I like to have the high quality picture, I couldn't care less about the special features and menus.

My question is, when I reauthor the disc, the only English audio I find is 5.1. Is this possible? How does this format play back for people who aren't set up for 5.1 audio? Is DVD Shrink simply not seeing or mis-labeling the audio streams for me? It has French and Spanish AC3 2Channel audio listed, but onlye 5.1 English. It has done this quite a bit lately, and therefore I have been making quite a few 2 hour movie backups that result in only about 80% quality.

If this is legit, is there a way to convert my 5.1 to 2Channel?

What gives?

Kyle

[adam]

If you ever want to double check what all audio tracks are on the DVD, then just play it. Its very common for there to not be a 2.0 track for the main language. With AC3, you will always get at least stereo regardless of your setup. Your DVD player will downmix it to stereo for you. If you have a prologic reciever then you get 4.0 sound. And again, if you want to see how a particular audio track will play on your hardware then just stick it in and see for yourself.

Also you have to realize that the % of compression in a transcoder like DVD Shrink really means nothing. Its all relative to the quantization on the DVD. (transcoders just requantize co-efficients resulting in higher quantization=bad.) The Indiana Jones DVDs, for example, use a ridiculously high bitrate and have a very low Q. You could compress them by maybe 75% and it'd be the same as compressing another DVD by only 5%. Its all completely relative. You should take all factors into consideration and make decisions accordingly. Then do the transcode and just let your eyes be the judge.

[MysticE]

Time to move out of the Dark Ages and into the present. A large part of what makes DVD format worth having is the 5.1 sound. There's absolutely no need for commercial DVD's to have any 2 channel sound these days on the movie.

[cyflyer]

A friend and I usually backup the same movie for both of us. He has a 5.1 sound system, I have a standard two channel stereo. If we choose to keep the 5.1 sound instead of the two channel, what effect does this have on my standard stereo ? Will I still hear a normal stereo two channel decent sound, or are we both better off sticking to the two channel system when reauthoring ?

[quote]Also you have to realize that the % of compression in a
transcoder like DVD Shrink really means nothing. Its all relative to the quantization on the DVD etc-Adam

Adam can you explain, in terms that a newbie can understand, what is the actual effect of % compression ? What is the difference of my movie if it has 54% or 64% compression. What should it be ? That is the reason we take out all the extras, sound files etc. Thanks.

[MysticE]

.... He has a 5.1 sound system, I have a standard two channel stereo. If we choose to keep the 5.1 sound instead of the two channel, what effect does this have on my standard stereo ? Will I still hear a normal stereo two channel decent sound, or are we both better off sticking to the two channel system when reauthoring....

Most of the newer tiltles only have DD 5.1 for the movie, 2 channnel may be used for some extras, your player will downmix to 2 channel. If a movie has DTS you may want to drop that, although it sounds nice it is a very large file (almost a gig).

[Fluffbutt]

I take it to an extreme - I WON'T buy a dvd if it doesn't have 5.1 sound - what the hell are the makers thinking when they bring out some crappy stereo dvd (and a new release, not just an old movie converted!!!).

They rely on people being too stupid to know.. and they're mainly right, unfortunately.

[adam]

AC3 is designed to at least play on pretty much anything you can hook a DVD player up to. If you play a 5.1 audio track with just the dvd player hooked up to the tv, you will still get stereo audio. The DVD player will downmix the audio to 2 channels. The main reason for having a 2.0 track on the DVD is because that guarantees a studio downmix, which presumabably is going to be better than what your DVD player can do.

cyflyer: When comparing the same movie at one % and another, yes that is definitely meaningful. I'm just saying that it doesn't mean anything when you compare one movie to another, because they have different starting points.

Its not easy to explain transcoding in a nutshell. Basically, it just raises quantization. Think of it like an equation that represents your movie. One that is never perfectly accurate. By transcoding it essentially makes that equation less and less accurate, reducing quality, but also reducing size. The higher the compression ratio you use, the more it is compressed and the worse the quality becomes. But say a movie already has a quant level that is twice as high as another. Of course there are many other factors, but you could presumably compress this movie by 50% and it only then would be equal in quality to the other original untouched movie.

Transcoders work by compressing just one element of the stream (DCT data.) All movies are going to have different amounts of this type of data, as compared to other types (motion vectors), and that DCT data is going to be represented by different amounts of information (bitrate.) So there is no way to compare compression from one movie to another.

[cyflyer]

Thanks for the info guys. Re the % thing, in practical terms, does that mean if I'm veiwing a higher compression (one that has been compressed a lot) movie on a larger screen the resolution/sharpness of the movie appears lower (less quality ?) than if the compression was no so much ? Similar to low/high resolution still photo ? Someone mentioned that a compression of no less than 60% is desirable on a main movie only back-up. Is this correct ?

[bdf24]

Someone mentioned that a compression of no less than 60% is desirable on a main movie only back-up. Is this correct ?

This is still personal preference if you ask me. It's all about what you see. Some people will notice artifacts and pixilation at a much lower compression ratio then others. Also depends on you tv. I LCD or Plasma HD tv will show these things where a normal TV would not. And I think everyones eyes are different to. I see things sometimes that others don't. There really is no percentage where it goes from good to bad. That's something you need to decide for yourself by trial and error.

[adam]

Transcoding compresses DCT data. This causes particular artifacts like banding, blocking, mosquito noise, etc... These types of artifacts will be more noticable the higher compression % you use. Things like sharpness shouldn't be effected. The larger your tv, the more apparant artifacts will be.

Less compression is obviously better, but there are no rules. It varies too much from one movie to the next.

[lordsmurf]

I think mosquito noise is the #1 artifact of MPEG transcoding. Not as much of anything else, but can happen. Some of the mosquito can appear as "dancing pixels" too at high levels.