MP2 or AC3 DVD audio

[tobyed2]

For quite some time I've been encoding using Tmpgenc and its default audio encoding (MP2). I thought I'd play with AC3 ...

Extracted the Audio of the AVI movie to a WAV file (AVI2WAV util) total 4 mins 53s -> 55,094 bytes

Using Tmpgenc (Audio stream only) converted to MP2 -> 6,887 bytes

Using BeSweet convert to AC3 -> 6,339 bytes

Ok just for giggles AudioCatalyst to MP3 -> 6,635 bytes

So how come if AC3 is supposed to offer surpassed quality and compression, its of similar size to mp2 ?

Now I cant confess to being an audiophile, is AC3 really worth the added expense (Dolby license and cost of DVD authoring packages) compared to MP2 ??

[wwaag]

I've had the same experience as you. AC3 offers very little in file size reduction. Given that most of my sources (satellite, laserdisc, vhs) are not AC3 to begin with, I can't see any real advantage, especially given the fact that it takes extra time to do the encoding. Most (inexpensive)DVD authoring programs do not support AC3, although Ifoedit (free) does. For that reason, I've stayed with MP2--works in my 3 DVD players without any problem, although I believe, "technically", MP2 is not within the DVD NTSC standard.

wwaag

[nerdboy69]

I can't fully answer this question as I don't know the technical who's and where's regarding whether it has superior compression or not, but I can say this regardless ....

The resulting file size will depend entirely upon the bitrate you encode it in!!!

AC3 @ 192kbps will be the same size (or there abouts give or take a little overhead) as mpeg layer 2 @ 192kbps or MP3 @ 192kbps. That is what kbps is about - kilobits per second. Now whether you can hear the difference in quality between them all is a different matter - I can't.

As for the small discrepancy in size for your example ... it was a very small example, so the % overhead of the stream headers etc is a more noticeable factor.

Why use AC3 instead of MPA?
1. Because it will give you the best compatibility for one thing. As you have indicated, mpa is not 100% standard and not all DVD Players will be happy with it. Just check some of the threads on this site (I can recall at least 3 in the last few days). If you don't use AC3 and you want compatibility, you are stuck with the major space overhead of LPCM.

2. It allows more than two audio channels. ie. 5.1/6.1 Surround as well as numerous other combos.

3. Stuffed if I know, but I am sure there are more reasons that the audiophiles will pounce upon.

It is unfortunate that few "home" targetted packages don't support it, which may have something to do with royalties they need to pay if they include it in their package.

[ktnwin]

Well, there is a home targetted package that support AC3 (encode to AC3 automatically). Click on the link below.
http://www.mediostream.com/products/neodvdplus/index.html

[monoxide77]

the way i convert to ac3 is to extract the uncompressed WAV file from my original AVI file using Vdub, then have DVDit convert to ac3. the sound quality is much better than recompressing an already compressed mp2.

the major advantage that ac3 has is the compatibilty when it comes to set top players.

[mkelley]

Whatever anyone does, they should *not* convert an MP2 file to AC3 -- that's a double compression (and you'll lose quality).

AC3 is a lot more compatible for NTSC and that's why it's all I use for my projects. I've been using DVDLab, a $79 program that fully supports it (still in beta, but free now for the downloading) so along with BeSweet I can use AC3 for very little money.

But if MP2 works for you, don't worry about it (it would only be a concern for me if I were making DVDs for others, which I do, which is why it's a concern :>)..

[ktnwin]

By reading this thread, I learned one thing I wanted: extract WAV from AVI file using VirtualDub. Thanks monoxide77.
I have played around with VirtualDub for sometimes (for Divx encoding), now realize it could do other things as well.