"Newbie questions" about AC3 sound

[Maukka]

I have seen that MSP8 includes option to use 5.1. Dolby Surround Sound. I know next to nothing about Dolby Digital sound, so I thought I post a few "newbie questions" about it here:

1. AC3 is the same as Dolby Surround Sound, right?

2. Does the surround sound affect DVD sound if viewed on material not equipped for surround sound? In other words, can it make the sound actually worse, if it comes out from regular TV speakers instead of a surround sound system?

3. I have read that AC3 improves overall sound quality although it makes files smaller. Is this true?

4. Would AC3 sound bring any added value to a documentary soundtrack, which has a lot of voiceover and some music? Or is it something rather designed for movies with a more "spectacular" soundtrack?

Thanks,
Maukka

[Devil]

1. No. AC-3 is Dolby Digital, of which surround sound is just one type. It can vary from 1.0 (mono), 2.0 (stereo), 2.1, 4.0, 5.1, 7.1 etc. The term surround sound is usually applied to 5.1 or higher.

2. No. It comes out normally (otherwise, you would not appreciate most commercial DVDs, would you?) Actually the average TV speakers are pretty hopeless, anyway!

3. No. It does not improve sound quality; just think, how can it? You cannot add what isn't there. It compresses the sound well with minimum audible loss, giving smaller files.

4. Yes. I always use AC-3, usually straight 2.0 stereo at 192 kbit/s. I'm adventuring into 5.1 with music as surround, commentary straight ahead and incidental sounds according to the context. My first tries are fairly time consuming, according to the effect I want, but it is interesting.

[Gorf]

1. No. AC-3 is Dolby Digital...

Not quite right. Dolby Digital is AC3 (among other things. )You can't declare your work to be Dolby Digital unless it has been mastered to some pretty stringent standards set by Dolby.

You can't (for example) say your work has a Dolby Digital soundtrack if it's just a wedding recorded using the on-camera mike. You need to apply to the Dolby Laboratories Licencing Corporation to be allowed to use their name on your productions. Otherwise, it's still AC3, but it's not Dolby Digital. And if they did deign it acceptable enough for the Dolby name, it would be no different (at byte level) to the AC3 version.

Stoopid, eh?

[Maukka]

Thanks, guys, for very helpful answers.

My question about AC3/Dolby Digital was partly due to the fact that in MSP7 when you create a video file you can select audio compression option called Dolby Digital, but when you then export to disk (using MSP7 burner), you must choose option called AC3 Audio - Dolby Digital is not available. My understanding is that in this context the two refer to one and the same thing.

But it is a pity if I then cannot call it Dolby Digital on the cover of my DVD... After all, AC3 says absolutely nothing to most people whereas Dolby is something everybody recognizes and associates with quality sound.

Thanks again,
Maukka

[Maukka]

For anyone interested, one can ask for a license to use Dolby trademark here:

http://www.dolby.com/professional/licen ... demark.cfm

Maukka

[Sillyname]

1. No. AC-3 is Dolby Digital...

Not quite right. Dolby Digital is AC3 (among other things. )You can't declare your work to be Dolby Digital unless it has been mastered to some pretty stringent standards set by Dolby.

You can't (for example) say your work has a Dolby Digital soundtrack if it's just a wedding recorded using the on-camera mike. You need to apply to the Dolby Laboratories Licencing Corporation to be allowed to use their name on your productions. Otherwise, it's still AC3, but it's not Dolby Digital. And if they did deign it acceptable enough for the Dolby name, it would be no different (at byte level) to the AC3 version.

Stoopid, eh?

That's when you say your DVD has 5.1 Digital Surround Sound, instead of Dolby Digital 5.1.