Dolby 2.0 Prologic

[joshbm]

Hello,

I was wondering... I know how to create a 5.1 Dolby Digital file, yet I do not know how to go straight to 2.0 Prologic (with BeSweet). Could anyone help me out (I'm a bit of a newbie :-P). I have been creating a 5.1 file then downmixing it to 2.0.

Thanks,
-joshbm

[Soulhunter]

What's "2.0 Prologic" ?

You mean...
1.) DolbyPrologic 2
2.) DolbyPrologic (2Ch)
3.) DolbyDigital 2.0

DolbyPrologic 2 is an decoding alogo. for listen 2ch audio on 5.1 systems.

DolbyPrologic is nothing else than an normal stereo file (2ch with special algo.) that can be decoded with a DolbyPrologic decoder...

DolbyDigital 2.0 is a DolbyDigital file like the ones on DVD's (5.1) but only in stereo (2Ch)

Tell what you want to have as output-file DolbyDigital 2.0 (what you already did your self) or DolbyPrologic (stereo-file with dolby-algo. as you maybe have on some CD's/VHS-Tapes...)

When u want DolbyPrologic 2 as output... Sorry as far I know Prologic2 is only a algo. for 2ch decoding for 5.1 systems.

But maybe I misunderstod you...??? Sorry then ! :)

Bye

[brute]

I think he's meaning an AC3 file with Dolby surround content. I'm searching for an encoding way, too, but i wasn't successful.

I have The Matrix Reloaded Trailer in such format. If you play it, it's Dolby Pro Logic2 (I think, cause my receiver only recognizes pro logic) and it sound kewl. So It's a good alternative for MP3 Stereo in encoded films.

If anybody could explain how to create such a Dolby Pro Logic or Surroud AC3 file, it would be great!

[Soulhunter]

Oh, Ok ! A 2Ch AC3 file with Dolby-Surround...

Not sure but IIRC, HeadAC3he has a option to downmix AC3-5.1 to a 2Ch Surround file... Also I remember a option for Surround2 (Prologic2 ?).

Not sure at all, but maybe it works... Post back !

Bye

[joshbm]

So basically I need to convert my file to 5.1 then downmix it to Dolby Prologic (surround) and I can't go straight to 2.0?

Thanks,
- joshbm

[brute]

that would be ok, but if you downmix it to dolby surround, you get a wav or mp3 or whatever, but not a AC3 file.
I think you want get a AC3 file containing Dolby surround, but besweet and HeadAC3he aren't capable of creating such files. I dread, that there doesn't exist a tool that can do this.

[nuked]

I don't see why not. Azid handles the downmix to surround, not the encoder. Why can't you then just use ac3enc to encode in ac3? Granted ac3enc may not be as mature as some very expensive commercial solutions and last checked/tried it has gain problems.. but at least in principle, shouldn't this work fine?

[Soulhunter]

Uhm?
When you downmix the 5.1 AC3 file to a 2CH Prologic WAV file, is it not possible to encode it then to 2CH AC3 ???
Or would the prologic algo. be killed by encoding to 2CH AC3 ???
I thought it would stay inside the 2CH AC3... !?!

Dont know...

Bye

[nuked]

nope.. I explained this in one or 2 threads a couple of weeks ago(not meaning to sound snippy). There's nothing special about surround sound once it's encoded. You can put in on a cassette tape or even on vinyl and it will still be surround encoded.

[brute]

but I don't think that my receiver would recognized it as Pro Logic.

It's something like that:

If I play a real AC3 file, my receiver shows me, that it is a 5.1 Multichannel AC3 file.

If I play a AC3 File with Pro Logic encoded sound inside it, my receiver shows me that it is a digital Pro Logic Multichannel File. A little led indicates, that there is a ProLogic algo inside it.

But if I encode a Pro Logic wav or something like that in an AC3 file, my receiver only recognizes Stereo in this AC3 file.

So that cannot be what I'm searching.

[nuked]

hmmm... I would think the reciever should be willing to do a pro-logic decode whether it knows the source is pro-logic or not(which it is, it's just missing it's "label" as such). You can apply pro-logic decodes even to regular stereo content. I don't know much about the willingness of digitial recievers to do such things though. I guess try it and see if it sounds like it's working.

[nuked]

hmmm... I would think the reciever should be willing to do a pro-logic decode whether it knows the source is pro-logic or not(which it is, it's just missing it's "label" as such). You can apply pro-logic decodes even to regular stereo content. I don't know much about the willingness of digitial recievers to do such things though. I guess try it and see if it sounds like it's working.

might be nice to get support in ac3enc for the metadata flag to put the issue to rest.

[brute]

yes, thats right.

but why should I encode the file in AC3 then?
by the way, the file doesn't use the AC3Filter in wmp. I don't know why, but it isn't a real AC3 file what i get.

[nuked]

I see no good reason to encoded it in ac3, but that was the question asked. The gain bug in ac3enc is kinda a bummer, so better off with mp3 probably unless you want to mess with some expensive or questionably legal encoders. I ahd the problem with ac3 files that weren't ac3 files once. I think it was something stupid like I hadn't installed the ac3enc plugin.

[bleo]

I've heard about these fussy receivers that don't recognise digital AC3 streams as DPL and hence don't turn on DPL decoding.

There is a flag called dsurmod that identifies an AC3 as being Dolby Surround encoded (see http://www.atsc.org/standards/a_52a.pdf). But before you reach for your hex editor to change it, I think that it is in the header of every single AC3 frame...