2 Channel Stereo WAV file to AC3 5.1 Dolby Digital?

[sting_me]

DSPGuru (and others): I am very proficient at making my own DVD's, and have read all the FAQ's in regards to audio conversion (BESweet, AC3Machine, etc...).

The one thing I am having problems doing is converting a 48kHz 16-bit 2 channel wave file to AC3 true 5.1 dolby digital. When I use BeSweet or AC3machine, it will only create an AC3 2.0 Dolby Digital file even if I choose 5.1, presumably beause I'm starting with a 2 channel wave file.

Can I go right to 5.1 Dolby Digital from a 48kHz 16-bit 2 channel wave file (and if so, how?), and if not, what would be the best way for me to accomplish this?

Any help is appreciated!

--Sting_Me--

[Awatef]

It's not possible to get true 5.1 sound from a 2.0 source, and I insist: IMPOSSIBLE

Forget it

[E-Male]

if the 2.0 file contains dolby-surround information, you can do a dolby prologic 2 upmix
hypercube transcoder can do this and will output 6 mono waves

[sting_me]

Originally posted by Awatef
It's not possible to get true 5.1 sound from a 2.0 source, and I insist: IMPOSSIBLE

Forget it

If this is so, then how does a professional DVD released by Sony or Epic or whomever have 5.1 sound, and the actual audio recorning was made in let's say 1970 in analog 2 track stereo? I.E: all the Jimi Hendrix official DVD's have the audio in 5.1. The original tapes were made 30 years ago in 2 track stereo.

[sting_me]

If I understand you correctly, I could use BeSweet or AC3Machine to convert my 2 channel stereo wave file to AC3 Dolby Digital 2.0.

From there, I'd have to transfer the 2.0 Dolby Digital file in an upmix with Hypercube transcoder the get 6 wave files that could be used for 5.1. Do you have any information on hypercube transcoder, and how you use it?

[E-Male]

you're right
see http://hypercube.is.dreaming.org for more info
if there are still questions, i´ll help you as good as i can

oh, and just a small note about the 5.1 of DVDs with old recordings:
these 5.1 tracks are often made from the seperate recorded instruments, effects, dialouges....

[Awatef]

@ sting_me
The new 5.1 soundtracks are made from scratch, not converted from the old mono or stereo soundtracks. Only the dialogue is kept original.

As for that whole dolby surround story. This is still no where as good as a true 5.1 soundtrack, NOWHERE! I tell you it's impossible and I meant it. There is not a single human on this earth that can deliver true 5.1 from any kind of 2.0 source. Dolby Prologic II is not as good as you may think. I have a prologic II decoder, and it's not even worth a comparison with a true 5.1 soundtrack.

[sting_me]

AWATEF: I understand you, and I'm not disagreeing. 2 questions:

1) I'm just trying to figure out how an old 2 channel stereo audio track ends up being supposably true dolby digital 5.1 surround when professional engineers do the audio work on say, a Grateful Dead DVD. And I'm only talking about stereo music tracks.

2) If I have a VHS tape that I'm converting to DVD, and I take 15-20 hours with top of the line computer equipment making the video MPEG2 compliant using CCE encoder, I'd like to make the right choice on my audio. The audio is natively a 2-channel stereo wave file. Do I convert to AC3 Dolby Digital 2.0 with BeSweet or ACMachine and call it a day, or should I try to make the audio track software driven 5.1??

Please let me know your opinion, you seem to be very knowledgeable on this subject matter.

--Sting--

[E-Male]

1) if the new track really is 5.1 then in 99% of all cases the engineers had more than a 2 channel mix as source

2)the only reason to make a prologic 2 upmix for the dvd would IMHO be that
-your amp supports 5.1
-your amp does NOT support prologic 2
-the 2 channel track has phase-information that can be interpreted by prologic 2

in any other case 2 channel ac3 would be the best choice IMO

[daphy]

Hi,

if you have much spare time, try this (http://forum.doom9.org/showthread.php?s=&threadid=29277) :rolleyes: !
But its stil a 'kind' of 5.1 sound but it brings interestisting effects. Maybe if you use a DSP Processor Amp the effects are nice as well while choosing different rooms/halls/locations but saves you much time ;)

CYA Daphy

[Awatef]

@ sting_me

1) As said, the engineers take only the dialogue from the old source, and produce the music and the effects from scratch. That's true remastering, as done with the soundtrack of Neon Genesis Evangelion for example.
I'm aware that there is some DVDs that are *supposed* to have a remastered 5.1 soundtrack (what I would call fake remastering), but when you listen carefully you'll realize that it is just a spatialized 2.0 source, and many people prefer the old 2.0 source over the supposedly remastered 5.1 track

2) Just encode it in Dolby 2.0 and call it a day.
If you do any kind of virtual 5.1 upmixing, you'll be just destroying the sound.
As daphy said, the effects that your receiver may produce will be a lot better than any kind of unreversible screwing up of your audio ;)

[SeeMoreDigital]

Hey thanks,

I had completely forgotten about the HyperCube Transcoder.

Now does anybody have a copy of it they can email to me please?

As I was a bit surprised to find that it's only available in chunks and requires a download manager to get it in full!

I dont like download managers!

[Veech]

sting_me,

These pro engineers aren't making a 5.1 mix out of a stereo recording, they're making it out of the original 8-track or 16-track (or more) tapes. The original stereo recordings were made form the same 8-track or 16-track (or more) tapes.

Veech

[nuked]

You don't need dolby encoded stereo to upmix with a pretty nice effect. But I wouldn't bother to encode the process in the AC3. This type of surround wont be dead acurate, but it will give front to back sptial distiction that is reasonable. The diference signal from L-R even in unencoded material is coming from sounds that were off center or reverberated. If L-R is sent to back left and R-L is sent to back right (I may have that backwards but I don't think so) then you get an effect that pulls wide stereo sounds and echos to the back and sounds quite nice. The reaer channels are obvoulsy not independant but by having the sign of the phase matching with the diference signal from the fronts it's better than a single rear channel. This is all dolby surround decoding does anyway from everything I've ever heard. Dolby surround encoded material just takes advantage of it better than normal stereo. Center channel from R+L can also be created for the usual image stability. I created a very nice dolby surround decoder that was little more than an attenuator pot thats fed from a signal wired from the voltage between right positive and left positive amplifier outputs to the rear speakers in series but with reversed polarity. Obviously a simple upmix matrix before ac3 encoding will do the same thing. On the other hand... you can do this on playback just as well with something like MatrixMixer or with a your dolby surround amplifier which is already designed to do this. There's no need to encode it in the AC3. It doesn't improve quality and if you end up doing frequency filtering as part of a compression algorithm I'm guessing you'd end up replacing some good information with redundant information, unless you keep high bit rates of course but why mess with it?... again your reciever can do all this anyway.

nukeD

[nuked]

Don't mistake me, this is all dolby surround does, it's not quite all dolby pro-logic/II decoders do, but you probably have one of those in your reciever too at it will do a better job than the ac3 upmixer at "steering".

nukeD

[E-Male]

@nuked: to cut it short, you´re saying the same that i did in my last post at 2), right?

[nuked]

@e-male

yeah, right. With the noted exception of pointing out that yes a dobly "decode" can make surround even from non dolby-encoded sources, even sources without plain old vanilla dolby surround, and it's not a magic trick or completely artficial effect. I only repeated what you said casue I didn't want anyone thinking I was advocating storing such an upmix in a digital format.

nukeD

[E-Male]

well, maybe i should just have said:
"2.c) And if after comparing it sounds better to you" :D