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Topic: Dolby Pro Logic II (Read 14096 times) previous topic - next topic
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Dolby Pro Logic II

i need help i wanna kno if dere is a software dolby pro logic ii decoder or sumthin that i can leave on.  i kno that liek windvd has it but i want to leave it on so i can use it when i listen to mp3s and play games..... rite now i have a audigy xgamer card..... i also have a set of the logitech 4.1 speakers....

Dolby Pro Logic II

Reply #1 –
dddragon2,

You can't add surround detail if it isn't there ... unless you have the "poor man" solution (i.e. a small delay between the front and rear speakers). Pro Logic II has positioning information embedded in the bitstream.

For mp3's - forget it - generally adding EQ to mp3's distorts the signal so that artifacts are more obvious. I'd probably say get some DVD-Audio DVD's if you want to listen to surround sound music.

As for games, see if the games you are using support EAX or a similar technology for surround audio - a lot of them do like GTA3 and Half Life (iirc). Also have a look in the SoundBlaster AudioHQ (if it is still bundled with the Audigy), and look for surround presets. It can add "depth" to games and music, but its a static sound stage - compared to a true 4.1 or 4.1+ signal its no comparison.

Also, if you're going to be using these forums - please try and stick with the etiquette - use correct spelling and punctuation. Badly formed questions will generally be considered an insult to the users of this board.

Ruairi
rc55.com - nothing going on

Dolby Pro Logic II

Reply #2 –
Well now rc55.

Super confident aren't we? I suggest that before dispensing your advice you check your facts, or if you don't know just say say nothing. It is damaging to the nature of the Internet to have garbage floating around. I also believe that what you have done is far more discourteous to users of this site than to have poor linguistic skills!

Quote from Dolby's website
"Dolby Pro Logic II is an advanced matrix decoder that derives five-channel surround (Left, Center, Right, Left Surround, and Right Surround) from any stereo program material, whether or not it has been specifically Dolby Surround encoded"

See this link
http://dolby.custhelp.com/cgi-bin/dolby.cf...fcGFnZT0x&p_li=

Dolby Pro Logic II

Reply #3 –
Quote
Well now rc55.

Super confident aren't we? I suggest that before dispensing your advice you check your facts, or if you don't know just say say nothing. It is damaging to the nature of the Internet to have garbage floating around. I also believe that what you have done is far more discourteous to users of this site than to have poor linguistic skills!




Quote
Quote from Dolby's website
"Dolby Pro Logic II is an advanced matrix decoder that derives five-channel surround (Left, Center, Right, Left Surround, and Right Surround) from any stereo program material, whether or not it has been specifically Dolby Surround encoded"


Please explain to us. You have two stereo channels. How do you make 2=5, without, as rc55 said, using tricks to simulate the surround effect. Since it's mathemathically impossible, I really look forward to your argument.

PS. And if you'd read the link you posted more carefully, you'll see that Dolby does exactly what rc55 described.

Dolby Pro Logic II

Reply #4 –
Quote
i need help i wanna kno if dere is a software dolby pro logic ii decoder or sumthin that i can leave on.  i kno that liek windvd has it but i want to leave it on so i can use it when i listen to mp3s and play games..... rite now i have a audigy xgamer card..... i also have a set of the logitech 4.1 speakers....

Upgrade to hacked Audigy2 Drivers for Audigy1/Live! (info here) and enable CMSS in EAX console - it's not the same, but it might be the thing you want.

Dolby Pro Logic II

Reply #6 –
Quote
dddragon2

Read the following link. I believe this is what you are looking for
http://matrix-mixer.sourceforge.net/

Thank you for writing this message... 
Juha Laaksonheimo

Dolby Pro Logic II

Reply #7 –
Hey Garf

Nice to see people who dont blindly accept anything they see.

It IS mathematically possible through a technique (matrixing) developed for the original Dolby Pro-Logic, and now extended for the new Dolby Pro-Logic II. A simple example of this is the following. A recording of a person speaking. If the person is presented in the centre of the sound stage (ie the voice comming out of both speakers exactly the same), it is possible to determine that the voice should come out of only the centre channel. A simlar operation is applicable for the surround information with subtraction being performed between left and right channels.

All surround teqniques that use stereo as a source, including Dolby Pro-Logic II, are "tricks" to de-matrix the sound into a 5.1 channel sound stage!

When rc55 speaks of
Quote
"poor man" solution
, I believe he is referring to a system designed by David Hafler. See http://sound.westhost.com/project18.htm

Also it is not a
Quote
bitstream
that dolby pro-logic II uses, but rather the waveforms. Dolby Digital & DTS use bitstreams.

Quote
Please explain to us. You have two stereo channels. How do you make 2=5, without, as rc55 said, using tricks to simulate the surround effect. Since it's mathemathically impossible, I really look forward to your argument.

Dolby Pro Logic II

Reply #8 –
saun97,

dddragon2 was intending to use Pro Logic II or similar with mp3's. Using DSP's like this generally deteriorates the music being played by defeating the purpose of the compression in the first place - which is to psychoacoustically retain as much musical information as possible. Sometimes delays, inverted phases, EQ'ing etc can expose artifacts, so generally the rule to stick to is "Don't EQ!".

Hence we werent talking about your argument in question.

Next time think before you flame.

Ruairi
rc55.com - nothing going on

Dolby Pro Logic II

Reply #9 –
rc55

My disagreement comes with your first statement

Quote
You can't add surround detail if it isn't there ... unless you have the "poor man" solution (i.e. a small delay between the front and rear speakers). Pro Logic II has positioning information embedded in the bitstream.


I am an audiophile and don't like to compress music at all. My reasoning is that most people who compress would not have the ear / equipment to distinguish these artifacts anyway.

"Expose" the artifacts. I would say more like amplify / make more noticable.

This is not flamming, rc55. Are we not able to engage healthy debate.

Dolby Pro Logic II

Reply #10 –
I think everybody here knows what's the deal here.. only some interpretation differences..
Anyway, of course if you have no surround information added to the sound, it's impossible to create "correctly behaving" (compared to audio which has surround info included) surround sound. Sure, you can have somekind of surround sound, but that's not the same.

I don't agree that rc55 did anything disastorous like you said. You just didn't understand what he meant and you were quick to judge him in your first post.

Quote
I am an audiophile and don't like to compress music at all. My reasoning is that most people who compress would not have the ear / equipment to distinguish these artifacts anyway.

You shouldn't make any resoning like that. World is full of deaf audiophiles who do anything to avoid blind testing..
Juha Laaksonheimo

Dolby Pro Logic II

Reply #11 –
You cannot extract the original surround positioning from a 2 channel stereo source, just as much as you can't reconstruct the original stereo imaging from 1 channel source.

You can do so if that information was encoded with/in the stream. But not if it wasn't there in the first place. Then you can only simulate the effect with some tricks. This is what rc55 said.

Do you understand what I'm saying? If there is no positional information to begin with, you cannot correctly reconstruct the original image. It just isn't there!

Dematrixing uses the fact that the information WAS encoded into the 2 channel source to get the rest of the channels out of it. But this does NOT work if the information was not there. Then the decoder has to make a guess what to put where.

Quote
A recording of a person speaking. If the person is presented in the centre of the sound stage (ie the voice comming out of both speakers exactly the same), it is possible to determine that the voice should come out of only the centre channel. A simlar operation is applicable for the surround information with subtraction being performed between left and right channels.


This illustrates exactly why it doesn't work

There is nothing that says the sound should be in the center channel. It could just as well have been mixed so you were supposed to hear the same sound twice, once on the extreme right and once on the extreme left. You can't know which is correct unless that information is encoded!

Dolby Pro Logic II

Reply #12 –
Are you saying that Dolby Pro-Logic II is useless because it will never match the performance of Dolby Digital Steering (All decoders that use two channel sources "guess" where the sound should be steered?

I quote yet again from the "Surround sound kings"
Quote
Dolby Pro Logic II is an advanced matrix decoder that derives five-channel surround (Left, Center, Right, Left Surround, and Right Surround) from any stereo program material, whether or not it has been specifically Dolby Surround encoded

Dolby Pro Logic II

Reply #13 –
Exactly

Dolby Pro Logic II

Reply #14 –
I'm saying that no decoder can reconstruct the correct stereo/surround image if that information was not encoded.

Dolby Pro Logic II

Reply #15 –
Look. Let's start from the basics...

If you only have one channel (a mono recording) then it is impossible to determine where the sound is coming from.

If you have two channels (stereo) then you can determine where the sound in coming from in one axis, in this case left and right.

People only have two ears, which would lead you to believe that we can only determine the spatial location of a sound also in only one axis. But we have these three-dimensional constructs around our ears which modify the sound coming from different locations (behind, front, etc.) so that it sounds differently. In our formative years, we learn to distinguish where it is coming from.

I'm sure you, being an "audiophile", have seen the stereo microphones that look like a human head. These try to approximate the effect of the ear, but the problem is that each person's ear is different, so the colorations they place on the sound are different. This is why those "3D Expanders" for systems work really well for some people, and not as well for others.

It is just plain not possible to exactly know where a sound came from in 3D space with only two sensors. Of course, Dolby wants you to believe otherwise. It is called marketing. And to be quite honest, sometimes their tricks sound great. But personally, I just play the recording using the same amount of channels as the source. If it was originally stereo, I play it as such. No DSP trickery for me.

Dolby Pro Logic II

Reply #16 –
Ahh Garf
Dolby Labs disagrees, as do I. It is not meant to recreate the sound as it was exactly (that is impossible for any decoder including Dolby Digital EX decoders) but rather provide a reasonable experience of it. The reasons for this are varied but include things such as room acoustics, Loudspeaker Frequency response etc. Lucasfilms has tried to address this with their THX specification, but it still does not perfectly correct the situation.

Loki
Just like listening to a recording is vastly different to listening to a live performance, so is trying to recreate in your living room the same sound that the engineer hears when he is creating the soundtrack.

Furthermore Loki, how many speakers would you play Dolby Digital (5.1) Track that had been encoded into a 2 channel format with surround info? 2 or 5

also

Quote
It is just plain not possible to exactly know where a sound came from in 3D space with only two sensors


Is this not what humans do when invoking their auditory systems 

Dolby Pro Logic II

Reply #17 –
Thanks for the good summari Loki.

saun97:

Yeah, yeah, but this does not in any way invalidate what rc55 said:

Quote
You can't add surround detail if it isn't there ... unless you have the "poor man" solution (i.e. a small delay between the front and rear speakers). Pro Logic II has positioning information embedded in the bitstream.


A Dobly Pro Logic decoder can use some tricks to emulate surround sound if the source is plain stereo. The quality tends to be relatively low and varies from person to person. If the surround information is embedded, i.e. the source is not 'plain stereo', the image will be 'as correct as possible', although obviously not the same as a live source.

Dolby Pro Logic II

Reply #18 –
Quote
Furthermore Loki, how many speakers would you play Dolby Digital (5.1) Track that had been encoded into a 2 channel format with surround info? 2 or 5

A 2 channel format with surround info is vastly different than a normal 2 channel stereo recording.

Dolby Pro Logic II

Reply #19 –
Saun:

I don't see your point?

A recording made in a studio is meant to be played in a home-type venue. In fact, most of the spatial information will be lost, since most likely the engineer will be panning sounds left or right to make a pleasing composition. This final product might share no resemblance to the original positioning of the instruments.

In anything, passing a live performance thru the DSP should give you a better effect than with a studio recording. Remember, in a studio, every instrument gets it's own channel. Some instruments (drums for example) get more than one, but essentially you have a bunch of mono channels that later get mixed together.

--- Addendum ---

Hehehe these rapid-fire posting situations make for lots of editing

Saun: I explained how the human auditory system works in a post above... please read it, and try to understand it...

--- Some more ---

About the 5 -> 2 downmix... you WILL loose data. There are ways to preserve some information, such as placing the "rear" channels in an out-of-phase location (which is what ProLogic does). But what if the original source was very out of phase to begin with? You can't distinguish what was originally out of phase from what was encoded out of phase, so you might end up sending information to the rear that you didn't intend to. So on and so forth.

Look, it's like saying you can get 16bit resoultion out of a 4bit stream. You can't.

Dolby Pro Logic II

Reply #20 –
Loki

Not all studios record with a channel per instrument. That is only for musicians who aren't. Try a few Chesky Labs recordings (Stereo) on a proper audiophile system and tell me that you find no more depth and presence to the music, than ordinary studio recordings, where the sound is 'engineered'

My point is this is all about phsycho-acoustics, which as you have pointed out already is subjective.

Dolby Pro Logic II

Reply #21 –
Loki

I agree with you on your latest edit. (nearly missed it) 

The point is that its about what is appropriate for a user of a system. For the man we were trying to help in the begginging is some surround, even if it is not perfect, better than nothing?

Dolby Pro Logic II

Reply #22 –
Oh, I totaly agree that there are some AWSOME recordings out there that sound just great in a stereo setup.

But I believe that the argument was about using Dolby Pro Logic II to recover the surround sound information in the recording.

For the Chesky labs stereo recording, I would play that in stereo. And not using headphones. That would be my ideal. And DPL2 will not recover any surround data. If you personally like the sound of it, fine. But this board is really for objective data, not subjective data. Trying to pass of some Dolby propaganda as fact is not welcome.

Dolby Pro Logic II

Reply #23 –
Hey Boojum

You understand, good man. Nodoubt audiophile material B)

Dolby Pro Logic II

Reply #24 –
Loki

Certainly not, I think you misunderstand me. I would also use a 2 speaker setup to listen to these recordings as sound brilliant on their own. However in certain circumstances, a movie say that has a stereo track, DPL2 for me is a far better option as it localises dialog through the centre channel.