dolby 5.1 / games / doom 3

[AbRASiON]

Disclaimer: this may well be a long long post, PLEASE bear with me.

I need to understand Dolby Digital 5.1, and how it works with Decoders / Signals etc.
Before you read too far I'm a GAMER and I will be analysing this from a GAMERS perspective. (this is for a PC audio setup)


I wish to know for this for the primary reason of purchasing the right gear to get the most from something many of you may respect - Doom 3.
(and no doubt the many games which use the engine of it, and the games after that which use true dolby 5.1 after it finally takes off in the PC scene)



Now,....




What my problem is - not with the technlogy of how this works, but more the DOLBY side of things - the specification and what it's going to do to my signal (if anything) on it's way.


Are all Dolby decoders the same? - in saying this I mean will a dolby decoder always perform the same operations as another when it comes to decoding, and if not can they be setup to do this?

I notice that some "proper" receiver / decoders will decode the signal and offer an option of 10 / 15 / 20 ms delays on the surround signal - why not 0ms?

Does my decoder "get smart" on me and try to perform "tricks" on my 6 independant signals?
Where does the crossover / splitting of the low frequency stuff occur? - does my sub channel (coming from the digital source) only contain low frequencies, or does the actual sub channel simply get high frequencies stripped via the decoder?


Could I in theory connect up 6 identical speakers to my 5.1 setup (yes a normal sat to my sub channel)
Then after doing this could I send a DD 5.1 signal to the decoder (assuming I have an nforce which has a dolby ENCODER on the fly) and have 6 levels of identical volume - then hear it roughly identically on each speaker?

OR

Will the dolby signal be "parsed" by the decoder and have all kind of "filters" applied to the audio? (sending audio to the centre channel like pro-logic - or seperating low / high frequencies?)




As far as I'm aware, a 5.1 DD signal coming out of my PC via my SP/Dif connection contains 6 independant channels which will be decoded via a decoder and sent out (analog) to my speakers (5 sats and a sub)


Also, as far as I'm aware a 5.1 "analog" setup will be sending out pre decoded signal to 6 independant analog channels..... (3x headphone jacks on some nforce / 5.1 based boards) - which can then be amplified etc (see Klipsch 5.1 speakers without the DD addon decoder)



What I really want to know is this.


Can the dolby signal send this signal out and have the decoder "obey" the following rules.


centre - volume 0
left - volume 0
right - volume 0
rear left - volume 50
rear right - volume 0
sub - volume (whatever)




OR will my decoder "share" some of the signal with some of the other channels as per part of the Dolby specification - because that's just "how it's meant to be" ??


I'd LOVE (LOVE!!) to think that the standard is purely 100% 6 fully independant channels which can be manipulated in any particular way.

What this means is you could re-create the sound of an object circling you perfectly on a 360 degree field.
See example

Front left speaker - 10% volume of helicopter
Front right speaker - 75% volume of helicopter
Rear right speaker - 10% volume of helicopter
Rear left speaker - 0% volume of helicopter

Now. if we "gradually pan" this signal like this (over a few seconds)

Front right speaker - 10% volume of helicopter
Rear right speaker - 75% volume of helicopter
Rear left speaker - 10% volume of helicopter
Front left speaker - 0% volume of helicopter

You will notice the sound has moved from 01:30 "o-clock" to 04:30 "o-clock" - and has swept past us - if we continue this pattern of adjusting the volume of the helicopter - now moving the focus to the rear left, front left - and finally returning to the front right - we have done a 360 degree sweep of the sound of a helicopter moving around us in a circle.(I'd damn well love it if this is possible)



The thing I've recently discovered (according to a diagram I saw)

http://www.msicomputer.com/Newsrelease/images/dolby.jpg
http://www.programpower.com/Living_room_diagram.gif
http://www.programpower.com/diagram.gif



is that the "official" layout for the 5.1 spec of speakers is to actually NOT have rear left and rear right like most gamers would have, but to actually have speakers ("the sorrounds") which are at 3'oclock and 9'oclock to our sides - not meant to be exactly around us like a cube - this disapoints me, however if the specification complies with what I listed above, we could easily move the speakers into a cube like shape (I'm ignoring the centre here, yes) and technically create a "box" we are sitting inside for perfect 3D (well 360 degree) sound.


I will admit I got a copy of the Doom 3 Alpha, and I do know for a fact that the /sound/ dir contains audio in files named like this.
(this is an example mind you)

id_logo_l.wav
id_logo_r.wav
id_logo_c.wav
id_logo_rs.wav
id_logo_ls.wav
id_logo_lfe.wav



So can anyone answer my questions on Dolby 5.1 for gaming and the abilities of the Dolby specification and decoders?
I'm actually looking at a small home theatre setup for my 5.1 setup at the moment - using a Conia receiver (accepts 5.1 DD in optical and coax form) and 5 kit based speakers (small but nice for the price) as well as a woofer (obviously) I'm _NOT_ looking at a Logitech Z-680 "dedicated PC" 5.1 setup, nor a Creative 5700 / Klipsch 5.1 or any other PC based setup.

Can anyone (perhaps a nvidia DD driver coder or complete audiophile) help me out here with my questions?

thank you very much for your time.
(hopefully there's other Doom / 5.1 / 3d gaming / 3d audio freaks out there who will also get a kick out of any replies to this question)


- AbRASiON😕

 

[Accord99]

I wish to know for this for the primary reason of purchasing the right gear to get the most from something many of you may respect - Doom 3.
(and no doubt the many games which use the engine of it, and the games after that which use true dolby 5.1 after it finally takes off in the PC scene)

Dolby offers little, if any benefit to gamers. DD is a method of compression so that you can have reasonably high quality multichannel audio without requiring too much space.

I notice that some "proper" receiver / decoders will decode the signal and offer an option of 10 / 15 / 20 ms delays on the surround signal - why not 0ms?

You can add delays if your speakers are at different distances to ensure that the sound from the different speakers are synchronized. Unless your speakers are right next to your ear, there's not much point to having a 0ms delay.

Does my decoder "get smart" on me and try to perform "tricks" on my 6 independant signals?
Where does the crossover / splitting of the low frequency stuff occur? - does my sub channel (coming from the digital source) only contain low frequencies, or does the actual sub channel simply get high frequencies stripped via the decoder?

Depends, some receivers offer algorithms to add surround effects to stereo source like DPL2, and even stuff like Logic 7 to upmix normal 5.1 stuff into 7.1. Whether it sounds better is a personal opinion and is selectable. If a LFE channel ( the .1) exists, then the sub will get that channel which consists of audio up to ~120Hz. If you set your receiver to the small setting, then the bass management component will filter low frequencies away from the normal speakers to the sub. This is usually done because few speakers can match the subwoofer's performance in low frequencies.

Could I in theory connect up 6 identical speakers to my 5.1 setup (yes a normal sat to my sub channel)
Then after doing this could I send a DD 5.1 signal to the decoder (assuming I have an nforce which has a dolby ENCODER on the fly) and have 6 levels of identical volume - then hear it roughly identically on each speaker?

OR

Will the dolby signal be "parsed" by the decoder and have all kind of "filters" applied to the audio? (sending audio to the centre channel like pro-logic - or seperating low / high frequencies?)

Selectable, depends on receiver.

Can the dolby signal send this signal out and have the decoder "obey" the following rules.

centre - volume 0
left - volume 0
right - volume 0
rear left - volume 50
rear right - volume 0
sub - volume (whatever)

What would be the point when the relative volume of each channel is already set into DD data.

I'd LOVE (LOVE!!) to think that the standard is purely 100% 6 fully independant channels which can be manipulated in any particular way.

What this means is you could re-create the sound of an object circling you perfectly on a 360 degree field.
See example

Front left speaker - 10% volume of helicopter
Front right speaker - 75% volume of helicopter
Rear right speaker - 10% volume of helicopter
Rear left speaker - 0% volume of helicopter

Now. if we "gradually pan" this signal like this (over a few seconds)

Front right speaker - 10% volume of helicopter
Rear right speaker - 75% volume of helicopter
Rear left speaker - 10% volume of helicopter
Front left speaker - 0% volume of helicopter

This can be done with DirectSound3D or OpenAl and existing soundcards. Dolby is meant for compression, it does not automatically mean big budget movie soundtrack quality and the main reason its used is because it can compress the master source audio down to acceptable levels. On computers, where audio is generated on-the-fly and interactively like in a computer game, there's no point in DD or DTS etc. If Doom 3 does end up having good audio, it will not be because of DD, it will be because they spent the effort on the audio engine and used high quality samples.

So can anyone answer my questions on Dolby 5.1 for gaming and the abilities of the Dolby specification and decoders?
I'm actually looking at a small home theatre setup for my 5.1 setup at the moment - using a Conia receiver (accepts 5.1 DD in optical and coax form) and 5 kit based speakers (small but nice for the price) as well as a woofer (obviously) I'm _NOT_ looking at a Logitech Z-680 "dedicated PC" 5.1 setup, nor a Creative 5700 / Klipsch 5.1 or any other PC based setup.

The best gaming option for you would be the Audigy 2 connected to a receiver using the analog connections. This will give you the best overall sound quality. The NForce's DD solution is convenient but will suffer in quality.

 

[Pariah]

"Are all Dolby decoders the same? - in saying this I mean will a dolby decoder always perform the same operations as another when it comes to decoding, and if not can they be setup to do this?"

They're supposed to be. All the necessary information is stored in the DD stream, all the decoder does is read/decode the data and passes it along. Everything else you are asking about is receiver dependent. Some can do those things, some can't.

"Could I in theory connect up 6 identical speakers to my 5.1 setup (yes a normal sat to my sub channel)
Then after doing this could I send a DD 5.1 signal to the decoder (assuming I have an nforce which has a dolby ENCODER on the fly) and have 6 levels of identical volume - then hear it roughly identically on each speaker?"

The channels are independent, so even if all the speakers were the same, they would not be playing the same audio. It's not recommended to attach a satellite to the subwoofer channel, and it wouldn't really serve any useful purpose to do so. If you don't have a sub, set the speakers to large if the receiver has the option and connect nothing to the sub channel.

"is that the "official" layout for the 5.1 spec of speakers is to actually NOT have rear left and rear right like most gamers would have, but to actually have speakers ("the sorrounds") which are at 3'oclock and 9'oclock to our sides"

Yes, that is the proper setup for 5.1 to have the surrounds next to you, not behind you. Dolby-EX and DTS-ES add rear surround channel(s).

 

[AbRASiON]

Originally posted by: Accord99

I wish to know for this for the primary reason of purchasing the right gear to get the most from something many of you may respect - Doom 3.
(and no doubt the many games which use the engine of it, and the games after that which use true dolby 5.1 after it finally takes off in the PC scene)

Dolby offers little, if any benefit to gamers. DD is a method of compression so that you can have reasonably high quality multichannel audio without requiring too much space.

I refer to DD in the sense it's a method of outputting 6 channels from a device which will get it to 6 speakers.
It's also an established standard, therefore this means our speakers from the loungeroom can work in the computer room and our computer dolby setups work in the lounge room.

Our DVD's can work in the lounge and the computer room and acheive the same "sound" if we use dolby.

On the gaming side of it - it's handy purely because it can do "3d sound" with 5 independant sources of sound, very handy if you ask me.

I notice that some "proper" receiver / decoders will decode the signal and offer an option of 10 / 15 / 20 ms delays on the surround signal - why not 0ms?

You can add delays if your speakers are at different distances to ensure that the sound from the different speakers are synchronized. Unless your speakers are right next to your ear, there's not much point to having a 0ms delay.

I'd prefer not to have the delays, I want my rear speakers to act exactly like the front ones, adding delays will only ruin the illusion of a "live" 3d sound space.
My real problem is - do they have receivers / decoders which offer the removal of the MS delay - I don't think having one is appropriate for a 3d gaming setup (perhaps a movie watching setup, but not a gaming setup - where sounds need to be live and instantaneous)

The dolby encoding on the fly chip from nvidia is an amazing piece of technology - I firmly beleive within 3 years time, if nvidia release an independant card based on this chip - they will sweep the floor with creative and everyone will be using this chip or licensing this technology from nvidia and / or dolby.
There is NO solid standard for 4 speakers 5 speakers or 5.1 speakers on the PC besides dolby - I don't refer to the dolby compression routine, I am aware that the PC can generate live sound on the fly for 6 channels - I refer to the lack of a "defacto standard" of a 4 / 5 / 6 channel setup.

Does my decoder "get smart" on me and try to perform "tricks" on my 6 independant signals?
Where does the crossover / splitting of the low frequency stuff occur? - does my sub channel (coming from the digital source) only contain low frequencies, or does the actual sub channel simply get high frequencies stripped via the decoder?

Depends, some receivers offer algorithms to add surround effects to stereo source like DPL2, and even stuff like Logic 7 to upmix normal 5.1 stuff into 7.1. Whether it sounds better is a personal opinion and is selectable. If a LFE channel ( the .1) exists, then the sub will get that channel which consists of audio up to ~120Hz. If you set your receiver to the small setting, then the bass management component will filter low frequencies away from the normal speakers to the sub. This is usually done because few speakers
can match the subwoofer's performance in low frequencies.

That's good, it doesn't sound like it will "play with the signal" too much then.
I was thinking there might be some kind of option on the decoder which offers the ability to spread the sound over multiple speakers for some reason - or some strange default option to filter frequencies of XYZ to the centre channel, etc.

Could I in theory connect up 6 identical speakers to my 5.1 setup (yes a normal sat to my sub channel)
Then after doing this could I send a DD 5.1 signal to the decoder (assuming I have an nforce which has a dolby ENCODER on the fly) and have 6 levels of identical volume - then hear it roughly identically on each speaker?

OR

Will the dolby signal be "parsed" by the decoder and have all kind of "filters" applied to the audio? (sending audio to the centre channel like pro-logic - or seperating low / high frequencies?)

Selectable, depends on receiver.

This worries me, therefore I need the right receiver for the job.

Can the dolby signal send this signal out and have the decoder "obey" the following rules.

centre - volume 0
left - volume 0
right - volume 0
rear left - volume 50
rear right - volume 0
sub - volume (whatever)

What would be the point when the relative volume of each channel is already set into DD data.[/quote]

That's what I'm trying to establish - can the signal of 50 on only one channel be played by the decoder back as one channel only.
So someone writing audio on the nforce could literally make a CD called "TEST CD" which for 3 minutes makes sound come out of only one channel at a time so you could setup your speakers optimally - etc
Although others have replied to my question and advised me - that it's definately 6 independant channels so my question there has been answered (and satisfactorally i might add)

I'd LOVE (LOVE!!) to think that the standard is purely 100% 6 fully independant channels which can be manipulated in any particular way.

What this means is you could re-create the sound of an object circling you perfectly on a 360 degree field.
See example

Front left speaker - 10% volume of helicopter
Front right speaker - 75% volume of helicopter
Rear right speaker - 10% volume of helicopter
Rear left speaker - 0% volume of helicopter

Now. if we "gradually pan" this signal like this (over a few seconds)

Front right speaker - 10% volume of helicopter
Rear right speaker - 75% volume of helicopter
Rear left speaker - 10% volume of helicopter
Front left speaker - 0% volume of helicopter

This can be done with DirectSound3D or OpenAl and existing soundcards. Dolby is meant for compression, it does not automatically mean big budget movie soundtrack quality and the main reason its used is because it can compress the master source audio down to acceptable levels. On computers, where audio is generated on-the-fly and interactively like in a computer game, there's no point in DD or DTS etc. If Doom 3 does end up having good audio, it will not be because of DD, it will be because they spent the effort on the audio engine and used high quality samples.

I agree, we are confusing issues here and you don't understand what I mean.
I realise directsound 3d does this, the question is - how does directsound3d "send it" to the speakers? - does it use a CMI / ESS / (any?) audio chip with a valid (WHQL?) directsound 3d driver and the drivers / codec simply say in the game engine "sound front left" - then the directsound 3d engine / driver for the CMI card goes 'right ok - send that to speaker #2 - front left"

That's all fine and dandy, I udnerstand directsound 3d can do that.
HOWEVER!!!!!!!!
Doom 3 isn't using direct sound, it's using DD 5.1 from what I hear, so if I'm to use the coax / optical connection on the nforce board - how is the sound meant to come out of the speakers properly - when it's being decoded via a Dolby decoder?

So can anyone answer my questions on Dolby 5.1 for gaming and the abilities of the Dolby specification and decoders?
I'm actually looking at a small home theatre setup for my 5.1 setup at the moment - using a Conia receiver (accepts 5.1 DD in optical and coax form) and 5 kit based speakers (small but nice for the price) as well as a woofer (obviously) I'm _NOT_ looking at a Logitech Z-680 "dedicated PC" 5.1 setup, nor a Creative 5700 / Klipsch 5.1 or any other PC based setup.

The best gaming option for you would be the Audigy 2 connected to a receiver using the analog connections. This will give you the best overall sound quality. The NForce's DD solution is convenient but will suffer in quality.

Why would the nforce's suffer in quality?
The nforce offers an analog only solution also.
I refuse to use creative sound cards, plus Xian @ id does not recommend audigy's infact I recall seeing him post something negative about the creative cards recently - in id @ the moment they are specifically touting the Philips accoustic edge cards for the 5.1 sound.

What kind of receiver using analog connections - why would this stop the dolby decoding chip "playing" with the signal? and mean the receiver simply amplifies the signal and passes it to the speakers?

 

[AbRASiON]

Originally posted by: AbRASiON"Are all Dolby decoders the same? - in saying this I mean will a dolby decoder always perform the same operations as another when it comes to decoding, and if not can they be setup to do this?"

They're supposed to be. All the necessary information is stored in the DD stream, all the decoder does is read/decode the data and passes it along. Everything else you are asking about is receiver dependent. Some can do those things, some can't.

Surely if it's to be dolby compliant it has to follow some kind of guidelines 🙁

"Could I in theory connect up 6 identical speakers to my 5.1 setup (yes a normal sat to my sub channel)
Then after doing this could I send a DD 5.1 signal to the decoder (assuming I have an nforce which has a dolby ENCODER on the fly) and have 6 levels of identical volume - then hear it roughly identically on each speaker?"

The channels are independent, so even if all the speakers were the same, they would not be playing the same audio. It's not recommended to attach a satellite to the subwoofer channel, and it wouldn't really serve any useful purpose to do so. If you don't have a sub, set the speakers to large if the receiver has the option and connect nothing to the sub channel.

I was merely asking to clarify the ability of all 6 channels being independant 🙂

"is that the "official" layout for the 5.1 spec of speakers is to actually NOT have rear left and rear right like most gamers would have, but to actually have speakers ("the sorrounds") which are at 3'oclock and 9'oclock to our sides"

Yes, that is the proper setup for 5.1 to have the surrounds next to you, not behind you. Dolby-EX and DTS-ES add rear surround channel(s).

That's more for the home theatre though right?
I mean if you put them behind you - and change the delay to 0ms
then get an nforce which does it all on the fly - surely I can make a 3d sound space (hopefully)?!
I mean in the long run it's up to id software and how they impliment it,.....

 

[Accord99]

Originally posted by: AbRASiON

I refer to DD in the sense it's a method of outputting 6 channels from a device which will get it to 6 speakers.
It's also an established standard, therefore this means our speakers from the loungeroom can work in the computer room and our computer dolby setups work in the lounge room.
Our DVD's can work in the lounge and the computer room and acheive the same "sound" if we use dolby.

On the gaming side of it - it's handy purely because it can do "3d sound" with 5 independant sources of sound, very handy if you ask me.

Yes, but the issue with Dolby is that it cannot by itself give you surround sound. The master must have it and for gaming, this is done by DirectSound3D and OpenAL.

I'd prefer not to have the delays, I want my rear speakers to act exactly like the front ones, adding delays will only ruin the illusion of a "live" 3d sound space.
My real problem is - do they have receivers / decoders which offer the removal of the MS delay - I don't think having one is appropriate for a 3d gaming setup (perhaps a movie watching setup, but not a gaming setup - where sounds need to be live and instantaneous)

Having no delay will ruin surround effect because you will have sounds that do not match the action that you see. Since speakers are placed in wildly different configurations and spaced at different distances from the listener, the delay setting is there to ensure that the speakers don't play too early or late. And usually, these delay settings are given in distances anyway, as in how far your speaker is to you.

The dolby encoding on the fly chip from nvidia is an amazing piece of technology - I firmly beleive within 3 years time, if nvidia release an independant card based on this chip - they will sweep the floor with creative and everyone will be using this chip or licensing this technology from nvidia and / or dolby.
There is NO solid standard for 4 speakers 5 speakers or 5.1 speakers on the PC besides dolby - I don't refer to the dolby compression routine, I am aware that the PC can generate live sound on the fly for 6 channels - I refer to the lack of a "defacto standard" of a 4 / 5 / 6 channel setup.

There's no need for a defacto standard because DirectSound3D with a good gaming soundcard can generate 4, 5 or 6 discrete channels automatically. And in the home theater market, there's at least as much non-standardization with normal Dobly Surround, DD 5.0, DD 5.1, DTS 5.0, DTS 5.1, DD EX, DD EX, DTS ES matrix, DTS ES discrete, 5.1 setups, 6.1 setups and 7.1 setups. And now, the dream of audiophiles is for MLP which offers lossless multichannel PCM audio to become standard on HD-DVD or at least, full bit-rate DTS to replace Dolby Digital.

This worries me, therefore I need the right receiver for the job.

Its generally a higher-end thing, the more expensive the receiver, the more algorithms you can apply and stuff.

I agree, we are confusing issues here and you don't understand what I mean.
I realise directsound 3d does this, the question is - how does directsound3d "send it" to the speakers? - does it use a CMI / ESS / (any?) audio chip with a valid (WHQL?) directsound 3d driver and the drivers / codec simply say in the game engine "sound front left" - then the directsound 3d engine / driver for the CMI card goes 'right ok - send that to speaker #2 - front left"

Using DirectSound3D, you get positional information regarding the noise making objects within the game. This is passed to the soundcard, which determines how it should sound and the loudness, etc and then outputs into the proper channel. For example, the Audigy 2 can output into 2.0, 4.0, 5.0 or 6.0 configurations simply based on how many speakers you tell it you have.

That's all fine and dandy, I udnerstand directsound 3d can do that.
HOWEVER!!!!!!!!
Doom 3 isn't using direct sound, it's using DD 5.1 from what I hear, so if I'm to use the coax / optical connection on the nforce board - how is the sound meant to come out of the speakers properly - when it's being decoded via a Dolby decoder?

There's little information on how Doom is exactly going about to achieve this Dolby status. As there is no existing method to create interactive Dolby content, they would have to create everything from scratch. UT2003 also claims DD 5.1 support but in reality, all that it means is that the Nforce can compress its audio output into DD 5.1. It still uses OpenAL to create its audio. So, its all marketing. I wouldn't be suprised if Doom is the same.

Why would the nforce's suffer in quality?
The nforce offers an analog only solution also.
I refuse to use creative sound cards, plus Xian @ id does not recommend audigy's infact I recall seeing him post something negative about the creative cards recently - in id @ the moment they are specifically touting the Philips accoustic edge cards for the 5.1 sound.

The Audigy 2 supports a discrete rear center channel, EAX HD and superior audio quality. Using the real-time DD encoder results in lossy compression and creates a small latency. And considering the use of 3d sound in Quake 3, I wouldn't care too much about their opinions on sound.

What kind of receiver using analog connections - why would this stop the dolby decoding chip "playing" with the signal? and mean the receiver simply amplifies the signal and passes it to the speakers?

Yes, using the analog connections generally results in only amplification in non-high end products.