XBOX MCPX sound hardware details....

Kelly Scott Rickards

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I found this tidbit over at the beyond3d forums....
1) Comparing # of "3D" voices is a meaningless comparison. Do you even know what a 3D voice is? A 3D voice can be anything from a stereo-pan to an HRTF to a full wave trace. # of 3D voices is a meaningless comparison until you know what KIND of 3D voice it is, that is, what the virtualization algorithm is. And they different *tremendously* in their quality of amount of CPU required.
2) The X-Box is not limited to a "MAX" of 64 3D voices anymore than the gamecube was originally restricted to a MAX of 64. Both the GC and X-Box have programmable DSPs. The GC has a 16-bit 81Mhz DSP coupled to 81Mhz slow RAM and only 8kb of working RAM. The X-Box has two 200Mhz 24-bit DSPs coupled to an 800Mb/s bus, plus a 32 hardware mixers with per voice equalizers, and a voice processor that does HRTF in hardware. I'm sure NVidia could provide a device driver for the DSP that does more than 64 3D voices using a lightweight HRTF or lower quality 3D virtualization, if they wanted to. You can always trade off more voices for quality, especially if you have a 200Mhz DSP and 24-bit precision. Do you even realize the quantization errors you will get using 16-bit math, or the performance degradation of emulating higher precision on the 16-bit GC DSP? The more channels you mix, the more errors you have.
3) The X-Box 3D positional audio is advanced HRTF based with occlusions. The X-Box can simultaneously handle all 64 3D audio streams and an additional 192 2D streams, plus IDLS2 Music synthesis. Can you tell me the 3D virtualization algorithm used by Factor5 Musyx? I'll bet you that those 100 3D voices are not using a full HRTF.
4) Can the GC do 100 3D channels, plus mix in a another 192 2D Stereo channels, such as dynamic music synthesis?
5) The X-Box sends the final result to a second DSP that does Dolby Digital encoding. Those 3D channels will be sent digitally through your Dolby Digital Encoder and directly to the positionally located speakers. Does GC have this? (NO)
In addition to the software processing power of the 2 DSPs, the MCP has additional fixed function hardware to do HRTF. HRTF's are notoriously expensive to compute, but they are the only way to get high quality 3D positioning without going to a 7.1 setup with stereo panning. The equalizer is a 7-band parametric EQ FYI, according to NVidia, it is done in fixed function hardware, but of course, could also be done in software too. IDLS2 is most likely done in the programmable part of the DSP. Face it, the GC DSP is way inferior on paper, and will be inferior in reality. Why this troubles you so much, I have no idea. No one said "don't buy a GC because it has inferior audio". We are not talking purchasing decisions. Someone made the claim that the GC has the best audio. It's obviously wrong.
back to tech talk, because the[Gamecube's] DSP is limited to 16-bit operations, it must waste extra cycles to get higher precision. Without higher precision FP, you get quantization errors. This is similar to using a 16-bit framebuffer. The more voices and effects, the greater the error. Plus, the input samples are limited to 16-bit, with means you lose the part of the dynamic range you'd need for the .1 channel frequencies. All this means, the Macronix DSP has to spend extra cycles to emulate higher precision arithmetic.
In order for the Macronix DSP to come close to competing, it would have to have significant fixed function hardware to make up for its low clock rate and small data bus, in addition, it would probably need significant FP units plus superscalar issue. I find this highly unlikely, especially since the chip is embedded on the Flipper die. All that clucking you're doing about Mhz != Mhz would be true in other contexts, but here its not, and you know it (or maybe you don't)
Another advantage the X-Box has is that the DSPs have enough power to store audio samples in memory compressed and decode them in real time. This saves on system memory, since loading up a humungeous amount of sound effects and voice samples wastes precious ram, and streaming them has too much latency except for music.
The GC could do this to, but it won't be as adept. There's no way its going to do 64 3D HRTF voices plus decompression, plus equalization, plus occlusion, near-field, and macro effects.
Dual 200Mhz DSPs with 24 bit precision????
For sound hardware, this is insane!!
 

DaveF

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Why would you do both HTRF and DD5.1 processing? They claim that 7.1 sound is needed for "high quality" spatial positioning, but 5.1 does it quite well. Also, HTRF is generally used for two-speaker and headphone listeners. Are there suitable HTRF algorithms for 5.1 environments, much less ones robust enough to deal with the range of speaker setups of the typical gamer's family-room? (two speaker HRTF usually requires headphones or fairly specific speaker positions).
Finally, how much will this be taken advantage of? Yes, it will be great for those with a well setup HT system, and high-quality speakers. But for the average Xbox buyer, playing games through the TV speakers or pumped into a HTiB system, what's the point of all the DD5.1, HTRF-ed, beyond-CD quality sound processing? And given most can't use it, will developers develop for it or spend their time working on other game aspects (*cough* gameplay *cough*)?
This sounds like typical electronics mega-hype -- "MegaGameSys has got five, 100THz, iso-linear processor chips backed by 32 mega-quads of memory, capable of modeling the Big Bang as well as bringing unprecendented detail to Spyro the Dragon."

No slam to the X-Box in particular, as all electronic systems are over-hyped.
 

Jason Seaver

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Yes, it will be great for those with a well setup HT system, and high-quality speakers. But for the average Xbox buyer, playing games through the TV speakers or pumped into a HTiB system, what's the point of all the DD5.1, HTRF-ed, beyond-CD quality sound processing?
Right now, sure. Maybe MS knows something we don't, and figures HDTV/DD5.1 is going to hit the mainstream in a big way over the next couple of years. If that happens, they'll be in a pretty good position, supporting all that stuff out of the box while Nintendo and Sony have to scramble selling upgrades or new systems.
 

DaveF

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From 1) "Comparing # of "3D" voices is a meaningless comparison."
From 4) "Can the GC do 100 3D channels"
Uh... didn't you just tell us not to ask that question?

quote: The MCP sounds awesome in action, regardless of speaker configuration.[/quote]I'm sure it does, but does it sound HRTF, 5.1DD, 256 voice, "two 200Mhz 24-bit DSPs coupled to an 800Mb/s bus, plus a 32 hardware mixers with per voice equalizers" awesome? Or does it sound awesome like I get from my PC running through the stereo?
I've no doubt that the X-Box can do amazing sound, and may well be sonically surperior to the GameCube (my console of choice, btw). The quoted fanboy post just smacks of tech-jargon over-hype. The stuff we see for every new computer graphics card, and which is not realized in actual games.
I just wonder if the sound quality of the X-Box will be noticeably better than of the PS2, NGC, or even Dreamcast, to the typical gamer.
[Edited last by DaveF on August 31, 2001 at 02:14 PM]
 

Shayne Lebrun

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You do the HRTF to figure out which speakers the sound should be coming from.
In real life, you can do it perfectly with two speakers (after all, if you can hear 3d sound with two inputs, you can produce it with two outputs) but for that you need a HRTF that matches your head. And the two speakers need to be perfectly positioned.
Or you can take four speakers, figure out 'roughly' where the sound should be coming from, and natural physics will do more of the work for you.
Or you can take 5 speakers, a.k.a. four for ambience and one dedicated for voice, and do it all 'naturally.'
The Xbox is using DD because that's the multi-speaker setup most people will have. The HRTF will figure (70 percent from left rear speaker, 20 percent from right rear speaker) and let physics do the rest.
 

Troy LaMont

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Dave,

quote: Finally, how much will this be taken advantage of? Yes, it will be great for those with a well setup HT system, and high-quality speakers. But for the average Xbox buyer, playing games through the TV speakers or pumped into a HTiB system, what's the point of all the DD5.1, HTRF-ed, beyond-CD quality sound processing? And given most can't use it, will developers develop for it or spend their time working on other game aspects (*cough* gameplay *cough*)?


I'm starting to see a trend with some of the responses about the XBox's capabilities...it has too much to offer!?

Why do you think it not possible for a gaming company to produce quality games with great 'gameplay' AND great sound by utilizing the audio hardware capabilities?

From my perspective, I don't expect to see all that the XBox is capable of until at least 6 months or more after it's release. I mean look at the games out for PSX now, these current generation games for PSX utilize just about every ounce of technology you can squeeze from the system. And how long has that taken? Years.

I'm ecstatic that these types of capabilities are included in the XBox, so when the real potential is realized, we'll have one helluva gaming system on our hands.

Troy

------------------
quote::My teacher tells me beauty is on the inside.
:That's just something ugly people say.[/quote]

[Edited last by Troy LaMont on August 31, 2001 at 03:08 PM]
 

DaveF

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I'm starting to see a trend with some of the responses about the XBox's capabilities...it has too much to offer!?
I'm all for more power for my games! But I want the processing to be used on things that can be used and make a difference.
For instance, if a console could produce 2000x2000 resolution with 48 bit color depth, that would be cool, but useless, since very few people have display devices capable of that, and using a TV for that res and color fidelity would be a joke.
Likewise, with uber-sound processing, at a certain point money and effort can be wasted on details that will never be heard, simply because the TV/stereo/speaker arrangement can't produce it.
If the XBox's sound chips can be used to produce effects that will be heard by most of the users, then great!
But if 18 months from launch, only a miniscule portion of the owners can benefit from the features, then what's the point of them being there? It would make sense (to me) to either drop that feature, and reduce the system cost; or put the that portion of the development budget into e.g. testing, debugging, optimization -- things that amost all users will benefit from.
 

Gary King

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I'm sure it does, but does it sound HRTF, 5.1DD, 256 voice, "two 200Mhz 24-bit DSPs coupled to an 800Mb/s bus, plus a 32 hardware mixers with per voice equalizers" awesome? Or does it sound awesome like I get from my PC running through the stereo?
Given the two choices, I'd say it sounds "HRTF, 5.1DD, 256 voice, 'two 200Mhz 24-bit DSPs coupled to an 800Mb/s bus, plus a 32 hardware mixers with per voice equalizers'" awesome, as opposed to "PC running through the stereo" awesome.
In fact, it sounds so awesome that I'll probably be buying two of them this fall (one in the form of the Xbox, the other in the form of a new motherboard).
 

Troy LaMont

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Dave,

quote: I'm all for more power for my games!


You may think that, but that line of thinking isn't coming out in your words.

Future use! That's what comes to mind when I see specs like those that XBox is capable of. I mean, based on your logic, why should Lexicon offer an upgradeable processor on their receiver when you can't use it for anything 'NOW'
.

You're assuming that no game developers are hunkering down to take full advantage of all that the XBox has to offer. Who's to say that they aren't quote: put the that portion of the development budget into e.g. testing, debugging, optimization -- things that amost all users will benefit from.[/quote]

I can for the life of me, fathom anything that I buy or plan to buy as 'too much'. So what about all of those people who buy progressive scan DVD players and can't take full advantage of it's capabilities? Are they wrong for wanting what's 'best' or what has the most features? I think not.

You also don't take into consideration how much HT and gaming is growing, exponentially. So what if 'those of us' who can take advantage of all the XBox has to offer, are in small numbers? Is MS wrong for giving those few what they want? What about the thousands of DVDs that are anamorphically enhanced? Only a very small percentage of people can take advantage of that feature, but everybody wants it. Why? Because it'll be there for future use. When and if they do upgrade.

Yes I am partial to XBox, but this, IMO is only a logical, common-sensical debate, it's not wrong (or dumb or stupid) to offer more in a product, regardless of whether or not everyone can take full advantage of it now.

Nuff said.

Troy


------------------
quote::My teacher tells me beauty is on the inside.
:That's just something ugly people say.[/quote]

[Edited last by Troy LaMont on August 31, 2001 at 04:10 PM]
 

Kelly Scott Rickards

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Yes, its amazing when the discussion at hand involves the XBOX, suddenly doubts about gameplay quality and superfluous hardware features rears its head.....
Do you honestly think games from Konami,Capcom, Namco and Sega will have uninspired gameplay,just because they are on XBOX?
If so, prepare for a nasy shock!
As you recover from that jolt, try not to hold your breath waiting for those developers games to *NOT* take advantage of all they can extract from the XBOX.
I mean since when did developers have a reputation for NOT taking as much advantage as they can from gaming hardware???
As for the Dolby Digital support, I have since learned that one of those dual 200Mhz processors is used at the final stage of audio mixing for output, and is used *specifically* for the Dolby Interactive Content Encoder (and also accelerates that encoding)...
As it's own dedicated sound hardware/software soloution, it has *NO* performance hit on the XBOX hardware(unlike DTS on the EE) and a developer simply hits a switch in the sound API for Dolby Digital support in their game....
The end user can disable/enable Dolby Digital support in a setup screen, so expect widespread use by developers as no end user has to buy a Dolby Digital reciever/pre-pro "Just to play their game".
[Edited last by Kelly Scott Rickards on August 31, 2001 at 05:30 PM]
[Edited last by Kelly Scott Rickards on August 31, 2001 at 05:34 PM]
[Edited last by Kelly Scott Rickards on August 31, 2001 at 05:37 PM]
[Edited last by Kelly Scott Rickards on August 31, 2001 at 05:41 PM]
 

Dan B

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Kelly/Gary/anyone, do you know what the bitrate of the Dolby 5.1 will be on the Xbox games? How does it compare to Dolby 5.1 on a DVD?
-Dan
 

Gary King

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They can't really be compared - interactive soundscapes and premixed soundscapes are very different. I can't tell the difference between a Dolby Digital positional stream and an analog positional stream off of the MCP, though.
Technically, 640kbps compression should be easier than 448 or 320kbps.
 

DaveF

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What I was trying to get at (and failing), was whether the uber-hardware produces uber-sound that can be heard by a gamer in their living room, even with a pretty good HT system.
If not, then what's the point? Future use? Console systems are meant to have a relatively short market lifetime; unlike $3000 receivers, a game system can't be "future-proofed." Will people have the HT hardware setups required to hear the uber-sounds during the consoles lifespan?
But now Gary has said that the X-Box sounded super gee-whiz-neato-keen, and I'm glad -- my concerns were not realized.
 

Sean Oneil

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Dave,
The way I have read things, you are making the case that because most of the market will not be able to take advantage of the advanced audio/video output abilities of the X-Box, that the X-Box should be geared towards that greater number of people, and drop those abilities to cut costs. But Microsoft are already going to be selling each system at a HUGE loss, so the argument about cutting costs and passing the savings on to the consumer does not really apply as heavily as you might think.
By building a system that will make the most of nearly anyones gaming set up, Microsoft does not leave anybody out. It is better that they decided to make the system as advanced as possible so that people with advanced HT setups can take advantage of them. If you don't have an advanced set up, then you will not know that you are missing anything and will still be happy anyway, because you are getting the best out of whatever equipment that you do have to play the X-Box with.
Some of us will have the HT hardware that will take advantage of the audio/video capabilities of the X-Box, and some of us won't. Either way, we will all get the best out of our gaming gear.
 

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