
	Mikael Hagén and Mark Muschett take a look at 3D sound and Reverb APIs

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Gamer's Guide to 3D sound and reverb APIs

Mikael Hagén and Mark Muschett - Last updated January 8, 2002

DS3D

All cards that claim to support 3D sound should support DS3D, which is short for DirectSound 3D and part of DirectX. Despite what you may have read elsewhere, a game supporting DS3D will offer just as great a 3D sound experience as a game that supports A3D 1.0. It’s the card’s 3D sound engine, and not the API, that makes the difference in what you hear. If the card doesn’t support DS3D the developer can choose to use the 3D sound engine that’s part of DirectX7/8 but very few games do. It’s worth noting that the software 3D engine part of DirectX7/8 will only work if you use WDM drivers, when using the VXD drivers it will only be stereo panning. For more about this check out our A Gamer's Guide to Direct Sound 3D and A3D 1.x

EAX 1.0

EAX stands for Environmental Audio eXtension and is the reverb API Creative Labs introduced with the Live, early in fall 1998. It’s an extension to DS3D that lets the developer select what type of room you are currently located in. The soundcard will then use that info to add a reverb algorithm to each sound in an attempt to recreate the aural experience of that type of room. All positional info is done using Directsound 3D. There are some rare exceptions (e.g. Baldur’s Gate) where a game supports EAX without using DS3D to position the sound sources but for the most part all games supporting EAX 1.0 also supports and takes advantage of the positional aspects of DS3D.

Soundcards supporting EAX 1.0 includes Creative Labs’ Soundblaster Live and Audigy cards, Creative Labs PCI cards that are based on the ES137x chips, soundcards based on the Vortex2 chip, all cards using a reasonably new versions of Sensaura’s or QSound 3D sound/reverb engine. With reasonably new I mean the ones that were released early 1999 or later. For more about EAX 1.0 read our Gamer’s Guide to EAX 1.0. If your soundcard doesn’t support EAX 1.0 the game will either not offer any reverb or use its own reverb engine. For example, the games using the Unreal engine include their own reverb engine that can be enabled if your card doesn’t support EAX 1.0.

EAX 2.0

Just like EAX 1.0 it’s an extension to DS3D. One of the knocks on EAX 1.0 has been it’s not offering as dynamic experience as what Aureal’s A3D 2.0 provided through real time geometry based reflections and occlusions. Creative, backed up by Sensaura and QSound, continued to argue that statistically modeled reverb (which is a combination of first order and late order reflections) is more important than implementing the real time geometry based first order reflections of Aureal A3D 2.0. In my view both arguments have merits. With feedback from Sensaura, QSound and many others including the now departed Aureal, Creative took steps to add a mechanism for occlusions and obstructions, as well as exposing more of the reverb controls for developers to tweak in the new I3DL2 standard API.

Creative in 1999 released the EAX 2.0 API that offers the same functionality as I3DL2 with the addition of a few high-end parameters.

It’s important to recognize that even though EAX 2.0 offers occlusion and obstruction most EAX 2.0 games don’t take advantage of it. We had the same issue with A3D 2.0 games where only a few of them actually used the wavetracing feature. From the games we have played only Rogue Spear that was released quite some time ago takes good advantage of occlusion and obstructions. Even Soldier of Fortune which was one of the first games to use Creative’s Eagle, a development tool that should help developers/sound designers taking advantage of occlusion and obstruction, does not seem to offer any support for obstruction out of the box. However, Creative Labs has released EAX enhancements to 13 of the multiplayer levels, 7 of the CTF levels and for 8 of the single player levels that change this. Creative Labs has also released EAX enhancements for Unreal Tournament as well as an EAX 2.0 patch for that game.

While the developer support for occlusion in games has been disappointing the better control of the reverb that’s possible in EAX 2.0 is noticeable in far more games.

Soundcards supporting EAX 2.0 include Creative Labs Live and Audigy cards and soundcards using the later versions of Sensaura and QSound. In the case of QSound this includes Philips Acoustic Edge (PSC706, the newer Seismic Edge (PSC705) and Rhythmic Edge (PSC703) cards and the WDM drivers of the FM801 cards. For Sensaura cards support is more widespread where cards using the YMF744 (only Win9x/ME drivers), CS4630 (Santa Cruz/SonicFury and GameTheater XP), CS4624 (e.g. Fortissimo II, DMX Xfire), Canyon3D (Diamond’s MX400), Canyon3D 2 (IO Magic series), nVidia’s nForce (currently not in Windows 2000 but available in Windows XP/ME) and ENVY 24 (DMX 6fire 24/96) chips supports it.

EAX 2.0 games can provides backwards compatibility with the EAX 1.0 cards, but to take advantage of the more dynamic nature of EAX 2.0 and the new occlusion and obstruction calls the soundcard needs to support EAX 2.0. It’s important to point out that some EAX 2.0 titles like Final Fantasy VIII, MDK2 and Rogue Spear have turned out to not work on EAX 1.0 supporting cards. According to Creative there should be no extra work for programmers to offer the backward compatibility and it does seem that most EAX 2.0 games have done so.

I3DL2

This is very similar to EAX 2 but was developed by a consortium of industry representatives who belong to the Interactive Audio Special Interest Group, rather than just Creative (EAX2). Currently only soundcards using Sensaura offers support for I3DL2 and the only game we know that uses it is Slave Zero. DirectX8 features support for the I3DL2 API but currently there is no hardware support for it, that is it will use DirectX8 reverb engine. As far as we know no game currently use the I3DL2 as part of DirectX8. This may change when we start to see games developed for X-Box appearing in PC versions.

Back to Aureal's A3D APIs

On to Creative Labs EAX Advanced HD