EAX

About EAX

Environmental Audio eXtensions (EAX) is a collection of audio technologies designed by Creative Labs to bring interactive 3D audio to PC gaming. As the name suggests, it was originally built as a set of extensions for DirectSound3D. Later versions of EAX can use OpenAL instead of DirectSound3D to directly access the sound card hardware

EAX 1.0

Introduced in 1998 alongside the Sound Blaster Live! sound card. It was the first API for enabling real time environment effects for PC games. Developers writing to Microsoft's DirectSound API used its property set mechanism to gain access to the real-time on-board processing capabilities of the Sound Blaster Live! via the EAX 1.0 API. They would first query the system to see if EAX was available on the audio device. If it was, they were then able to choose from, and switch between the various factory-preset environments, designed to simulate different acoustic spaces such as "bathroom", "hall" and "cave". In addition to the preset environments, EAX 1.0 also allowed developers to customize the presets, such as controlling the reverb send level and reverb volumes. Notable game titles supporting EAX 1.0 included Unreal, Half Life, Sim City 3000, Aliens versus Predator and Baldur's Gate. EAX 1.0 features include:

• 8 simultaneous voices processable in hardware
• 32 individual 3D voices
• Environmental Effect Presets
• Per-channel individual environmental presets
• Hardware DSP rendering
• Specification released in 1998

EAX 2.0

Introduced in 1999 alongside the updated drivers for the Sound Blaster Live! sound card. With EAX 2.0, Creative presented the concept of a "listener" object and a number of "source" objects for sound. Sources could be "occluded" or "obstructed" depending on their position relative to the listener and any objects in the game, such as walls, pillars etc., that lay between. EAX 2.0 can also be used to recreate the effect of varying types of materials, such as wood, glass or concrete, accurately recreating how the sounds would be masked. As with EAX 1.0, Creative decided to make the EAX 2.0 specification public, allowing other sound card manufacturers to support EAX 2.0 via software. Notable game titles supporting EAX 2.0 included Rainbow Six: Rogue Spear, Diablo 2, Warcraft 3, Baldur's Gate 2 and No One Lives Forever 2. EAX 2.0 features include:

• 32 simultaneous voices processable in hardware
• Occlusion Effects
• Material-specific reverb parameters
• Specification released in 1999

EAX 3.0

Introduced in 2001 alongside the Sound Blaster Audigy sound card. The API was developed around a completely redesigned environmental reverb engine, more sophisticated than its predecessor thanks to the increased DSP power that the Audigy processor offered. Now, rather than simply switching from one environment to another as the player moved around the game world, the technique of “morphing” from one effect to another became possible. Environment Panning allowed developers to place both the early reflections and the late reverb components of an environment anywhere in 3D space. Notable game titles supporting EAX 3.0 included NeverWinter Nights, Grand Theft Auto: Vice City, Call of Duty, Splinter Cell, and Knights of the Old Republic. EAX 3.0 features include:

• 64 simultaneous voices processable in hardware
• 'Smoothing' between 3D audio environments
• Direct access to all reverb parameters
• Environmental Panning
• New reverb engine
• Beginning of the AdvancedHD Designation from new reverb engine
• Specification released in 2001

EAX 4.0

Introduced in 2003 alongside the Sound Blaster Audigy 2 sound card. The EAX 4.0 API provided developers with access to this additional processing power, and Audigy owners were able to download and install an updated driver that supported it. With EAX 4.0, developers could build incredibly sophisticated soundscapes using "Multi-Environment" effects. In addition to reverb effects, EAX 4.0 also provided access to special effects, including distortion, flanger and auto wah. Notable game titles supporting EAX 4.0 included Star Wars Jedi Knight: Jedi Academy, Thief: Deadly Shadows, and Colin McRae Rally 04. EAX 4.0 features include:

• Real-time hardware effects
• Multiple simultaneous environments
• Flanger
• Echo
• Distortion
• Ring modulation effects
• Specification released in 2003

EAX 5.0

Introduced in 2005 alongside the Sound Blaster X-Fi sound card. EAX 5.0 increased the hardware voice count to 128, added a dedicated bass feed for each of the 128 voices and introduced several new features which allowed game developers to create an even more realistic soundstage. Notable game titles supporting EAX 4.0 included Quake 4, Prey, Battlefield 2, Battlefield 2142 and Colin McRae: DiRT. EAX 5.0 features include:

• 128 simultaneous voices processable in hardware and up to 4 effects on each
• EAX Voice (processing of microphone input signal)
• EAX PurePath (EAX Sound effects can originate from one speaker only)
• Environment FlexiFX (four available effects slots per channel)
• EAX MacroFX (realistic positional effects at close range)
• Environment Occlusion (sound from adjacent environments can pass through walls)
• Specification released in 2005

EAX Features

This section will cover various EAX features in more detail. The primary source of information for how these features work is the material included on Creative's X-Fi Demo Disc.

Reverb

First introduced in EAX 1.0. Environment Reverb allows audio environments to be created by using reverbs that profile the environment you are in, for example a cave, cathedral, cavern, corridor or room. They can be of varying proportions. Without reverb, a listener can tell where each sound source is located, but has no idea of the environment in which the sources are located. For example, a sword clanked in a small padded cell should sound much different than the same sword clanked in a large cathedral. Using this EAX feature, developers were able to choose from, and switch between the various factory-preset environments, designed to simulate different acoustic spaces such as "bathroom", "hall" and "cave". In addition to the preset environments, EAX 1.0 also allowed developers to customize the presets, such as controlling the reverb send level and reverb volumes.

Obstruction

First introduced in EAX 2.0. As its name implies Obstruction recreates the effect of sound being partially blocked by a solid object, such as a large pillar or short wall. When sound is obstructed you can hear it, but it’s not the same as if there were no obstacle, nor is it as muffled as if the obstacle was a closed room between you and the sound. This is because the direct sound is being only partially blocked by the obstacle, some of the sound is ‘leaking’ around and over the top of the obstacle. The sound therefore is only partially muffled while a pure version can be heard, but does not seem to be coming from the sound source.

Occlusion

First introduced in EAX 2.0. Occlusion recreates the effect of sound being completely blocked by a solid object. Audio can be affected by walls, windows and doors in the game levels. It can even recreate the effect of varying types of materials, such as wood, glass or concrete, accurately recreating how the sounds would be masked. However unlike Obstruction, the object is all encompassing, like a room. Think of times when you have been inside your home and someone outside has been trying to speak to you through a closed window or door. Their voice sounded slightly muffled, and that’s what occlusion represents. Different materials affect sound more or less, depending on how dense they are. Technically high-frequency sound waves are affected more by obstacles than low-frequency waves. That’s why the thicker or denser the obstacle is (brick instead of glass, perhaps) the more muffled the sound gets. What’s happening is that the high frequencies are not getting through but the bass is.

Related links

• List of games with EAX support
• EAX appreciation thread - forum discussion with screenshots