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 was first introduced in 1998, alongside the Sound Blaster Live! sound card.

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. Some of the notable EAX games titles 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. 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 that supported 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 that supported 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. 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

Related links

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