Environmental audio extensions

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The environmental audio extensions (or EAX) are a number of digital signal processing presets for audio, present in Creative Labs later Sound Blaster sound cards and the Creative NOMAD/Creative Zen product lines. EAX displaced the alternative A3D (Aureal 3-Dimensional) in 2001.

1 Sound card versions
- 1.1 Environment perception
2 Audio player versions
3 References
4 See also
5 External links

[edit] Sound card versions

[edit] Environment perception

The aim of EAX is to create more ambience within games by more accurately simulating a real-world audio environment. Up to EAX 2.0, the technology simply was based around the effects engine aboard the Sound Blaster Live!'s EMU10K1 audio chip. The effects engine, actually an E-mu 8011 DSP integrated into the audio chip, was historically used to enhance MIDI output by adding effects (such as reverb and chorus) to the sampled instruments on sample-based synthesis cards (also known as wavetable). In fact, this effects DSP was similarly present on Creative's cards all the way back to AWE 32. However, the EMU10K1's DSP was more flexible and was able to affect not only MIDI output but also all other outputs, including the digital sound section. A person who has been exposed to MIDI effects processors will quickly recognize the parameters that EAX controls, and the names of many of the presets.

Creative, seeing the rising popularity and marketing significance of having a proprietary sound API, gave the functionality of this effects engine the name EAX. EAX is a library of extensions to Microsoft's DirectSound3D API, adding environmental audio presets to DS3D's audio positioning. Developers taking advantage of EAX literally choose an environment for their game's setting and the sound card will use the mathematical DSP filter presets for that environment. The original EAX was quite primitive, only offering 26 presets and 3 parameters for more accurate adjustment of the listener parameters and 1 parameter for the sources. Each new revision of the technology increases the available effects. EAX Advanced HD (also known as EAX 3) and up add support for new environmental transitions, new effects, and multiple active effects. Further additions include smooth changes between EAX environment presets and audio occlusion effects (that is, a wall between player and sound source).

EAX has nothing to do with actual 3D audio positioning. Positioning is done by Microsoft's DirectSound3D API. An alternative to DirectSound3D, called Open Audio Library (OpenAL), surfaced in 2003 in several titles. OpenAL allows direct hardware acceleration of audio, like DirectSound, including EAX. As of 2006, the API has been used in many popular titles including Doom 3 and Prey. These games support EAX 4.0 if audio hardware with an OpenAL-supporting driver is present. Because hardware acceleration for DirectSound and DirectSound3D will be dropped in Windows Vista [1], OpenAL will likely become more important for game developers who wish to use EAX in their games.

Most releases of EAX versions coincide with increases in the number of simultaneous voices processible in hardware by the audio processor: the original EAX 1.0 supports 8 voices, EAX 2.0 allows 32 (Live!), EAX Advanced HD (EAX 3.0) supports 64 (Audigy), EAX 4.0 again supports 64 (Audigy 2), and EAX 5.0 allows 128 voices (and up to 4 effects applied to each) (X-Fi).

Games that use EAX

[edit] Audio player versions

In the portable audio players produced by Creative, especially the Creative NOMAD and Creative Zen lines, EAX means something else than for sound cards. Here, it applies a few possible effects to played back audio on the device, including:

Different reverb-like environments (most similar to the sound card EAX)
Speed-shifting (slower or faster)
Environment adaptation (train, plane, public place etc)
Sound image (broad, narrow etc)
A simple graphical equalizer

The first NOMAD jukebox also had support for pseudo-surround sound using rear speakers by supporting two different audio output plugs on the device.

The addition of these effects to the audio is not very popular, will use up additional battery resources and is generally a quite mysterious feature to most owners. It might have been introduced only to sell players to computer-game people who were familiar with the EAX concept and would therefore hold this feature in high regard.