The environmental audio extensions (or EAX) are a number of digital signal processing presets for audio, present in Creative Technology's later Sound Blaster sound cards and the Creative NOMAD/Creative ZEN product lines. EAX displaced the alternative A3D (Aureal 3-Dimensional) in 2001.
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The aim of EAX is to create more ambience within computer and video games by more accurately simulating a real-world audio environment. Up to EAX 2.0, the technology was based around the effects engine aboard the EMU10K1 on Creative Technology's and the Maestro2 on ESS1968 chipsets driven Sound Cards. The hardware accelerated effects engine is an E-mu 8011 DSP integrated into the Creative Technology's audio chip and 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 synthesis). This effects DSP was also present on Creative's cards back to the AWE 32. However, the EMU10K1's DSP was more flexible and was able to produce not only MIDI output but also 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 Technology, 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 DS3D API, adding environmental audio presets to DS3D's audio positioning. Developers taking advantage of EAX choose an environment for their game's setting and the sound card uses the mathematical DSP digital 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 revision of the technology increased the available effects. EAX Advanced HD (also known as EAX 3) and up provide 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).
The aim of EAX has nothing to do with 3D audio positioning. This is usually done by a sound library like Microsoft's DirectSound3D or OpenAL. Rather, EAX can be seen as a library of hardware-accelerated sound effects. EAX is 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 was 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 processable in hardware by the audio processor: the original EAX 1.0 supports 8 voices, while EAX 5.0 allows 128 voices (and up to 4 effects applied to each).
EAX has had many iterations, each with an increasing number of features. Below is an overview of the currently available versions of EAX and their added features in respect to the previous version.
EAX 2.0 was used in Sound Blaster Live! sound cards.
EAX 3.0 was used in Sound Blaster Audigy sound cards.
EAX 4.0 is present in Sound Blaster Audigy 2 and the X-Fi Xtreme Audio sound cards.
EAX 5.0 is present in Sound Blaster X-Fi sound cards (except the Xtreme Audio cards).
According to Creative's OpenAL 1.1 specification, EAX should be considered deprecated as a developer interface. New development should use OpenAL's EFX interface, which covers all the EAX functionality and is more tightly coupled with the overall OpenAL framework.[2]
In addition to hardware devices, Creative also released EAX emulation drivers for computers with only onboard audio.
The differences lie in the software bundle. Sound Blaster Audigy ADVANCED MB includes Creative Audio Center, Creative MediaSource 5 Player/Organizer, Creative WaveStudio 7, Creative ALchemy; Sound Blaster X-Fi MB includes Entertainment Console, Creative Karaoke Player, Creative MediaSource 5 Player/Organizer, Creative WaveStudio 7, Creative Audio Console, Creative ALchemy.
Also known as Sound Blaster Audigy ADVANCED MB, it is similar to Audigy 2 SE, but the software supports EAX 3.0, which supports 64-channel software wavetable with DirectSound acceleration, but without hardware accelerated wavetable synthesis. DAC is rated 95dB Signal-to-Noise Ratio.
It is available as an integrated option for Dell Inspiron, Studio and XPS notebooks.
Later versions of the driver supports EAX 4.0.
It features:
Unlike its predecessor, Audigy Advanced MB, X-Fi MB does not include a software-based SoundFont synthesizer. Another difference is that it has the option to run in 30-day trial mode.
EAX-like technology is also present in several digital audio players by Creative Technologies, such as the NOMAD and ZEN lines. In these devices, the following effects and features are implemented: