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. The first sound card to support EAX 1.0 was the original Sound Blaster Live!, but other audio solutions soon appeared that supported EAX 1.0 via software emulation. This was by design, as Creative Labs made the API specification public shortly after Sound Blaster Live! was released. 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 hardware voices
• Environment Reverb Effects

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 hardware voices
• Obstruction Effects
• Occlusion Effects

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 hardware voices
• Environment Morphing
• Environment Filtering
• Environmental Panning
• Environment Reflections

EAX 4.0

Introduced in 2003 alongside the Sound Blaster Audigy 2 sound card. The EAX 4.0 API provided developers with access to additional processing power of the DSP, and even Audigy 1 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:

• Multi-Environments
• ExtendedFX

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 5.0 included Quake 4, Prey, Battlefield 2, Battlefield 2142 and Colin McRae: DiRT. EAX 5.0 features include:

• 128 simultaneous hardware voices
• EAX Voice
• EAX PurePath
• Environment FlexiFX
• EAX MacroFX
• Environment Occlusion

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, as well as Creative's old EAX website (archived here).

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. This video showcases the use of EAX Reverb in-game.

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. This video showcases the use of EAX Occlusion in-game.

Environment Morphing

First introduced in EAX 3.0. Environment Morphing delivers seamless transitions between environments. When game developers create the worlds that gamers explore, virtual ‘borders’ separate the different rooms and areas. Without Environment Morphing, crossing over a ‘border’ can cause an abrupt change in the audio: when moving from a large cavern to a small room the reverb and echoes of the cavern would suddenly stop. Environment Morphing smoothly transitions the listener from one environment to another, just as in real life. This video showcases the use of various EAX 3.0 features, including Environment Morphing.

Environment Filtering

First introduced in EAX 3.0. Environment Filtering offers more precise modelling of high and low frequencies in an environment to recreate how sound is affected as it passes through the air. The air is absorbing higher frequencies so sounds not only become quieter but more muffled. The technical name for this is ‘attenuation’ and Environment Filtering recreates this very accurately. Environment Filtering also supports the creation of more accurate audio environments. It takes into account the type of objects in your surroundings and what they are made of. Different materials will absorb or reflect certain frequencies – in outdoor environments high frequencies are more likely to be reflected than low frequencies, and low frequencies will be reduced in level due to the lack of surrounding reflective surfaces.

Environment Panning

First introduced in EAX 3.0. Environment Panning gives developers the ability to accurately position not only an object’s sound in 3D but also its environment. This provides the realistic delivery of 3D audio environments. Imagine you are walking along a corridor, and you notice a doorway to your right. The doorway leads into a room containing a noisy, clanking machine. While your footsteps echo all around you in the corridor, you can also distinctly hear a different reverberation emanating from the room. Obviously, you can hear that the machinery is on your right. But crucially you can also hear the acoustic reverberation from the room reaching you through the opening on the right-hand side of the passageway. In the gaming world, you can often hear sounds from several distinct environments. With EAX 4.0, these environments can be rendered simultaneously, and each one localized to indicate the positions of the different acoustic spaces. Environmental Panning enables the game developer to accurately pan and focus each environmental reverberation effect, simulating reverb reaching you from any type of opening, anywhere around your head.

Environment Reflections

First introduced in EAX 3.0. Environment Reflections allows the simulation of the reflection of sound waves bouncing off objects in a gaming environment. Environments truly come alive as the reflections in a vast space or even small corridor can be added to deliver that extra element of realism. The Environment Reflections feature simulates early reflections (the first reflections of a sound) from walls, floors, ceilings and other surfaces. These reflections give important clues about the surrounding environment. In small, enclosed spaces walls are close to the listener and sound reflections will be bounced back to the listener quickly and loudly. In large spaces sound must travel further to reach a reflecting object, and will therefore be delayed and quieter. Environment Reflections allows developers to model such different environments modeled. Together with Environment Panning the direction of sound reflections can also be controlled.

Multi-Environments

First introduced in EAX 4.0. This feature has the ability to recreate multiple environments simultaneously, so you can hear an opponent’s sounds coming from the correct environment. For example, if you are in a corridor and the enemy is in a cave and shoots at you, you will hear the reverb of the cave as well as the shot. The second feature allows developers to use the full range of hardware effects in real time – such as, to recreate varying degrees of radio static via the distortion hardware effect. Multi-Environment achieves this by feeding each environment's acoustical energy into the others, allowing rich and highly defined audio landscapes to be created.

ExtendedFX

First introduced in EAX 4.0. Extended effects, which were formerly only used in music creation (Flanger, Echo, Distortion and Ring Modulation) can now be used for real-time manipulation of audio streams. This allows developers to create new and unique audio effects, such as alien voices or robotic sounds, in real-time.

128 Hardware Voices

First introduced in EAX 5.0. The initial version of EAX supported 8 simultaneous voices (sounds). If more were required then the 'oldest' voice (the one that had been playing longest) was shut-off. With the introduction of the Sound Blaster X-Fi, the number of simultaneous hardware voices was increased to 128. This allows developers to add even more sound detail into their games. Actions such as firing a machine gun in a cave environment, where reverb and occlusion effects are added into the mix, will sound richer due to the increased number of hardware voices. Multiplayer games with a large number of combatants firing their weapons at the same time can also benefit from this feature. Notable examples include Battlefield 2 and Unreal Tournament 2004.

EAX Voice

First introduced in EAX 5.0. Using a microphone connected to an EAX 5.0 compliant audio device in any game title, you can speak and hear your voice with the same effects as the environment your character is in. Furthermore if the game title supports 3D Voice Over IP then other players in the game will be able to hear your voice as you do and coming from the correct direction. EAX Voice works by feeding the microphone input into the EAX hardware effects engine and at that point becomes another gaming sound element which you can hear. It is then transmitted along with the environment properties over the LAN and when it reaches another players PC system their EAX 5.0 compliant card translates the environment properties and adds them to your voice in real-time. In order for this feature to work the game must support the 3D voice transmission and EAX 4.0 or above. This video showcases the use of EAX Voice in-game.

EAX PurePath

First introduced in EAX 5.0. EAX PurePath delivers delivers the same level of precision surround as you would experience in a DTS or Dolby Digital encoded movie. This technology has been used for many years in movie sound, but is relatively new to gaming audio. In previous versions of EAX, developers could specify where, in a 360 degree space a particular sound should come from. The sound card would then map the sound to the correct position within the current speaker array. However, there was no way to specify a specific speaker, or combination of speakers that a sound should come from other than by using 3D positional coordinates. With EAX PurePath, developers now have total control over exactly which speaker (or speakers) the sound should be played through. This is particularly useful, for instance, for controlling bass reproduction through the subwoofer for Low Frequency Enhancement. Additionally, EAX PurePath gives control of the Low Frequency Enhancement (LFE) channel to game developers, so they can now feed as many or as few of the 128 available voices to the subwoofer. This means a far more powerful bass for those sounds that need it, and beautifully precise highs for those sounds that don't. Among other things, this can add more realism to in-game explosions.

Environment FlexiFX

First introduced in EAX 5.0. Environment FlexiFX gives developers total access to the hardware effects engine of the X-Fi Processor, which allows them to deliver the ultimate audio experience. With previous versions of EAX ADVANCED HD, developers had to live with some restrictions. For example, there were limits on the number of hardware effects they could use to create the game's audio environment. They had four effects slots available, but two of those had to be used for Environment Reverb and Chorus. This meant that they only had two slots left to use for additional effects. EAX 5.0 has completely re-designed how the effects engine operates and therefore provides developers with 4 fully flexible slots to use. This means that if they want to create audio for a level that has no reverbs (for example, if you are outside in an open area) but they want to add other sound effects to the weapons or monsters, then they can. This features supersedes EAX ExtendedFX, Environment Reverb and Multi-Environment.

EAX MacroFX

First introduced in EAX 5.0. With EAX MacroFX, close-up audio can be very accurately recreated, so bullets and laser blasts will never have sounded so frightening as they zip past your head only centimeters away. Previous versions of EAX were very good at recreating medium-range and long-distance sounds. However it couldn't handle close-up sounds - effects that could sound as though they were just 20cm away from your ears. Someone whispering in your ear, a sword slashing just past your head, or a laser blast zipping past your ear. Now, with EAX MacroFX, developers can recreate the sound of a machine-gun firing from a distance and have the bullets whizzing past your head, for example.

Environment Occlusion

This feature makes gaming audio more realistic by recreating the effect of sound from adjacent environments passing through solid objects. It can even recreate how different materials affect sound, such as wood vs. brick vs. stone and has been enhanced to be even more realistic than previous versions. Previous versions of EAX supported a feature called occlusion. This feature recreated the effect of sound passing through a solid object. However the basic Occlusion effect only occluded the direct sound, but not the environmental reverb associated with that sound. This reduced the effectiveness and impact of the overall effect. Environment Occlusion improves the realism by allowing the reverb effect itself as well as the direct sound to be muffled due to occluding objects.

X-Fi Specific Features

X-RAM

X-RAM is provided on the top-end Sound Blaster X-Fi solutions (Sound Blaster X-Fi Fatal1ty FPS and Sound Blaster X-Fi Elite Pro). It is 64MB in size and can only be used for audio purposes. With the availability of X-RAM, developers can now improve performance issues related to playing audio in their applications and increase the overall quality of their sound when X-RAM is available. X-RAM improves slow memory access due to paging by allowing the driver or the game to load its audio data on to the sound card itself, where it can be accessed by the audio processor at the highest possible speeds. A game that detects X-RAM can decompress its data at load time into it so that it does not have to spend processor cycles decompressing data during runtime. A game that detects X-RAM can use higher quality audio assets that it might not be able to use otherwise. In essence, X-RAM will allow developers to deliver the highest quality gaming audio and/or reduce the impact on performance of handling the gaming audio assets.

X-Fi S-SRC

X-Fi S-SRC (Super Sample-Rate Conversion) was introduced with Sound Blaster X-Fi sound cards. Sample rate conversion plays an important role in digital connectivity, 3D audio modeling, music synthesis and the ability to play and mix multiple sounds recorded at differing sample rates. The X-Fi Sample Rate Converter engine is incredibly powerful at over 7,000 MIPS equivalent processing power and has a new and unique hybrid architecture that produces outstanding audio quality. An audio clip could actually be converted many times with no detectable degradation. Despite the transparent sample-rate conversion qualities of X-Fi we recognized that there would still be applications that don't require sample rate conversion of any kind and therefore the flexible routing architecture of X-Fi allows the sample rate conversion to be bypassed when not needed. Advanced caching technology is also used for low latency and excellent PCI bandwidth utilization, and the architecture is optimized such that there is near zero device driver overhead to control the sample rate converters.

Elevation Filter

This option can be used when playing DirectSound or OpenAL games, or 3DMIDI sources, in headphone, 2-speaker, or 4-speaker configurations. Turning on the Elevation Filter effect enables the elevation filter for all game sounds located above or below the listener's horizontal plane. The Elevation Filter effect is useful, for instance, in first-person 3D games. For third-person games, it might be better do disable this option.

CMSS

Creative Multi-Speaker Surround (CMSS) 3D makes ordinary two-channel (Left and Right Stereo) sound seem to surround you, even through only two speakers. For users with 5.1 or 6.1 multichannel speaker systems, CMSS can also simulate surround sound from ordinary stereo. This is useful for watching DVDs and VCDs, which contain only stereo soundtracks. On Sound Blaster X-Fi cards, CMSS has additional modes, as described below.

X-Fi CMSS-3D Interactive

Exclusive to Sound Blaster X-Fi cards. CMSS-3D Interactive is a 3D positional audio engine that allows you to hear up to 128 simultaneous sound sources moving around you in 3D space. When combined with CMSS-3D Headphone or CMSS-3D Virtual, this allows you to hear your enemies coming at you from behind, above or below, regardless of the number and location of your speakers. This means that whether you are using headphones or any type of speakers from 2.1 to 7.1, X-Fi Technology will simultaneously deliver audio from to up to 128 virtual positions anywhere around you.

X-Fi CMSS-3D Headphone

Exclusive to Sound Blaster X-Fi cards. Aimed at headphone users, CMSS-3D Headphone reproduces the sound of a multi-speaker audio implementation using advanced 3D audio algorithms. Combined with CMSS-3D Interactive, it provides seamless reproduction of all audio positions in 3D space. You might be wearing headphones, but you’ll enjoy the equivalent of a virtual multi-channel speaker experience.

X-Fi CMSS-3D Virtual

Exclusive to Sound Blaster X-Fi cards. Aimed at users of desktop stereo speakers, CMSS-3D Virtual turns your two-channel speaker system into a virtual surround-sound system. It uses advanced algorithms to achieve a highly convincing surround-sound effect. CMSS-3D Interactive extends this surround-sound experience to achieve seamless full-sphere 3D audio. The combination of CMSS-3D Virtual and CMSS-3D Interactive can provide a vivid illusion of sounds above, below or near the head.

Related links

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