Exploring EAX with onboard audio


A crack in the crab's shell?
by Geoff Gasior — 12:00 AM on November 3, 2006

ANALOG DEVICES RECENTLY published a document challenging reviewers not only to benchmark the CPU utilization of integrated audio solutions, but also to explore how well those implementations handle EAX positional 3D audio. According to the document, most motherboards don't handle EAX properly, despite the fact that they claim to support the standard. Analog Devices diplomatically avoids naming names, but with the vast majority of integrated audio solutions powered by Realtek codecs, the writing's on the wall.

The question, of course, is whether it's true. Analog Devices' whitepaper cites tests conducted in Creative's, er, labs, but we're not happy until we can explore an issue with our own systems in an environment we can control. So, we've rounded up a couple of nearly identical motherboards with Analog Devices and Realtek codecs to see how they handle EAX positional 3D audio, with conclusive results.

Much ado about EAX
EAX, otherwise known as Environmental Audio eXtensions, is a positional 3D audio standard with roots in Creative's SoundBlaster Live. The standard tags in-game sounds with information about their position in the world, allowing for more realistic interactions with the player. Through EAX, positional audio is mapped to the appropriate speakers in a multi-channel setup, giving the player a sense of direction associated with each sound. EAX can also modify in-game sounds to take into account obstructions like walls and pillars, and the occlusion effect of different materials, such as wood and glass, between the player and a given sound.

The most recent incarnation of EAX is EAX Advanced HD 5.0, which can be found on Creative's latest X-Fi audio cards. You don't need a fancy audio card to enjoy EAX effects, though. Creative made EAX 2.0 a public spec—ostensibly to push its own 3D audio technology as the standard for positional audio in games—allowing other sound card and codec manufacturers to support it.

EAX 2.0 was originally handled in hardware by the SoundBlaster Live's EMU10K1 audio chip. On motherboards, EAX 2.0's positional audio calculations are now most often handled in software by the onboard audio codec's driver. In fact, core logic chipset makers have largely washed their hands of 3D audio support, deferring to codec makers, whose sound drivers do the heavy lifting via Microsoft's standard High Definition Audio bus.


Realtek's ALC882D audio codec

Codec chips from Analog Devices and Realtek currently dominate the scene for integrated motherboard audio, and the latter is far and away more popular than the former. Fear the crab, baby.

Back in the day, it was nearly impossible to find a motherboard that didn't use Realtek's ALC650 codec. The company has done an admirable job of maintaining its strong market share since, becoming the de facto standard for eight-channel AC'97 codecs and now for the new wave of high-definition "Azalia" audio chips.


Analog Devices' AD1988B audio codec

Analog Devices' codecs haven't been nearly as popular among motherboard makers as those from Realtek, but that may be starting to change. Asus recently switched from Realtek to Analog Devices codecs for its high-end motherboards, and since they sent us a copy of Analog Devices' EAX whitepaper, we suspect it had something to do with their decision to buck the crab.