The Benefits of Dedicated Hardware Acceleration for Audio

A Diamond Multimedia White Paper

For years, computers have benefited from boosts in performance provided by graphics accelerator cards. It would almost seem unheard of to have a system that didn't have one inside. To some extent this is true with audio. However, most FM/Wavetable sound cards are built to play back one monophonic or stereo digital channel and don't have a dedicated processor to deal with digital mixing and other CPU-intensive tasks. Due to the demands placed on today's gaming, applications and the Internet, changes need to be made in the way audio is handled. Even though there may be a sound card in your current system (or on the motherboard), there may be reason to upgrade the audio quality of your machine, especially if you are a game player. Read on, and you will see there are many benefits in having a sound card quite different from the one you own today.

For the purpose of this article, dedicated hardware acceleration can be defined as a device having an on-board processor that provides additional computational power for sound-related processing, thus freeing the CPU to concentrate on tasks other than those intended by the additional processor.

Some of the benefits from having a dedicated accelerator include:

Reducing CPU drain to increase overall performance

Although computers are increasing in speed, it has been shown that even with the speed of today's machines there is always a need for more power, especially with newer games and applications.

Example: Many applications use multiple streams of audio. A 90Mhz Pentium takes a hit of around 1 percent per stream to digitally mix individual audio streams. Adding tasks such as pitch transposition, bit-rate conversion and positional 3D imaging raises the CPU usage exponentially. If enough streams are mixed and modified there is little horsepower left for graphics, video and the engine needed to run the application. Although the standard computer model has moved away from P-90's to faster machines, the horsepower demands continue to drive on.

Higher quality audio through complex algorithms

In 1995, Microsoft introduced DirectX™ technology (software algorithms to accelerate graphics, 3D, sound, etc) along with the release of Windows 95®. Even though DirectX was designed to make use of the CPU for these computations, the quality and speed of the designated tasks are raised significantly if a DirectX-certified accelerator is present.

Example: If DirectSound™ is called by an application and a sound accelerator is installed, DirectSound will offload the computations to the card for processing of the audio function. If not present, the workload will revert back to the CPU. The point of this is to note that DirectX is a scaleable architecture. Dedicated processors allow DirectX to work best. That means smoother mixing, higher quality audio and more believable 3D sound in the game you are playing right now!

3D positional audio

The advent of 3D graphics technology has created the need to hear in 3D to complete the total experience. It would be confusing to visualize a three dimensional world, and only hear sounds in stereo. How would it be possible to hear the roar of a lion behind you or a torpedo blast overhead? Without 3D sound in 3D graphics applications, you only receive part of the overall experience.

Although 3D sound comes in different flavors, there is a drastic difference between "true" 3D audio and extended stereo enhancement. An extended stereo field is wider and presents sound in a half circle on a horizontal plane. This gives the listener the perception of sound coming from farther positions to the left and right. It does not position sounds above, below or behind the ears. Widening a stereo field achieves only part of the full 3D experience. True 3D positional sound produces imaging that appears to come from behind, above, below and the sides, and can be heard in headphones and speakers alike (either 2 or 4 speakers). It also accounts for the reflections of surfaces and boundaries in the present sound field.

Because 3D algorithms take quite a bit of horsepower, a dedicated accelerator can be of great help. Having a dedicated accelerator for 3D audio makes games much more realistic and exciting to play. Using the CPU to do the math can make a game slow to a crawl just from a few bullets being sent 3D calls. On the other hand, the game doesn't flinch when an accelerator is present.

Increased throughput of data via the PCI bus

The PCI bus moves data at rates many times faster than the ISA bus. It is by this means that multiple streams of digital audio can run across the bus with relative ease. Using the PCI bus for audio also keeps the system from being bogged down due to the lack of processor cycles needed to bridge the ISA and PCI bus together. Using a higher bandwidth bus makes for much more efficient audio. Once again, that means higher powered, more interactive and more exciting game play.

Freeing up system memory for applications

All Windows® operating systems are made to multitask. In order to multitask, there must be sufficient memory to run all relevant applications. Every time an application runs out of system memory, it moves to the hard drive to temporarily store it's work. With many applications running, the hard drive spins constantly. Offloading unnecessary math and computations to the dedicated hardware processor allows much of the precious system memory to be freed up and used for applications. This allows you to enjoy the freedom of playing a game without unnecessary waiting.

With the release of DirectX architecture and the enthusiasm of the development community, dedicated hardware accelerators for audio are the natural next step for the game player. New games are already making use of 3D audio as well as other DirectX technologies. These games and technologies bring entertainment to a level of realism and excitement never before experienced on the PC.

Freedom 5600

Diamond Multimedia Systems, Inc. has announced that it has developed its first multimedia audio processor, Freedom 5600, for Microsoft DirectSound and DirectSound 3D applications running on the Windows 95 operating system. Designed to provide an immersive 3D audio experience, Freedom 5600 will be an integral component of next-generation audio solutions from Diamond Multimedia planned for the first quarter of 1997.

Diamond's Freedom 5600 will allow computer game and entertainment developers to fully utilize Microsoft's DirectSound and DirectSound 3D APIs for multi-stream audio processing. Current sound technology is limited to ISA-based, single-stream audio. Freedom 5600 can support up to 24 independent audio streams without incurring any significant CPU overhead. The design of Freedom 5600 facilitates the integration of DSP and CODEC technologies to provide interactive 3D positional sound for headphone, dual- and quad-speaker output.

Diamond's Freedom 5600 is expected to be one of the first Windows 95, Plug and Play, PCI-bus enabled solutions on the market. Diamond Multimedia plans to incorporate Freedom 5600 into a family of products along with Analog Devices' DSP and audio CODEC components in the first quarter of 1997.