What's an API?
Short for Application Program Interface, this software allows the game developer to write into games the ability to communicate with hardware in certain ways and take full advantage of it. The object is to create greater game immersion, giving a better gaming experience. OpenGL is a common video API used in 3D graphics cards that you might have encountered as a gamer. Advancements in sound card technology have been made just as quickly, if not more so, than in video cards.
In most cases, Aureal's A3D for positional audio faces off against Creative's EAX for environ-mental audio. However, after a long period of filing suits against each other regarding technology patent breaches, in September 1999 Creative (which utilises its own EAX API in its sound card line) acquired Aureal (creators of the A3D API).
These two APIs control the way sound is delivered to your sound card. Both work optimally with at least a four-speaker setup but can mimic 3D sound even with two speakers. It has been said that A3D draws more heavily on the CPU than does EAX, which may result in loss of frames during gameplay. It is important to note that framerates can also be affected by the number of streams a sound card can play using acceleration (EAX or A3D) rather than just DirectSound3D calls.
Surround sound technologies put certain sounds in certain speakers. These are often pre-encoded and are useful for applications such as Dolby Digital Sound when watching a DVD. When material is encoded with surround formats, users of the SoundBlaster Live! card - for example - can apply Multi Speaker Effects to hear sound in the front and rear speakers. A speaker setup such as the Cambridge SoundWorks or even an Altec Lansing system that supports Dolby AC-3 surround can aid greatly in bringing gaming alive. 3D from two speakers is not as effective, as the gamer has to sit in a 'sweet spot' between the speakers. When you're thinking of purchasing a card, keep in mind the speakers you're going to use; even consider buying a new set specifically for this purpose.
Tip: visit your sound card vendor's Web site to find out which APIs your card supports or check the readme file normally found in the installation folder of the sound card's utilities. Additionally, it is quite common for these proprietary APIs to have their own icon under Control Panel. If so, you can usually find some technology demonstrations as well.
This is the audio section of DirectX, which features high-response mixing of different sounds at once, as well as 3D positioning. It can utilise existing hardware, but in its absence DirectSound3D operates with the aid of RAM and the CPU.
A3D (Aureal 3D)
Supported in sound cards from manufacturers such as Turtle Beach and Terratec, this API gives the gamer a wealth of functionality. Some provide effects such as sound reflecting off different surfaces, or let you determine where you are in relation to objects in a game. A3D 2.0 is designed to be cross-platform, which it accomplishes by sending DirectSound3D messages to the hardware in certain cases, such as when the system doesn't have an Aureal sound card but does have another hardware-accelerated PCI sound card that supports DirectSound3D under Windows, as most do. The advantage is that the developer only needs to write for one API but the gamer still gets support - although this may affect sound quality.
Slightly less sophisticated than A3D 2.0, this API - like A3D 1.0 - adds to DirectSound3D's functionality. EAX works in Creative's current line of sound cards, the Live! series, where it is optimised for use with at least four speakers for positional audio, making it great for gaming. EAX is an extremely powerful API and is justifiably popular among the gaming fraternity. It boasts a growing list of supported games; the list, and more information, can be found at www.eax.creative.com.