OpenAL is a cross-platform 3D audio API designed for use with games and other types of Multimedia applications. The OpenAL SDK includes documentation, sample code, demo applications, and a re-distributable run-time installer for OpenAL.
OpenAL features an extension mechanism allowing OpenAL vendors to add new features to the library. Creative Labs has added a number of extensions to OpenAL including EAX and X-RAM. This new release of OpenAL introduces the "Effects Extension" to OpenAL.
The Effects Extension is designed to provide a generic, cross-platform framework for adding advanced DSP effects to OpenAL. This framework offers the OpenAL programmer two new ways to process audio. Firstly, Sources can be processed through filters. Secondly, Auxiliary Effect Sends are introduced, so that effects processing can be applied to groups of Sources. The output of the Auxiliary Effects is fed into the final mix. It is also possible to filter Sources as they are fed into each Auxiliary Effect.
A good analogy here is with a traditional studio mixing desk. OpenAL on its own would map to a very simple mixing desk. Each channel strip will have Minimal controls : volume, 3D or stereo pan, plus pitch (Frequency). There are no auxiliary buses. In contrast, the equivalent mixer for OpenAL with Effects Extension has an arbitrary number of auxiliary effects buses, into which you can patch a variety of effects processors with adjustable parameters. On the channel strip, a filter control is added. There are also adjustable sends to each auxiliary bus, each with a filter control as well.
