The Intel High Definition Audio Specification describes an architecture and infrastructure to support high quality audio implementations for PCs. The Specification defines the register-level interface, physical link characteristics, and codec programming model as well as codec architectural components. This specification is intended for hardware component designers, system builders and device driver (software) developers.

Implementation of the High Definition Audio Specification requires a license from Intel. Contributors to the High Definition Audio Specification have signed the High Definition Audio (“Azalia”) Developers Agreement and have provided input to the specification under the terms outlined in that agreement. Implementers that have signed the High Definition Audio Specification (“Azalia”) Adopter Agreement are licensed to produce products based on the specification under a reciprocal, royalty-free license to certain intellectual property rights from Intel and other Contributors and Adopters for their products that are compliant with the licensed versions of the High Definition Audio Specification.

Intel intends to continue including suitable inputs, comments and suggestions from Contributors to refine and update the High Definition Audio Specification through a series of specification releases that will be marked as being Revision 1.x of the specification.

The latest revision of the specification is Revision 1.0. Subsequent Revision 1.x levels of the specification will be completed by Intel at its discretion as time and circumstances permit.

http://www.intel.com/standards/hdaudio/