DirectX Video Acceleration can be extended with support for H.264/AVC decoding, and Microsoft is offering a resource designed to streamline the process. DirectX Video Acceleration Specification for H.264/AVC Decoding is a whitepaper authored by Microsoft's Gary J. Sullivan that is currently up for grabs via the Download Center. With the specification, the Redmond company makes sure to define extensions to DirectX Video Acceleration (DXVA) with the purpose of introducing support for decoding of the video compression standard developed as a joint effort by ITU-T Recommendation H.264 and ISO/IEC 14496 (MPEG-4) Part 10.

“DXVA consists of a DDI for display drivers and an API for software decoders. Version 1.0 of DXVA is supported in Windows 2000 or later. Version 2.0 is available starting in Windows Vista. The data structures used for decoding are the same in both versions, and the information in this specification applies to both. Any relevant differences between the two versions are noted,” Sullivan stated.

At the same time Microsoft is offering extensive information on DirectX VA: Accelerating Video Codec Processing and DirectX Video Acceleration 2.0. Both DXVA versions 1.0 and 2.0 specifications offer the same set of components. First off, developers are able to leverage a DirectX application programming interface (API) that needs to be used in conjunction with a device driver interface (DDI) designed to enable video codec processing acceleration.

“In DXVA, some decoding operations are implemented by the graphics hardware driver and are executed in the GPU. This set of functionality is termed the accelerator. Other decoding operations are implemented in software and executed in the CPU. The set of functionality implemented in software is termed the host decoder. Processing performed by the accelerator is called off-host processing. Whenever the accelerator performs a decoding operation, the host decoder must convey to the accelerator buffers containing the information needed to perform the operation,” Sullivan added.