AVIVO HD and the new UVD
The Radeon HD 2400 and 2600 families of GPUs feature a new AVIVO HD video engine with better performance and more functionality than the version found in the Radeon X1K family of products.
Update: The R600 used in the Radeon HD 2900 XT does not feature the new video engine, but rather the same engine that's found in R580. As such, it is not cabable of bitstream processing or entropy decoding, and will have higher CPU utilization during playback of encoded titles than the other members of the Radeon HD 2000 family. With the HD 2900, the GPU's stream processors are used to assist in HD video playback functions.
The new AVIVO HD engine features AMD's Universal Video Decoder technology, which basically offloads every major aspect of HD video processing from the host CPU and performs the functions on the GPU. In the last gen AVIVO engine, bitstream processing and entropy decoding was not performed on the GPU, bit rather was handled by the system's host CPU. Now though, AVIVO HD with UVD handles every major step in the process which makes them better suited to handle HD DVD and Blu-Ray video disc playback. The UVD supports full 40Mbps bit-rates for HD optical disk playback and decode data is handled internally, removing passes to memory between the decode stages.
Another improvement to the way the Radeon HD 2000 series handled HD content has to do with audio output. Cards in the Radeon HD 2000 series now feature an integrated HD audio controller that supports 32kHz, 44.1kHz, 48kHz 16-bit PCM stereo and AC3 (5.1) Compressed multi-channel audio streams such as Dolby Digital & DTS. The digital audio it actually output through the cards' DVI connectors and can be accesses through the use of a new DVI to HDMI adapter that also carries audio signals.