Elite Bastards posted a preview on the RV635 and RV620 GPUs

UVD (Universal Video Decoder) for fully GPU-accelerated video playback is also supported, but all of the boards being launched today have seen some small improvements to this aspect of their architecture, offering support for hardware video decoding at resolutions up to what ATI have dubbed 1440p (a resolution of 2560x1440, which is being touted as the successor to 1080p in the Home Theater space) over the maximum 1920x1080 support available to RV670 and Radeon HD 2000 series parts equipped with UVD. While this may not be particularly relevant at the start of 2008, it offers a little potential future-proofing if you're looking to build a Home Theater PC to last, on the Radeon HD 3600 at least - Radeon HD 3400 boards are unlikely to have enough processing power to handle such a large video stream.

RV635 and RV620 - Radeon HD 3600 and 3400 series preview