The X Video Extension provides seamless video support for X. It supports playback of video streams from different sources: software provided video data as well as video data captured from hardware are supported.
Hardware decoding of compressed video is supported by the XvMC (Xvideo Motion Compensation) extension.
Video playback can easily be implemented using components of ATI AVIVO technology.
Traditionally video playback from software content (XvPutImage) was implemented using a video overlay scaler as it provides the lowest overhead implementation possible for displaying Luminance/Chrominance based content. The R600 series chipsets seems to provide one video overlay scaler per display controller. Still this infrastructure would limit us to a single video stream per output, furthermore the converted content would not be compositable. Therefore we would instead opt for utilizing the 3D engine to composite the video content to the scan-out buffer.
The R600 chipset generation supports hardware color space conversion. If this engine is capable of converting most Y/V formats to (A)RGB at up to HDTV resolutions it may most likely provide a back end for a compositable, low overhead, Xv implementation. It could also serve as a starting point to implement non-RGB visuals for X.
It should be possible to involve the AVIVO's Advanced Video Processor with both of the above options, which could dramatically increase the quality of playback, even with lesser quality content.
Another option is to relegate color conversion to a shader. The shader language for this is readily available, so it would be easy to implement, once the necessary driver support for shaders is provided.
Also Glucose would provide another opportunity here: NOVELL has implemented fully compositable Xv support for Xgl. This could easily be added to Glucose.
A time estimate depends on the chosen path and its possible prerequisites as well as on more detailed hardware knowledge.
Accelerating Media Decoding
The XvMC extension, as it stands today, is capable of supporting hardware accelerated MPEG1 and 2 decompression. This provides support for motion compensation, iDCT and slice decoding (VLD). It has wide media player support and the existing acceleration could be readily implemented for R600.
To utilize more of the capabilities of the AVIVO's Universal Video Decoder, it would be possible to extend this support to other video codecs such as MPEG-4, DiVX, WMV9 and H264/AVC. Since this will require more than just adding additional driver side support it might provide a good opportunity to reevaluate the current XvMC specification.
In the 'radeon' driver there exists support for the ATI Rage Theater 200 video decoder. This has been unmaintained since X.Org X11 R6.9. Furthermore it has neither been updated for AVIVO, nor a possibly revised capture engine, and may require significant work. Both direct XVideo and V4L (Video4Linux) support for video input can be provided.