Faced by high CPU usage with video decoding and just a poor experience overall when playing back video files with GStreamer, Benjamin has been hacking away at using Cairo/Pixman with GStreamer and providing better hardware acceleration for this open-source multimedia framework. His mailing list messages regarding the details of what exactly he is doing can be found here and here. Benjamin's work has come to fruition and has now vastly improved the desktop experience when watching videos in WebKit, after making changes to GStreamer, Cairo, Pixman, and the X Server. This work though hasn't yet hit the mainline trees nor is it complete, but this is the focus of the Barcelona video hackfest next month.
Developers from Cairo, GStreamer, Pixman, and Intel will be taking part in the video hackfest at Collabora's Barcelona offices. Also what will be discussed is using OpenGL or X Render for video handling, adding support for more image formats (YUV and un-multiplied RGBA) to Pixman/Cairo/X Render, improving SIMD acceleration in Pixman, integrating GStreamer threading better in OpenGL/X/Cairo, and discussing other hardware-accelerated video decoding such as what is offered by XvMC, VA-API, VDPAU, and XvBA.
More information on this work to improve Linux video playback can be found in this mailing list message, a blog post, and a Wiki page.