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XvMC With iDCT Now Working On Gallium3D

Mesa

Published on 21 November 2010 08:47 PM EST
Written by Michael Larabel in Mesa
9 Comments

A month ago there was the surprising work done by Christian K├Ânig to bring XvMC and VDPAU support to the open-source ATI Radeon "R600g" Gallium3D driver for the Radeon HD 2000/3000/4000/5000 series graphics cards. The XvMC state tracker with Gallium3D began working shortly thereafter for accelerating XvMC using shaders with this ATI Gallium3D driver, however, iDCT support was not implemented. Christian though has now added support for inverse discrete cosine transforms to this X-Video Motion Compensation code for Gallium3D.

Christian announced this Sunday morning on the mesa-dev mailing list that the first implementation of XvMC iDCT is now working. The pure matrix multiplication with iDCT is working but the luma/chroma scaling and clamping code is still a bit buggy. It's also inefficient and causing issues for some GPUs when driving the video playback at higher resolutions due to the GPU calculations hitting a bottleneck. This work also led to discovering a few bugs in the Radeon DRM command checker and also required introducing support for signed normalized color buffers in the R600g driver.

The inverse discrete cosine transform (iDCT) is one of the processes (along with motion compensation, which the XvMC state tracker already utilizes) for offloading these tasks from the CPU to the GPU. A discrete cosine transform (DCT) expresses a sequence of finitely many data points in terms of a sum of cosine functions oscillating at different frequencies. For more information on iDCT, see Wikipedia.

Kudos to this German developer for tackling XvMC Gallium3D support for ATI Radeon hardware after previously adding HDMI audio support to the Radeon DRM driver and the now-defunct RadeonHD DDX driver.

As already said on Facebook, we have benchmarks coming soon of this Gallium3D driver compared to its classic Mesa R600 driver and also AMD's proprietary Catalyst driver.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
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