Digging Deeper Into AMD's UVD Code Drop
Yesterday it was exclusively announced on Phoronix that AMD was releasing open-source UVD code so that their open-source Linux graphics driver can finally benefit from GPU hardware-accelerated video playback. Here's some more details.
Now with the Linux kernel and Mesa/Gallium3D code having been published and having time to go through this code myself, after Fatima's article earlier, here's some more details. Of course, if you didn't already, first read AMD Releases Open-Source UVD Video Support for the overview.
- Aside from needing new Radeon DRM (to be found in the Linux 3.10 kernel) and updates to Gallium3D (to be found in the next Mesa release late in 2013), there's also new microcode required.
- From Alex Deucher's Radeon microcode repository, there's new _uvd microcode files as well as updated _rlc microcode files. These UVD microcode binary files are significantly larger in file-size than the other microcode files for the same GPU family. AMD is likely concealing a bunch within these microcode blobs, but NVIDIA is reportedly doing this through a similar method. Other open-source Linux drivers like WiFi adapters also commonly ship microcode/firmware blobs for key functionality, but at least it will continue to work with new kernels...
- "RUVD" is the Gallium3D "driver" that is common code to R600g and RadeonSI but not some entirely new GPU hardware driver. The Mesa changes to support UVD on the HD 4000 through HD 7000 series GPUs amount to around two thousand lines of new code in user-space.
- The kernel-side bring-up of AMD's Unified Video Decoder is also over a thousand lines of code to the Radeon DRM.
- Something from Bridgman: "We actually expected the next round of power management IP to get approved for release before UVD, but it didn't work out that way."
- Some integrated Radeon graphics parts with UVD aren't working on the open-source driver at the moment.
- Based upon copyrights on new files, it looks like AMD has been working on this open-source UVD support since at least 2011.
- The UVD support largely seems to be the work of Christian König, one of AMD's hires for their open-source team two summers ago.
Tests of this open-source AMD UVD support exposed over VDPAU is forthcoming on Phoronix.
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