Moonlight Gets Generic GPU Video Acceleration
Written by Michael Larabel in Free Software on 23 March 2011 at 08:12 PM EDT. 16 Comments
Miguel de Icaza, David Reveman, and their Novell team working on Mono/Moonlight began working on GPU acceleration support. This initial GPU acceleration support was largely focused on accelerating 3D transforms of objects -- just not videos, but all of the Silverlight content -- and other surfaces. They also landed a new rendering pipeline and other work. Pushed into Moonlight's Git repository today is more GPU acceleration work, but this time focusing upon optimizing Moonlight's engine for video rendering operations.

This video acceleration work in Moonlight, which makes Microsoft Silverlight content available under Linux and other non-Windows platforms, does not use VA-API, VDPAU, or any of the other Linux video acceleration APIs. It's a custon OpenGL shader-based solution.

Up to this point when handling video playback, Moonlight has converted H.264 video frames to YUV buffers, perform YUV to RGB conversions, scaled the frame (as an RGB bitmap) to the desired size, and then displayed the frame via transferring its contents through X. Thus it's very dependent upon the CPU and system memory.

With the just-committed GPU hardware accelerated video playback method, the H.264 video frame is still decoded to a YUV buffer by Moonlight, but then submitted directly to the graphics processor. There is then a custom OpenGL shader that's doing the pixel scaling/conversion. That transformed buffer is then composited using the new rendering pipeline already introduced in Moonlight 4.

Using this method, Moonlight is still doing the H.264 video decoding on the CPU, but the frames are being immediately offloaded to the GPU for the rest of the work. On the plus side, this should be quite portable with any OpenGL GPU/driver and does not depend upon any particular video API (VA-API, XvBA, X-Video, XvMC, VDPAU, etc) or Gallium3D state tracker.

For those not concerned with Microsoft Silverlight but the much more abundant Adobe Flash/SWF content, Gnash is carrying VA-API support, Lightspark is using an OpenGL engine (they've even debated having their own Gallium3D state tracker), and Adobe's official Flash Linux plug-in as of a few months back officially supports NVIDIA VDPAU and Broadcom's Crystal HD chipset. Intel VA-API support is forthcoming. Right now though for NVIDIA customers with the binary graphics driver, VDPAU with Flash works well.

This video acceleration work that was just pushed into their Git repository was mentioned on Miguel's blog.
Although native video playback solutions have been doing similar things for a while on Linux, we had to integrate this into the larger retained graphics system that is Moonlight. We might be late to the party, but it is now a hardware accelerated and smooth party.

And what does this looks like? It looks like heaven.

We were watching 1080p videos, running at full screen in David's office and it is absolutely perfect.

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Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter or contacted via

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