[mythtv-users] Nvidia CUDA / HD decoding

Michael T. Dean mtdean at thirdcontact.com
Sun Feb 18 18:48:11 UTC 2007


On 02/18/2007 06:19 AM, Mark Kendall wrote:
> On 2/18/07, Blammo <blammo.doh at gmail.com> wrote:
>   
>> Short of doing something like that, are there any other optimizations
>> that come to mind, making that type of playback easier? XvMC can't do
>> anything for, H.264 for example, as far as I can tell...
>>
>> For what it's worth, I can play back some of the most intensive 1080p
>> content I've found (several of the BBC demos) on a Athlon 64 x2
>> @2.9ghz, at about 80% CPU. I'd imagine that's about 50% more
>> horsepower than most people are packing in their front ends right
>> now.. certain more than my main frontend.
>>
>> thoughts?
>>     
>
> Well, I'm sure there's plenty that can be offloaded to the GPU (and
> Google will give you a starter for 10 with h264 offload) but I'm not
> sure CUDA is the way I'd go. It's specific to Nvidia hardware (and top
> end at that) and it's not exactly a standard. Before I'd invest a
> large amout of time in working with something like this, I'd llike it
> to be a portable standard that doesn't require a special version of
> the driver to run.
>
> What's more, a lot of the power (but maybe not as flexible) can be
> accessed through opengl already.

Yep.  And, with OpenGL and OpenGL Shading Language (GLSL)--which is a 
mandatory part of OpenGL 2.0+, and, therefore, supported by ATI and 
NVIDIA drivers--and a sufficiently new video card (i.e. GeForce 6800+ or 
Radeon R520 (don't remember which cards use that chip)), you can program 
the programmable shaders to do 100% of the decoding on the GPU (rather 
than just motion compensation and inverse discrete cosine transform, as 
with XvMC).  You have to have a pretty new card to get support for 
sufficiently complex programming to allow decoding on GPU.

NVIDIA and ATI have both demonstrated this on Windows (and, AIUI, have 
based Pure Video and AVIVO, respectively, around the concept).  Granted, 
NVIDIA announced the capability when they announced the GeForce 6800, 
but took forever (until after the release of the 7800) to actually get 
it working, and ATI didn't release a card that could do it until about 
the time got it working.  But,IMHO, this is the way to go.

Mike


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