[mythtv-users] Nvidia CUDA / HD decoding

Michael T. Dean mtdean at thirdcontact.com
Mon Feb 19 16:06:34 UTC 2007

On 02/18/2007 03:53 PM, Todd Ignasiak wrote:
> On 2/18/07, Michael T. Dean <mtdean at thirdcontact.com> wrote:
>> 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.
> That sounds excellent.    Since it's part of OpenGL, does this mean
> that it will be more open, and definitely be available in Linux (and
> Mac OS X)?

It would be available wherever OpenGL 2.0+ or OpenGL 1.4 with GLSL 
support is available.  Are there any GLSL-compliant drivers available 
for OS X?

> As we all know, hardware capabilities have not always
> translated into usable features..

GLSL gives direct access to programming the programmable pixel shaders 
of modern GPU's.  So, it doesn't depend on drivers providing specific 
support for specific functions--only that drivers support GLSL.  You 
then program the shaders to do what you want (i.e. iDCT and MC, decode, 

> Radeons have been doing MPEG2 accel
> for over a decade, but you still can't use it in Linux.

That's what XvMC is--MPEG-2 accel.  XvMC allows using the video card to 
do Motion Compensation (MC) and inverse Discrete Cosine Transform 
(iDCT)--which are required mathematical operations for decoding MPEG-2.  
It could also be implemented to accelerate MPEG-4 and some other 
CODEC's, but isn't worth the driver vendor's time in most 
cases--especially now that they've opened up much more ("unlimited") 
capability with GLSL (as unlimited as the hardware's programmable shader 
implementation, that is).


More information about the mythtv-users mailing list