RFC: Video decode acceleration API

Jerome Glisse j.glisse at gmail.com
Wed Mar 28 08:16:19 PDT 2007

On 3/28/07, Roderick Colenbrander <thunderbird2k at gmx.net> wrote:
> I wonder if we need a new extension at all. Modern videocards from ati/nvidia/s3 and perhaps intel too which support formats like mpeg4, vc-1 and others all utilize the fragment shader engine of the gpu. They don't have dedicated decoding hardware for specific compression schemes. Perhaps it is a smarter idea to implement such a library using lets say GLSL. You could have code which works on all cards with fragment shader support. (For modern card this is being worked on).
> Regards,
> Roderick Colenbrander
> > Hi,
> >
> > Attached is a proposal for a video decode acceleration API that I would
> > like to get feedbacks from the X.org community. The main motivation for
> > this proposal is to enable hardware accelerated video decode at various
> > entry-points (VLD, IDCT, Motion Compensation etc.) for the prevailing
> > coding standards today (MPEG-2, MPEG-4, H.264/AVC and VC-1).  After
> > looking at extending XvMC but due to its original design for MPEG-2
> > MotionComp only, it seems making more sense to design an interface from
> > scratch that can fully expose the video decode capabilities in today's
> > GPUs.
> >
> > The current interface is focused on video decode only and is window
> > system independent, so that potentially it can be used with graphics
> > sub-systems other than X.  In a nutshell it is basically a scheme to
> > pass various types of data buffers from the application to the GPU for
> > decoding a compressed bit-stream.  This is very much a work-in-progress
> > and the current draft only defines data structures for MPEG-2 and VC-1
> > decode at the VLD (or slice level) entry-point.  I would like to get
> > this out for critic and feedback before going too much further, and also
> > hopefully make it a community collaborative effort.
> >
> > Thanks,
> >
> > Jonathan Bian
> >
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Actually i believe ATI & Nvidia changed there mind on that and make
dedicated pipeline for video decoding on their newer hardware (as
they did in some of their older hw). Thus i believe such new interface
would definitely help expose such things and if it's not available then
the software can switch to a glsl or fragment program implementation.

Jerome Glisse

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