[x264-devel] Re: Speed-up method

[Tomas Carnecky]

Guillaume POIRIER wrote:
> x264 spends the vast majority of its time doing integer computations,
> not floats.
> 
> Last time I looked at it, integer performance on GPU isn't that great
> compared to its float performance.
> I'd like to point out that communications between CPU and GPU are
> expensive, and that there's no shared memory between them.

PCI-E has a very big bandwidth, even for GPU->CPU transport (maximum 
with my 7800 is ~1150 MB/s).

> 
> All in all, I think it's pretty damn hard to get great speed-ups on
> integer code with current generations of GPUs.
> 

It would be theoretically possible to extend x264 to run completely on 
the GPU, after all, cuda is nothing more than an 'extension' to C. Also, 
one of the advantages of cuda is the threading, you get that for free 
basically.

I'm sure the next generation (G90?) will have a much better integer 
performance. x264-cuda would be a nice project :)

tom

-- 
This is the x264-devel mailing-list
To unsubscribe, go to: http://developers.videolan.org/lists.html