Question re. Purevideo/Avivo/GPU MPEG2 decoding perfomance

[Titanio]

Wasn't quite sure where to put this, if it's in the wrong forum, sorry! I've looked around for this information but haven't had much luck so I thought I'd ask here - basically I'm looking for any data that might be out there on the relative performance of GPU MPEG2 decoding versus a CPU. I believe Avivo and Purevideo claim to accelerate MPEG2 decoding using the GPU, but any tests or comparisons I've seen focus on quality benchmarks or comparisons based on CPU utilisation, whereas I really need a comparison of their performance or their speedup (or any other GPU acceleration) versus the CPU.

You might wonder why I care once it's realtime, but the project I'm working on benefits from better-than-realtime decoding performance (the faster the better). I really need to be able to say just as part of a presentation that "this is how fast a GPU can do it compared to a CPU". If anyone has any info or knows where I could get it - on any GPU-based decoding solution - I'd really greatly appreciate it! Thanks!

 

[Geo]

Good luck on that. Thot it would be a piece of cake until I started looking around. Apparently mpeg2 acceleration has gotten ubiquitous enough in gpus to not get compared to straight cpu (without gpu assist) much anymore. You might have to go back some years, at which point its pretty useless because it won't have much relevance to today's cpus.

 

[Titanio]

Hehe, yep, it's tricky to find this info. But thanks for trying

It's true that the common concern has shifted from performance to quality/cpu utilisation, but I'm processing decoded video (not for display), and the faster I can decompress the better. I don't need to implement the GPU decoding myself, I just need to be able to say it's faster, and preferably by what margin.

To perhaps take a different angle..does anyone know of any available libraries, commercial or otherwise, that use GPU mpeg decoding? I could perhaps get in touch with the people providing them and look for help there (or if they're free, download and test myself). I'll also email nVidia and ATi, although I kind of doubt I'll get much help there

 

[Geo]

You might try pinging Cyberlink or someone like that. They might be moderately more willing to talk about that, and spent a bit more time on it in a general non-vendor specific kind of way.

Come to think of it, isn't this something you could test for yourself by uninstalling your vid drivers, forcing the card to vanilla vga drivers and making the cpu do the work that way? Then compare to some of the standard results that are out there for gpu-assisted. Wavey had X1900 Avivo ~ 6% a few months back for mpeg2.

 

[Titanio]

Come to think of it, isn't this something you could test for yourself by uninstalling your vid drivers, forcing the card to vanilla vga drivers and making the cpu do the work that way? Then compare to some of the standard results that are out there for gpu-assisted. Wavey had X1900 Avivo ~ 6% a few months back for mpeg2.

That's an interesting idea. To clarify, will a mpeg player I'm using automatically use Purevideo (on my 7800GT), or do only specifc players use it?

Framerate is usually capped at the framerate of the video, though, so I'd need a way to disable that cap too to get the full fps (and I'd need a player that could show me that fps). If I could uncap the framerate, measure it with just the CPU and then measure with purevideo enabled, that'd be reasonable enough I think.

Your reference to wavey's avivo figure - is that 6% figure referring to decoding in 6% of realtime or..?

 

[Geo]

http://www.beyond3d.com/previews/ati/avivo/awu/index.php?p=04 My bad on the percentage --reading too quick.

 

[chavvdarrr]

but... with "vanilla vga" drivers you'll be capped because of supported output formats no?
I may be wrong but I think videocards mainly accelerate output to screen via comfortable pixel formats+overlays+iDCT... not through processing the whole stream... my understandng is that today almost all decoders split the job between cpu and gpu, finding any decoder thats runs only gpu will be hard. I may be wrong...

 

[Titanio]

It does not need to a GPU-only solution, anything that accelerates using the GPU is fine.

I've downloaded a trial of the purevideo decoder..if I could get a player to play a file with the framerate uncapped (i.e. not 24fps but however fast it's decoded), and can compare with hardware acceleration enabled and disabled, that would probably be OK. The first part I'm not sure how to do.. getting a player to display frames as they're decoded rather than at a fixed framerate.

Thanks for the link geo. I think I need absolute performance figures like frames per second to compare performance with and without the GPU though..CPU utilisation doesn't say much about how much faster the decoding is or isn't going unfortunately (as far as I can tell anyway!?).

 

[Geo]

Hmm. I think I'm back to "ask Cyberlink, Nero, or someone like that!"