How Many Cuda Cores to Best my CPU?

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bobbo123

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I currently have an AMD QuadCore cpu running at 3.1 Ghz and a low end video card without Cuda. My time to transcode an h.264 file to mp4 is 125% realtime or one hour of video takes one hour 15 minutes to transcode. I would like to get faster times and keep reading that CUDA is faster "but" I've googled and read that "it all depends." A fast cpu and underpowered CUDA card may result in the CPU being faster than the CUDA card.

So...I'm trying to find a source for how fast can X number of CUDA cores transcode a video file?

How many cuda cores do I need to at least reach real time transcoding? If I got twice as many CUDA cores, would it transcode twice as fast?? Doing an hour video in 30 minutes would be my goal.

thank you.
 
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bobbo123

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Cuda cores do not equal speed. /// I agree, its just a quick and easy proxy all other variables being equal. The linked article below demonstrates this very well. I will still use Cuda Cores as my first filter when choosing a card, THEN go to the other variables including $$$. If I over buy for my current rig, it should still be usable in my next one?

look up benchmarks to see the transcoding speed of your gpu, and then the transcoding speed of each nvidia cuda gpu //// Ah....thats the very issue. As best as I can read the websites, these speeds are listed according to benchmarks or other video cards==IE they all are reported to an unknown standard or one I can't (myself) relate to simple absolute real time on a video file. Most of the sites I find are for gamers and they go off onto fps or frame rates displayed which is exactly the kind of "absolute" measure I want, only for encoding/transcoding which to me means a comparison to "real time" transcoding a 1080 HDTV file?

I'm sure such info is out there, I'm just not finding it. After I find this real time capability, THEN I can compare the value against my AMD Quad Core transcoding "on its own" and if I would rather spend the money on a faster cpu. This is an excellent general review though that echo's what you say:

http://www.studio1productions.com/Articles/PremiereCS5.htm

To restate: does anyone know of a website that charts the time it takes the various video cards to transcode a given video file?
 
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bobbo123

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Here is a tantalizing clue that allows some parallel comparisons: " I use CUDA myself for converting MKV's to MPEG with subtitles, so my 360 can play it (doing over a CPU takes 2 hours, over my GPU takes 15 minutes). /// Thats 8 times faster and just what I want. His Intel cpu is Q9450@3.2 ((thats much faster than my cpu ...so the video card is really fast??? /// and the video card is==EVGA GTX 670. I have to assume his other variables. xxxxxxx So NewEgg shows that card for $350. It has 1344 Cuda Cores. I wonder if half the cores would be half as fast and cost 1/3 as much? That would give me 4x the encoding times I have now which I would happily pay $150 to get.

I'm going to keep looking...at least for another first person report if nothing else. His post is here: http://www.tomshardware.co.uk/forum/326421-33-reason /// Thank you Boris.

He says he is using GTX 285 but posted system spec say the other. Thats ok. "I'm on the trail."
 
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hunter315

hunter315

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You have to pick your video transcoding program and codec first, you get vastly different results depending on both. Some programs can only use a limited number of CPU cores, some can support GPU acceleration, some can use as many CPU cores as you have but no GPU acceleration. Some codecs are lossy and more forgiving, others provide better video quality and compression but also take far longer to render, you will get vastly different render times depending on if you convert to H.264 or MPEG-2.

Its like asking how long every car takes to drive around a track but without specifying a track. You are going to get vastly different lap times between Dayton and Nürburgring. You have to specify your experiment before you can get meaningful results.
 
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bobbo123

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Hunter--I'm just a self taught non-Geek "trying" to make an informed decision somewhere in the ballpark. Not a perfect or exact decision. To restate: My AMD CPU on its own transcodes at %125 Real Time. Boris above said that his card in his system was 8 times faster than his cpu. I do take that as a VERY ROUGH report of Cuda performance, all other variables left unnoticed. I have read, but not confirmed that unlike cpu cores, when you double the Cuda cores ((on a given card)) you do get double the speed. So. I'm just looking for ballpark. Would 16 Cores do what I want with the high $$ cards only needed by Gamers, or do I actually have to get nearer to 500 Cuda Cores...or to be realistic I need 1344 Cuda Cores and the speed boost I would like to have is simply out of my price range.

Right now, I'm starting to think around 500 Cuda Cores at around $150 will give me real time encoding around 30-40% of real time. I could easily be wrong, but so far that is the path/destination of my hurricane tracking gut feel. (sic!)

Something like GeForce GTX 650 Ti. $130. 768 Cuda Cores using 128 Bit GDDR5 Memory. ((http://www.newegg.com/Product/Product.aspx?Item=N82E16814125447))

I'm guessing this card will give me real time encoding of from 30-50% real time?....at a very good price and I prefer Gigabyte to go with my Gigabyte MotherBoard.

I welcome any and all disagreements, ..... other ideas. Charts????
 
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bobbo123

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Well, I'm getting closer to a decision point. This page gives the time to transcode a 15 min video: http://www.xilisoft.com/cuda.html

Interesting they have an Intel i-7 920 processor that WITH 96 Cuda Core Video Card takes 200% real time to transcode. My Lowly AMD quadcore without cuda does the job at 125%. Somehow that doesn't seem right...? (i-7 is 2.66 Mhz-slower than me, gt 240 has 96 Cuda Cores and my card has zero)

AND as you'all counsel, a better program runs the same equipment 5 times faster. Actually looks like my target transcoding rate could be hit by simply getting the software program and having zero cuda cores?=====roughly speaking.

Fun to balance the issues $42 for software, or maybe spend $160 for the Hauppage Capture Box that would hardware encode in the final format requiring NO TIME at all to transcode. Irritating, I am using my brand new AverMedia USB Capture and it records out of synch about 2/3rds of the time. Too much time spent transcoding and WAY too much time spent getting the transcoded file into synch.

I see every card gets complaints about synch issues. Hard to tell which is better, or more relevantly==not so bad. My current DVR records with only about 5% out of synch...but it max's out at 480p.===and I've been thinking about making my collection at that resolution just for synch and speed issues and just get a good upscaling TV or player. Fact Is--I most often rewatch broadcast with my recordings mostly being just a hobby.

Too many variables!
 
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