Not sure why I'm seeing so much CPU usage when using CUDA

[rob79]

Hi everyone,

So, I'm new to MediaCoder but so far it's the best piece of software I've found for "downscaling" HD videos to SD (I need to do this because my streaming device doesn't support HD). Everything is working great, but I'm a bit perplexed at one issue I've run into.

I have a CUDA enabled card (Nvidia GeForce 9800GT) and I've got MediaCoder set to use it, and I know it is using it (to a certain extent), but for some reason when I transcode something my GPU usage never goes above ~12% usage while my CPU (AMD Athlon 3800+ - dual core, 2.2ghz) usage jumps to 90%-100% on both cores.

Is that normal? Shouldn't MediaCoder be offloading the majority of the work to my GPU and leaving my CPU alone? As I said, I know that it's using CUDA since it only takes around 15 minutes for me to transcode an hour long video, whereas if it was using my CPU only it would take, well, about an hour.

I'm using the 64 bit version of MediaCoder in Win7 (64 bit, obviously LOL). Besides the other specs I've mentioned I have 4GB of RAM and *tons* of free HDD space.

tl;dr: Why does MediaCoder use 100% of my CPU and only 12% of my CUDA enabled GPU when transcoding?

Thanks for reading, I look forward to any insight you can provide!

[sharkbite]

matey - short answer is that decoding is done by Mencoder by the CPU which passes data to the CUDA encoder done by the GPU....

You have a comparativly low spec CPU and a whopper of a gpu....I doubt the athlon could decode fast enough to stress the 9800..

(I have a phenom x6 1090t feeding a GTS250 and have almost the opposite problem....)

both CPU and GPU are at 30% - and i would like mediacoder to use more resources so that my encodes go faster....

can't seem to get that happening

[oldfart59]

I seem to have a cpu vs. gpu issue to. Although I assume this is the norm. I have a Phemon II x6 1090T also. Win7x64 w/8GB ram and an NVidia 560GTX. With Mediacoder I get 90% cpu (mencoder does the decoding) and GPU-Z says 34-40% gpu. I have another program that uses 30-35% cpu and about 60% gpu but Mediacoder still encodes faster. Its weird. But why wouldn't Mediacoder use more gpu? I'm not complaining though. I re-encode 1920x1080 to the same size but remove subs and extra languages and reduce bitrate to 8000k and I get around 100 fps. I was just wondering why.

[alexisrgl]

Same "problem" here.
I have a Core 2 Quad Q8400 and a GTX560TI HAWK.

CPU use 100% all the time
GPU use 20%

mencoder.exe and cudaH264Enc.exe uses all my CPU

[madisonbrooks]

I have Intel T8100 CPU with Nvidia GeForce 8600M runnnin Windows 7 x64. Since I'm on Windows 7, my task manager shows that CUDA takes 50% CPU, since other 2 CPU tasks share 50%. When I was on Vista it was okay, CUDA used not more than 1-3%, and the rest used by CPU tasks. Any hints what could be the problem? My Boinc version is 6.10.17 and Nvidia driver version is

NVIDIA GPU 0: GeForce 8600M GS (driver version 18681, CUDA version 2020, compute capability 1.1, 256MB, 32 GFLOPS peak)

Boinc shows that CUDA uses 0.01 CPUS + 1.00 NVIDIA GPUs. Task manager tells that CUDA uses 50% CPU.

One more thing I've noticed, all Boinc processes run in *32 bit mode.. Strange, I've installed x64 version of Boinc...

Thank you.

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