1 Topic by oviano (edited by oviano 05-01-2014 18:51:35)

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Topic: Question about CPU usage

As per my other posts I've been experimenting a lot with SVP lately, but one thing that I consistently notice is that when I dial-up the settings for higher quality - let's say by reducing the motion vectors grid - then of course the CPU usage (as shown inside the SVP profile popup) increases but once I get to about 40-50% CPU usage I start to get stutter.

Is this normal? I would have expected stutter to occur when the CPU maxes out, but this happens quite some way before maximum CPU usage.

I've noticed this with both 720p and 1080p sources, both of which are directshow captures from a USB3 device. The difference is with 720p I can use higher quality settings (vs 1080p) before CPU rises to 40-50% and stutter kicks in again.

The hardware is as I've mentioned in another post an Intel NUC 54250WYK which is Intel HD graphics 5000 but the CPU is an i5 Haswell. SVPMark gives me a score of the order of about 1000 (you can see my details under my username on your excellent online spreadsheet).

I apologise if my question is a stupid one, I'm trying to better understand how all this fits together - maybe my GPU is maxing out as I increase the settings, if so how can I check that?

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Re: Question about CPU usage

Not too sure if this has anything to do with it, but in my case I had to connect the drive through one of the SATA connections on the mother board. My USB3 connection couldn't handle the flow of information and in my case it was probably because my external hard drive caddy was only running at USB2 speeds.
With that said it makes me wonder if USB3 is fast enough, regardless.

3 Reply by Fanty1972 (edited by Fanty1972 06-01-2014 02:17:31)

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Re: Question about CPU usage

@Jeff:
As long as it takes maximum 90 minutes  to copy a 90 minutes movie to that harddrive, the speed should be fast enough. wink

EDIT:
I imagine one exception. If that HDD is in use (because you download more stuff to that drive at the moment you watch the movie), then it MAY cause problems, depends on the speed you are downloading (More than 100Mbit etc) Maybe you are doing even more like moving stuff from one HDD to another AND downloading AND watching the movie, all from the same device...

In that case I would suggest to copy the movie you are actually watching to a physically different HDD, that is not in use atm. to watch it glitch free, while the other HDD work like hell.

4 Reply by Jeff R 1 (edited by Jeff R 1 06-01-2014 02:17:08)

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Re: Question about CPU usage

Fanty1972
Yes probably, but Oviano has nothing to loose by trying. I always found part of trouble shooting is the process of elimination, even if one of the possible solutions may be improbable.  wink

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Re: Question about CPU usage

@Jeff: yes.

@Oviano:

hen I dial-up the settings for higher quality - let's say by reducing the motion vectors grid

What for example? To 6px?

Its the same for me then. with 6px grid I get stutter @ 60% CPU usuage and 30% GPU usuage. A 7px grid gives me stutterfree motion @30% CPU usuage. (wow, amazing difference  hmm  )

Cant tell you, why it stutters before the hardware hits its limits (100%) but one can say this: smaller grids are not automatically better. They give little bit more fluidity (theoretically) on the cost of ugly artefacts. The 12px pre-setting is a very good compromise already.

6 Reply by oviano (edited by oviano 06-01-2014 06:31:43)

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Re: Question about CPU usage

@Fanty

Well it's with any of the settings, not just the motion vectors grid and yes I'm not hung up about getting that setting particularly low, it was just an example. Basically any combination of settings that pushes CPU up at some point around 40-50% introduces stutter.

However I did notice on closer inspection that the Windows CPU utilisation as reported by Windows 8.1 task manager runs about 10-20% higher than the CPU usage reported by SVP, so typically if SVP reports 40-50 it can be up to 70% for Windows as a whole when it starts stuttering.

Also, the stuttering does coincide with the SVP index becoming less stable, so maybe I just have unrealistic expectations of being able to use the whole CPU, or maybe these stats are averages and don't show the occasionally peaks where it maxes out the CPU and causes frame drops or something.

Finally, I downloaded GPU-Z and found that with SVP hardware acceleration turned on the GPU Load was around 16% maximum and 0% when I turned off SVP hardware acceleration.

I suppose this makes sense because my USB3 capture is uncompressed and I'm not re-encoding or saving it so the GPU doesn't have much to do? Still, it struck me as a bit odd - wouldn't the act of getting the uncompressed frames onto the screen use any GPU at all?

How are you measuring GPU load - are you using the same utility?

@Jeff

Well, with SVP turned off or settings not too high it captures flawlessly so presumably if the bottleneck was the USB speed it would stutter before SVP gets involved?

Unless I've misunderstood you, which is highly likely!

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Re: Question about CPU usage

Uh. I must admid that I just NOW realised that you are talking about video CAPTURE and not playing video from a external HDD as I initially thought you try.

The CPU load I mentioned was the windows task manager numbers. (stutter at 60% windows task manager CPU load, thousands of dropped frames after a few seconds etc)
And it was by playing 1080p MKV, no real life video capture (no epxerience with this in modern times. Last time I experimented with video capturing into the computer was like 1999 when I used an old (maybe 80s) Sony Hi8 Camera over a TV-Card in a Desktop-PC for early Video Chat.  big_smile

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Re: Question about CPU usage

Right, so it seems that 60-70% CPU usage (Windows task manager) is the point at which stutter occurs at least for our scenarios. Maybe that is just the way it is then.

It's interesting that the actual uncompressed capture and display of the HDMI signal uses almost no CPU or GPU, it must literally whack the data from the usb3 capture device (I'm using Inogeni) to the screen.

Re: Question about CPU usage

Remember of hyper-threading  wink
As a example - on a 1-core CPU with HT with one computation thread running you'll get only 50% load in task manager and it'll be not exactly true.

  • Thanks: 5

Re: Question about CPU usage

Thanks, Chainik.

So I guess I need to take these CPU load measurements with a pinch of salt then basically.