Vegas only uses 50% cpu

bogosity wrote on 2/23/2005, 3:23 PM
When rendering anything in vegas 5, if I check the cpu usage, it's only at 50%. A two hour render could take only 1 hour! What is limiting vegas??? I have an enabled hyperthreading P4, maybe vegas isn't picking that up?

I've tried checking "disable multiprocessor avi rendering" but my cpu usage is still locked at 50%.

Comments

busterkeaton wrote on 2/23/2005, 4:03 PM
There are many, many threads on this.

Render to mpeg or wmv and tell us what your cpu says.

One thing you know is that with your CPU, you will be able to work in multiple instances of Vegas with no problem
chaboud wrote on 2/23/2005, 4:11 PM
One thing to keep in mind is that the graph reporting processor usage for a hyperthreading processor is highly inaccurate.

In this case, the bulk of Vegas' work is being done on a given thread that is quite likely coming close to maxing out the execution core of your processor, which, in the end, is the limiting factor.

handleyj wrote on 2/23/2005, 10:00 PM
I believe this is normal. The two CPU meters represent total system resources. Even though you only have one CPU, the HyperThreading appears in Windows (and other OSes like Linux) as dual CPUs. If each of the two CPUs hit 50%, then Vegas is using 100% of your CPU.

If you had two physical CPUs, I believe you would see the exact same thing. Each CPU would never show higher than 50%. If you had 4 CPUs, they'd only hit 25% each.

I could be wrong, and maybe someone with a true multi-CPU setup can correct me. But this is what I've seen...
Hulk wrote on 2/23/2005, 11:42 PM
handleyj-

You are exactly right. Each processor in a HT P4, the physical processor and the logical processor would have to be under full load, 50% each to achieve a 100% cpu usage.

This will only occur in highly multithreading optimized applications. TMPGEnc and Nero Recode will floor at HT P4 at 100%.

Right now I believe, from my observations that Vegas will create one thread for audio and one for video. Since audio overhead is generally quite low cpu usage doesn't get that high. But, certain rendering codecs such as wmv are a little better multithreading optimized so you'll see more cpu usage when rendering out to wmv.

I have a feeling that with multicore processors coming very soon we're going to see a lot of software (finally) being optimized for multi cpus.

We've just gone through the era a multi instruction parallelism, that is cpu's executing more than one instruction at a time, now hopefully we'll see multithreading finally come to fruition.

But I have noticed, beyone apps that are multithread optimized that my HT system is MUCH more responsive when say rendering a Vegas project in the background while image editing, or web browsing, or simply changing applications and so on. I turned HT off for a few days for testing purposes and literally couldn't stand it, I guess my workflow has changed since having a HT chip. My next PC will either have HT on a single chip or dual cpus.

- Mark
farss wrote on 2/24/2005, 12:15 AM
Running on dual Xeons Vegas uses only one thread to recnder but all 4 to encode. This I knew, it's not Vegas's fault, there's just no way to multithread DV rendering. But I can run two Vegas renders and each one takes around the same time as it would if only it was running.
Bob.
Hulk wrote on 2/24/2005, 10:46 PM
I'm a little confused. What do you mean by render and what do you mean by encode?

Hulk wrote on 2/25/2005, 11:33 AM
My bad Bob. I know what you mean. Rendering is the "assembly" of the project by Vegas while encoding is taking the assembled or rendered project video stream and encoding to MPEG-2 or some other final delivery format.

And you are right. Very little multithreading occurs during assembly or rendering while quite a bit occurs during encoding to MPEG-2.

If you simply encode a video file straight to MPEG-2 with no filters, fades, etc.. it will show HT processor usage of 90%+. But if you load up a very complicated project with 2D track motion, color correction, etc.. then HT processor usage will drop to less than 60% as the burden of processing is spent on rendering rather than encoding.

Good point.

- Mark