Vegas 9 very high CPU usage

depasan

depasan

Active member
Hi everybody,

I have just purchased a brand new Dell Studio XPS. Ram 12 gig 3 channel, processor i7 2.93ghz, 1 T hardrive and another hardrive 500 gig, 512 ati card. However when I render from .m2ts to mpg2 DVD architect Video Stream Pal the CPU usage jumps to 98-99% and stays constant to 98-99%. The ram stays to 3.75 GB and CPU to 98%. It works pretty fast, actually like twice as fast as the normal video time but I am worried for the fact that it uses so much CPU power. Is there anything I can do to lower that value.
I did check Options-Preferences-Video and the Dynamic Ram Preview shows Max 350 when there is 11254 MB available and and the maximum number of rendering threads is set to 16. I have no idea how to change these settings, if they need to be changed at all.

When I render from .m2ts to .m2ts or blueray or any kind of HD format everything works perfect.
 
I can give you some general feedback since I have a similar system, although I have 6GB RAM and Vegas Movie Studio, not Pro.

The #threads means the number of simultaneous, parallel processes Vegas will initiate to do the rendering. Since a process requires a CPU to run it this number cannot be more than the number of CPUs your system has. The i7 chip is a quad processor, meaning it has 4 separate processor modules on it, but each processor is a dual CPU, so that yields a total of 8 CPUs to do work.

This in turn means that 8 is the max # threads that can be running at any one time. Vegas Pro has an upper limit of 16, but this is just a limit. The actual number of threads it uses can be no more than 8 because that's all there are.

I've read postings here from people who claim that setting the # threads to less than your actual number of CPUs helpd keep Vegas from crashing. I do not know if this is actually true. What I do know is that if you specify 8 then one (or more) of those CPUs has to stop what its doing (rendering) and do something else if anything else happens on your system (like you open another program or scroll a window that's already open.)

As far as memory (RAM) usage goes, you can specify the max buffer size Vegas uses. For a system with 12GB RAM (that's a lot!) I'd feel safe setting the buffer size to 4 GB. In general the bigger the better since if the buffer size is exceeded Windows intervenes and writes the overage to disk.

Your 100% CPU usage is to be expected since you have all CPUs dedicated to rendering. My systems does that too and I also notice the variable speed fan speed up during rendering. (On my system the fan slows down when the CPU is not busy to make for a quieter system.)

If you cut down the # threads your total CPU usage should drop, but of course so will your speed of rendering. I find that when I render my system takes about 2 1/2 minutes for every 1 minute of realtime video. That's for rendering full HD video @ 24FPS with stereo sound.
 
Why don't you want 100% CPU usage? That means the application is making full use of the processor and rendering out the fastest that it can... this is a good thing!

Also, what OS are you running? It's gotta be Vista or Windows7 or else you won't be utilizing all the nice RAM. If it's a Dell I suspect it's Vista.
 
yabyum said:
Why don't you want 100% CPU usage? That means the application is making full use of the processor and rendering out the fastest that it can... this is a good thing!

Also, what OS are you running? It's gotta be Vista or Windows7 or else you won't be utilizing all the nice RAM. If it's a Dell I suspect it's Vista.
Click to expand...
I totally agree with you on working full speed processor but what if widows needs some processor power for some other application? This specific system that I have bought should have enough processor power for every possible application and what I am trying to understand is why on earth Sony Vegas needs 98% processor power to render on it's fastest speed?
 
yabyum said:
Why don't you want 100% CPU usage? That means the application is making full use of the processor and rendering out the fastest that it can... this is a good thing!

Also, what OS are you running? It's gotta be Vista or Windows7 or else you won't be utilizing all the nice RAM. If it's a Dell I suspect it's Vista.
Click to expand...
It is Vista Home Premium and yes that is quite a lot of ram it is using (even if there are 12 gig available)
 
Rendering CPU Usage explained

Rendering CPU Usage explained

Suppose (for argument's sake) it will take 10 min. of CPU time to render a 5 min. video. At 100% CU usage it will then take 10 min. for that render operation to complete. It can't take less than 10 min. because you can't get more than 100% usage out of a CPU.

However, if you reduce your CPU usage to 50% then the render will take 20 min. That's because you are making the CPU work only 50% of the time; the rest of the time it is idle, meaning it is not doing anything. Consequently 10 min CPU/20 min. real time = 50% CPU utilization.

Rendering is a CPU intensive task, meaning that Vegas will use as much CPU as it can to get the job done. On a system with 8 processors (like in i7) you can specify 8 threads (use all processors for rendering) and Vegas well always consume 100% total CPU while it renders.

Alternatively you could specify (for example) 4 threads, which means Vegas could use at most 50% of the available CPU power during rendering. Of course, it will 100% of those 4 CPUs, but the other 4 will either be idle or doing something else. So depending what else is going on in the computer the usage may be anything from 50 - 100%.

Most people who render want it to go as quickly as possible, so they usually specify the max # threads appropriate for their system and just let it alone while it renders. That way the rendering takes the minimum amount of time.

Your question about what happens if Vegas is running at 100% and the computer has to do something else is quite valid. The answer is both clear and obscure: The clear part is Windows interrupts one (or more) of the Vegas threads and diverts it/them to the other task. This is called "task switching" and is one of the most fundamental parts of every computer operating system.

The obscure part is what happens to Vegas when this occurs. What's supposed to happen is that Vegas simply continues rendering at a somewhat reduced speed until it gets back the processers that were switched away from it. "Supposed to" is the key phrase here. Only the Vegas software developers know how the program actually responds to task switching. It may have to re-render the frames that were in process at the time of the task switch. The worst case, which I don't believe happens, would be for Vegas to simply drop the frames that were interrupted. Rendering is a frame-by-frame activity and my sense is that Vegas does a good job of keeping all the frames properly sequenced. So although I try not to interrupt rendering with other activities I am not afraid to do so if needed.
 
Thank you very much for the detailed and very well done description bbinnard. Rendering does take a lot of processor speed and I do believe that .mpeg2 has got something to do with it. It does not take that much processor speed when rendering in .m2ts or BlueRay, on the contrary the processor usage stays at 40% and the rendering speed is terrific.
 
Running an i7 as well. Cpu is always 100% when rendering. Strange thing is I also tried a phenom quad 1st and it never went to 100%. So I thought I would try the i7..and it whent to 100%. Strange I know. Thought maybe vegas just prefers intel over amd ? But I use 64bit version. FYIt
 
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