abnormally high CPU usage during rendering

drw wrote on 7/11/2010, 6:26 PM
I just installed a larger hard drive in my laptop that I use for video editing and imaged the partitions over from the smaller drive that was there prior to the upgrade.

I'm noticing my rendering times have increased after installing the larger drive, and after doing a little searching I noticed my CPUs (dual-core) are maxed out at 100% during rendering, when previously they would be at about 40-50% or so with the old drive rendering the same clip (I have a test clip I've been using for this kind of thing).

Does anybody have any suggestions as to what could cause this high CPU utilization? Or what other system parameters can be measured that could provide more insight into the problem? The high CPU usage is definitely due to VMS according to the Vista system performance utilities, which are the only insight I have currently into the issue.

I'm rendering a short .MOV clip to MPEG-2, which is the same thing I've always done in the past.

Comments

musicvid10 wrote on 7/11/2010, 6:50 PM
You're looking at this from the wrong side. The higher the CPU utilization during render, the better. All that 100% CPU usage means is that something else in the chain is not the bottleneck.

If you are pulling video from one partition and rendering it to another partition on the same large drive, you may be experiencing longer seek times. Setting it up that way certainly is not the preferred configuration because you are performing multiple read-write operations to-from different partitions on the same drive.

drw wrote on 7/11/2010, 9:33 PM
Yeah, I posted too soon on this one before thinking it through. The new disk is behaving just like the old one, after swapping it back and comparing.

The time I was getting lower CPU utilization was when I was getting excessive page faults because I had cranked up the preview memory setting and had less RAM available. After I reduced the preview RAM setting the CPU usage went back up.

For some reason my test render is now taking 11:00 on either disk, when it was taking 6:00 a month ago when I fixed the preview RAM issue. For now I'm not going to worry about it, but it is strange. Its possible I'm confusing which file I was doing the test render on, but I don't think so.
musicvid10 wrote on 7/11/2010, 9:38 PM
1) Put the source files and render folder on separate drives,.
2) Set your Preview RAM for maximum CPU %age during render.
3) eSATA or Firewire is the preferred connection method for an external laptop drive.

I get 99% CPU utilization during render on my laptop this way. That is a good thing.
drw wrote on 7/13/2010, 9:53 AM
I finally figured out what was affecting my render times so significantly, it was the full frame rendering quality setting.

Up until recently I had only been rendering DV format files to MPEG-2 for DVD playback. It seemed that whichever quality setting I chose the render times were very similar so I never paid much attention to that setting.

Lately I started rendering .MOV files, which are not similar to MPEG-2, thus require more processing during rendering. Because they require more processing to convert the differing video and audio formats to MPEG-2, the render quality setting has a significant effect on the render time, as would be expected. Because I had grown accustomed to ignoring the quality setting from the DV rendering experience, I had apparently changed that setting without realizing it, and my render times went way up.