Can I encode video faster with quad core processors?

In this excerpt from Answercast #4, I’ll examine the way video software uses your processors and outline a way to determine if your software is capable of accessing multiple CPU cores at the same time.

Using multiple cores

To be honest, I don’t know. I don’t know if Windows Live Movie Maker actually uses multiple processors but there’s any easy way for you to tell. And I’ll tell you how to do that in a second.

The concept here is that encoding video is a very processor intensive task. So, what you would like is to be able to throw as much processing resource at it as possible.

One way is to simply get a faster processor and hope that the software that you’re using is written so that it will actually understand and use multiple CPU cores at the same time.

Some of the software that I use, like Camtasia video encoder or the Sony Vegas video encoders, absolutely use as many cores as I can give them. So, on my quad core desktop, they throw all four cores at the process. Now, how to tell if it will do it?

Encode a video.

Well, first of all, go grab  Process Explorer (procexp); Download it; let it run and if you like, sort the display by CPU usage so that the process that’s using the most CPU bubbles to the top of the list. Now, go encode a video with Windows Live Movie Maker. If the CPU usage goes to around 50%, then Windows Live Movie Maker only knows how to use one core, no matter how many cores your system has.

So, going from a dual core to a quad-core system will not help you much at all. On the other hand, if you see that the processor usage goes up to 100% and Windows Live Movie Maker is using all of it, that means it’s using both cores. It also means that there’s a pretty good chance that if you put in a quad-core processor or take this to a machine having a quad-core processor, it will indeed use all four cores to do the job.

Will it be faster?

Now, to actually answer the bottom-line question, “Will it run double the speed?” Probably not. There’s some inefficiency in the process of actually doing the encoding and spreading it out over four cores. Not to mention that you’re probably doing some other things on your machine.

But the good news is it will get pretty close. It’s certainly not going to be twice as fast, but it will certainly be more than half again as fast and perhaps somewhere in the 1.8 or 1.9 times as fast. If the software takes advantage of multiple cores, then, yes, it’s actually a potentially pretty good way to get those renders happening a little bit faster.