Parallel processing? What good is that?

I have a Core i7 950 CPU.  It has four physical cores (and 4 virtual cores due to hyperthreading).  I started a batch video conversion job and noticed that the CPU usage stayed at around 20% with all the video rendering workload assigned to a single core (well, it cycled through the cores to avoid uneven workload).  I thought to myself, “Well this is lame.  What good is a quad-core CPU if video encoders aren’t multithreaded?”  Turns out they are:

ffmpeg -threads 8

ffmpeg -threads 8

All I had to do was read the ffmpeg manpage to know that ffmpeg will multithread if you tell it to.  I figured since I had 4 physical and 4 virtual cores, 8 was a good number of threads.  Seems to be working well.  Now the overall CPU use is about 45% instead of 20%.  I think the bottleneck is now IO actually as I’m running this from a USB2.0 external drive.


  1. #1 by Phillip on August 6, 2011 - 2:04 PM

    I know Nvidia has CUDA, and ATi has AVT or Stream, and if memory serves me right you have 2 ATI cards SLIed together. I’m just curious why you don’t use that? I know when I try to convert something by CPU processing it takes quite a bit longer than if I were to just let my video card do it.

    • #2 by Joshua on August 6, 2011 - 6:12 PM

      I have to Nvidia cards SLId together. And I was thinking about that but (a) I don’t know how to use CUDA and (b) My CPU is liquid cooled and my video cards are air cooled. I trust my CPU not to overheat more than I trust my two video cards not to overheat.

      • #3 by Phillip on August 7, 2011 - 6:54 AM

        I know it’s just a command line thing in Windows. I’ve used it for cracking passwords before and caught a glimpse of the process when MediaCoder did it.

        Depending on who made the GPU, I can say that every time I’ve had one RMAd I got one back that was better.That’s how I went from a 9800GX2 to a GTX285, one of the 2 fans died. (Thanks EVGA!)

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