jit.desktop speed Mac vs. PC


    Feb 23 2009 | 4:10 pm
    I am working on a patch which processes video taken from different sources. We have already set it up to read video from a file, but we would also like people to be able to capture any video on the screen, i.e. online videos they can't download.
    To accomplish this we've installed a jit.desktop object in the patch. This works fine on our PCs, but not so well on the Macs. I did some testing and found that at our desired size (720x405) the PC, powerful as it is, could run this operation up to almost 200 fps. On my lowly PC laptop (Windows XP, 1.6 GHz), I was still able to get about 20 fps.
    However, running the same basic patch (just the example patch for jit.desktop, modified to our dimensions and with a jit.fpsgui), I only achieved 2.5 fps. This was on a Mac running OS X 10.5.6 with 2 2.8 GHz Quad-Core Intel Xeon processor and an ATI Radeon HD 2600 graphics card. All of these were running Max 5.0.5. I also tried running on several Mac laptops (Macbook Pro with core 2 duo, OS X 10.5.6) with similar slow results when compared with the PC.
    I was able to get better results on a Mac which is a little older, running OS X 10.4.11 with Dual 2 GHz Power PC G5 processors and an ATI Radeon 9600 XT graphics card. That ran at about 14 fps.
    Any idea why there might be such a large gap between systems? Or maybe any other workarounds that could work when distributed?
    Thanks.

    • Feb 28 2009 | 5:35 pm
      Not sure if any of this will help, but...
      In my experience, XP is faster for matrix-based video than OS X. I based this on non-scientific tests of various XP machines vs. various OS X machines. When I tested Max 5/Jitter 1.7 on OS X 10.4.x vs. XP on the same MacBook Pro 2.x core2duo processor, I documented an approx. 20% improvement in XP over OS X using the same patches.
      Also in my experience, I found that QT 6.x on XP seems to make Max/Jitter happier than any 7.x version. I recently downgraded QT to 6 and it improved movie load times with jit.qt.movie.
    • Feb 28 2009 | 7:19 pm
      Thanks for the response. Unfortunately the slowdown we've experienced is on the order of 40 times. If we could get it down to 20%, that would be great.
      Are there any other workarounds we could try to capture video outside the Jitter window?
    • Mar 01 2009 | 11:38 am
      Something changed in recent versions of OSX, whereby the Apple function we are using in jit.desktop for copying the screen contents to a matrix is now much slower than it once was.
      The object will have to be rewritten, which will hopefully happen sooner than later, but I can't say for sure when.
      jb