Forums > Jitter

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 (720×405) 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?


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

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.


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