Jumpy/Jerky video in Isadora


This question gets asked plenty of times a month over at the Isadora forum. I decided to write a post about it so that it is available to see. This post is more for new users so apologies to the pro users there is nothing new here I’m afraid!

First of all; this post will soon become less important since Mark Conglio discovered that QuickTime had a problem and was resulting in crashes after about 2 hours of running. (see my earlier post called Isadora 1.3 status update)

Anyway…. There are a number of reasons why your video may be jumping or acting strangely. It may seem obvious but the first thing I would like to point out is that we are pushing our machines harder and harder these days and sometimes they simply can’t cope. There is a lot of data in a 1080p movie and in today’s technological era I think (sometimes) we expect too much.

So in no particular order:

Do you need it that big?
This is obviously only my opinion but I have spoken to technicians and artists who are still projecting 640*480 images and they look good (not mind blowing but good for the job). Do you really really need it to be 720 or 1080 in size? Some users will be screaming YES at the screen at me which is fine, read on. But many will not. I have only recently started creeping up to 800*600 for VJ sets. For many years I have had no problem with 320*240. Now obviously that because of the context I use the clips… In a VJ style I add effects, layer images and mix with live feed so it’s not vital that my media is 100% crystal clear. I have also used good projectors which is important, this is mentioned further down.

Can your machine handle it?
I am much more of a software person so this is not my strongest area, saying that I know enough to offer some advise. Make sure you either run your media off a FireWire hard drive – a 7200rpm one ideally. I wouldn’t bother with USB, it’s good but really you need FireWire or sata. Solid State Drives (SSD) are all the rage and I have heard nothing but good reports. Expensive for the size of the storage but even a 64gig one could be a life saver; instead of using it for storage or back up use it as a performing drive?

I have managed to play 4 layers of 720p videos each with motion blur on the very latest MacBook Pros (quad core 2.2Ghz with 8gig ram on 7200rpm drive with snow leopard) but my Intel Core duo is lucky to play two. There is much more about this on the forum but the bottom line is simply – be realistic and sometimes you may have to back down and admit your machine can not handle it.

Does the projector mater?
Yes it does, a good projector will upscale and make your image look good. Let it do the work rather than your machine/isadora doing it. Make sure you use a good quality cable, try not to use many adapters as this will alter with the signal flow. If you need to consider (and please check it out before hand but) cat5/6 cable with some good converters.

Do Isadora effects matter?
Yes in some instances. Some effects don’t use much CPU whilst others, such as motion blur use considerably more. I have seen students turn motion blur up to 100% which has resulted in Isadora practically locking up. This can happen if you connect a midi fader to the motion blur amount, move the slider and the amount of blur goes sky high… Scale the blur to maximum 30% or something appropriate to stop jumping video output. Lots off effects will obviously slow down the video, use the bypass function when you can.

Stage settings?
I try to match my video resolution to the stage output. If most of my videos are 680*480 then I match my stage output to that. Then it’s 1:1 and it makes life a little easier. I will then also set my second window output to 640*480 in system/display settings.

Does core video help?
100% yes! Most, all the pro users on the forum run the core video upgrade. For pro shows I use the core actors as they provide significant video improvements in terms of frames per second and stability. Other users can explain why much better than me but in lay mans terms: core actors send the information to the heart of your machine rather than isadora and the QuickTime framework processing it. (not the best or most accurate description but you get the idea).

Why should I preload video?
This helps isadora load the first part of the video before you even start play it. There is a bulk of information at the begging of a video telling an application how long it is, the size, the format, the compression, the audio, subtitles, etc. So by processing this first it can stop jumps or glitches when triggering a video.

What video format?
This is a very subjective one. I always stick to motion JPEG at 60-90%, others use h.264 and windows tends to be avi. I can only suggest you research this and experiment as much as you can. I often export two or three lots of video in various sizes, format and colour profile as a ‘just in case’. If I am really clever I even export to a native windows format such as avi or wmv so I know I can use a windows machine if things go wrong.

What else?
Well, I always try to keep my laptop cool and well ventilated. This seems to indirectly help in terms of performance. I have used a free app called SMC fan for a number of years to force my internal fan to stay on. I also put my Mac on stand and keep it away from hot equipment; for instance don’t put it on top of an amp or near power supplies. Don’t have any other unnecessary applications open and there is even a way to quit Finder so it does not run any background system processing.

So… Hopefully this helps a few of you. As always please check out the isadora forum, manual and YouTube channel for more information.

Skulpture

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One thought on “Jumpy/Jerky video in Isadora

  1. Pingback: VJ Skulpture Gives us the Lowdown on Jumpy Vid in Isadora

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