Forums > Jitter

A few questions on video and cv.jit

January 7, 2011 | 3:47 pm

Hi again. Just need some clarification on the following and any feedback would be greatly welcomed. Sort of a checklist before I get stuck in.

1. Is it possible through whatever methods/type of camera to get video latency down to a level that it’s not noticeable? It is for use in musical performance so anything under 10 milliseconds would be desired. Video quality is not an issue as it will be used for color and blob detection.

2. Can findbounds be combined with cv.jit be used to track and give the dimensions of more than one different colored shapes? I am aware that cv.jit uses grayscale so this might be an issue. Multiple findbounds works well work tracking position of multiple colors but only gives an average of their position and not their size, so this is where the cv.jit objects would come in. The desire behind this is to track xyz coordinates of colored shapes.

3. Just a quicky, when using the max runtime would you still need to download cv.jit if the patch contains those objects. For other people to use.

Thanks for any input. Searching the forums is a bit of a treasure hunt so I thought I would put a few important things in here.


January 8, 2011 | 3:35 pm


Q1: For lower latency, you need a camera with a fast frame rate. For something less than 10ms, you need at least 100 fps. Some industrial cameras allow you to get very fast frame rates at the expense of resolution. For most people on artists’ budgets, your best best may probably be to complement the camera input with another sensing technology.

Q2: If you use cv.jit, there is very little reason to use jit.findbounds, as it is very, very crude. With a combination of colour filters (see the cv.jit.shift help file for some pointers) and objects such as cv.jit.blobs.centroids, or cv.jit.blobs.bounds you can track multiple coloured objects.

Q3: Other people who use patches that use 3rd party externals such as cv.jit must also have the externals somewhere on their computers. You can distribute it as a collective, which is a bundle that will contain these kinds of dependencies.


January 8, 2011 | 10:41 pm

Ah you wonderful man.

I was saving my appreciation for when I had finished working with some of your objects but you are really advancing the work of so many people I have seen.

I suspected I would be parting company with findbounds and it’s temperment.

I usually get around 150fps with my built in camera but there is still a noticeable delay on the video feed. I say noticeable, I mean for people who have worked with midi latency; long enough to see your eyes still closed after blinking. This I am sure will be graphics card and processor related but I will be moving to a decent desktop soon.

Thank you again for the information and tips. With your efforts I am sure I can create something really special. But I won’t spoil it all just yet.


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