Forums > Jitter

looppoints for live video

Jul 13 2009 | 1:07 pm

greetings users,

noob here.

I’m trying to make an interactive video project/installation.
I would like to be able to grab live video when a user steps in front of the camera and then somehow, set looppoints to playback based on movements or maybe the peak sound of the user.

is there some kind of buffer~ for video that is similar to audio buffer?

I know I should use jit.qt.grab but I’m wondering how I can have the live video play back to some random loop points. I know I’ll probably use peakamp~ as well.

I wonder if this makes sense. I’m new to the forum.

thank you for your time.


Jul 13 2009 | 9:01 pm

I’m trying to do something very similar with a pre-recorded video file. I have a Kenton Killamix MIDI controller, 9 buttons & 9 knobs. I want to have the following setup:

1. Push button 1 and if the value of a number field (will be a frame number from the file) is equal to zero, it grabs the current frame number and loads it into the field. The field does not continuously update, it saves one specific value when the button is pushed.

2. If button 1 is pushed and the frame number field is greater than zero (ie a position has already been saved), it jumps to that frame.

I want to do this entire function with 1 button to leave the other buttons open. It needs to set a loop point on the first press and then go back to that point with any subsequent presses.

Any thoughts from anyone?

PowerMac G5 Quad 8.5 GB, Mac Mini 1 GB, MacBook Pro 4 GB.

Jul 14 2009 | 5:34 pm

To trigger a response based on audio, you could just use the adc~ and past objects. Take a look at the following example:

-- Pasted Max Patch, click to expand. --
Jul 14 2009 | 5:50 pm

To start to record video when the user steps in front of the camera, you will need to set up a simple motion tracking patch, and use the "past" object to trigger an event (recording the video).

Below is an example of how to do this, I am not saying that this is the best way, or only way, just a simple way. You will have to improve on this, making it better (more efficient/ smaller).

-- Pasted Max Patch, click to expand. --
Jul 14 2009 | 5:52 pm

To record frames of video for callback later, i would use the jit.matrixset object.

Jul 30 2009 | 3:24 pm

hi oliver,

thanks for the response. your motion tracking patch doesn’t work as a motion tracker for me. is it working for you?

this is what I have so far:

when a person speaks or says something loud the video clears up.

— Pasted Max Patch, click to expand. —

what I would like to do is set loop/playback points when the peak is at a certain level for a certain length of time thus creating glitch-like video loops of the video when it is not distorted. maybe it continues looping until it is triggered to turn off and go back to grab mode from the persons voice again. I would like it to be completely handsfree.
hope that makes sense.

can someone help me out or point me to the exact tutorial which can explain this? thank you for your time.

Jul 30 2009 | 4:57 pm

Sorry that the motion tracker is not working for you.

You almost have what you are looking for. You just need to plug your audio line into your counter through a "past" object, not a jit.change object. This is because you are not really concerned about the video changing, but changes in the audio… right?

I have created a patch, without your video effect. Take a look.

-- Pasted Max Patch, click to expand. --
Jul 30 2009 | 7:06 pm

hi oliver. please post patches to the forum using the copy-compressed method. see the sticky topic in the main forum for more info.

Oct 16 2009 | 11:24 am

hey oliver,

forgot to thank you. your patch definitely led me in the direction in what I needed to do.

much obliged!

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