bill car

Hi everyone, I'm trying to set up an art project that involves a live webcam input to an iMac, the fullscreen video output then needs to slowly and steadily fall out of sync with the input eg recorded at 25fps and played back at 24fps perhaps. This needs to run for about 3 days continuously so that by the end it is about 3 hours behind the live input.

This is my first time using Jitter or anything like it so any help whatsoever would be greatly appreciated, even if it is just pointing me to the correct learning resources. I have literally no idea where to start.

total-newbie-question

I'm not sure it's entirely possible but someone might have a solution. The problem with video delays is that they are memory expensive because the computer has to store the data before it plays it. I just wanted to give you the heads up that it might be a machine limitation. I had a friend do the exact same project (slowly adding a frame every 2 seconds) but by the time the delay was offset by 3 full seconds the Macbook Pro started to work it's guts out. Then again he was also using motion tracking objects which are memory expensive too and that was all before I learned about optimizing the image.

The object we used primarily was jit.matrixset. It can be a bit complicated to wrap your head around if you are first starting out. Work with a copy of the help patch to start out with and maybe you can develop some more specific questions.

I'm not sure it's entirely possible but someone might have a solution.  The problem with video delays is that they are memory expensive because the computer has to store the data before it plays it.  I just wanted to give you the heads up that it might be a machine limitation.  I had a friend do the exact same project (slowly adding a frame every 2 seconds) but by the time the delay was offset by 3 full seconds the Macbook Pro started to work it's guts out.  Then again he was also using motion tracking objects which are memory expensive too and that was all before I learned about optimizing the image.

The object we used primarily was jit.matrixset.  It can be a bit complicated to wrap your head around if you are first starting out.  Work with a copy of the help patch to start out with and maybe you can develop some more specific questions.

perhaps it would work to just write still frames to disk, and then read them back at whatever rate you need. i guess it depends on how quickly your computer can write to disk and read back from disk one frame of video, but seems very possible it could work.

look at jit.qt.grab, jit.qt.record and jit.qt.movie.

you're going to have to start with the jitter tutorials of course. no way you can just jump into a project like this.

good luck. post your progress along the way and people will be able to offer you specific advice.

perhaps it would work to just write still frames to disk, and then read them back at whatever rate you need.  i guess it depends on how quickly your computer can write to disk and read back from disk one frame of video, but seems very possible it could work.

look at jit.qt.grab, jit.qt.record and jit.qt.movie.
you're going to have to start with the jitter tutorials of course. no way you can just jump into a project like this.

good luck.  post your progress along the way and people will be able to offer you specific advice.


I was trying to read pictures on the fly into jitter last year and 

whenever I read/asynchread/importmovie in jit.qt.player/jit.matrix/ 

jit.gl.texture the processing/display for jitter would stop for a 

second during the read. I ended up having to compile all the pictures 

into a movie file and just read that once.

So I don't think your method would work, but if it did somehow it 

On Mar 8, 2008, at 12:07 PM, Robert Ramirez wrote:

> perhaps it would work to just write still frames to disk, and then 

> read them back at whatever rate you need. i guess it depends on how 

> quickly your computer can write to disk and read back from disk one 

> frame of video, but seems very possible it could work.

> look at jit.qt.grab, jit.qt.record and jit.qt.movie.

> you're going to have to start with the jitter tutorials of course. 

> no way you can just jump into a project like this.

> good luck. post your progress along the way and people will be able 

I was trying to read pictures on the fly into jitter last year and  
whenever I read/asynchread/importmovie in jit.qt.player/jit.matrix/ 
jit.gl.texture the processing/display for jitter would stop for a  
second during the read. I ended up having to compile all the pictures  
into a movie file and just read that once.

So I don't think your method would work, but if it did somehow it  
would be freakin' great!

> perhaps it would work to just write still frames to disk, and then  
> read them back at whatever rate you need.  i guess it depends on how  
> quickly your computer can write to disk and read back from disk one  
> frame of video, but seems very possible it could work.
>
> look at jit.qt.grab, jit.qt.record and jit.qt.movie.
> you're going to have to start with the jitter tutorials of course.  
> no way you can just jump into a project like this.
>
> good luck.  post your progress along the way and people will be able  
> to offer you specific advice.


if you just need the fullscreen output to *very slowly* fall out of 

sync with the input and that's all, why not set your video buffer to 

the maximum size needed (jit.matrixset is the easiest way to go) and/ 

or capable, and ever so slightly move it backwards? you won't get 

three hours, but you might get three minutes.

On Mar 8, 2008, at 9:42 AM, Anthony Trory wrote:

> Hi everyone, I'm trying to set up an art project that involves a 

> live webcam input to an iMac, the fullscreen video output then needs 

> to slowly and steadily fall out of sync with the input eg recorded 

> at 25fps and played back at 24fps perhaps. This needs to run for 

> about 3 days continuously so that by the end it is about 3 hours 

> This is my first time using Jitter or anything like it so any help 

> whatsoever would be greatly appreciated, even if it is just pointing 

> me to the correct learning resources. I have literally no idea where 

if you just need the fullscreen output to *very slowly* fall out of  
sync with the input and that's all, why not set your video buffer to  
the maximum size needed (jit.matrixset is the easiest way to go) and/ 
or capable, and ever so slightly move it backwards?  you won't get  
three hours, but you might get three minutes.

>
> Hi everyone, I'm trying to set up an art project that involves a  
> live webcam input to an iMac, the fullscreen video output then needs  
> to slowly and steadily fall out of sync with the input eg recorded  
> at 25fps and played back at 24fps perhaps. This needs to run for  
> about 3 days continuously so that by the end it is about 3 hours  
> behind the live input.
>
> This is my first time using Jitter or anything like it so any help  
> whatsoever would be greatly appreciated, even if it is just pointing  
> me to the correct learning resources. I have literally no idea where  
> to start.
>
> Thanks.
>
> Anthony


I did a similar thing writing and reading jxf files via a jit.matrix. The limitation is of course disk speed since it's uncompressed data, but if you got one or two fast drives I think you'll be all right.

Total newbie question