Total newbie question

Mar 8, 2008 at 2:42pm

Total newbie question

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

#36264
Mar 8, 2008 at 3:14pm

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.

Best of luck.

#124323
Mar 8, 2008 at 5:07pm

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.

#124324
Mar 9, 2008 at 10:23pm

hey rob

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!

(())_n

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
> to offer you specific advice.

#124325
Mar 10, 2008 at 2:50am

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
> 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

#124326
Mar 10, 2008 at 4:08pm

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.

#N comlet curFrame;
#P outlet 408 487 15 0;
#N comlet on/off;
#P inlet 330 75 14 0;
#N comlet videoIn;
#P inlet 412 152 15 0;
#P window setfont “Sans Serif” 9.;
#P window linecount 1;
#P newex 425 374 63 196617 v storePath;
#P newex 46 124 63 196617 v storePath;
#P newex 569 460 168 196617 jit.matrix 1 char 320 180 @thru 0;
#N counter;
#X flags 0 0;
#P newobj 408 266 66 196617 counter;
#P newex 425 397 142 196617 sprintf write %sstore.%i.jxf;
#P newex 393 234 40 196617 t b b l;
#P newex 393 207 29 196617 gate;
#P newex 408 293 27 196617 t i i;
#P newex 46 78 48 196617 loadbang;
#P message 46 101 63 196617 /Users/…..;
#P newex 425 344 27 196617 t b i;
#P newex 330 169 27 196617 t i i;
#P newex 347 202 32 196617 sel 1;
#P newex 347 226 27 196617 1;
#P fasten 9 0 11 0 430 431 574 431;
#P fasten 8 2 11 0 428 255 574 255;
#P fasten 3 1 9 1 447 366 562 366;
#P fasten 0 0 10 2 352 261 441 261;
#P connect 13 0 9 0;
#P connect 3 0 13 0;
#P connect 6 1 3 0;
#P connect 14 0 7 1;
#P connect 6 0 16 0;
#P connect 10 0 6 0;
#P connect 8 1 10 0;
#P connect 7 0 8 0;
#P fasten 2 0 7 0 335 195 398 195;
#P connect 1 0 0 0;
#P connect 2 1 1 0;
#P connect 15 0 2 0;
#P connect 4 0 12 0;
#P connect 5 0 4 0;
#P window clipboard copycount 17;

#124327

You must be logged in to reply to this topic.