sascha pohflepp

what's the best way to time-stretch video in jitter, coming either 

from a file or (ideally) from jit.qt.grab ?

what's the best way to time-stretch video in jitter, coming either  
from a file or (ideally) from jit.qt.grab ?

         www.blinksandbuttons.net
blog.plugimi.com


time-stretch-live-video

yes it is possible for live video, but you might want to think 

if video is a series of still images, what does it mean to time 

stretch video? does it mean to throttle the flow of frames? this will 

cause a delay from real-time and the longer you want the slow down, 

the more memory you will need. eventually you'll have to stop or 

speed up the video. in fact, if you want to 'speed up' live video, 

you'll either have to start with a delay or build a time machine (not 

possible until Max 8.0 comes out around 2057). either way you will 

another issue is what happens between frames. if you just slow down a 

video, slow down the flow of frames, it will look choppy. the easiest 

solution i can think of is to create some sort of fade between 

successive frames the lasts as long as the time between frames.

you can make a video buffer with jit.matrix, jit.matrixset, an array 

of jit.matrix objects in javascript, or an array of jit.gl.texture 

objects in javascript. i'm sure there are other ways. maybe an array 

On Oct 24, 2006, at 7:51 AM, Gary Lee Nelson wrote:

> Use rate message to jit.qt.movie for file. Not sure it would be 

> On 10/24/06 6:45 AM, "sascha pohflepp" wrote:

>> what's the best way to time-stretch video in jitter, coming either 

>> from a file or (ideally) from jit.qt.grab ?

https://cycling74.com/mailman/listinfo/jitter

yes it is possible for live video, but you might want to think  
through this some more.

if video is a series of still images, what does it mean to time  
stretch video? does it mean to throttle the flow of frames? this will  
cause a delay from real-time and the longer you want the slow down,  
the more memory you will need. eventually you'll have to stop or  
speed up the video. in fact, if you want to 'speed up' live video,  
you'll either have to start with a delay or build a time machine (not  
possible until Max 8.0 comes out around 2057). either way you will  
need to make a video buffer.

another issue is what happens between frames. if you just slow down a  
video, slow down the flow of frames, it will look choppy. the easiest  
solution i can think of is to create some sort of fade between  
successive frames the lasts as long as the time between frames.

you can make a video buffer with jit.matrix, jit.matrixset, an array  
of jit.matrix objects in javascript, or an array of jit.gl.texture  
objects in javascript. i'm sure there are other ways. maybe an array  
of matrices or textures in a poly~?

> Use rate message to jit.qt.movie for file.  Not sure it would be  
> possible with live video.
>
>
> On 10/24/06 6:45 AM, "sascha pohflepp"  wrote:
>
>>
>>  hi there
>>
>> what's the best way to time-stretch video in jitter, coming either  
>> from a file or (ideally) from jit.qt.grab ?
>>
>>
>> cheers
>> sascha
>>

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https://cycling74.com/mailman/listinfo/jitter


the simplest way to timestretch frames which are being displayed 

slower than realtime (as jonathan says 'fade between successive 

there is also a gl shader (gpu) version of jit.slide located in 

i would also plug 'tap.jit.delay' abstraction in the Tap Tools 

Collection which is a convenient way to make a delay buffer (just 

specify N frames of delay) on its own it just delays the output, 

(doesn't allow you to manipulate the buffer) - however its an 

excellent example of how to use and control jit.matrixset.

> another issue is what happens between frames. if you just slow down 

> a video, slow down the flow of frames, it will look choppy. the 

> easiest solution i can think of is to create some sort of fade 

> between successive frames the lasts as long as the time between 

> you can make a video buffer with jit.matrix, jit.matrixset, an 

> array of jit.matrix objects in javascript, or an array of 

> jit.gl.texture objects in javascript. i'm sure there are other 

> ways. maybe an array of matrices or textures in a poly~?

the simplest way to timestretch frames which are being displayed  
slower than realtime (as jonathan says 'fade between successive  
frames' ) is to use jit.slide or you can also try the  jsinterpframes-example.patexample patch.

there is also a gl shader (gpu) version of jit.slide located in  
shaders folder for those so inclined.

i would also plug 'tap.jit.delay' abstraction in the Tap Tools  
Collection which is a convenient way to make a delay buffer (just  
specify N frames of delay) on its own it just delays the output,  
(doesn't allow you to manipulate the buffer) - however its an  
excellent example of how to use and control jit.matrixset.

> another issue is what happens between frames. if you just slow down  
> a video, slow down the flow of frames, it will look choppy. the  
> easiest solution i can think of is to create some sort of fade  
> between successive frames the lasts as long as the time between  
> frames.
>
> you can make a video buffer with jit.matrix, jit.matrixset, an  
> array of jit.matrix objects in javascript, or an array of  
> jit.gl.texture objects in javascript. i'm sure there are other  
> ways. maybe an array of matrices or textures in a poly~?
>
> best,
> jonathan


Sorry, I dont know the answer to this off the top of my head... Just saying hi and whatnot. I did not know that you posted in this forum ;-)

As for time-stretching... I wonder if Max can exploit the time-stretching features found in Quicktime 7. Open a movie or audio file and then press apple+k (on a Mac, not sure on Windows) and you will get options for pitch shifting audio as well as time-stretching audio/video.

Seeing as Max/Jitter and Quicktime are good buddies (^_^) maybe this functionality is exposed in Max/Jitter - if it's not perhaps we can ask the developers to add it in a future version.

Next time we meet we should have a Max hacking session I really want to come to Berlin in January). It's where I spend most of my time ;-)

Sorry, I dont know the answer to this off the top of my head... Just saying hi and whatnot.  I did not know that you posted in this forum ;-)

As for time-stretching... I wonder if Max can exploit the time-stretching features found in Quicktime 7.  Open a movie or audio file and then press apple+k (on a Mac, not sure on Windows) and you will get options for pitch shifting audio as well as time-stretching audio/video.

Next time we meet we should have a Max hacking session I really want to come to Berlin in January).  It's where I spend most of my time ;-)

time-stretch (live) video?