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Index › Programming Questions & Help › Video Capture,  Movie Playback,  Vision Libraries › JMC: display several video frames simultaneously
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JMC: display several video frames simultaneously? (Read 1231 times)
phling
JMC: display several video frames simultaneously?
Feb 4th, 2010, 2:29pm  
i'm trying to display about 200 instances of one video, as described here.
Using JMC to draw the video texture in OpenGL works fine, frameRate is a-okay.

i'm looping through all tiles and setting the position in the video accordingly, however it is displaying the same video frame for all tiles in the loop, even if it should offset the playback position by some amount for each tile, i.e. it should look like this:

...

but does look like this:

...


Code:
import processing.opengl.*;
import peasy.*;
import javax.media.opengl.*;
import java.util.*;
import jmcvideo.*;


PGraphicsOpenGL pgl;
GL gl;
PeasyCam cam;
JMCMovieGL3D scan;
float count = 0;

void setup()
{
	size(800, 600, OPENGL);
	cam = new PeasyCam(this, 1000);
 	cam.setRotations(.8, 0, 0);
 	cam.setMinimumDistance(50);
 	cam.setMaximumDistance(4000);
	
	scan = new JMCMovieGL3D(this, "scan1.mov", RGB);	
}

void draw()
{
	background(0);
	doGLStuff();
	count+=0.00005;
}

void drawSlices(int num)
{
	float perc = 0;
	for(int i = 0; i < num; i++) 
	{
		perc+= 1.0/num;
		perc = (perc+count)%1;
		pushMatrix();
		scan.setPlaybackPercentage(perc);
		scan.image(gl, -scan.width/2, -scan.height/2, -(num/2*27)+i*27, scan.width, scan.height*1.4);
		popMatrix();
	}
}

void doGLStuff()
{
	pgl = (PGraphicsOpenGL) g;
	gl = pgl.beginGL();
	gl.glDisable(GL.GL_DEPTH_TEST);
	gl.glEnable(GL.GL_BLEND);
	gl.glBlendFunc(GL.GL_SRC_ALPHA, GL.GL_ONE);
	
	drawSlices(200);
	
	pgl.endGL(); 		
}


it seems that setPlaybackPercentage() does not update during the loop?
does the setPlaybackPercentage() method not update quick enough, or only at the end of draw() or something? i've had a look at the JMC source, but couldn't do anything helpful to it...

is there a better way to access the pixels of the video directly …?
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« Last Edit: Feb 14th, 2010, 6:00am by phling »  
 
koogy
Re: JMC: display several video frames simultaneously?
Reply #1 - Feb 4th, 2010, 2:40pm  
have you checked that this:

perc+= 1.0/num;

isn't returning the same number all the time (num is an int...). actually, that looks ok

but do you mean this:

perc = (perc+count)%1;

or should that be %100 as it's a percentage?
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phling
Re: JMC: display several video frames simultaneously?
Reply #2 - Feb 4th, 2010, 2:51pm  
that should be okay, the percentage function wants a 0.0 - 1.0, not real percentage…

just doublechecked:

perc+= 1.0/(float)num;
perc = (perc+count)%1.0;
println(perc)

this is not the culprit.
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koogy
Re: JMC: display several video frames simultaneously?
Reply #3 - Feb 4th, 2010, 3:23pm  
ah, ok. docs and examples does seem to support that (badly named variable though)

http://www.mat.ucsb.edu/~a.forbes/PROCESSING/jmcvideo/javadoc/

all the examples use centerImage:

"centerImage(javax.media.opengl.GL gl)
Draws the image across the center of the parent canvas, preserving the original aspect ratio of the video."

and you're using image:

"image(javax.media.opengl.GL gl, float x, float y, float w, float h)
Draws the video texture at the specified coordinates."

and i wonder whether there's a difference between 'the image' and 'the video texture' and whether you need to call texture() before image():

"texture(javax.media.opengl.GL gl)
Binds the video frame to this object's texture."

um, "Not needed if you are calling the automatic "image" methods.". what does that mean?
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koogy
Re: JMC: display several video frames simultaneously?
Reply #4 - Feb 4th, 2010, 3:28pm  
</strawclutching>
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phling
Re: JMC: display several video frames simultaneously?
Reply #5 - Feb 4th, 2010, 4:25pm  
hmmm i think the first argument to image() does take care of the texture() thing already…
(adding texture() doesn't seem to do anything at least)

in the JMC source there's one thing called MediaProvider, which seems to hold the video data and probably provides low level access… .dunno maybe one can force it to update the video  - however i can't find a javadoc for it. hmmm….

edit: mediaProvider is part of sun's internal jmc API, so it's not public and discouraged to use etc etc… hrmpfff..
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« Last Edit: Feb 4th, 2010, 5:27pm by phling »  
 
phling
Re: JMC: display several video frames simultaneously?
Reply #6 - Feb 6th, 2010, 12:15pm  
so i actually went and installed Windows, to be able to use the glgraphics and gsvideo libraries instead, as it looked like there is more accurate access to video data from it. What can i say?

  • nope. i couldn't get any closer to what i want to do.
  • jmcvideo is much faster at rendering videos as gl textures, at least in my setup.


conclusion: stuck.
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