getframe not updating when outputting video/images

Hello, thanks for reading this,

I have a image that I'm outputting to a gif/avi video, and neither one seems to work.

When I use the code:

    lseg = getframe(h);
    set(gcf,'InvertHardCopy','off')
    imwrite(lseg.cdata, outputFileName, 'WriteMode', 'append');
    camorbit(1, 0, 'data', [0 0 1])
    drawnow

and see my image stack, they're all the same image: the lseg frame never gets updated when I rotate with camorbit. Additionally, when I try to make a video with:

    fps = 60; sec = 10;

    vidObj = VideoWriter('newfile.avi');
    vidObj.Quality = 100;
    vidObj.FrameRate = fps;

    open(vidObj);
    for i=1:fps*sec
      camorbit(0.9,-0.1);
      writeVideo(vidObj,getframe(gcf));
    end
    close(vidObj);

I get a 10 second video of a static frame: again, getframe never gets updated to the frame rotated by camorbit.

When I view the image as its writing, I can see the figure rotating. Its just when MATLAB writes to file, the written file frames are not updated.

Any ideas?

[Brian]

Actually, I got the video export to work by including the line

    drawnow

after camorbit.

Answer 1

[Brian]

Use drawnow after camorbit and it works.

Answer 2

[Chad Greene]

I've had troubles with getframe in the past. I've had better luck using export_fig . The syntax would be

frame = export_fig(gcf); 
writeVideo(vidObj,frame);

[Brian]

Thanks, I tried out this function but I got a different error: this one pertaining to frame dimensions.

I think my frame size must change during the animation, because a few frames in I get the error: Frame must be 435 by 344.

Is it possible to force my current axes handle to a set resolution?

[Brian]

Just a update, I manually switched the axis to a value, and while it ran a bit longer, I wasn't able to get a full 360 degree turn, it stopped midway.

Why would the resolution of the movie suddenly change?

[Chad Greene]

I think you'd need the -nocrop option in export_fit. That's because by default export_fig crops the frame to the dimensions of where plotted objects appear on the figure. If some data being plotted in your figure starts to go near the edge of the frame, export_fig will increase need to increase the size of the frame. Using the -nocrop option prevents the automatic frame sizing.