Errors Using videoWriter and problems closing video writer

EDIT

I have added a basic, minimum working example to highlight my problem below.

% test out the movie making

clear;

start = -1;
ending = 1;

f1 = figure(1);
ax1 = axes;
video = VideoWriter('test.mp4','MPEG-4');
video.FrameRate = 5;
open(video);

for i = 1:100;
    start = start - .1;
    ending = ending + .1;
    xDomain = start:0.1:ending;
    y = xDomain.^2;
    pt1 = plot(ax1,xDomain,y);
    drawnow
    pause(.1)

    F = getframe(f1);
    writeVideo(video,F);
end
close(video)

When trying to run this code, I run into the same error as before:

Error using VideoWriter/writeVideo
Could not write a video frame.

Thank you to those who have responded so far, and I appreciate any further insights people may have.

Thank you!

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ORIGINAL POST

Hello,

I have a script that iterates through a while loop and with each iteration creates a figure that is then saved as a frame and ultimately added to a video. A couple weeks ago this script worked just fine for me, but today I found that I am no longer able to save a video using videoWriter. I haven't made any modifications to the script since it was previously working.

The code to create the figures is:

while t<=tmax+dt/2

  q1=real(ifft2(qh1.*trunc));
  ph1=invert(qh1,wv2inv);
  [u1,v1]=caluv(ph1,k,l,trunc);
    
  dqh1dt=-advect(q1+top,u1+U1,v1,k,l)-beta1*i*k.*ph1-rek*qh1+forcingSpec;  % removed the fft2(r.*q1) term

  if(rem(tc,tpl)==0)
    ts=[ts,t];
    stat=[stat,[0.5*sqrt(mean(vec(u1).^2+vec(v1).^2));sqrt(mean(mean(u1.^2))/mean(mean(v1.^2)));max(max(q1));min(min(q1))]];
    figure(1)
    contourf(x,y,q1,8);title(sprintf('q : t = %g',t));
    colorbar
    drawnow;
    pause(0.1)
    F(counter) = getframe(gcf); % save the frame to a variable F
    counter = counter + 1; % get ready for the next frame
    drawnow;
  end
  

And the code for writing the frames to a video is

%Make a video
video = VideoWriter('withBeta.mp4','MPEG-4');
video.FrameRate = 20;
open(video);
writeVideo(video,F);
close(video);

After the script runs in its entirety, I get the following error:

Error using VideoWriter/writeVideo
Could not write a video frame.

Error in qg1p_step_12810mods (line 98)
writeVideo(video,F);

Futhermore, when testing on the code on just a small subset of the frames, I seem to be able to successfully run

open(video);
for i=1:20; %total number of frames is 50
    i
    writeVideo(video,F(i));
end
close(video);

for about 10 or so, but then I arrive at the same error as before.

Additionally, whenever I try to call

close(video);

I appear to get stuck in an infinite loop in lines 282-292 of VideoWriter.close

while obj(ii).InternalFramesWritten ~= ...
            obj(ii).Profile.VideoProperties.FrameCount
        drawnow('limitrate');
    end

Any advice or suggestions is much appreciated! As I mentioned before, the code worked just fine a couple weeks ago, and I have not made any modifications since then.

[Walter Roberson]

Out of disk space?

[Paul]

My computer is relatively new and according to my storage report I have several hundred Gb available, so I don't think that is the culprit.

[VBBV]

It seems that all frames have not been recorded /captured correctly to F due to loop conditions. Some frames are just empty or nonexistent. Check the loop conditions so that all frames are present in F

[Paul]

Ok thank you for the suggestion. I modified the code so that

F = getframe(gcf);
writeVideo(video,F)

is called inside the loop, immediately after I call

contourf(x,y...)

With my thinking that this would ensure that F is never empty or nonexistant, assuming the the contour call is done correctly (which is appears is the case). Does that seem reasonable?

Even with the change however, I still run into the same error.

[VBBV]

Ok. That's something strange.

[Bruno Luong]

F = getframe(gcf);

That is not robust, since gcf can change if user clicks on another figure.

Also makesure you plot in the right figure (contour with proper target handle). I see you do not control any target handle in your code. I never do such thing in mine.

IIRC, if you can the size of the figure during the loop, writeVideo might also fails.

[Paul]

Thanks for the reply. I have just edited my original post to include a basic, minumum working example. Even when I make sure to not change the size of the figure or click on any other figures, I still run into the same problem.

[Walter Roberson]

perhaps you do not have write permission for the current directory?

[Paul]

I have tried in several different directories and have been able to write other files to those directories, just not videos. I am quite puzzled at this point haha.

[Bruno Luong]

Your MWE code works fine on my PC, meaning no error occurs.

Shooting in the dark, I can see 2 potential causes on your PC:

• Haddware issue
• Some SW/services (may be OS; antivirus) running in the background takes over the file that beeing created and preventing videowrite to work.

[Walter Roberson]

When I look through what has been posted, I cannot be sure that this is Windows. If it were Linux there would be additional potential problems with shared libraries.

If it is Windows then maybe there is a problem with Windows Media Services.

[Bruno Luong]

@Paul Can your drive your code by removing the pause?

[Paul]

@Walter Roberson This is on mac.

@Bruno Luong I tried removing the pause but with no luck.

Thank you for your contined time!

[Walter Roberson]

I did not have any trouble on my R2022b installation on Ventura.

Which MacOS release are you using?

Answer 1

[Paul]

@Walter Roberson Ventura 13.4. I just tried restarting my computer again, and after the restart, I was able to run the code successfully. I am not sure what changed, but I appreciate your help and time!

[Bruno Luong]

"I am not sure what changed"

It could be that the same file are opened by dead zombie videobject that open but not close.

To prevent such thing happens, instead of

open(video);
...
close(video)

do

open(video);
close_trigger = onCleanup(@() close(video));
...
clear close_trigger

If third party SW opens the file without closing it properly, then either you chase to find the culprit or restart your computer.