Create a movie from images

I have saved some images to a directory and would now like to play these as a movie.

This is what i have done:

% load the images
 images    = cell(30,1);
 for i=1:30
     images{i} = imread(sprintf('%d.jpg',i));
 end
 % create the video writer with 30 fps
 writerObj = VideoWriter('Velocity.avi');
 writerObj.FrameRate = 30;

   % open the video writer
   open(writerObj);
   % write the frames to the video
    for u=1:30    
       % convert the image to a frame
       frame = im2frame(images{u});
       for v=1:30
           writeVideo(writerObj, frame);
       end
   end

   % close the writer object
   close(writerObj);
   implay('Velocity.avi');

This creates a video, but the frame rate is not what i expected; it creates a video of 900 frames and jumps 30 frames a second.

I guess writerObj.FrameRate = 30 doesn't do what i originally thought. Nut now i'm unsure how to get it to play at a rate of 30 frames per second.

Also, why does the video have 900 frames when i only have 30 images?

Help much appreciated.

Answer 1

[N B]

Scratch that.

Just figured it out. I didn't need:

for v=1:30
           writeVideo(writerObj, frame);
       end

in the loop.

It's odd, spent an hour trying to figure this out and within seconds of posting this the solution came to me.

[Josep Llobet]

True!

I did the same.

Thank you for the code

Answer 2

[Guillaume]

I don't think that the call to im2frame is necessary. You can directly write the image returned by imread to the video. (I've never used im2frame, I'm not sure what effect it has in your case).

For each image, you have a v loop that writes it 30 times. 30 images written 30 times = 900 frames. The frame rate does what you asked it. It plays the video at 30 frames per second, but since each group of 30 frame is identical you have in effect 1 different image per second.

Why are writing the same image 30 times?