MATLAB: Movie via Frames from Loaded Images

framesimagemovie

I am trying to design a basic visual stimulus (full-field vertical grating with contrast reversal), but am very new to MATLAB. I have created the images I want to use as frames and saved them as jpegs, but when I have tried to use the code to turn these into a movie, I just get a gray screen as my result. If anyone sees what I am doing wrong, I would greatly appreciate any help/guidance.

Here is my code:

reruns = 10;
fps = 4;
nframes = 2;
Frames = moviein(nframes);
load VerticalBars1.jpg
Frames(:,1) = getframe;
load VerticalBars2.jpg
Frames(:,2) = getframe;
movie(Frames, reruns, fps)

Thanks so much in advance for any help you can provide!

Best Answer

Ah, that did seem to help some - thanks! Unfortunately, though, when I repeat the same commands for my second frame (I only have 2 total), the movie I end up with only shows the first frame correctly, and a gray screen for the other. All I changed in my second frame was the file name and the end to "Frames(:,2) = getframe" since I figured the rest of the commands should stay the same. Am I wrong in that assumption, though?

Related Solutions

MATLAB: I keep trying to convert a video grayscale but it gives me an error

Instead of rgb2gray(), use read() and pass it the frame number. Should look something like this:

% Loop through the movie, writing all frames out.
for frame = 1 : numberOfFrames
	% Extract the frame from the movie structure.
	thisInputFrame = read(inputVideoReaderObject, frame);
	
	% Display it
	image(thisInputFrame);
        if ndims(thisInputFrame) == 3
            thisInputFrame = rgb2gray(thisInputFrame);
        end
	axis on;
	axis image;
	caption = sprintf('Frame %4d of %d.', frame, numberOfFrames);
	title(caption, 'FontSize', fontSize);
	drawnow; % Force it to refresh the window.
	
	% Resize the image.
	outputFrame = imresize(thisInputFrame, [outputVideoRows, outputVideoColumns]);
	
	% Write this new, resized frame out to the new video file.
	writeVideo(outputVideoWriterObject, outputFrame);
	
	% Update user with the progress.  Display in the command window.
	progressIndication = sprintf('Processed frame %4d of %d.', frame, numberOfFrames);
	disp(progressIndication);
	% Increment frame count (should eventually = numberOfFrames
	% unless an error happens).
	numberOfFramesWritten = numberOfFramesWritten + 1;
end

MATLAB: Getting error: “Movie cdata must be of type uint8 array” despite the fact that the movie cdata is of type uint8 array.

Double-check that ALL the data is uint8.

 isUint8 = arrayfun(@(x) isequal(class(x.cdata), 'uint8'), frames) % Not tested but should work

If any of the elements of isUint8 are false, check the corresponding frames. My suspicion is that you previously had data in frames and that the T you're using this time has fewer elements than the T you used the first time you created frames. That "leftover" data may be interfering. If the last several elements of isUint8 are false, this would support that guess.

Best Answer

Related Solutions

MATLAB: I keep trying to convert a video grayscale but it gives me an error

MATLAB: Getting error: “Movie cdata must be of type uint8 array” despite the fact that the movie cdata *is* of type uint8 array.

Related Question

MATLAB: Getting error: “Movie cdata must be of type uint8 array” despite the fact that the movie cdata is of type uint8 array.