MATLAB: Randomly picking a fram from a video in matlab

randomvideo

my problem is that i want to randomly pick a frame from a video , using mmreader , and also i am getting the last frame of the video so that i can set limit, so that when using rand function the number can be picked from 1 to the last frame number,the code is;

    readerobj = mmreader(myvideoname);
    last_Frame_number = read(readerobj, inf);
    end_frame=readerobj.NumberOfFrames;
    random_frame=randi([1,end_frame]);

can someone tell a better solution because this take alot of time because every video has a varying size , and i want to make it more efficient.

Best Answer

For videos that are not variable-frame-rate, the NumberOfFrames property will be set when the object is created. If you are not getting a warning when you create the object (before you even do anything to it) then the NumberOfFrames will reflect the total number in the file.

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MATLAB: Can i start reading frames from a specific index with aviread

Just read the whole movie in:

mov = aviread(movieFullFileName);
% movie(mov);

Then start processing from where you want.

% Determine how many frames there are.
numberOfFrames = size(mov, 2);
for frame = startingFrame : numberOfFrames
    % Extract the frame from the movie structure.
    thisFrame = mov(frame).cdata;

Alternatively, use the VideoReader class and read().

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);
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	% Increment frame count (should eventually = numberOfFrames
	% unless an error happens).
	numberOfFramesWritten = numberOfFramesWritten + 1;
end

Best Answer

Related Solutions

MATLAB: Can i start reading frames from a specific index with aviread

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

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