Reading video file to Matlab?

Hi friends can any one help me how to read video file(.avi) and process it frame by frame as an image. I tried with

vid1=mmreader('1.avi')

img = getsnapshot(vid1) ;

figure,imshow(img);

but its not working. Any suggestions

[Amith Kamath]

http://www.mathworks.com/matlabcentral/newsreader/view_thread/324666 may help out. Could you also please specify what error you get, and what version of Matlab you're using?

[srikanth]

friends can some one help me on this...... i got stuck because of this

[srikanth]

i am getting an error saying

Undefined function or method 'getsnapshot' for input arguments of type 'uint8'

[srikanth]

version of matlab i am using is 7.9.0.529(R2009b)........

Answer 1

[Image Analyst]

See if this demo helps you any:

% Demo macro to extract frames and get frame means from an avi movie
% and save individual frames to separate image files.
% Also computes the mean gray value of the color channels.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures.
clear;  % Erase all existing variables.
workspace;  % Make sure the workspace panel is showing.
fontSize = 14;

% Change the current folder to the folder of this m-file.
% (The line of code below is from Brett Shoelson of The Mathworks.)
if(~isdeployed)
  cd(fileparts(which(mfilename)));
end

% Check that user has the Image Processing Toolbox installed.
hasIPT = license('test', 'image_toolbox');
if ~hasIPT
  % User does not have the toolbox installed.
  message = sprintf('Sorry, but you do not seem to have the Image Processing Toolbox.\nDo you want to try to continue anyway?');
  reply = questdlg(message, 'Toolbox missing', 'Yes', 'No', 'Yes');
  if strcmpi(reply, 'No')
    % User said No, so exit.
    return;
  end
end

% Open the rhino.avi demo movie that ships with MATLAB.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
movieFullFileName = fullfile(folder, 'rhinos.avi');
% Check to see that it exists.
if ~exist(movieFullFileName, 'file')
  strErrorMessage = sprintf('File not found:\n%s\nYou can choose a new one, or cancel', movieFullFileName);
  response = questdlg(strErrorMessage, 'File not found', 'OK - choose a new movie.', 'Cancel', 'OK - choose a new movie.');
  if strcmpi(response, 'OK - choose a new movie.')
    [baseFileName, folderName, FilterIndex] = uigetfile('*.avi');
    if ~isequal(baseFileName, 0)
      movieFullFileName = fullfile(folderName, baseFileName);
    else
      return;
    end
  else
    return;
  end
end

try
  videoObject = VideoReader(movieFullFileName)
  % Determine how many frames there are.
  numberOfFrames = videoObject.NumberOfFrames;
  vidHeight = videoObject.Height;
  vidWidth = videoObject.Width;
  
  numberOfFramesWritten = 0;
  % Prepare a figure to show the images in the upper half of the screen.
  figure;
  %   screenSize = get(0, 'ScreenSize');
  % Enlarge figure to full screen.
  set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
  
  % Loop through the movie, writing all frames out.
  % Each frame will be in a separate file with unique name.
  meanGrayLevels = zeros(numberOfFrames, 1);
  meanRedLevels = zeros(numberOfFrames, 1);
  meanGreenLevels = zeros(numberOfFrames, 1);
  meanBlueLevels = zeros(numberOfFrames, 1);
  for frame = 1 : numberOfFrames
    % Extract the frame from the movie structure.
    thisFrame = read(videoObject, frame);
    
    % Display it
    hImage = subplot(2, 2, 1);
    image(thisFrame);
    caption = sprintf('Frame %4d of %d.', frame, numberOfFrames);
    title(caption, 'FontSize', fontSize);
    drawnow; % Force it to refresh the window.
    
    % Calculate the mean gray level.
    grayImage = rgb2gray(thisFrame);
    meanGrayLevels(frame) = mean(grayImage(:));
    
    % Calculate the mean R, G, and B levels.
    meanRedLevels(frame) = mean(mean(thisFrame(:, :, 1)));
    meanGreenLevels(frame) = mean(mean(thisFrame(:, :, 2)));
    meanBlueLevels(frame) = mean(mean(thisFrame(:, :, 3)));
    
    % Plot the mean gray levels.
    hPlot = subplot(2, 2, 2);
    hold off;
    plot(meanGrayLevels, 'k-', 'LineWidth', 2);
    hold on;
    plot(meanRedLevels, 'r-');
    plot(meanGreenLevels, 'g-');
    plot(meanBlueLevels, 'b-');
    grid on;
    
    % Put title back because plot() erases the existing title.
    title('Mean Gray Levels', 'FontSize', fontSize);
    if frame == 1
      xlabel('Frame Number');
      ylabel('Gray Level');
      % Get size data later for preallocation if we read
      % the movie back in from disk.
      [rows columns numberOfColorChannels] = size(thisFrame);
    end
    
    % 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;
    
    % Now let's do the entropy filter.
    % First get a gray level image
    grayImage = rgb2gray(thisFrame);
    subplot(2, 2, 3);
    imshow(grayImage);
    caption = sprintf('Gray Scale Image, frame #%d', frame);
    title(caption, 'FontSize', fontSize);
    % Display the filtered image.
    entropyFilteredImage = entropyfilt(grayImage);
    subplot(2, 2, 4);
    imshow(entropyFilteredImage, []);
    caption = sprintf('Entropy Filtered Image, frame #%d', frame);
    title(caption, 'FontSize', fontSize);
  end
  
  % Alert user that we're done.
  finishedMessage = sprintf('Done!  It processed %d frames of\n"%s"', numberOfFramesWritten, movieFullFileName);
  disp(finishedMessage); % Write to command window.
  uiwait(msgbox(finishedMessage)); % Also pop up a message box.
  
catch ME
  % Some error happened if you get here.
  stError = lasterror;
  strErrorMessage = sprintf('Error extracting movie frames from:\n\n%s\n\nError: %s\n\n)', movieFullFileName, stError.message);
  uiwait(msgbox(strErrorMessage));
end

[srikanth]

Thanks Image Analyst this demo helped me a lot.............. but in matlab 2009 as "VideoReader" is not there i used "mmreader" instead

[Image Analyst]

OK. But after 4 years it sounds like it's time to upgrade.

[rock]

what about other formats like 3gp,flv,mp4 etc.....................

[Image Analyst]

I don't know. It might depend on what decoders you have on your system, but I haven't tried any of those formats personally.