How can I programmatically display specific frames in a video using Video Viewer?

I am using MATLAB's Video Viewer app to play videos, and I want to display some selected frames. Specifically, I have a vector containing specific frame indices that I wish to display in sequence, with a pause between each. Currently, the app only provides a manual option to jump to frames using an icon. Is there a method to achieve this programmatically?

Answer 1

[MathWorks Support Team]

Currently, the Video Viewer app does not provide a built-in programmatic interface for controlling playback or displaying specific frames. However, you can use MATLAB functions directly to achieve a similar outcome.

As a workaround, you can use the "VideoReader" object to access frames and then display them using the "imshow" function. Below is an example of how to display a sequence of frames from a video with a pause of 1 second between each frame:

% Create a VideoReader object to read the video file
v = VideoReader('xylophone_video.mp4');

% Vector of frame numbers you want to display
frameIndices = [1, 25, 50, 75, 100];

% Loop through the frame indices
for i = 1:length(frameIndices)
  % Set the current time of the video reader object
  frameIndex = frameIndices(i);
  if frameIndex >= 1 && frameIndex <= v.NumFrames
    % Get the timestamp of video frame to read
    v.CurrentTime = (frameIndex-1) / v.FrameRate;
    % Read the frame at the specified time
    frame = readFrame(v);
    % Display the frame
    imshow(frame);
    title(['Frame index: ' num2str(frameIndex)]);
    % You can apply a fixed pause duration
    pause(1); % Pauses for 1 second
  else
    disp(['Frame number ' num2str(frameIndex) ' is out of range.']);
  end
end

For more details about "VideoReader", "readFrame", and "writeVideo", please refer to the following links:

VideoReader:

https://www.mathworks.com/help/releases/R2023b/matlab/ref/videoreader.html

readFrame: 

https://www.mathworks.com/help/releases/R2023b/matlab/ref/videoreader.readframe.html

writeVideo: 

​​​​​​​​​​​​​https://www.mathworks.com/help/releases/R2023b/matlab/ref/videowriter.writevideo.html