How to pause and resume my video which is being displayed on a particular axis in MATLAB app frame by frame.

Right now I'm using this code on the Pause button in the MATLAB app.

if strcmp(app.PauseButton.Text,'Pause')

app.PauseButton.Text='Resume';

pause

elseif strcmp(app.PauseButton.Text,'Resume')

app.PauseButton.Text='Pause';

pause('off')

end

Answer 1

[Sameer]

Hi Rishika

From my understanding, you want to implement a feature in your MATLAB App Designer application that allows users to pause and resume video playback on a specific axis, with the ability to control this action using a single toggle button. Your current approach using pause and pause('off') is not achieving the desired frame-by-frame video control. What you need is a method to programmatically control the video playback, allowing it to be paused at any frame and then resumed from that point, using a flag to manage the playback state within a video display loop.

To control the playback of a video in a MATLAB App Designer app, especially to pause and resume it frame by frame, you need a different approach than just using pause and pause('off'). The “pause” function is used to halt the execution of the MATLAB code for a specified amount of time and doesn't directly control the video playback. To achieve frame-by-frame control, you would typically use a loop to display each frame of the video and a flag variable to control the pause/resume functionality.

Here's a conceptual approach to implement pause and resume functionality for video playback in MATLAB App Designer:

• Initialization: Load the video and initialize variables to control playback.
• Display Loop: Use a loop to read and display each frame of the video on the app's axis. Inside the loop, check the status of a flag variable to determine whether to pause the video.
• Pause/Resume Button Callback: Change the flag variable's value when the button is pressed to control the video playback.

Below is an example code snippet demonstrating this approach:

% Assume you have a video file named 'myVideo.mp4'
videoFile = 'myVideo.mp4';
v = VideoReader(videoFile);

% Initialize a flag for pause/resume
isPaused = false;

% Display Loop
while hasFrame(v) % reads and displays each frame of the video.
    frame = readFrame(v);
    image(frame, 'Parent', app.UIAxes); % Assuming app.UIAxes is the axes where you display the video
    drawnow;
    
    % Check if the pause button was pressed
    while isPaused
        pause(0.1); % Small pause to prevent MATLAB from becoming unresponsive
    end
    
    % You might want to include a small pause here to control the playback speed
    % pause(1/v.FrameRate); % Uncomment to control playback speed
end

% Callback function for the Pause/Resume Button
function PauseButtonPushed(app)
    if strcmp(app.PauseButton.Text, 'Pause')
        app.PauseButton.Text = 'Resume';
        isPaused = true; % Pause the video
    elseif strcmp(app.PauseButton.Text, 'Resume')
        app.PauseButton.Text = 'Pause';
        isPaused = false; % Resume the video
    end
end

I hope this helps!

Sameer