Watch preview while recording snapshots?

Hello! I am trying to watch a video from my IP camera live while also recording the output. My code, below, is successful at showing the first frame, and will record for my specified duration. I have just removed the IP address out of caution. The preview screen and recording will end when I hit the quit key.

Is this watching the preview and recording snapshots in real time possible? How would I implement this?

Thanks!

cam = ipcam('http://<URL>','USER','PASS'); % calls the camera, obscured for privacy :)
KbName('UnifyKeyNames');
quit = KbName('q'); 
preview(cam) % how to continue viewing live footage until closePreview?

frames = 200; 
videoRecord = VideoWriter('camera_test', 'MPEG-4');
open(videoRecord) 
for i =1:frames
    img = snapshot(cam); 
    writeVideo(videoRecord,img) 
    [keyIsDown,~,keyCode]=KbCheck(-1); 
    if (keyIsDown==1 && keyCode(quit)) 
        KbReleaseWait();
        break
    end
    frames = frames+1;
end
closePreview(cam); 
close(videoRecord)

Answer 1

[Abhiram]

Hi @Katie,

To watch a live preview of the IP camera while recording frames in real time in MATLAB, you can create a custom live preview & recording loop which manually shows each frame in a figure using “imshow” or “image” and update it in real time. A sample implementation is mentioned below:

cam = ipcam('http://<URL>','USER','PASS');  % your IP cam
KbName('UnifyKeyNames');
quit = KbName('q');

framesToCapture = 200;
videoRecord = VideoWriter('camera_test', 'MPEG-4');
open(videoRecord);

% Create a figure window for live preview
hFig = figure('Name', 'Live Camera Feed', 'NumberTitle', 'off');
set(hFig, 'KeyPressFcn', @(obj, evt) assignin('base','keyPressed',evt.Key));
assignin('base','keyPressed','');

for i = 1:framesToCapture
    if ~isvalid(hFig)  % Exit if figure is closed
        break;
    end

    img = snapshot(cam);

    if i == 1
        hImage = imshow(img);  % Show first frame
    else
        set(hImage, 'CData', img);  % Update image data
    end
    writeVideo(videoRecord, img);  % Record frame
    drawnow;  % Force update of GUI

    % Check for 'q' key to quit early
    keyPressed = evalin('base','keyPressed');
    if strcmp(keyPressed, 'q')
        break;
    end
end

close(videoRecord);
clear cam;
close(hFig);
disp('Recording finished.');