Timestamp of frame processing using peopleDetect

I am using peopleDetect function to detect human object from video. I got the score from the peopleDetect method but now i need the time at which each frame was processed by peopleDetect function because i need to plot time vs score for some purpose. following code return score for each frame:

frameLeft = readerLeft.step();

    % Detect people.
    [bboxes,scores] = step(peopleDetector, frameLeft);

    if ~isempty(bboxes)
        % Find the centroids of detected people.
        centroids = [round(bboxes(:, 1) + bboxes(:, 3) / 2), ...
            round(bboxes(:, 2) + bboxes(:, 4) / 2)];

        dispFrame = insertObjectAnnotation(frameLeft, 'rectangle' ,bboxes,scores);
    else
        dispFrame = frameLeft;
    end

    % Display the frame.
    step(player, dispFrame);

how can i edit it to get time at each step as well?