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How to use a mobile front camera for video recording and show the captured image with face detection?

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ramyakrishna bapanapalli
ramyakrishna bapanapalli on 5 Sep 2019
Answered: Kritika Bansal on 7 Jan 2020
Hello...
Ia m trying to record the video using mobile front camera and do the face detection.
I am able to capture the image and detect the face but not able to record the video.
I want to record the video and show the image with detected face at the same time,
Thanks in advance.
m=mobiledev;
% Create the face detector object.
faceDetector = vision.CascadeObjectDetector();
% Create the point tracker object.
pointTracker = vision.PointTracker('MaxBidirectionalError', 2);
% Create the webcam object.
cam = camera(m,'front');
% Capture one frame to get its size.
videoFrame = snapshot(cam,'immediate');
frameSize = size(videoFrame);
% Create the video player object.
videoPlayer = vision.VideoPlayer('Position', [100 100 [frameSize(2), frameSize(1)]+30]);
runLoop = true;
numPts = 0;
frameCount = 0;
while runLoop && frameCount < 400
% Get the next frame.
videoFrame = snapshot(cam);
videoFrameGray = rgb2gray(videoFrame);
frameCount = frameCount + 1;
if numPts < 10
% Detection mode.
bbox = faceDetector.step(videoFrameGray);
if ~isempty(bbox)
% Find corner points inside the detected region.
points = detectMinEigenFeatures(videoFrameGray, 'ROI', bbox(1, :));
% Re-initialize the point tracker.
xyPoints = points.Location;
numPts = size(xyPoints,1);
release(pointTracker);
initialize(pointTracker, xyPoints, videoFrameGray);
% Save a copy of the points.
oldPoints = xyPoints;
% Convert the rectangle represented as [x, y, w, h] into an
% M-by-2 matrix of [x,y] coordinates of the four corners. This
% is needed to be able to transform the bounding box to display
% the orientation of the face.
bboxPoints = bbox2points(bbox(1, :));
% Convert the box corners into the [x1 y1 x2 y2 x3 y3 x4 y4]
% format required by insertShape.
bboxPolygon = reshape(bboxPoints', 1, []);
% Display a bounding box around the detected face.
videoFrame = insertShape(videoFrame, 'Polygon', bboxPolygon, 'LineWidth', 3);
% Display detected corners.
videoFrame = insertMarker(videoFrame, xyPoints, '+', 'Color', 'white');
end
else
% Tracking mode.
[xyPoints, isFound] = step(pointTracker, videoFrameGray);
visiblePoints = xyPoints(isFound, :);
oldInliers = oldPoints(isFound, :);
numPts = size(visiblePoints, 1);
if numPts >= 10
% Estimate the geometric transformation between the old points
% and the new points.
[xform, oldInliers, visiblePoints] = estimateGeometricTransform(...
oldInliers, visiblePoints, 'similarity', 'MaxDistance', 4);
% Apply the transformation to the bounding box.
bboxPoints = transformPointsForward(xform, bboxPoints);
% Convert the box corners into the [x1 y1 x2 y2 x3 y3 x4 y4]
% format required by insertShape.
bboxPolygon = reshape(bboxPoints', 1, []);
% Display a bounding box around the face being tracked.
videoFrame = insertShape(videoFrame, 'Polygon', bboxPolygon, 'LineWidth', 3);
% Display tracked points.
videoFrame = insertMarker(videoFrame, visiblePoints, '+', 'Color', 'white');
% Reset the points.
oldPoints = visiblePoints;
setPoints(pointTracker, oldPoints);
end
end
% Display the annotated video frame using the video player object.
step(videoPlayer, videoFrame);
% Check whether the video player window has been closed.
runLoop = isOpen(videoPlayer);
end
% Clean up.
clear cam;
release(videoPlayer);
release(pointTracker);
release(faceDetector);

Answers (1)

Kritika Bansal
Kritika Bansal on 7 Jan 2020
Hi,
You can possibly use VideoWriter to save the video. In order to do so, you can make use of the following code snippet and add it in your code at the appropriate places:
%add the following where you are creating objects (before the loop)
v = VideoWriter(<filename>); %make sure that your current directory is writable
open(v);
%add the following inside the loop
writeVideo(v, videoFrame);
%add the following where you are releasing all the objects
close(v);
For more information, you can refer to the examples in the documentation page here: https://www.mathworks.com/help/matlab/ref/videowriter.html

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