Hand detection code not working while playing video?

Question

I'm working on hand detection and tracking. the problem is i have developed the code(shown below) for detecting hand in an image and its works(shown in image) but the problem is this that when i use a recorded video to run the same code no hand is detected or even tracked(shown in image).

the code for the video is

filename = 'hand_2.wmv';
video = vision.VideoFileReader(filename);
player = vision.DeployableVideoPlayer('Location', [10,100],'FrameRate',60);

while ~isDone(video)
    img_orig = step(video);

    % Capture the dimensions
    height = size(img_orig,1);
    width = size(img_orig,2);

    %Initialize the output images
    out = img_orig;
    bin = zeros(height,width);

    %Convert the image from RGB to YCbCr
    img_uint8 = uint8(img_orig);
    img_ycbcr = rgb2ycbcr(img_uint8);
    Cb = img_ycbcr(:,:,2);
    Cr = img_ycbcr(:,:,3);

    %Detect Skin
    [r,c,v] = find(Cb>=67 & Cb<=137 & Cr>=133 & Cr<=173);
    numind = size(r,1);

    %Mark Skin Pixels
    for i=1:numind
        out(r(i),c(i),:) = [0 0 255];
        bin(r(i),c(i)) = 1;
    end

    % Detect radius
    [x1,y1] = find(out(:,:,3) == 255, 1,'first');
    [x2,y2] = find(out(:,:,3) == 255, 1, 'last');
    if isempty(y1) && isempty(y2)
        y1 = 2; y2 = 0;
    end

    % Detect Hand Center
    hits = 0;
    hitsArr = zeros(1,height);
    for i = 1:height
        hits = numel(find(bin(i,:) == 1));
        hitsArr(i) = hits;
    end
    maxHitr = max(hitsArr);
    y =  find(hitsArr == maxHitr,1,'first');

    hitsArr = zeros(1,width);
    for i = 1:width
        hits = numel(find(bin(:,i) == 1));
        hitsArr(i) = hits;
    end
    maxHitc = max(hitsArr);
    x = find(hitsArr == maxHitc,1,'first');

    label = 'Hand';
    position = [x y abs(y2-y1)/2; x y 1];
    img_out = insertObjectAnnotation(img_orig,'Circle',position,label);
    step(player, img_out);

end

release(video);
release(player);

and for detecting a single image the code is:

%Read the image, and capture the dimensions
tic;
img_orig = imread('65.png');
height = size(img_orig,1);
width = size(img_orig,2);

%Initialize the output images
out = img_orig;
bin = zeros(height,width);

%Convert the image from RGB to YCbCr
img_ycbcr = rgb2ycbcr(img_orig);
Cb = img_ycbcr(:,:,2);
Cr = img_ycbcr(:,:,3);


%Detect Skin
[r,c,v] = find(Cb>=67 & Cb<=137 & Cr>=133 & Cr<=173);
numind = size(r,1);
numcol = size(r,2);

%Mark Skin Pixels
for i=1:numind
    out(r(i),c(i),:) = [0 0 255];
    bin(r(i),c(i)) = 1;
end

% Detect radius
[x1,y1] = find(out(:,:,3) == 255, 1,'first');
[x2,y2] = find(out(:,:,3) == 255, 1, 'last');

% Detect Hand Center
hits = 0;
hitsArr = zeros(1,height);
for i = 1:height
    hits = numel(find(bin(i,:) == 1));
    hitsArr(i) = hits;
end
maxHitr = max(hitsArr);
y =  find(hitsArr == maxHitr,1,'first');

hitsArr = zeros(1,width);
for i = 1:width
    hits = numel(find(bin(:,i) == 1));
    hitsArr(i) = hits;
end
maxHitc = max(hitsArr);
x = find(hitsArr == maxHitc,1,'first');

label = 'Hand';
position = [x y abs(y2-y1)/2; x y 1];
img_out = insertObjectAnnotation(img_orig,'Circle',position,label);
imshow(img_orig);
figure; imshow(img_out);title('Detected hand');
imwrite(img_out,'hand_detect.jpg');
% viscircles([x y],abs(y2-y1)/2,'EdgeColor','r');
% viscircles([x y],1,'EdgeColor','r');
% figure; imshow(out);
figure; imshow(bin);
toc;

I first thought that it was because the frame rate of the video but changing it doesn't help either. and as said above when i run the video to do the detection and tracking the code fails. Any help will be appreciated.

Answer 1

This is happening because when you read an image from a png file you get a uint8 image with pixels values between 0 and 255. On the other hand, vision.VideoFileReader gives you an image of class single with pixel values normalized to be between 0 and 1. You can fix this by setting 'VideoOutputDataType' to 'uint8':

video = vision.VideoFileReader(filename, 'VideoOutputDataType', 'uint8');

On a different topic, if you want to track the hand you may want to try using vision.HistogramBasedTracker or vision.PointTracker.