real time video background replacement

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david csernay
david csernay 2017-10-10
编辑： Walter Roberson 2017-10-20
Hello
I need to "cut out" a person from a real time webcam video and replace the background.
Based on the code of the following thread i tried to do the background replacement:
https://stackoverflow.com/questions/26958833/matlab-webcam-background-replacement
If i use the 2 webcams from my laptop, following error occurs:
winvideo: Image acquisition device is not accessible.
Insufficient system resources to perform the requested service.
Make sure no other objects or applications are accessing the same device.
If i try it with another usb camera (kinect), following error occurs:
Undefined operator '-' for input arguments of type 'videoinput'.
Error in Backgroundreplacement2 (line 32) diffMask = ((img1 - img2) > threshVal) | ((img2 - img1) > threshVal);
Here's my code:
while 1
% User Input:
threshVal = 0;
% Tolerance for difference between 'webcam' background and foreground
images
%%%%%%%%%%%%
% End User input
% Read in some images
% img1 is the webcam background image
cam = webcam('Intel(R) RealSense(TM) 3D Camera (Front F200) RGB');
img1 = snapshot(cam);
% bkgdImg is the image to replace the background of img1 with
bkgdImg = imread('http://i.imgur.com/dIMct6u.jpg');
% Resize bkgdImg so it is the same size as img1. With two images from
the same webcam this will not be necessary.
bkgdImg = imresize(bkgdImg, [size(img1, 1), size(img1, 2)]);
% Draw on 'webcam' image to make it different
% In actual algorithm, img2 would be a second image captured with the
% webcam with the same background but different foregrounds, such as a
% person now standing in front of camera.
img2 = videoinput('kinect',1);
% Take difference of background and foreground images
% If difference is greater than threshVal, then add those pixels to the
% mask.
% The operation has to be done both ways because images are unsigned
% integers and negative values are ignored.
diffMask = ((img1 - img2) > threshVal) | ((img2 - img1) > threshVal);
% Reduce mask by taking any value along 3rd dimension as logical true
diffMask = any(diffMask, 3);
% Replicate replacement background
bkgdImgReplace = bkgdImg;
% In regions where mask is true (ie where background ~= foreground from
% webcam) replace those pixels in the replacement background image with
the
% foreground pixels
bkgdImgReplace(repmat(diffMask, 1, 1, 3)) = img2(repmat(diffMask, 1, 1,
3));
% Display
figure()
subplot(2, 2, 1)
imshow(img1)
title('Original Background')
subplot(2,2,2)
imshow(img2)
title('Modified Background w/ New foreground')
subplot(2,2,3)
imshow(bkgdImg)
title('Replacement Background')
subplot(2,2,4)
imshow(bkgdImgReplace);
title('Replacement Background w/ New foreground')
end
What do I have to change to make it work?
Thank's for any help!

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回答（1 个）

Arun Mathamkode
Arun Mathamkode 2017-10-20
Most hardware will not allow you to acquire data from multiple sources simultaneously. This is a limitation imposed by the hardware, and not by the Image Acquisition Toolbox. Maybe you can try to use 2 USB cams instead, it may help.
Refer to this answer provided by MathWorks Technical Support: Does the Image Acquisition Toolbox 1.0 (R13.0.1+) support simultaneous image capture from multiple cameras?
The second error occurs because the 'videoinput' creates a video input object, not an image. So in your case, img1 is an image but img2 is a video object. You may first need to extract frames from the video object using 'getsnapshot' and then find the difference with img1.
  1 个评论
david csernay
david csernay 2017-10-20
Thanks for your reply. I managed to run the code with 'getsnapshot'. Unfortunately it runs very slow, so it's unusable.
I also tried it with 'peekdata' and 'getdata'. Same result.
Is there a way to do faster real time image processing?

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