readFrame to slow, is there a faster way?

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david csernay
david csernay 2017-11-18
评论： david csernay 2017-11-20
Hello
I want to "cut out" objects that are placed in front of a green screen in real time, and replace the background with a video.
The object extraction itself works fine (tested with a simple image as background).
Then i tried to implement a background video with 'readFrame', but the background video runs in slow motion (see files attached), plus the live stream gets laggy too.
Is there a faster way to acquire single video frames and process them?
Thanks for any help!
function example1
% webcam
cam = videoinput('winvideo',1);
% get background image
img1 = getsnapshot(cam);
% video objekt
vidobj1 = VideoReader('Testvideo.mp4');
% background
background = readFrame(vidobj1,'native');
background = imresize(background, [size(img1, 1), size(img1, 2)]);
img = imshow(background,'InitialMagnification','fit');
% Set a custom preview function
setappdata(img,'UpdatePreviewWindowFcn',@mypreview_fcn);
% Call preview with the custom image
preview(cam,img);
function mypreview_fcn(obj,event,himage)
% receive the image in event.Data
foreground = event.Data;
background = readFrame(vidobj1,'native');
[overlayed,a] = greenScreen(foreground, background);
% Display
set(img, 'CData', overlayed);
end
end

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采纳的回答

Walter Roberson
Walter Roberson 2017-11-18
  5 个评论
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Walter Roberson
Walter Roberson 2017-11-20
There is im2double instead of im2single() . Without testing it is difficult to say which would lead to faster code.
david csernay
david csernay 2017-11-20
Ok, with im2double the extraction works, but the video is still slow.
How would you approach the problem? Is there another way for object extraction? Actually, i would like to keep the green screen method, because of its good extraction results.

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更多回答（1 个）

Image Analyst
Image Analyst 2017-11-19
You could store the video on a solid state drive instead of a hard drive.

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