matlabvideocomputer-visionmatlab-cvstopticalflow

vision.OpticalFlow is not showing the video nor the value of the flow

I am trying to see the velocity of an object by using Matlab so I came up with this code

reader = vision.VideoFileReader ('C:\folder1\objectsandflow.avi');
viewer = vision.DeployableVideoPlayer;
optical = vision.OpticalFlow;
optical.OutputValue = 'Horizontal and vertical components in complex form';
videoPlayer = vision.VideoPlayer('Name','Motion Vector');

while isDone (reader)
I = step(reader);
of = step (optical, rgb2gray(I));
y = of .* conj(of);
step(viewThresh,y>mean(y(:)));
step(videoPlayer)
end
release(videoPlayer);
release(reader);

The problem is I cannot see either the values of the flow (I mean I am looking for the velocity of some objects and I can use Matlab for it, can I?), nor the video

At the same time I do not know whether this will work to calculate all the velocities of my objects in the case that this code can't, how can I calculate multiple velocities in Matlab?

Solution

  • Your problem is in these two lines:

    step(viewThresh,y>mean(y(:)));
step(videoPlayer)

    Try replacing them with these:

    viewThresh = y;
viewThresh(y < mean(y(:))) = 0;
step(videoPlayer, viewThresh);

    You do not need the step method for thresholding y, because you are not using any objects. And when you call step on the videoPlayer object, you have to pass in the video frame you wish to display.