Most efficient way to track multiple small objects in MATLAB? - matlab

Question

I am relatively new to image processing, and have never attempted to do anything with images in MATLAB, so forgive me if i am making some very rookie errors.
I am attempting to make a program that will track ants in a video. The video is taken from a stationary camera, and records the ants from a birds-eye perspective. I am having issues making reliable tracks of the ants however. Initially, i used the ForegroundDetection function, however there were multiple issues:
1.) Stationary ants were not detected
2.) There was too much overlap between objects (high levels of occlusion)
A friend of mine recommended having a larger gap between compared frames, so instead of subtracting frame 1 from frame 2, do frame 1 from frame 30 instead (1 second apart), as this will make the ants that do not move as much more likely to appear on the subtracted image.
Below is the code i have so far. It is a bit of a shot-in-the-dark attempt to solve the problem, as i am running out of ideas:
i = 1;
k = 1;
n = 1;
Video = {};
SubtractedVideo = {};
FilteredVideo = {};
videoFReader = vision.VideoFileReader('001.mp4',...
'ImageColorSpace', 'Intensity', 'VideoOutputDataType', 'uint8');
videoPlayer = vision.VideoPlayer;
blobby = vision.BlobAnalysis('BoundingBoxOutputPort', true, ...
'AreaOutputPort', true, 'CentroidOutputPort', true, ...
'MinimumBlobArea', 1);
shapeInserter = vision.ShapeInserter('BorderColor','White');
while ~isDone(videoFReader) %Read all frame of video
frame = step(videoFReader);
Video{1, i} = frame;
i = i+1;
end
%Perform subtraction
for j=1: 1: numel(Video)-60
CurrentFrame = Video{1,j};
FutureFrame = Video{1,j+60};
SubtractedImage = imsubtract(CurrentFrame, FutureFrame);
SubtractedVideo{1,j} = SubtractedImage;
ImFiltered = imgaussfilt(SubtractedImage, 2);
BWIm = im2bw(ImFiltered, 0.25);
FilteredVideo{1,j} = BWIm;
end
for a = n:numel(FilteredVideo)
frame = Video{1, n};
bbox = step(blobby, FilteredVideo{1, k});
out = step(shapeInserter, frame, bbox);
step(videoPlayer, out);
k = k+1;
end
currently, when i run the code, i get the following error on the line out = step(shapeInserter, frame, bbox):
'The Points input must be a 4-by-N matrix. Each column specifies a different rectangle and is of the form [row column height width].'
My questions is:
1.) Is this the best way to try and solve the problem I'm having? Is there potentially an easier solution?
2.) What does this error mean? How do i solve the issue?
I appreciate any help anyone can give, thank you!