How to train ACF detector with groundTruthMultisignal object

I have labeled a data set of sonar images using the ground truth labler, and I want to use the lables in the trainACFObjectDetector function, to create a detector for further labeling. I used the ground truth labeler app because I can play a rgb video alongside the sonar feed, aiding with identifying objects in the sonar images. However the ground truth app producess a groundTruthMultisignal object, and I am unsure how to use this to train an ACF detector.

%% train acf detector
imds = sonar_files;     % conatins path to each image
load("rec0gt.mat")
T = table(gTruth.ROILabelData.processed_sonar);
blds =  boxLabelDatastore(T);
ds = combine(imds,blds);
acfDetector = trainACFObjectDetector(ds,NegativeSamplesFactor=2);

Answer 1

[Malay Agarwal]

Hi @Liam Viney,

I understand that you want to train an ACF detector using labeled data you've created using the Ground Truth Labeler App.

This is possible using the "gatherLabelData" function, which takes in a "groundTruthMultisignal" object and extracts the label data from it.

Please refer to the following link for an example on how to use the "gatherLabelData" function to create a training dataset for an object detector model: https://www.mathworks.com/help/driving/ref/groundtruthmultisignal.gatherlabeldata.html#mw_740aa793-a8dc-497a-b997-becab36ace46.

In the example, after this code:

imds = imageDatastore(fileNames{1});
blds = boxLabelDatastore(labelData{1});

You can combine the two datastores using the "combine" function and then use the combined datastore with "trainACFObjectDetector" to train an ACF detector.

Please refer to the following links for more information:

• "gatherLabelData" documentation - https://www.mathworks.com/help/driving/ref/groundtruthmultisignal.gatherlabeldata.html
• "combine" documentation - https://www.mathworks.com/help/matlab/ref/matlab.io.datastore.combine.html

Hope this helps!

[Liam Viney]

Thank you, I got it working.

Another issue I had was that I was using rotated rectangles for my labeling, which I dont think is supported by trainACFObjectDetector. I switched to axis orientated rectangles and everything seems to be working.