YOLOv3 Model Structure: Why is filters = (classes + coords + 1) * num? Here's a tutorial about doing custom training of YOLO (Darknet): https://medium.com/@manivannan_data/how-to-train-yolov3-to-detect-custom-objects-ccbcafeb13d2

The tutorial guides how to set values in the .cfg files:


classes = Number of classes, OK
filters = (classes + 5) * 3


Why is it 'plus 5' then 'times 3'?

Some say it's (classes + coords + 1) * num, but I can't guess it out the meaning.
As said by @brale in the comment below the question:

filters = (classes + 5) * 3
= (classes + width + height + x + y + confidence) * num
= (classes + 1+1+1+1+1) * num
= (classes + 5) * num


YOLOv3 dectects 3 boxes per grid cell, so it is:

filters = (classes + 5) * 3