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YOLOv8 Custom Dataset Training: Unexpected Output Shape

I’m trying to train a YOLOv8 model on my custom dataset. Each time I export the model, the output shape is (1, 15, 8400). Since I have 11 classes, the expected output shape should be (x, y, w, h, objectness score, 11 labels). With the same dataset, when I train a YOLOv5 model, it correctly outputs (1, 25200, 16). Why is YOLOv8 giving an unexpected output shape?

What kind of pre-processing is used for image intensity values in YOLOv8?

Searching in GitHub and in the code I see contradictory statements. Does the normalization is just dividing the image intensity values (in range [0, 255]) by 255 (so it’s in float range [0,1]) or it does normalization using z-score with some values (e.g. ImageNet mean and std as is suggested here)?

Yolov8 bbox decoding

From image bellow (taken from here), we can see that bbox output in yolov8 has size 4 x reg_max. In yolov8 implementation, the reg_max is set to 16 (16 predicted bboxes) so the output has size 64.