YOLOv3

29 July 2020

Photo by Huper Earle

Origin: YOLOv3: An Incremental Improvement

Improvement

1. New structure

2. Mutiscale Structure

3 scales and 3 anchors per scale per grid:

• small scale (13 x 13) ——> large anchor
• mid scale (26 x 26) ——> medium anchor
• large scale (52 x 52) ——> small anchor

3. Change Classfication

• 80 classes, from softmax ——> logistic

Using a softmax imposes the assumption that each box has exactly one class which is often not the case. A multilabel approach better models the data.

4. Use FPN

Summary

Output

• 13 x 13 x 3 * (4+1 + 80)
• 26 x 26 x 3 * (4+1 + 80)
• 52 x 52 x 3 * (4+1 + 80)