12. Non-Maximal Suppression

Non-Maximal Suppression Steps

In practice Non-maximal Suppression is implemented in a few steps.

1. Look at the output vector of each grid cell. Recall that each grid cell will have an output vector with a Pc value and bounding box coordinates.
2. Remove all bounding boxes that have a Pc value less than or equal to some threshold, say 0.5. Therefore, we will only keep a bounding box, if there is more than a 50% chance of an object being inside of it.
3. Select the bounding box with the highest Pc value.
4. Remove all the bounding boxes that have a high IoU* with the box selected in the last step.

* A high IoU usually means a that the IoU is greater than or equal to 0.5.