You Only Look Once

Definition

You Only Look Once (YOLO) is a proposal-free object detection model, that predict bounding boxes and class probabilities from an image in a single evaluation.

Architecture

Input image is divided into a grid, and each grid cell produces bounding boxes centered within it and predicts class probability.

YOLO: Divide the input image into a grid ($S\times S$), each grid cell produces bounding boxes and predicts class probability. And drop low-probable bounding boxes and make a final result.

The final output is a tensor of shape $S\times S\times (B\times 5+C)$, where $5$ represents (x, y, w, h, confidence) for each bounding box.