Adapted from SSD implemented by zhreshold, the results still need to be tuned. Currently we use the PASCAL VOC mAP metric which measures under IoU threshold 0.5, not the COCO AP metric.
Demo Results
Differences from SSD
We build FPN (P3 to P7) to replace the "multi_layer_feature" function;
We build cls_subnet and bbox_subnet in the "multibox_layer" function, and the bias is initialized according to the Focal Loss paper (only for FL strategy
);
We use the anchor setting in the focal loss paper which is tested on COCO, but the best setting for PASCAL VOC still needs to be tuned;