def bbox2delta_v2(src_boxes,
                  tgt_boxes,
                  delta_mean=[0.0, 0.0, 0.0, 0.0],
                  delta_std=[1.0, 1.0, 1.0, 1.0]):
    """Encode bboxes to deltas.
    Modified from bbox2delta() which just use weight parameters to multiply deltas.
    """
    src_w = src_boxes[:, 2] - src_boxes[:, 0]
    src_h = src_boxes[:, 3] - src_boxes[:, 1]
    src_ctr_x = src_boxes[:, 0] + 0.5 * src_w
    src_ctr_y = src_boxes[:, 1] + 0.5 * src_h

    tgt_w = tgt_boxes[:, 2] - tgt_boxes[:, 0]
    tgt_h = tgt_boxes[:, 3] - tgt_boxes[:, 1]
    tgt_ctr_x = tgt_boxes[:, 0] + 0.5 * tgt_w
    tgt_ctr_y = tgt_boxes[:, 1] + 0.5 * tgt_h

    dx = (tgt_ctr_x - src_ctr_x) / src_w
    dy = (tgt_ctr_y - src_ctr_y) / src_h
    dw = paddle.log(tgt_w / src_w)
    dh = paddle.log(tgt_h / src_h)

    deltas = paddle.stack((dx, dy, dw, dh), axis=1)
    deltas = (
        deltas - paddle.to_tensor(delta_mean)) / paddle.to_tensor(delta_std)
    return deltas
Encode bboxes to deltas.
    Modified from bbox2delta() which just use weight parameters to multiply deltas.
    
ppdet/modeling/bbox_utils.py