Run demo on videos,the predicted bbox does not exactly match the person of each frame

Thanks for your excellent work！
When i run demo on video, I found the predicted bbox does not exactly match the person's position of each frame，It looks like the bounding box is jumping around person. I tried to read the visualization code, then i found each input clip only predicts the bbox of the middle frame，and this only one bbox is drawn on each frame of input clip.
Then i tried to modify the visualization code to predict the bounding box of each frame and display it, but I encountered a threading problem. Hope you can provide some help，thanks for your reply.