Abstract: Implementations of the present specification disclose methods, apparatuses, and devices for training an object detection system by using a gradient fine-tuning technique. In one aspect, the method includes: providing a training image as input to the object detection system; processing the training image by the object detection system; determining a gradient norm of each neural network layer based on object annotation data and the detection result corresponding to the training image; and updating, for each neural network layer, parameter values of the neural network layer based on an average of gradient norms and the gradient norm of the neural network layer.

Abstract: Implementations of the present specification provide a video retrieval method and apparatus. In the method, a video frame in a video to be matched is obtained; an image feature and a text feature are extracted from the video frame; the image feature and the text feature are fused based on a center variable used to represent a cluster center to obtain a fused feature, where the center variable is used to associate features of different modes of a same video; and video retrieval is performed in a video database based on the fused feature to determine a video in the video database that matches the video to be matched, where a plurality of videos and video features corresponding to the plurality of videos are stored in the video database.