Code rate control method and device for image block level of P frame or B frame

The invention discloses a code rate control method of an image block level of a P frame or a B frame. And calculating the target coding bit number of each to-be-coded image block in the to-be-coded P frame or B frame according to the ratio of the inter-frame coding complexity of the to-be-coded image block in the to-be-coded P frame or B frame to the inter-frame coding complexity of the to-be-coded P frame or B frame and in combination with the target coding bit number of the to-be-coded P frame or B frame. And according to the target coding bit number and the inter-frame coding complexity of the to-be-coded image block in the to-be-coded P frame or B frame, combining the actual coding bit number, the quantization parameter and the inter-frame coding complexity of the image block at the same position in the previous coded P frame or B frame, and calculating the quantization parameter of the to-be-coded image block in the to-be-coded P frame or B frame. The image block level quantization parameter is used as a