Based on the code rate controlled by the first order distortion model, the feedback mechanism is added in the invention in order to change the target code rate, making the code rate control more accurate and the calcualting speed of the first order model quicker. Using statistical frame loss history averages the interval of the frame loss. Meanwhile, when frame loss happens, the user is allowed choosing the trade-off decision between the image quality and the frame rate by referencing the magnitude of the quantization factor. The invention possesses the advantages of fast speed, high accuracy as well as smooth change of the image quality compressed. |