| 摘要 |
In accordance with the present invention, a method is described which achieves a constant bit rate output when coding multiple video objects. This implementation makes use of a quadratic rate-distortion model. Each object is described by its own set of parameters. With these parameters, an initial target bit estimate is made for each object after a first frame is encoded. Based on output buffer fullness, the total target is adjusted and then distributed proportional to a parameter set representative of the activity of the objects in the frame. Activity is determined by reference to weighted ratios derived from motion, size and variance parameters associated with each object. A shape rate control parameter is also invoked. Based on the new individual targets and second order model parameters, appropriate quantization parameters can be calculated for each video object. This method assures that the target bit rate is achieved for low latency video coding. <??>In order to provide a suitable bit rate control system based on a quadratic rate-distortion model, it has been found that control information may be applied jointly with respect to video objects (VO's), rather than entire frames. <IMAGE> |
