Method and apparatus for moving picture compression rate control using bit allocation with initial quantization step size estimation at picture level

An apparatus for rate control in moving picture compression using bit allocation with initial quantization step size estimation at picture level, comprising:

• a motion estimation unit receiving a current picture to be encoded in a set of consecutive pictures of a video sequence, for calculating a total activity measure for the current picture to be encoded while performing block matching for motion estimation;
• a complexity estimator for estimating a complexity measure of the current picture based on the total activity measure of the current picture and an activity-to-complexity ratio of a previously encoded picture of the same type;
• a target allocator updating an instantaneous complexity measure for the set of consecutive pictures with the estimated complexity measure of the current picture, for allocating a target bit budget to the current picture depending on the estimated complexity measure and the instantaneous complexity measure;
• a MQUANT estimator for determining an initial value for an average quantization step size to be used to encode the current picture based on a function of the total activity measure of the current picture, the target bit budget for the current picture and the activity-to-complexity ratio of the previously encoded picture of the same type;
• and
• a parameter updater for computing the activity-to-complexity ratio for the current picture based on the total activity measure, actual bits consumed by the current picture and the average of actual quantization step sizes used to encode the current picture,
• wherein the activity-to-complexity ratio of the current picture varies directly with the total activity measure of the current picture and inversely with the actual consumed bits and the average of actual quantization step sizes used to encode the current picture.