Patent ID: 6982762

Claim:
A moving pictures encoder for encoding pictures in a moving pictures sequence according to an overall target bit-rate, each picture having an assigned picture coding type, the moving pictures encoder including: a quality factor estimator including means for determining a picture complexity for each assigned picture coding type based on a number of bits used for past coded pictures of that type, and an average quantization step-size for past coded pictures of that type; a bit allocation processor for determining a target number of bits for coding a picture according to the overall target bit-rate, the assigned picture coding type and a quality factor for the assigned picture coding type, the quality factor being defined as the product of a visual quality and the average quantization step-size for past coded pictures of that type; a bit-rate controller for determining a reference quantization step-size based on the target number of bits and the number of bits used for the picture; and an adaptive quantization processor for determining a coding quantization step-size based on the reference quantization step-size and picture activities for the picture, and for determining said average quantization step-size for past coded pictures, wherein the quality factor estimator includes means for determining the quality factor of the assigned picture coding type as a function of a ratio of the picture complexity of the assigned picture coding type to the picture complexity of at least one other picture coding type.