DEVICE AND METHOD FOR CODING VIDEO PICTURES

摘要

The bitrate control of known video encoders is based on a control of the quantization step size per picture block. In transform coding of relatively large picture blocks, the video picture comprises a too small number of picture blocks to obtain a desired number of bits per picture. In conformity with the invention, the target value for the number of bits per picture block is divided into N sub-targets (R<SUB>t</SUB>(k,n)). The series of coefficients of a picture block is divided into N segments (L(n)) with reference to an estimation for the cumulative distribution 20 of the bit cost per picture block. The quantization step size is subsequently adapted per segment to the corresponding sub-target. Since the number of segments is N times larger than the number of picture blocks, an accurate bitrate control is possible. If desired, the estimation for the cumulative distribution is adapted from picture to picture.