Patent ID: 7092441
Filing Date: 2006-08-15
Classification: H04N

Abstract:
1. A method for use in a moving pictures encoder for encoding a sequence of segments each having at least one image, the method comprising the steps of: a) determining an overall target bit rate for encoding the sequence of segments; b) determining a bit allocation and target quantization step size for encoding a first segment on the basis of a segment target bit rate calculated using said overall target bit rate; c) encoding said first segment using a variable bit rate encoding method according to the target quantization step size; d) determining a difference between the number of bits used to encode said first segment and said first segment bit allocation; e) distributing said difference for use in encoding at least one subsequent segment to determine a subsequent segment bit allocation; f) determining a new target quantization step size for encoding the at least one subsequent segment on the basis of a new target segment bit rate calculated using said segment target bit rate and the distributed difference; and g) encoding said subsequent segment using a variable bit rate encoding method according to a new target quantization step size; wherein variable bit rate encoding is employed for encoding pictures within a segment whilst maintaining a substantially constant bit rate over said sequence, wherein the steps d) to g) are carried out iteratively using the number of bits used to encode the subsequent segment and the subsequent segment bit allocation for determining said difference, and wherein the difference between the number of bits used to encode the first segment and said first segment bit allocation is determined according to: where: bits_diff is said difference, overall_BR is the overall target bit rate, N bits_segment is the actual number of bits used to encode the first segment.