Patent ID: 8848788

Claim:
An encoder comprising: a processor and associated memory, the processor configured to: define a quantization step size value for a picture, create a map representing variations of quantization step sizes among blocks within the picture (ΔQP map), calculate a rounding offset value of the picture according to the quantization step size value for said picture, calculate a rounding offset difference for each block of the picture; create a rounding offset map (RO map) representing rounding offset values for respective blocks in the picture, said rounding offset values being based on a first characteristic of respective blocks; and a rate control module configured to calculate a base quantization step size index (base QP) based on the created ΔQP map and RO map; said encoder encoding each block using the calculated base quantization step size index (base QP), corresponding variation of quantization step size from said ΔQP map, and corresponding rounding offset value from said RO map.