Adaptive quantization based on bit ratio

Abstract

There is provided a method of adapting a Quantization parameter of digitally encoded video, comprising using a look-ahead encoding pass to provide look-ahead bit costs for each macroblock in a picture of interest, calculating an activity metric for each macroblock in the picture of interest, determining at least an accumulated look-ahead bit cost threshold for a low macroblock activity category, wherein the low macroblock activity category comprises macroblocks having an activity metric below a pre-determined level, sorting the macroblocks according to the calculated activity metrics of each macroblock to provide sorted macroblocks, adding sorted macroblocks to the low macroblock activity category in ascending activity order and accumulating bit costs of the added sorted macroblocks up to the determined accumulated look-ahead bit cost threshold, and applying a change in quantization parameter, Qp, to the macroblocks of the picture of interest comprising decreasing the Qp value of the macroblocks in the low macroblock activity category.