Patent ID: 7813575
Filing Date: 2010-10-12
Classification: G06T

Abstract:
1. A method for transcoding compressed data for further compression while said compressed data remains in the transform domain including steps of entropy decoding said compressed data to form a plurality of quantized transform coefficient values, reducing, using a computer, dynamic range of said plurality of quantized transform coefficient values to form quantized transform coefficient values of reduced dynamic range, wherein values of some or all quantized transform coefficients at different zig-zag scan order positions are reduced in dynamic range in different manners other than or in addition to scaling, altering at least one value in a first quantization table to form an altered quantization table having values based on said dynamic range reduction of quantized coefficient values of reduced dynamic range in said different manners at respective zig-zag scan order positions, entropy encoding said quantized transform coefficient values of reduced dynamic range using statistics derived from entropy coding of said compressed data to form further compressed data, and transmitting or storing said further compressed data with said altered quantization table.