Patent ID: 7391916

Claim:
A quantization matrix adjusting method for quality improvement, the adjusting method comprising the steps of: updating a used bits BB_X and an average quantizer scale Avg_Q; allocating the bit budget BB_C for a current picture; calculating an estimated quantizer scale EstQ_C according to at least the used bits BB_X, the average quantizer scale Avg_Q and the bit budget BB_C; deciding the operation mode, when the estimated quantizer scale EstQ_C is smaller than a threshold Th_Q, assigning the operation mode as an adjusting mode, otherwise remaining at normal mode; scaling down a default quantization matrix as a new quantization matrix when the operation mode is the adjusting mode; and coding the current picture using the new quantization matrix and default quantization matrix in the adjusting mode and normal mode, respectively; wherein the estimated quantizer scale can be calculated by the equation: EstQ_C=(BB_X/BB_C)*Avg_Q; wherein the new quantization matrix is calculated according to the default quantization matrix and an adjustment factor; wherein the adjustment factor equals the estimated quantizer scale EstQ_C divided by a safer value SQ_X; wherein the method comprises a plurality of quantized adjustment factor and a plurality of pre-calculated quantization matrixes, and in the adjusting mode the method selects a pre-calculated quantization matrix with the quantized adjustment factor closest to the adjustment factor as the new quantization matrix.