Patent ID: 8326067
Filing Date: 2012-12-04
Classification: H04N

Abstract:
1. A method of optimal encoding for an image defined by image data, comprising: transforming a block of the image data to DCT coefficients; quantizing the DCT coefficients using a quantization table to generate quantized DCT coefficients, wherein the quantization table includes a plurality of quantization step sizes; and entropy coding the quantized DCT coefficients using zero run-length coding and a Huffman codebook to generate run-size pairs and indices, wherein the quantization table, run-length coding and Huffman codebook are selected to minimize a Lagrangian rate-distortion cost function and wherein the minimization includes iteratively determining the optimal run-size pairs and in-category indices for minimizing the rate-distortion cost function until the incremental improvement in the Lagrangian cost is less than a threshold value, and wherein the rate-distortion cost function includes a perceptual weighting factor applied to a quantization error, the perceptual weighting factor adjusting the rate-distortion cost function to apply greater weight to quantization error occurring at smaller quantization step sizes in the quantization table than to quantization error occurring at larger quantization step sizes in the quantization table.