Adaptive modulus quantizer design for matching pursuit video coding
Overcomplete signal decomposition using matching pursuits has been shown to be an efficient technique for coding motion residual images in a hybrid video coder. Unlike orthogonal decomposition where computation of the transform coefficients is decoupled from quantization, matching pursuit uses an in-loop quantizer which must be specified before coding begins. Optimal quantizer design thus depends on the computed matching pursuit coefficients, but these in turn depend on the chosen quantizer. To resolve this interdependency, we propose frame-adaptive quantization for matching pursuit based on adaptive dead-zone subtraction followed by uniform threshold quantization. Practical 2-pass and 1-pass algorithms are developed which jointly find the quantizer parameters and the number of coded basis functions which minimize coding distortion for a given rate. The compromise 1-pass scheme performs nearly as well as the full 2-pass algorithm, but with the same complexity as a fixed quantizer design. The adaptive schemes are shown to outperform the fixed quantizer used in earlier works, especially at high bit rates where the gain is up to 1.7 dB.