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A method on entropy constrained RVQ design

Entropy constrained residual vector quantization (EC-RVQ) has been shown to be a competitive image compression technique. In this paper, we propose a new algorithm for EC-RVQ design. The main features of the algorithm are: (i) in the encoder update step, we propose a variation of the exhaustive search encoder that significantly speeds up encoding at no expense in terms of the rate-distortion performance; (ii) in the decoder update step, we propose a new method that simultaneously updates the codebooks of all stages; the method is to form and solve a certain least squares problem and we show that both tasks can be done very efficiently; (iii) the Lagrangian of rate-distortion is shown to decrease at every step and thus this guarantees the convergence of the algorithm.