An audio coding device that optimizes quantization parameters for fast convergence of iterations. A quantized bit counter calculates a codeword length representing the number of bits of a Huffman codeword corresponding to quantized values. The quantized bit counter also calculates a codebook number bit count representing how many bits are consumed for optimal Huffman codebook numbers, and a scale factor bit count representing how many bits are consumed for scale factors of each subband. In a first stage of quantization, the quantized bit counter accumulates lengths of Huffman codewords corresponding to quantized values of every nth subband. A bit count estimator calculates a total bit count estimate by adding up n times the accumulated codeword length, the codebook number bit count, and the scale factor bit count. A parameter updater updates quantization parameters if the total bit count estimate exceeds a bit count limit.