Fujitsu Corporation

Fujitsu Semiconductor Limited

Nobuhide Eguchi

Naoji Fujino

Toshiaki Nobumoto

Mitsuru Tsuboi

Naoshi Matsuo

Noboru Kobayashi

Toshiyuki Ohta

Yutaka Moriyama

Miki Murakawa

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.

Audio coding device with two-stage quantization mechanism

An apparatus synchronizes a voice coder and a voice decoder which are of the vector-coding type in order to prevent a false synchronization even when a signal having the same period as a string of synchronizing bits is inputted. A noise component adding unit adds a noise component to an input voice signal. Therefore, even if the input voice signal has the same period as that of a string of synchronizing bits and is completely periodic, the periodicity of the input voice signal is lost by the added noise component. Based on the input voice signal which is no longer periodic, a vector-coding unit, a quantizing signal vector generating unit, and a code book index transmitting unit generate code book indexes and transmit the generated code book indexes to a voice decoder. Therefore, the voice decoder is prevented from developing a false synchronization.

Apparatus for synchronizing a voice coder and a voice decoder of a

The coder generates code information A.sub.1 -A.sub.N, each representing one of Q quantization points of an input signal, where Q is an integer equal to or less than 2.sup.x and X is a positive number, synthesizes the code information A.sub.1 -A.sub.N into a code H through an operation:

Coding/decoding apparatus and method

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Fukuoka, Japan

Nobuhide Eguchi