Sanyo Electric Co., Ltd.

Shozo Sugishita

Takeo Inoue

Akira Tsukihashi

Hiroshi Tanaka

Masayuki Iida

Masanori Miyatake

Hideharu Nishida

Teruo Hoshi

At a time of compression, two sound waveform segments each having single pitch length are cut-out from an input sound waveform at a time point represented by a current pointer and at a time point advanced from the time point by a single pitch period, respectively, and then, by adding the two sound waveform segments to each other after being multiplied by window functions, a single sound waveformn segment being compressed is produced. Next, the pointer is moved on the input sound waveform according to a compression rate, and then, a similar operation is repeated to produce a sound signal being compressed. At a time of expansion, two sound waveform segments each having double pitch length are cut-out from the sound waveform thus compressed at a time point represented by the current pointer and at a time point delayed from the time point by the single pitch period, respectively, and then, by adding the two sound wave segments to each other after being multiplied by window functions, a single synthesized sound wave form segment is obtained. Next, the pointer is moved on the sound waveform being compressed according to an expansion rate, and then, by repeating a similar operation, a sound signal being expanded is obtained.

Compression/expansion method of time-scale of sound signal

In a voice speed converting system according to the present invention, an input sound signal is subjected to voice speed conversion processing by a voice speed conversion processing device. Output from the voice speed conversion processing device is written to a ring memory. Data written to the ring memory are read out at a predetermined speed. The amount of stored data in the ring memory is calculated on the basis of a write signal and a read signal for the ring memory by stored data amount calculating device. The voice speed converting device includes a section judging device that judges which of a voice section and a silence section corresponds to the input sound signal. The input sound signal is subjected to compression and expansion processing or deletion processing, in response to an output of the section judging device and an output of the stored data amount calculating device by a signal processing device.

System for controlling voice speed of an input signal

The present invention relates to an audio signal coding and decoding device for coding and decoding an audio signal using an adaptive differential coding system. The audio signal coding and decoding device according to the present invention comprises an adaptive differential pulse code modulation coding device for coding an audio signal, an adaptive differential pulse code modulation decoding device for decoding the audio signal coded, an integrator provided in the preceding stage of the coding device and for decreasing the variation between unit samples of the input audio signal of the coding device, and a differentiator provided in the succeeding stage of the decoding device and for processing the audio signal decoded by the decoding device so that the variation decreased by the integrator is restored to the original one. Since the integrator is provided in the preceding stage of the coding device, the variation between the unit samples of the input audio signal of the coding device is decreased. Therefore, a prediction error signal obtained by the coding device is decreased. As a result, quantizer step-size is decreased, resulting in a reduced quantization error.

Audio signal coding and decoding device

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Hirakata, Japan

Shozo Sugishita