Mitsubishi Denki Kabushiki Kaisha

Hideaki Ebisawa

Yushi Naito

Yukimasa Sugino

Shigeaki Suzuki

Yoshihiko Shirokura

Nobuyoshi Horie

Wataru Fushimi

Hisashi Yajima

Mihoko Satoh

A speech coding apparatus includes a frequency parameter generating unit that generates LSP coefficients of an input signal. When the input signal is a non-speech signal, it generates the LSP coefficients of the non-speech signal in such a manner that they approach the LSP coefficients of the speech signal. Thus, even when the input signal is the non-speech signal, its LSP coefficients are quantized by referring to the LSP quantization codebook which is specifically prepared for the speech signal. Although a conventional speech coding apparatus has a problem in that even when it transmits the non-speech signal in a good condition, a conventional speech decoding apparatus cannot always decode the non-speech signal correctly, the present speech coding apparatus can solve the problem even when the receiving side uses the conventional speech decoding apparatus.

Speech coding apparatus capable of implementing acceptable in-channel transmission of non-speech signals

In establishing an audio one link connection wherein an audio signal is not encoded/decoded in a relay station, loud noises may be produced if the states of two audio tandem relay devices which make a pair during relay are changed from a normal connection state to a relay connection state at different times. In order to solve this problem, comfort noise generators are provided. In detail, when a first pattern signal is detected while a relay call is connected via a relay exchange, switches are switched to be connected at a contact point,, and a switch is at a contact point,. Upon detection of a second pattern signal, the switches are connected at the contact points,, while the switches are connected at the contact points,. With this arrangement, outputs from the comfort noise generators are selected and outputted during a period from first pattern signal detection to second pattern signal detection, during which the states of the two devices of a pair are different. As a result, occurrence of loud noises is prevented.

Tandem relay device

A reset signal generating part outputs reset signals RV and RD to a signal discriminating part, based on an output from a 2100 Hz detecting part which detects whether or not a tone of 2100 Hz exists in an input signal. When the 2100 Hz tone is detected, the signal discriminating part firstly resets a discrimination state at 'speech' and secondly sets the discrimination state at 'data' based on the reset signal. Therefore, a signal discrimination apparatus, wherein it is possible to reset the discrimination state at 'speech' at the beginning of a facsimile call even when no call control information is received, can be provided.

Signal discrimination apparatus, a method for discriminating a signal,

Improvements in a method of processing wideband audio signals by a sub-band coding system are provided. Linear codes having frequency components in which audio signal power is concentrated are selected from linear codes separated into a plurality of frequency band components and decoded. The presence or absence of sound in the audio signals is detected by referring to the selected linear codes and/or a gain coefficient is determined. Level control of the decoded linear codes is performed by using the thus determined gain coefficient.

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Tokyo, Japan

Hideaki Ebisawa