Abstract: A compressive encoding-decoding system is provided specifically for the realization of the lossless encoding system having a good efficiency. Herein, input signals are subjected to analog-to-digital conversion to generate a series of linear PCM data. Then, the system generates a series of difference value data, each representing a difference between adjacent samples of the linear PCM data, which are then combined with respect to each frame. Requantization is performed on the difference value data on the basis of a word length. In a first mode, the word length is determined to coincide with a minimum number of bits which are required to represent the difference value data having a maximum absolute value within the difference value data contained in each frame.

Abstract: An audio encoding-decoding system is constructed between a transmitting station and a receiving station which are connected together through communication lines. The transmitting station corresponds to an encoder which performs an encoding process on audio signals input thereto to produce compressive coded bit streams. Herein, the encoder uses a code book or conjugate structure code books to perform vector quantization on residual signals corresponding to residuals of an analysis of linear predictive coding which is performed on the audio signals. Indexes are produced in response to a result of the vector quantization. The encoder produces the compressive coded bit stream based on the indexes and a result of the analysis of the linear predictive coding. A bit rate mode is determined for the compressive coded bit stream in response to conditions of the communication lines.

Abstract: Tone waveform data is divided into plural data segments, so that frequency and magnitude of respective spectra contained therein are analyzed for each of the data segments. Analyzation parameters indicative of the frequency and magnitude of the respective spectra for each said data segment which has been obtained through the analyzation is stored into a memory. The analyzation parameter for each data segment is sequentially read out from the memory, and the tone waveform data is reanalyzed on the basis of the read-out parameter. To control the frequency of a resulting tone, a data shift circuit may be provided which serves to shift the value of the frequency data contained in the analyzation parameters.

Abstract: A pitch extraction apparatus for extracting (detecting)a pitch of an acoustic signal which includes circuitry for calculating the stability of the acoustic signal. The stability calculation exhibits a larger value as the amplitude of the acoustic signal is larger and when the frequency is low. Pitch extraction is performed using the calculated stability. In addition, a pitch extraction apparatus which includes a pitch extractor for extracting a pitch of an acoustic signal by discriminating whether or not an input is a voiced or voiceless sound. Based on the determination that the input is a voiceless sound, the input to or the output from the pitch extractor will be inhibited.

Abstract: A method of rehabilitating underground pipes which comprises the steps of: (a) forming a liner pipe (5) by winding a strip (4) made of a synthetic resin into a helical shape so that the side edges of the convolutions of the wound strip (4) are interengaged with each other; (b) continuously introducing the liner pipe (5) into an underground pipe (1) while the liner pipe (5) is being advanced inside the underground pipe (1); inserting a slip restraining member in the form of a wire rod (6) continuously to the interconnected edges of the convolutions of the said strip (4), and then removing the said strip (4) when the diameter of said liner pipe (5) is to be increased at the same rate as said strip (4) for forming said helical liner pipe (5) is conveyed.