In an encoder operable in response to a discrete pattern signal divisible into a succession of segments to produce an output code sequence, a pitch parameter and a spectral parameter are extracted in a parameter calculator from each segment and from a spectral interval. In an excitation pulse producing circuit, each spectral interval is divided into a plurality of subframes, namely, pitch periods with reference to the pitch parameter to divide each segment. A minor group of excitation pulses is ...

Speech is analyzed to derive the parameters of a synthesis filter and the parameters of a suitable excitation which is selected from a codebook of excitation frames. The selection of the codebook entry is facilitated by determining a single-pulse excitation (e.g., using conventional multipulse excitation techniques), and using the position of this pulse to narrow the codebook search.

A method and implementing apparatus for low-bit rate speech band signal coding. An input signal in the speech band is represented by a pulse excitation sequence and a spectral parameter sequence over a frame of predetermined frame length using a selected one of a plurality of pulse determining processing modes. The selected pulse determining processing mode sequentially determines the amplitudes g.sub.i and locations m.sub.i of the pulses of the pulse excitation sequence on the basis of the ampl...

In coded speech communication, discrete speech samples are analyzed to generate a first signal indicating the fine pitch structure of the speech samples and a second signal indicating their spectral characteristic. The amplitudes and locations of main excitation pulses are determined from the fine pitch structure and spectral characteristic and a third signal indicating the determined pulse amplitudes and locations is generated. The difference between the speech samples and the main excitation p...

A multipulse excitation signal estimate is followed by chronological adjustment.

A speech analysis and synthesis system where pitch information for excitation is transmitted during voice segments of speech and pulse excitation or noise excitation is transmitted during unvoiced speech segments along with linear predictive coding (LPC) parameters. The decision of whether to transmit noise excitation or pulse excitation is performed by comparing the variance of the residual to the square of the mean amplitude of the rectified residual for each frame. If the result of this compa...

A variable frame length vocoder extracts a feature vector for each given frame, a predetermined number of frames being defined as a section. The feature vectors in each section are stored, changes in feature vectors within a section being approximated by a given number of variable time length flat sections with a constant time length portion between adjacent flat sections, adjacent flat sections being interconnected by an inclined section of the constant time length duration. A feature vector of...

A method and apparatus is provided for determining the lag of a long term filter in a code excited linear prediction speech coder. An open loop lag is first determined using an autocorrelation function. The open loop lag is then utilized to generate a limited range over which a closed loop search is performed. The range for appropriate values includes lags that are harmonically related to the open loop lag as well as adjacent lags.

A second approximation of the multipulse excitation signal is derived from a difference signal developed from use of a first approximation of the multipulse excitation signal. Also, spectrum parameters are weighted by a periodicity measure.

The set of possible excitation signals is subdivided into a plurality of subsets, the first of which provides the contribution to the coded signal necessary to set up a transmission at a minimum rate guaranteed by the network, while the others supply a contribution which, when added to that of the first subset, causes a rate increase by successive steps. At the receiving side, a decoded signal is generated by using the excitation contribution of the first subset alone if the coded signals are re...