Abstract: A transmission system includes a transmitter with a signal encoder and a codebook entry selector. The signal encoder has an input for a signal to be encoded. The codebook entry selector selects a codebook entry for obtaining a synthetic signal giving a best approximation of a signal representative of the input signal. The codebook entry includes samples that can assume more than two values and is identified with a sequence of symbols. A receiver has a decoder with a codebook for deriving the codebook, where the codebook entries corresponding to sequences of symbols that differ in one particular symbol value also differ in one signal sample value.

Abstract: A transmission system includes a speech decoder, the speech decoder having a detector which determines a level of background noise in a speech signal and a post filter in electrical communication with an output of the decoder when the level of the background noise is equal to or less than a threshold value. A synthesis filter is connected to the output when the level of the background noise is greater than the threshold value.

Abstract: In a speech transmission system, an input speech signal is applied to a speech encoder (12, 36) for encoding the input speech signal. The encoded speech signal is transmitted via a communication channel (10) to a speech decoder (30, 48).

Abstract: In a transmission system a signal to be transmitted is applied to a source encoder (4) for being encoded. The encoded signal is applied to a channel encoder (6) which applies an error correcting code on the encoded input signal. The output signal of the channel encoder (6) is transmitted to a receiver (14) which processes the received signal by means of a channel decoder (18) and a source decoder (20).

Abstract: A transmission system comprising a transmitter with a signal encoder, the signal encoder having an input for a signal to be encoded and a codebook entry selector for selecting a codebook entry for obtaining a synthetic signal giving a best approximation of a signal representative of the input signal, wherein the codebook entry includes a plurality of samples that can assume more than two values and is identified with a sequence of symbols, a receiver having a decoder with a codebook for deriving the codebook entry from the sequence of symbols received from the transmitter, wherein the codebook entries corresponding to sequences of symbols that differ in one particular symbol value also differ in one single sample value.

Abstract: A speech transmission system with an input speech signal applied to a speech encoder for encoding the speech signal which is transmitted via a communication channel to a speech decoder. Background noise dependent processing elements in the speech encoder and/ or speech decoder are introduced to improve the performance of the transmission system. The parameters of the perceptual weighting filter in the speech encoder are derived by calculating linear prediction coefficients from a speech signal which is processed by means of a high pass filter. An adaptive post filter in a speech decoder is bypassed when the noise level exceeds a threshold value.

Abstract: In a transmission system a variable length encoder is used to reduce the average bitrate of a sequence of symbols.

Abstract: In a speech encoder (4), a speech signal is encoded using a voiced speech encoder (16) and an unvoiced speech encoder (14). Both speech encoders (14,16) use analysis coefficients to represent the speech signal. The analysis coefficients are determined more frequently when a transition from voiced to unvoiced speech or vice versa is detected. This has been found to achieve significantly improved quality of speech reproduced from the encoded speech signal.

Abstract: In a harmonic speech encoder (16) a speech signal to be encoded is represented by a plurality of LPC parameters which are determined by a LPC parameter computer (30), a pitch value and a gain value. The speech encoder comprises a (coarse) pitch estimator (38) for determining a coarse pitch, and a refined pitch computer (32) to determine a refined pitch from the coarse pitch value. The refined pitch value is determined in an analysis by synthesis way, in which a refined pitch value is selected which results in a minimum error measure between a representation of a synthesized speech signal and a representation of the original speech signal.

Abstract: In a CELP coder a comparison between a target signal and a plurality of synthetic signals is made. The synthetic signal is derived by filtering a plurality of excitation sequences by a synthesis filter having parameters derived from the target signal. The excitation signal which results in a minimum error between the target signal and the synthetic signal is selected. In order to reduce the complexity of the search for the best excitation signal, thee selection is done in two stages. First a preselection of a small number of excitation sequences is made using a reduced complexity synthesis filter. Thereafter, with this small number of excitation sequences, a full complexity search is made. Due to the reduced number of excitation sequences involved in the final selection the required computational complexity is reduced.

Abstract: A transmission system contains a speech coder which utilizes a pitch detector that is arranged to select a characteristic auxiliary signal portion from the signal to be coded in order to improve the quality of the pitch detection. The pitch is found by searching in the speech signal for signal portions that correspond to the characteristics auxiliary signal portion and by calculating the time difference between the respective signal portions.

Abstract: In a transmission system for a quasi-periodic signal, an encoder (12) transmits to a decoder (28) no more than a single period from a total number of periods of the quasi-periodic signal in encoded form. In this decoder (28) the lacking periods of the quasi-periodic signal are reconstructed by means of interpolation. For obtaining an enhanced quality of the reconstructed signal, a signal segment is transmitted that is representative of two successive periods of the quasi-periodic signal. This signal segment may contain two successive periods, but may also be a signal segment having the length of a single period and being determined by a weighted sum of two successive periods.

Abstract: A receiver for transmitted signals which represent digital symbol values includes a low-pass filter to minimize transmission noise by reducing the receiver bandwidth. However, this creates pulse distortion which can cause intersymbol interference when the filtered signal is supplied to a symbol detector. Such interference is minimized by the inclusion of a feedback loop between the output of the symbol detector and the input to the filter, in which a detected symbol is multiplied by correction factor and supplied to a subtractor where it is subtracted from the signal to be filtered. The result of the subtraction is supplied to the filter. The noise reduction filter is thus also used for matching the intersymbol distortion characteristic of a filtered detected symbol to the intersymbol distortion characteristic of a filtered received signal pulse.

Abstract: A digital transmission system wherein only certain of the samples in a series of signal samples are transmitted by the transmitter to a receiver over a channel. In addition, various characteristic parameters of the series of signal samples are determined in the transmitter and transmitted to the receiver. The characteristic parameters are used at the receiver to reconstruct the missing single samples by assigning to them values such that the resulting reconstructed series of signal samples approximates the characteristic parameters as closely possible. If the series has a periodicity having a period longer than the time duration of the series of signal samples, reconstruction of the series may have a considerable interpolation error. By determining such period in the transmitter and transmitting it over the channel to the receiver, where the same periodicity is introduced into the reconstructed series of signal samples, the interpolation error is considerably reduced.

Abstract: A coupling network for a data processor is described, including, one or more cross bar switches having inputs and outputs and one or more arrays of silos. A series connection is formed in which these components are alternately arranged in a succession having at least three elements. A retrocoupling network is used for coupling outputs of a data processor to its inputs, and it also provides external communication. The configuration offers ample freedom of mapping, notably in cyclostatic processors.

Abstract: A data processing system buffers sequential data for the duration of cyclically recurrent delay times. Memory location allocation is performed in such a way, that the memory is used efficiently without data-shifting after a read-out, and that the address generator is fairly simple.

Abstract: The invention describes a processor system suitable for processing video signal samples on a real-time basis. Signals are derived from the samples for driving an imaging unit. For this purpose, one or more processor modules are provided with processor elements, operating in parallel in time, which are connected to a crossbar switch. A module contains at least one arithmetic/logic processor element and at least one memory processor element. Moreover, there is a clock device, the frequency of which bears a fixed relationship to the frequency with which the video signal samples are obtained.

Abstract: A data processor system having at least one arithmetic/logic processor element and at least one memory processor element which can be coupled in circuit using a crossbar switch. The arithmetic/logic processor element is provided with an ALU and a program memory. The ALU has an input for instructions. The instructions can be made up of data from the program memory and data from the crossbar switch via a channel specifically present for the purpose.

Abstract: A digital speech coder of the baseband RELP-type (Residual-Excited Linear Prediction) comprises a transmitter (1) having an LPC-anaylser (10), a first adaptive inverse filter (11), a decimation lowpass filter (26) for selecting the baseband prediction residue and an encoding-and-multiplexing circuit (17), and a receiver (2) having a demultiplexing-and-decoding circuit (21), an interpolator (27) and a first adaptive synthesizing filter (14). The occurrence of "tonal noises" due to the spectral folding in interpolator (27) is effectively counteracted by arranging prior to the decimation lowpass filter (26) in the transmitter (1) a second adaptive inverse filter (28) which with the aid of an autocorrelator (31) removes possible periodicy from the speech band residue, and by including subsequent to the interpolator (27) in the receiver (2) a corresponding second adaptive synthesis filter (32), which reintroduces the desired periodicity in the excitation signal.

Abstract: An integrated and programmable processor for word-wise digital signal processing. The processor has a multiplier element, an arithmetic and a logic unit, a data memory and a connection for a control memory which may be integrated on-chip. The elements are interconnected by means of a double bus on which addresses as well as data may be transported by means of suitable selectors. Consequently, a pipeline operation can take place within one instruction cycle.