Abstract: The invention aims at constructing improved dictionaries of CELP excitation vectors for coding/decoding digital audio signals. Usually, each vector of dimension N comprises pulses capable of occupying N valid positions. The invention concerns the construction of dictionaries with particular structure by: providing a common sequence of pulses forming a base pattern; and assigning the base pattern to each excitation vector of the dictionary, based on one or more occurrences at one or more respective positions among said N valid positions. The invention also concerns a combination of dictionaries thus constructed with optionally standard multipulse dictionaries, by union or summation or cascading.

Abstract: A method of concealing transmission error in a digital audio signal, wherein a signal that has been decoded after transmission is received, the samples decoded while the transmitted data is valid are stored, at least one short-term prediction operator and one long-term prediction operator are estimated as a function of stored valid samples, and any missing or erroneous samples in the decoder signal are generated using the estimated operators. The energy of the synthesized signal that is thus generated is controlled by means of a gain that is computed and adapted sample by sample.

Abstract: The invention relates, in particular, to a system for managing communication sessions between first terminals adapted to send audio and/or video and/or data streams during these sessions and second terminals accessible via an external data transmission network. The first terminals are connected to a stream concentrator itself connected to the external network. Since the streams sent by at least some of the first terminals are coded or intended to be coded by hierarchical encoders, the system includes means for processing said streams so that each of them is sent to the external network by the concentrator at a given hierarchy level and means for determining said hierarchy level as a function of parameters relating to the number and nature of the sessions set up between the first terminals and the second terminals.

Abstract: A telecommunications system SYST including a local area network WLAN, a main network INTNW, and an intermediate element INTM through which data packets Dpo, Epi/Tepi must pass in transit between the local area network WLAN and the main network INTNW. The system evaluates a volume of calls supported by the local area network WLAN, and truncates data packets if said volume is above a predetermined threshold. In the event of an overload, the size of data packets in transit through the local area network is automatically reduced without recourse to systematic and discriminatory elimination of a particular type of data.

Abstract: A method of concealing transmission error in a digital audio signal, wherein a signal that has been decoded after transmission is received, the samples decoded while the transmitted data is valid are stored, at least one short-term prediction operator and one long-term prediction operator are estimated as a function of stored valid samples, and any missing or erroneous samples in the decoder signal are generated using the estimated operators. The energy of the synthesized signal that is thus generated is controlled by means of a gain that is computed and adapted sample by sample.

Abstract: The invention relates to compression coding and/or decoding of digital signals, in particular by vector variable-rate quantisation defining a variable resolution. For this purpose an impulsion dictionary comprises: for a given dimension, increasing resolution dictionaries imbricated into each other and, for a given dimension, a union of: a totality (D?i<N>) of code-vectors produced, by inserting elements taken in a final set (A) into smaller dimension code-vectors according to a final set of predetermined insertion rules (F1) and a second totality of code-vectors (Y?) which are not obtainable by insertion into the smaller dimension code vectors according to said set of the insertion rules.

Abstract: A method of concealing transmission error in a digital audio signal in which a signal that has been decoded after transmission is received, the samples decoded while the transmitted data is valid are stored, at least one short-term prediction operator and one long-term prediction operator are estimated as a function of stored valid samples, and any missing or erroneous samples in the decoder signal are generated using the operators estimated in this way, the method being characterized in that the energy of the synthesized signal as generated in this way is controlled by means of a gain that is computed and adapted sample by sample.

Abstract: The invention aims at constructing improved dictionaries of CELP excitation vectors for coding/decoding digital audio signals. Usually, each vector of dimension N comprises pulses capable of occupying N valid positions. The invention concerns the construction of dictionaries with particular structure by: providing a common sequence of pulses forming a base pattern; and assigning the base pattern to each excitation vector of the dictionary, based on one or more occurrences at one or more respective positions among said N valid positions. The invention also concerns a combination of dictionaries thus constructed with optionally standard multipulse dictionaries, by union or summation or cascading.

Abstract: The present invention relates to a telecommunications system SYST including a local area network WLAN, a main network INTNW, and an intermediate element INTM through which data packets Dpo, Epi/Tepi must pass in transit between the local area network WLAN and the main network INTNW. The system according to the invention includes: means for evaluating a volume of calls supported by the local area network WLAN; and means for truncating data packets if said volume is above a predetermined threshold. In the event of an overload the invention automatically reduces the size of data packets in transit through the local area network without recourse to systematic and discriminatory elimination of a particular type of data.

Abstract: A maximum of Nmax bits for encoding is defined for a set of parameters which may be calculated from a signal frame. The parameters for a first sub-set are calculated and encoded with N0 bits, where N0<Nmax. The allocation of Nmax?N0 encoding bits for the parameters of a second sub-set are determined and the encoding bits allocated to the parameters for the second sub-set are classified. The allocation and/or order of classification of the encoding bits are determined as a function of the encoding parameters for the first sub-set. For a total of N available bits for the encoding of the total parameters (N0<N=Nmax), the parameters for the second sub-set allocated the N?N0 encoding bits classified the first in said order are selected. Said selected parameters are calculated and encoded to give the N?N0 bits. The N0 encoding bits for the first sub-set and the N?N0 encoding bits for the selected parameters for the second sub-set are finally introduced into the output sequence of the encoder.

Abstract: The invention relates, in particular, to a system for managing communication sessions between first terminals adapted to send audio and/or video and/or data streams during these sessions and second terminals accessible via an external data transmission network. The first terminals are connected to a stream concentrator itself connected to the external network. Since the streams sent by at least some of the first terminals are coded or intended to be coded by hierarchical encoders, the system includes means for processing said streams so that each of them is sent to the external network by the concentrator at a given hierarchy level and means for determining said hierarchy level as a function of parameters relating to the number and nature of the sessions set up between the first terminals and the second terminals.

Abstract: The invention relates to compression coding and/or decoding of digital signals, in particular by vector variable-rate quantisation defining a variable resolution. For this purpose an impulsion dictionary comprises: for a given dimension, increasing resolution dictionaries imbricated into each other and, for a given dimension, a union of: a totality (D?i<N>) of code-vectors produced, by inserting elements taken in a final set (A) into smaller dimension code-vectors according to a final set of predetermined insertion rules (F1) and a second totality of code-vectors (Y?) which are not obtainable by insertion into the smaller dimension code vectors according to said set of the insertion rules.

Abstract: A maximum of Nmax bits for encoding is defined for a set of parameters which may be calculated from a signal frame. The parameters for a first sub-set are calculated and encoded with N0 bits, where N0<Nmax. The allocation of Nmax?N0 encoding bits for the parameters of a second sub-set are determined and the encoding bits allocated to the parameters for the second sub-set are classified. The allocation and/or order of classification of the encoding bits are determined as a function of the encoding parameters for the first sub-set. For a total of N available bits for the encoding of the total parameters (N0<N=Nmax), the parameters for the second sub-set allocated the N?N0 encoding bits classified the first in said order are selected. Said selected parameters are calculated and encoded to give the N?N0 bits. The N0 encoding bits for the first sub-set and the N?N0 encoding bits for the selected parameters for the second sub-set are finally introduced into the output sequence of the encoder.

Abstract: An improved EX-CELP or RCELP encoding scheme is proposed, in which, at the encoder side, a speech signal is perceptually weighted signal prior to entering a time scale modification module, then the modified signal is transformed into another domain, such as the speech or LP short-term residual domain, using the corresponding inverse filtering operation directly or possibly combined with another processing, for instance a short-term LP filtering. A shift function is calculated in the time scale modification process to associate the position of each sample in the modified signal with its original position before the modification. The positions of the samples in the modified signal that correspond to sub-frame boundaries of the original signal are evaluated to switch filters for the inverse filtering at the appropriate instants. Therefore, the synchronization between the inverse filters and the modified signal is maintained.

Abstract: A method of concealing transmission error in a digital audio signal in which a signal that has been decoded after transmission is received, the samples decoded while the transmitted data is valid are stored, at least one short-term prediction operator and one long-term prediction operator are estimated as a function of stored valid samples, and any missing or erroneous samples in the decoder signal are generated using the operators estimated in this way, the method being characterized in that the energy of the synthesized signal as generated in this way is controlled by means of a gain that is computed and adapted sample by sample.

Abstract: A process and a device for creating comfort noise for discontinuous speech transmission in which, following the end of each detected active period, a silence descriptor frame is generated as a set of parameters describing the comfort noise. For every successive current inactive frame, the frequency spectrum is analysed and then compared with a reference spectrum stored previously. Upon identity of the reference frequency spectrum and the current frame spectrum, no new silence descriptor frame is transmitted. Upon absence of identity of these spectra, a new silence descriptor frame is transmitted.

Abstract: A long-term analysis of an input speech signal is carried out to adaptively select parameters of a pitch synthesis filter in respective variation ranges. Successively selected values of said parameters are processed to estimate maximum magnitudes of an error component of the output signal of the pitch synthesis filter. The variation range of at least one of said parameters is determined on the basis of the estimated maximum magnitudes.

Abstract: The present invention relates to a device and process for the digital coding and decoding of speech comprising a short term prediction, a long term prediction and a residual wave coding technique using a synthesis analysis method. The LTP analysis module uses a dictionary of delays having a pseudo-logarithmic structure, in which the delays are arranged in increasing order. This dictionary is constituted by segments, each having a given resolution, the resolutions of the successive segments decreasing geometrically in a rational ratio k>1, while the number of elements of each segment remains constant. The invention defines the use of .lambda. delay elements of said dictionary extending the LTP analysis techniques to high time resolution. The invention also relates to a process for the rapid scanning of such a pseudo-logarithmic delay dictionary. It also relates to a process for implementing a selection criterion of the delay in closed loop with perceptual filtering.

Abstract: An analog parallel device for the local processing of a bidimensional signal comprises an input means, a processing means and an output means, the input means receiving the bidimensional signal and supplying, on a group of elementary input points organized in matrix-like manner, a group of parallel electrical input signals, the processing means receiving said input signals and supplying, on a group of elementary output points organized in matrix-like manner, a group of parallel electric output signals, each of which is obtained by a linear or non-linear combination of a plurality of input signals, the output means receiving said output signals, said means being realized in the form of thin films on a substrate.This device may be particularly applied to local image processing.