Abstract: Disclosed is a system and method for implementing compression coding of audio signals, such as speech signals, using two long-term prediction (LTP) models. The method determines the parameters of a second long-term prediction model on the basis of the parameters of at least one first LTP model. The present invention is aimed at switching from an LTP model with a single coefficient (monotap) to an LTP model with several coefficients, (multitap) and vice versa, as well as at switching between two multitap LTP models. The complexity of the method may be adjusted, especially as a function of a desired compromise between a target complexity and a desired quality. A device for implementing the method according to the invention is, moreover, very useful for multiple codings in cascade (transcodings) or in parallel (multi-codings and multi-mode codings).

Abstract: The invention relates to the code conversion of digital signals, particularly voice signals, and in particular coding according to a second format from information obtained by carrying out a coding according to a first format. These first and second formats use LPC (linear predictive coding) short-term prediction models on digital signal sample blocks while using filters represented by respective LPC coefficients. The LPC coefficients of the second format are determined from an interpolation on the representative values of the LPC coefficients of at least the first format, between at least one given block and a preceding block. According to the invention, the interpolation (43), is dynamically effected while selecting (42), for each current block, at least one interpolation factor (?) among a preselection of factors according to a predetermined criterion such as a stationarity criterion of the digital signal (41).

Abstract: The invention relates to the code conversion of digital signals, particularly voice signals, and in particular coding according to a second format from information obtained by carrying out a coding according to a first format. These first and second formats use LPC (linear predictive coding) short-term prediction models on digital signal sample blocks while using filters represented by respective LPC coefficients. The LPC coefficients of the second format are determined from an interpolation on the representative values of the LPC coefficients of at least the first format, between at least one given block and a preceding block. According to the invention, the interpolation (43), is dynamically effected while selecting (42), for each current block, at least one interpolation factor (?) among a preselection of factors according to a predetermined criterion such as a stationarity criterion of the digital signal (41).

Abstract: The invention relates to compressive transcoding between pulse coders using multipulse dictionaries in which each pulse occupies a position marked by an index. For each current pulse position supplied by a first coder, a neighborhood (Vge, Vde) is formed around that position. As a function of the pulse positions accepted by the second coder, pulse positions are selected in an ensemble constituted by a union of the neighborhoods. The second coder finally receives this selection (sj), involving a number of pulse positions smaller than the total number of pulse positions in the dictionary of the second coder.

Abstract: Disclosed is a system and method for implementing compression coding of audio signals, such as speech signals, using two long-term prediction (LTP) models. The method determines the parameters of a second long-term prediction model on the basis of the parameters of at least one first LTP model. The present invention is aimed at switching from an LTP model with a single coefficient (monotap) to an LTP model with several coefficients, (multitap) and vice versa, as well as at switching between two multitap LTP models. The complexity of the method may be adjusted, especially as a function of a desired compromise between a target complexity and a desired quality. A device for implementing the method according to the invention is, moreover, very useful for multiple codings in cascade (transcodings) or in parallel (multi-codings and multi-mode codings).

Abstract: The invention relates to compressive transcoding between pulse coders using multipulse dictionaries in which each pulse occupies a position marked by an index. For each current pulse position supplied by a first coder, a neighborhood (Vge, Vde) is formed around that position. As a function of the pulse positions accepted by the second coder, pulse positions are selected in an ensemble constituted by a union of the neighborhoods. The second coder finally receives this selection (sj), involving a number of pulse positions smaller than the total number of pulse positions in the dictionary of the second coder.