Method for adapting for an interoperability between short-term correlation models of digital signals

A code conversion module, for coding a digital signal according to a second format, from information obtained by carrying out at least one coding of the signal according to a first format, the first and second formats using, for coding a speech signal, LPC short-term prediction models on digital signal sample blocks, by using filters represented by respective LPC coefficients, the module comprising:

• an input for receiving information representative of the LPC coefficients obtained by the first format;
• and
• a processing unit for determining the LPC coefficients of the second format from an interpolation on values representative of the LPC coefficients obtained from the first format between at least one first block and a second block, preceding the first block,
• wherein the processing unit performs a detection of a break in stationarity of the digital signal at least between the given block and the preceding block, and
• the processing unit performs said interpolation dynamically, by choosing for each current block at least one interpolation factor from a preselection of factors, according to said detection, and wherein:
• the processing unit detects a moment of break in stationarity between a given block and a preceding block,
• this break moment is compared with a time position of a current block in the second format, and,
• in the interpolation, more weight is assigned to the LPC coefficients of the first format that are associated with the given block if the block of the second format occurs after the detected break moment, or to the LPC coefficients of the first format that are associated with the preceding block if the block of the second format occurs before the detected break moment.

A non-transitory computer storage medium storing a computer program product, designed to be stored in a memory of a code conversion module, to code a signal according to a second format, from information obtained by carrying out at least one coding of the same signal according to a first format, the first and second formats using, for coding a speech signal, LPC short-term prediction models on digital signal sample blocks, by using filters represented by respective LPC coefficients,

• the computer program comprising the steps of:
• determining values representative of the LPC coefficients of the second format from an interpolation on values representative of the LPC coefficients obtained from the first format between at least one first given block and a second block, preceding the first block;
• and
• dynamically performing said interpolation, by choosing for each current block at least one interpolation factor from a preselection of factors, according to a detection of a break in stationarity of the digital signal at least between the given block and the preceding block, and wherein:
• a moment of break in stationarity is detected between a given block and a preceding block,
• this break moment is compared with a time position of a current block in the second format, and,
• in the interpolation, more weight is assigned to the LPC coefficients of the first format that are associated with the given block if the block of the second format occurs after the detected break moment, or to the LPC coefficients of the first format that are associated with the preceding block if the block of the second format occurs before the detected break moment.

A signal coding system for a speech signal, comprising:

• a coder according to a first format and a coder according to a second format, using LPC short-term prediction models on digital signal sample blocks, by using filters represented by respective LPC coefficients;
• and
• a code conversion module for adapting the coding of the signal to the second format, from information obtained by carrying out the coding of the same signal according to the first format, wherein the module includes:
• an input for receiving information representative of the LPC coefficients obtained by the first format;
• and
• a processing unit for determining the LPC coefficients of the second format from an interpolation on values representative of the LPC coefficients obtained from the first format between at least one first given block and a second block, preceding the first block, wherein the processing unit performs a detection of a break in stationarity of the digital signal at least between the given block and the preceding block, and the processing unit performs said interpolation dynamically, by choosing for each current block at least one interpolation factor from a preselection of factors, according to said detection, and wherein:
• the processing unit detects a moment of break in stationarity between a given block and a preceding block,
• this break moment is compared with a time position of a current block in the second format, and,
• in the interpolation, more weight is assigned to the LPC coefficients of the first format that are associated with the given block if the block of the second format occurs after the detected break moment, or to the LPC coefficients of the first format that are associated with the preceding block if the block of the second format occurs before the detected break moment.