Method and Device for Carrying Out Optimal Coding Between Two Long-Term Prediction Models

A device for coding according to a second coding format, designed to use coding information obtained by implementing a coding according to a first coding format, the first and second coding formats implementing, in particular for the coding of a speech signal, a search for long-term prediction (LTP) parameters by exploring a dictionary comprising candidate parameters, one at least of the first and second coding formats using a filtering with several coefficients for a fine search for the LTP parameters, the device comprising:

• a memory storing a correspondence table defining, as a function of LTP parameters determined by the first coding format, orders of a dictionary that the second coding format uses;
• means for recovering a signal giving at least one a priori information on LTP parameters in the course of a coding according to the first coding format;
• means active on reception of said signal for consulting said correspondence table and selecting at least one order of said dictionary of the second coding format;
• and
• calculation means for:
• ordering said dictionary of the second coding format according to the selected order, with a view to choosing a plurality of first candidates from the dictionary;
• and
• continuing the coding according to the second coding format, by conducting the LTP search only among the plurality of candidates.