DEPTH-FIRST SEARCH BY ALGEBRAIC ENCODING BOOK FOR FAST CODING OF SPEECH Russian patent published in 2001 - IPC

FIELD: encoding of audible signals. SUBSTANCE: while encoding audio signal one searches by encoding book made up of set of encoding vectors each composed of 40 positions and including N pulses of non-zero amplitude which are assigned in advance to certain valid positions. Depth-first search which proposes tree structure with levels arranged in order from 1 to M is used to diminish complexity of search. At each level operation of path acquisition is conducted as result of which path-candidate from preceding level is continued by way of selection of certain number of pulses determined beforehand and by way of selection of valid positions for specified new pulses in correspondence with given rule of specified pulses and given criterion of selection. Path occurring at first level and continued by operations of path acquisition of subsequent levels determines proper positions of N pulses of non-zero amplitude of encoding vector-candidate. Usage of estimation of probability of position of pulse proceeding from signal during first several levels makes it feasible to carry out look ahead of pulses to start search for favorable conditions. Selection criterion based on maximization of relation is employed to evaluate result and to select most optimum encoding vector from number of competing encoding vectors-candidates that enables difficulty of search to be diminished which is technical result achieved by realization of group of inventions. EFFECT: diminished difficulty of search. 61 cl, 7 dwg