Rcelp Coder

摘要

An improved method of speech coding for use in conjunction with speech coding methods wherein speech is digitized into a plurality of temporally defined frames, each frame including a plurality of sub-frames, a nd the digitized speech is partitioned into periodic components and a residual signal. For each of a plurality of sub-frames of the residual signal, the improved method of speech coding selects and applies a time shift T to the s ub- frame by applying a matching criterion to (a) the current sub-frame of the residual signal, and (b) a sample-to-sample (sub-frame-to-subframe) pitch de lay determined by applying linear interpolation to known pitch delays occurring at or near frame-to-frame boundaries of previous frames. The matching criterion is applied by minimizing .epsilon., where: .epsilon. = .SIGMA.(r(n-T)-r(n-D(n)))2. n (r(n-T)) is the residual signal of the current frame shifted by time T, r(n- D(n)) is the delayed residual signal from a previously-occurring frame, n is a positi ve integer, r is the instantaneous amplitude of the residual signal, and D(n) i s the sample-to-sample pitch delay determined by applying linear interpolation to known pitch delay values occurring at or near frame-to-frame boundaries.