Michele Rosso

Pitch detection for use in a predictive speech coder

A pitch detector to adjust long term prediction in a pulse excitation speech coder. A residual signal r(n) is first derived from the speech signal s(n) by short term filtering. Then, r(n) is processed to calculate a prediction error signal e(n) which is subsequently pulse excitation encoded. The processing of e(n) entails prediction of a residual by measuring a pitch related factor M, employing two steps. First calculating a coarse M value through peak clipping and sign transition detection, and then adjusting the M value by autocorrelation--calculations about the roughly spaced peaks.

MPE/LTP speech coder for moblie radio application

Abstract In this paper, we describe our contribution to the CEPT effort for the definition of a European standard for the cellular mobile radio. We first give an overview of the Multipulse excitation with long term prediction (MPE/LTP) algorithm. Then, we report details on the implementation (constants, quantizing tables) respectively in the analysis part, the error protection/correction, and the synthesis part of the codec. Finally, we report detailed figures about the implementation efficiency (ROM/RAM/Cycles).

Adaptive code excited predictive coding

A novel way to use the code excited linear prediction (CELP) concept that decreases the processing load while keeping the same speech quality is discussed. Rather than performing individual weighting of each candidate sequence, a global implementation of the perceptual weighting function at the codebook level is proposed. As a result, the analysis-by-synthesis procedure does not require the processing of all the candidate sequences through the synthesis and weighting filters; the complexity requirement of the algorithm is therefore much reduced. The concept is carried out with an adaptive codebook. Two fixed-point implementations of the adaptive CELP (ACELP) algorithm are reported: a 7.2 kb/s block coder (7 MIPS), and a 12 kb/s low-delay coder (11 MIPS). Both coders have been rated to provide the same quality as the 13 kb/s block coder adopted by the GSM for the European cellular telephone. >

7 KBPS — 7 MIPS — High Quality ACELP for Cellular Radio

In this chapter, we propose a modification of the classical CELP (Code Excited Linear Predictive) algorithm in order to reduce its computational complexity and required memory size, while preserving the quality of the reconstructed speech.