Speech coding system

• US 7,050,967 B2
• Filed: 04/04/2002
• Issued: 05/23/2006
• Est. Priority Date: 04/09/2001
• Status: Active Grant

• Current Assignee: Callahan Cellular LLC (Intellectual Ventures LLC)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Gigi, Ercan Ferit
• Primary Examiner(s): Dorvil, Richemond
• Assistant Examiner(s): Pierre, Myriam
• Application Number:
  US10/116,550
• Publication Number:
  US 20020184005A1
• Time in Patent Office: 1,510 Days
• Field of Search: 704/203, 704/200.1, 704/205, 704/212, 704/216, 704/219, 704/223, 704/224, 704/226, 704/227, 704/234, 704/265, 704/200, 704/759
• US Class Current: 704/206
• CPC Class Codes: G10L 19/00 Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis in musical instruments G10H
• CPC Class Codes: H04B 14/068 with adaptive feedback

Abstract

In a speech coding system with an encoder and a decoder cooperating with said encoder, the speech encoder comprises a pre-processor and an ADPCM encoder with a quantizer and step-size adaptation means, while the speech decoder comprises an ADPCM decoder with similar step-size adaptation means as in the ADPCM encoder and with a decoder, and a post-processor. The quantizer is provided with storage means containing values for a correction factor α(c(n)) of the step-size Δ(n), said correction factor being dependent on the quantizer output signal c(n). The step-size adaptation occurs in accordance with the relation:

$\Delta \left(n+1\right)=\Delta \left(n\right)·A·\{\begin{array}{cc}\alpha \left(c\left(n\right)\right)& \mathrm{if}\alpha \left(c\left(n\right)\right)<1\\ \alpha \left(c\left(n\right)\right)+b& \mathrm{if}\Delta \left(n\right)·A·c_{\max }<{\Delta }_{\max }\\ 1& \mathrm{otherwise}\end{array}.$

Claims

1. Speech coding system with a speech encoder and a speech decoder cooperating with said speech encoder, the speech encoder comprising a pre-processor and an adaptive differential pulse code modulation (ADPCM) encoder with a quantizer and step-size adaptation means and the speech decoder comprising an ADPCM decoder with similar step-size adaptation means as in the ADPCM encoder and with a decoder, and a post-processor, the quantizer being provided with storage means containing values for a correction factor α

(c(n)) of the step-size Δ

(n), said correction factor being dependent on the quantizer output signal c(n), characterized in that the step-size adaptation occurs in accordance with the relation;

2. Speech coding system according to claim 1, characterized in that the storage means in the quantizer contain values of correction factors α

(c(n)) in accordance with the tables FIGS. 3A–

3F.

3. Speech coding system according to claim 1, characterized in that the correction factors α

(c(n)) are adapted for a coding system, wherein in the pre-processor phase-smearing filter means are applied and in the post-processor inverse phase-smearing filter means are applied within the speech decoder.