Speech signal decoding device and method for decoding speech signal

• US 10,347,266 B2
• Filed: 05/20/2016
• Issued: 07/09/2019
• Est. Priority Date: 08/05/2015
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Inventors: Ehara, Hiroyuki
• Primary Examiner(s): Tzeng, Feng-Tzer
• Application Number:
  US15/736,501
• Publication Number:
  US 20180182407A1
• Time in Patent Office: 1,145 Days
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 19/08 Determination or coding of the excitation function; Determination or coding of the long-term prediction parameters
• CPC Class Codes: G10L 19/12 the excitation function being a code excitation, e.g. in code excited linear prediction [CELP] vocoders
• CPC Class Codes: G10L 19/125 Pitch excitation, e.g. pitch synchronous innovation CELP [PSI-CELP]
• CPC Class Codes: G10L 19/16 Vocoder architecture
• CPC Class Codes: G10L 21/003 Changing voice quality, e.g. pitch or formants
• CPC Class Codes: G10L 25/90 Pitch determination of speech signals
• CPC Class Codes: H03M 7/30 Compression speech analysis-synthesis for redundancy reduction G10L19/00; for image communication H04N; Expansion; Suppression of unnecessary data, e.g. redundancy reduction

Abstract

A speech signal decoding device includes an adaptive code-book decoder, a fixed code-book decoder, a ratio calculator, a determination unit, and an attenuator. The adaptive code-book decoder generates an adaptive code-book vector using an adaptive code-book code of an encoded signal encoded by a CELP method. The fixed code-book decoder generates a fixed code-book vector using a fixed code-book code of the encoded signal. The ratio calculator calculates an amplitude ratio or an energy ratio between the adaptive code-book vector and the fixed code-book vector. The determination unit determines whether the amplitude ratio or the energy ratio exceeds a predetermined threshold. When the amplitude ratio or the energy ratio is determined to exceed the predetermined threshold, the attenuator attenuates an excitation signal that has been defined by adding the adaptive code-book vector to the fixed code-book vector.

Claims

1. A speech signal decoding device, comprising:

an adaptive code-book decoder that generates an adaptive code-book decoded component using an adaptive code-book (ACB) code of an encoded speech signal encoded by a code-excited linear prediction (CELP) method;

a fixed code-book decoder that generates a fixed code-book decoded component using a fixed code-book (FCB) code of the encoded speech signal;

a ratio calculator that calculates an ACB/FCB amplitude ratio between the adaptive code-book decoded component and the fixed code-book decoded component;

a determiner that determines whether there is an error in the encoded speech signal based on whether the amplitude ratio exceeds a predetermined threshold or not, the predetermined threshold being set to a value exceeding a maximum value of the ACB/FCB amplitude ratio that possibly appears upon decoding of the encoded speech signal without an error,

wherein, when the ACB/FCB amplitude ratio exceeds the predetermined threshold, the determiner determines the encoded speech signal has an error, and when the ACB/FCB amplitude ratio is equal to or less than the predetermined threshold, the determiner determines the encoded speech signal has no error; and

an attenuator that attenuates an excitation signal that has been defined by adding the adaptive code-book decoded component to the fixed code-book decoded component, when the determiner determines that the ACB/FCB amplitude ratio exceeds the predetermined threshold.

2. The speech signal decoding device according to claim 1, further comprising:

a demultiplexer that separates the encoded speech signal into the adaptive code-book code and the fixed code-book code for each frame.

3. The speech signal decoding device according to claim 2,

wherein, when a frame whose ACB/FCB amplitude ratio is determined to exceed the predetermined threshold by the determiner is present, the attenuator attenuates excitation signals of a predetermined number of frames subsequent to the determined frame.

4. The speech signal decoding device according to claim 1, further comprising;

a synthesis filter that generates a decoded speech signal from the excitation signal attenuated by the attenuator.

6. The speech signal decoding device according to claim 1,

wherein the predetermined threshold is equal to 50.

5. A method for decoding a speech signal, comprising:

generating an adaptive code-book decoded component using an adaptive code-book (ACB) code of an encoded speech signal encoded by a code-excited linear prediction (CELP) method;

generating a fixed code-book decoded component using a fixed code-book (FCB) code of the encoded speech signal;

calculating an ACB/FCB amplitude ratio between the adaptive code-book decoded component and the fixed code-book decoded component;

determining whether there is an error in the encoded speech signal based on whether the ACB/FCB amplitude ratio exceeds a predetermined threshold or not, the predetermined threshold being set to a value exceeding a maximum value of the ACB/FCB amplitude ratio that possibly appears upon decoding of the encoded speech signal without an error,

wherein, when the ACB/FCB amplitude ratio exceeds the predetermined threshold, the encoded speech signal is determined to have an error, and when the ACB/FCB amplitude ratio is equal to or less than the predetermined threshold, the encoded speech signal is determined to have no error; and

attenuating an excitation signal that has been defined by adding the adaptive code-book decoded component to the fixed code-book decoded component, when the ACB/FCB amplitude ratio is determined to exceed the predetermined threshold.