Speech coding/decoding method and apparatus

• US 6,768,978 B2
• Filed: 05/02/2003
• Issued: 07/27/2004
• Est. Priority Date: 01/22/1999
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Amada, Tadashi, Tsuchiya, Katsumi
• Primary Examiner(s): Dorvil, Richemond
• Assistant Examiner(s): Lerner, Martin
• Application Number:
  US10/427,948
• Publication Number:
  US 20030195746A1
• Time in Patent Office: 452 Days
• Field of Search: 704/205, 704/206, 704/212, 704/220, 704/221, 704/223, 704/211, 704/219
• US Class Current: 704/212
• CPC Class Codes: G10L 19/12 the excitation function being a code excitation, e.g. in code excited linear prediction [CELP] vocoders

Abstract

An input speech signal to an input terminal is supplied to a speech synthesizer section through a speech analyzer section and frequency parameter quantizer section to form a synthesis filter, and the input speech signal is expressed by quantized LPC coefficients representing the characteristics of the synthesis filter and an excitation signal for exciting the synthesis filter. In this case, in a pulse excitation section, a pulse position selector selects pulse position candidates from the integer pulse positions and non-integer pulse positions stored in a pulse position codebook, and an integer position pulse generator and non-integer position pulse generator respectively generate integer position pulses set at sampling points of the excitation signal and non-integer position pulses set at positions located between sampling points. These pulses are synthesized into a pulse train serving as a source of an excitation signal.

Claims

1. A speech decoding method, comprising:

extracting, from a coded stream, a first index indicating a frequency characteristic of speech and a second index indicating a pulse train of an excitation signal;

reconstructing a synthesis filter by decoding the first index;

reconstructing the excitation signal including a pulse train that includes pulses selected from first pulses and second pulses, the first pulses being set on sampling points of the excitation signal and the second pulses being set at positions located between the sampling points of the excitation signal based on the second index; and

generating a decoded speech signal by exciting the synthesis filter using the reconstructed excitation signal.

2. A speech decoding method, comprising:

extracting, from a coded stream, a first index indicating a frequency characteristic of speech and a second index indicating an excitation signal including a pitch vector and a stochastic vector;

reconstructing a synthesis filter by decoding the first index;

reconstructing the excitation signal based on the second index, the excitation signal including a pulse train including pulses selected from first pulses and second pulses, the first pulses being set on sampling points of the excitation signal and the second pulses being set at positions located between sampling points of the excitation signal; and

generating a decoded speech signal by exciting the synthesis filter using the reconstructed excitation signal.

3. A speech decoding method, comprising:

extracting, from a coded stream, a first index indicating a frequency characteristic of speech and a second index indicating an excitation signal;

reconstructing a synthesis filter by decoding the first index;

reconstructing the excitation signal based on the second index, the excitation signal including a pitch vector and a stochastic vector formed of a pulse train generated by arranging pulses at a predetermined number of pulse positions selected from pulse position candidates subjected to adapting based on a shape of the pitch vector, and the pulse position candidates including first pulse position candidates set on sampling points of the stochastic vector and second pulse position candidates set at positions located between the sampling points of the stochastic vector; and

decoding a speech signal by exciting a synthesis filter using the excitation signal.

4. The speech decoding method according to claim 3, wherein the pulse train is made periodic in units of pitches in accordance with pitch period information.