Voice encoding and decoding device

• US 4,610,022 A
• Filed: 12/14/1982
• Issued: 09/02/1986
• Est. Priority Date: 12/15/1981
• Status: Expired due to Term

• Current Assignee: Kokusai Denshi Denwa Company Limited (KDDI Corporation)
• Original Assignee: Kokusai Denshi Denwa Company Limited (KDDI Corporation)
• Inventors: Kitayama, Seishi, Yato, Fumihiro, Kurematsu, Akira
• Primary Examiner(s): KEMENY, EMANUEL
• Application Number:
  US06/449,760
• Time in Patent Office: 1,358 Days
• Field of Search: 381/41-43, 381/36, 381/37, 381/38, 381/39, 381/40
• US Class Current: 704/205
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients

Abstract

In a speech transmission or storage system using LPC parameters and a Baseband Signal derived from the prediction error signal, the synthesis excitation signal is formed from the baseband plus high-frequency regeneration, which is then spectrum-flattened for proper synthesis.

Claims

1. A voice encoding and decoding device comprising a first predictor consisting of a linear predictor which analyzes an input voice to a predictive parameter, a first encoder which is connected to said linear predictor and encodes the predictive parameter and a first filter whose frequency characteristics are controlled by the encoded predictive parameter and which outputs a predictive error signal, a low-pass filter which is connected to said first filter and passes only a base band component of the predictive error signal, a second encoder which is connected to said low pass filter and encodes the base band component, transmission or memory means which is connected to said first and second encoders and transmits or stores the encoded base band component and the encoded predictive parameter, first and second decoders which are connected to said transmission or memory means, said first decoder decoding the encoded base band component, and said second decoder decoding the encoded predictive parameter, a nonlinear circuit which is connected to said first decoder via a low pass filter and produces a higher harmonic component of the base band component, an emphasis circuit which is connected to said nonlinear circuit and emphasizes the high frequency range of the higher harmonic component, a second predictor which is connected to said emphasis circuit and consists of a second linear predictor and a filter whose frequency characteristics are controlled by a predictive parameter of said second linear predictor, a high-pass filter which is connected to said second predictor and which produces a high frequency output signal component having a flat high frequency range spectrum, level detecting means which receives said high frequency component and said base band component and detects the level difference therebetween, a variable gain amplifier which is connected to said level detecting means and compensates to equalize the level of said base band component with that of said high frequency component, an adder circuit which receives the base band component and the high frequency component of the same level and produces an exciting signal, and a voice composite filter which is connected to said adder circuit and said second decoder and composes said exciting signal and the decoded predictive parameter to reproduce a voice.

2. A voice encoding and decoding device as claimed in claim 1, wherein said level detecting means comprises a first level detector for detecting the level a of said decoded base band component and another level detector for detecting the input level b of said variable gain amplifier, said variable gain amplifier being operable at a gain a-b/b proportional to the level difference (a-b).

3. A voice encoding and decoding device as claimed in claim 1, wherein said level detecting means comprises a first level detector for detecting the level c of the predictive error signal out of said predictor of the encoding side, another level detector for detecting the level a of said base component and still another level detector for detecting the input level b of said high frequency component, said variable gain amplifier being operable at a gain c-a/b supplementing the level difference c-a between the predictive error signal before encoding and said decoded base band component.

4. A voice encoding and decoding device as claimed in claim 1, wherein said level detecting means comprises a level comparator detecting the level difference (c-a'"'"') between the level c of said predictive error signal from said predictor before encoding and the level a'"'"' of said base band component before encoding, and another level detector detecting the input level b of said high frequency component of said variable gain amplifier, said variable gain amplifier being operable at a gain c-a'"'"'/b supplementing the level difference (c-a'"'"') of said level comparator.