Title:
FILTERING METHOD AND LOW BIT RATE VOICE COMMUNICATION SYSTEM
Document Type and Number:
Japanese Patent JPH1145100
Kind Code:
A
Abstract:
PROBLEM TO BE SOLVED: To provide a filtering method including two filters which can be used as a reinforced filter of a mix excitation linear prediction voice coder or a post filter of a code book excitation linear prediction voice coder. SOLUTION: A first filter 62 has a transfer function of 1-P[z/(β.sig- prob)]}/ 1-P[z/(α.sig-prob)]} assuming that P is a prediction value, α and βare magnification, z is an inverse of unit delay operator for conversion- displaying of a transfer function, and sig-prob is a signal probability estimation value, a second filter 65 has a transfer function of 1-μz<-1> .sig-prob assuming that μ is magnification. Then sig-prob a signal probability value obtained by comparing signal power of the present frame with a long term estimation value of noise power in a signal probability estimation device 63, when signal power is larger than a value in which 30dB is added to noise power, a value of sig- prob is 1, and when signal power is smaller than a value in which 12dB is added to noise power. a value of sig-prob is 0. Between two states, sig-prob is (logarithm gain - 12dB - noise gain)/18.
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Inventors:
MCCREE ALAN V
Application Number:
JP16294997A
Publication Date:
February 16, 1999
Filing Date:
June 19, 1997
Export Citation:
Assignee:
TEXAS INSTRUMENTS INC
International Classes:
G10L19/06; G10L19/14; H03H17/02; H03H21/00; H04B1/66; (IPC1-7): G10L9/14; H03H17/02; H03H21/00
Attorney, Agent or Firm:
Akira Asamura (3 outside)