Encoder and method for encoding an audio signal with reduced background noise using linear predictive coding

Patent metadata

Field	Value
Publication number	US-2018204580-A1
Application number	US-201815920907-A
Country	US
Kind code	A1
Filing date	Mar 14, 2018
Priority date	Sep 25, 2015
Publication date	Jul 19, 2018
Grant date	—

Abstract

It is shown an encoder for encoding an audio signal with reduced background noise using linear predictive coding. The encoder includes a background noise estimator configured to estimate background noise of the audio signal, a background noise reducer configured to generate background noise reduced audio signal by subtracting the estimated background noise of the audio signal from the audio signal, and a predictor configured to subject the audio signal to linear prediction analysis to obtain a first set of linear prediction filter (LPC) coefficients and to subject the background noise reduced audio signal to linear prediction analysis to obtain a second set of linear prediction filter (LPC) coefficients. Furthermore, the encoder includes an analysis filter composed of a cascade of time-domain filters controlled by the obtained first set of LPC coefficients and the obtained second set of LPC coefficients.

First claim

1 . Encoder for encoding an audio signal with reduced background noise using linear predictive coding, the encoder comprising:
a background noise estimator configured to estimate a representation of background noise of the audio signal; a background noise reducer configured to generate a representation of a background noise reduced audio signal by subtracting the representation of the estimated background noise of the audio signal from a representation of the audio signal; a predictor configured to subject the representation of the audio signal to linear prediction analysis to acquire a first set of linear prediction filter (LPC) coefficients and to subject the representation of the background noise reduced audio signal to linear prediction analysis to acquire a second set of linear prediction filter (LPC) coefficients; and an analysis filter composed of a cascade of time-domain filters controlled by the acquired first set of LPC coefficients and the acquired second set of LPC coefficients to acquire a residual signal from the audio signal.

2 . Encoder according to claim 1 , wherein the cascade of time domain filters comprises two-times a linear prediction filter using the acquired first set of LPC coefficients and one-time an inverse of a further linear prediction filter using the acquired second set of LPC coefficients.

3 . Encoder according to claim 1 , wherein the cascade of time-domain filters is a Wiener filter.

4 . Encoder according to claim 1 ,
wherein the background noise estimator is configured to estimate an autocorrelation of the background noise as representation of the background noise of the audio signal; wherein the background noise reducer is configured to generate the representation of the background noise reduced audio signal by subtracting the autocorrelation of the background noise from an autocorrelation of the audio signal, wherein the autocorrelation of the audio signal is the representation of the audio signal and wherein the representation of the background noise reduced audio signal is an autocorrelation of a background noise reduced audio signal.

5 . Encoder according to claim 1 , wherein the representation is an autocorrelation.

6 . Encoder according to claim 1 , further comprising a transmitter configured to transmit the second set of LPC coefficients.

7 . Encoder according to claim 1 , further comprising a transmitter configured to transmit the residual signal.

8 . Encoder according to claim 1 , further comprising a quantizer configured to quantize and/or encode the residual signal before transmission.

9 . Encoder according to claim 1 , further comprising a quantizer configured to quantize and/or encode the second set of LPC coefficients before transmission.

10 . Encoder according to claim 8 , wherein the quantizer is configured to use code-excited linear prediction (CELP), entropy coding, or transform coded excitation (TCX).

11 . System comprising:
the encoder for encoding an audio signal with reduced background noise using linear predictive coding, said encoder comprising:
a background noise estimator configured to estimate a representation of background noise of the audio signal;
a background noise reducer configured to generate a representation of a background noise reduced audio signal by subtracting the representation of the estimated background noise of the audio signal from a representation of the audio signal;
a predictor configured to subject the representation of the audio signal to linear prediction analysis to acquire a first set of linear prediction filter (LPC) coefficients and to subject the representation of the background noise reduced audio signal to linear prediction analysis to acquire a second set of linear prediction filter (LPC) coefficients; and
an analysis filter composed of a cascade of time-domain filters controlled by the acquired first set of LPC coefficients and the acquired second set of LPC coefficients to acquire a residual signal from the audio signal;
a decoder configured to decode the encoded audio signal.

12 . Method for encoding an audio signal with reduced background noise using linear predictive coding, the method comprising:
estimating a representation of background noise of the audio signal; generating a representation of a background noise reduced audio signal by subtracting the representation of the estimated background noise of the audio signal from a representation of the audio signal; subjecting the representation of the audio signal to linear prediction analysis to acquire a first set of linear prediction filter (LPC) coefficients and subjecting the representation of the background noise reduced audio signal to linear prediction analysis to acquire a second set of linear prediction filter (LPC) coefficients; and controlling a cascade of time domain filters by the acquired first set of LPC coefficients and the acquired second set of LPC coefficients to acquire a residual signal from the audio signal.

13 . Non-transitory digital storage medium having a computer program stored thereon to perform the method for encoding an audio signal with reduced background noise using linear predictive coding, said method comprising:
estimating a representation of background noise of the audio signal; generating a representation of a background noise reduced audio signal by subtracting the representation of the estimated background noise of the audio signal from a representation of the audio signal; subjecting the representation of the audio signal to linear prediction analysis to acquire a first set of linear prediction filter (LPC) coefficients and subjecting the representation of the background noise reduced audio signal to linear prediction analysis to acquire a second set of linear prediction filter (LPC) coefficients; and controlling a cascade of time domain filters by the acquired first set of LPC coefficients and the acquired second set of LPC coefficients to acquire a residual signal from the audio signal,
when said computer program is run by a computer.

Assignees

• Fraunhofer Ges Forschung

Inventors

• Fischer Johannes
• Bäckström Tom
• Jokinen Emma

Classifications

• G10L19/06 Primary

  Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients · CPC title

• G10L19/16

  Vocoder architecture · CPC title

• G10L21/0224

  Processing in the time domain · CPC title

• G10L21/0308

  characterised by the type of parameter measurement, e.g. correlation techniques, zero crossing techniques or predictive techniques · CPC title

• G10L21/0208

  Noise filtering · CPC title