Encoder, decoder and method for encoding and decoding

Patent metadata

Field	Value
Publication number	US-2016372128-A1
Application number	US-201615256996-A
Country	US
Kind code	A1
Filing date	Sep 6, 2016
Priority date	Mar 14, 2014
Publication date	Dec 22, 2016
Grant date	—

Abstract

An encoder for encoding an audio signal has a predictor, a factorizer, a transformer and a quantize and encode stage. The predictor is configured to analyze the audio signal to obtain prediction coefficients describing a spectral analog of the audio signal or a fundamental frequency of the audio signal and subject the audio signal to an analysis filter function dependent on the prediction coefficients to output a residual signal of the audio signal. The factorizer is configured to apply a matrix factorization onto an audiocorrelation or covariance matrix of synthesis filter function defined by the prediction coefficients to obtain factorized matrices. The transformer is configured to transform the residual signal based on the factorized matrices to obtain a transformed residual signal. The quantize and decode stage is configured to quantize the transformed residual signal to obtain a quantized transformed residual signal or an encoded quantized transformed residual signal.

First claim

1 . An encoder for encoding an audio signal into a data stream, comprising:
a predictor configured to analyze the audio signal in order to acquire prediction coefficients describing a spectral envelope of the audio signal or a fundamental frequency of the audio signal and to subject the audio signal to an analysis filter function dependent on the prediction coefficients in order to output a residual signal of the audio signal; a factorizer configured to apply a matrix factorization onto an autocorrelation or covariance matrix of a synthesis filter function defined by the prediction coefficients to acquire factorized matrices; a transformer configured to transform the residual signal based on the factorized matrices to acquire a transformed residual signal; and a quantize and encode stage configured to quantize the transformed residual signal to acquire a quantized transformed residual signal and comprising an entropy encoder comprising an input for the prediction coefficients and configured to entropy encode the quantized transformed residual signal with detecting the probability based on the prediction coefficients to acquire an encoded quantized transformed residual signal.

2 . The encoder according to claim 1 , wherein the synthesis filter function is defined by a matrix comprising weighted values of the synthesis filter function.

3 . The encoder according to claim 1 , wherein the factorizer calculates the autocorrelation or covariance matrix based on the product of a transformed- conjugated version of the synthesis filter function and a regular version of the synthesis filter function.

4 . The encoder according to claim 1 , wherein the factorizer factorizes the autocorrelation or covariance matrix based on the formula C=V*DV or based on the formula R=V*DV;
wherein V is the Vandermonde matrix, V* the transformed-conjugated version of the Vandermonde matrix and D a diagonal matrix with strictly positive entries.

5 . The encoder according to claim 4 , wherein the factorizer is configured to perform a Vandermonde factorization.

6 . The encoder according to claim 1 , wherein the factorizer is configured to perform an eigenvaluedecomposition and/or a Cholesky factorization.

7 . The encoder according to claim 4 , wherein the transformer transforms the residual signal based on the formula y=D 1/2 Vx or based on the formula y=DVx.

8 . The encoder according to claim 1 , wherein quantize and encode stage quantizes the transformed residual signal to acquire the quantized transformed residual signal based on an objective function

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9 . The encoder according to claim 1 , wherein the quantize and encode stage comprises an optimizer for optimizing the quantizing by applying noise filling to provide a noise-filled spectral representation of the audio signal, the residual signal or the transformed residual signal and or by optimizing the quantized transformed residual signal regarding dead-zones or regarding other quantization parameters.

10 . The encoder according to claim 1 , wherein the transformation of the residual signal is a transformation from a time-domain of the residual signal to a frequency-like domain of the transformed residual signal.

11 . The encoder according to claim 1 , wherein the quantize and encoding stage comprises an coder configured to perform an encoding of the quantized transformed residual signal to acquire an encoded quantized transformed residual signal.

12 . The encoder according to claim 11 wherein the encoding performed by the coder is out of a group comprising arithmetic coding.

13 . The encoder according to claim 11 , wherein the encoder further comprises a packer configured to packetize the encoded quantized transformed residual signal and the prediction coefficients to the data stream to be output by the encoder.

14 . The encoder according to claim 1 , wherein the predictor comprises a linear predictor (and/or a long time predictor.

15 . A method for encoding an audio signal into a data stream, the method comprising:
analyzing the audio signal in order to acquire prediction coefficients describing the spectral envelope of the audio signal or a fundamental frequency of the audio signal and subjecting the audio signal to an analysis filter function dependent on the prediction coefficients in order to output a residual signal of the audio signal; applying a matrix factorization onto an autocorrelation or covariance matrix of a synthesis filter function defined by the prediction coefficients to acquire factorized matrices; transforming the residual signal based on the factorized matrices to acquire a transformed residual signal; and quantizing and encoding the transformed residual signal to acquire a quantized transformed residual signal and entropy encoding using the prediction coefficients the quantized transformed residual signal with detecting the probability based on the prediction coefficients to acquire an encoded quantized transformed residual signal.

16 . Using the method of claim 15 in place of discrete Fourier transformation, discrete cosine transformation, modified discrete cosine transformation or another transformation in signal processing algorithms.

17 . A decoder for decoding a data stream into an audio signal, comprising:
a decode stage configured to output a transformed residual signal based on an inbound encoded quantized transformed residual signal using entropy decoding with detecting the probability based on prediction coefficients describing a spectral envelope of the audio signal or a fundamental frequency of the audio signal; a retransformer configured to retransform a residual signal from the transformed residual signal based on factorized matrices representing a result of a matrix factorization of an autocorrelation or covariance matrix of a synthesis filter function defined by the prediction coefficients; and a synthesis stage configured to synthesize the audio signal based on the residual signal by using the synthesis filter function defined by the prediction coefficients.

18 . The decoder according to claim 17 , wherein the decoder comprises a factorizer configured to apply the matrix factorization onto the autocorrelation or covariance matrix of the synthesis filter function defined by inbound prediction coefficients to acquire factorized matrices.

19 . The decoder according to claim 17 , wherein the decoder comprises a prediction coefficients-generator configured to deviate the prediction coeff

Assignees

• Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E V

Inventors

• Baeckstroem Tom
• Fischer Johannes
• Helmrich Christian

Classifications

• G10L19/028

  Noise substitution, i.e. substituting non-tonal spectral components by noisy source (comfort noise for discontinuous speech transmission G10L19/012) · CPC title

• G10L19/08 Primary

  Determination or coding of the excitation function; Determination or coding of the long-term prediction parameters · CPC title

• G10L19/032

  Quantisation or dequantisation of spectral components · CPC title

• G10L19/107

  Sparse pulse excitation, e.g. by using algebraic codebook · CPC title

• G10L19/038

  Vector quantisation, e.g. TwinVQ audio · CPC title