Audio encoder, audio decoder, methods for encoding and decoding an audio signal, and a computer program

• US 9,043,203 B2
• Filed: 01/11/2011
• Issued: 05/26/2015
• Est. Priority Date: 07/11/2008
• Status: Active Grant

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Rettelbach, Nikolaus, Grill, Bernhard, Fuchs, Guillaume, Geyersberger, Stefan, Multrus, Markus, Popp, Harald, Herre, Juergen, Schuller, Gerald, Hirschfeld, Jens, Wabnik, Stefan
• Primary Examiner(s): Godbold, Douglas
• Application Number:
  US13/004,508
• Publication Number:
  US 20110170711A1
• Time in Patent Office: 1,596 Days
• Field of Search: 704200-201, 704/206, 704/208, 704/210, 704/214, 704/215, 704227-228, 704500-501
• US Class Current: 704/226
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: G10L 19/02 using spectral analysis, e.g. transform vocoders or subband vocoders
• CPC Class Codes: G10L 19/0204 using subband decomposition
• CPC Class Codes: G10L 19/028 Noise substitution, i.e. substituting non-tonal spectral components by noisy source comfort noise for discontinuous speech transmission G10L19/012
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components
• CPC Class Codes: G10L 19/035 Scalar quantisation
• CPC Class Codes: G10L 25/18 the extracted parameters being spectral information of each sub-band

Abstract

An encoder for providing an audio stream on the basis of a transform-domain representation of an input audio signal includes a quantization error calculator configured to determine a multi-band quantization error over a plurality of frequency bands of the input audio signal for which separate band gain information is available. The encoder also includes an audio stream provider for providing the audio stream such that the audio stream includes information describing an audio content of the frequency bands and information describing the multi-band quantization error.

A decoder for providing a decoded representation of an audio signal on the basis of an encoded audio stream representing spectral components of frequency bands of the audio signal includes a noise filler for introducing noise into spectral components of a plurality of frequency bands to which separate frequency band gain information is associated on the basis of a common multi-band noise intensity value.

Claims

1. A decoder for providing a decoded representation of an audio signal on the basis of an encoded audio stream representing spectral components of frequency bands of the audio signal, the decoder comprising:

a noise filler configured to introduce noise into spectral components of a plurality of frequency bands, to which separate frequency band gain information is associated, on the basis of a common multi-band noise intensity value;

wherein the noise filler is configured to receive a plurality of spectral bin values representing different overlapping or non-overlapping frequency portions of the first frequency band of a frequency domain audio signal representation, and to receive a plurality of spectral bin values representing different overlapping or non-overlapping frequency portions of the second frequency band of the frequency domain audio signal representation; and

to replace one or more spectral bin values of the first frequency band of the plurality of frequency bands with a first spectral bin noise value, a magnitude of which is determined by the multi-band noise intensity value, and to replace one or more spectral bin values of the second frequency band of the plurality of frequency bands with a second spectral bin noise value comprising the same magnitude as the first spectral bin noise value;

wherein the decoder further comprises a scaler configured to scale spectral bin values of the first frequency band of the plurality of frequency bands with a first frequency band gain value, to acquire scaled spectral bin values of the first frequency band, and to scale spectral bin values of the second frequency band of the plurality of frequency bands with a second frequency band gain value, to acquire scaled spectral bin values of the second frequency band,

such that the replaced spectral bin values, replaced with the first and second spectral bin noise values, are scaled with different frequency band gain values, and

such that the replaced spectral bin value, replaced with the first spectral bin noise value, and un-replaced spectral bin values of the first frequency band representing an audio content of the first frequency band are scaled with the first frequency band gain value, and that the replaced spectral bin value, replaced with the second spectral bin noise value, and un-replaced spectral bin values of the second frequency band representing an audio content of the second frequency band are scaled with the second frequency band gain value.

2. A decoder for providing a decoded representation of an audio signal on the basis of an encoded audio stream representing spectral components of frequency bands of the audio signal, the decoder comprising:

a noise filler configured to introduce noise into spectral components of a plurality of frequency bands, to which separate frequency band gain information is associated, on the basis of a common multi-band noise intensity value;

wherein the noise filler is configured to replace spectral bin values of spectral bins quantized to zero with spectral bin noise values, magnitudes of which spectral bin noise values are dependent on the multi-band noise intensity value, to acquire replaced spectral bin values, only for frequency bands comprising a lowest spectral bin index above a predetermined spectral bin index, leaving spectral bin values of frequency bands comprising a lowest spectral bin index below the predetermined spectral bin index unaffected;

wherein the noise filler is configured to selectively modify, for the frequency bands comprising a lowest spectral bin index above the predetermined spectral bin index, a band gain value of a given frequency band in dependence on a noise offset value, if the given frequency band is entirely quantized to zero; and

wherein the decoder further comprises a scaler configured to apply the selectively-modified or unmodified band gain values to the selectively-replaced or un-replaced spectral bin values, to acquire a scaled spectral information, which represents the audio signal.

3. A decoder for providing a decoded representation of an audio signal on the basis of an encoded audio stream representing spectral components of frequency bands of the audio signal, the decoder comprising:

a noise filler configured to introduce noise into spectral components of a plurality of frequency bands, to which separate frequency band gain information is associated, on the basis of a common multi-band noise intensity value;

wherein the decoder is configured to receive an audio stream comprising a quantized, entropy-encoded representation of spectral bin values for a plurality of frequency bands, wherein a plurality of spectral bin values is associated with a first frequency band of the plurality of frequency bands, and wherein a plurality of spectral bin values is associated with a second frequency band of the plurality of frequency bands,

an encoded representation of band gain values, wherein a first band gain value is associated with the first frequency band and a second band gain value is associated with the second frequency band, and

an encoded representation of the multi-band noise intensity value;

wherein the decoder further comprises a spectral decoder configured to provide a quantized, decoded representation of the spectral bin values on the basis of the quantized, entropy-encoded representation of the spectral bin values;

wherein the decoder further comprises an inverse quantizer configured to inversely quantize the quantized decoded representation of the spectral bin values, to acquire an inversely quantized, decoded representation of the spectral bin values;

wherein the decoder further comprises a scale factor decoder configured to decode the encoded representation of the spectral gain values, to acquire a decoded representation of the spectral gain values; and

wherein the noise filler is configured to selectively replace spectral bin values inversely quantized to zero of multiple frequency bands with spectral bin replacement values of identical magnitudes, to acquire replaced spectral bin values of multiple frequency bands; and

wherein the decoder further comprises a scaler configured to scale a set of all spectral bin values of a first frequency band, some of which spectral bin values of the first frequency band are original inversely quantized, decoded spectral bin values provided by the inverse quantizer and some of which spectral bin values are spectral bin replacement values, with a decoded representation of a scale factor associated with the first frequency band, to acquire a set of scaled spectral bin values of the first frequency band, and to scale a set of all spectral bin values of a second frequency band, some of which spectral bin values of the second frequency band are original inversely quantized, decoded spectral bin values provided by the inverse quantizer and some of which spectral bin values are spectral bin replacement values, with a decoded representation of a scale factor associated with the second frequency band, to acquire a set of scaled spectral bin values of the second frequency band.