Apparatus and method for decoding or encoding an audio signal using energy information values for a reconstruction band

• US 10,332,531 B2
• Filed: 01/18/2018
• Issued: 06/25/2019
• Est. Priority Date: 07/22/2013
• 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: Niedermeier, Andreas, Ertel, Christian, Geiger, Ralf, Ghido, Florin, Helmrich, Christian
• Primary Examiner(s): Serrou, Abdelali
• Application Number:
  US15/874,536
• Publication Number:
  US 20180144760A1
• Time in Patent Office: 523 Days
• 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 19/0208 Subband vocoders
• CPC Class Codes: G10L 19/0212 using orthogonal transformation
• CPC Class Codes: G10L 19/022 Blocking, i.e. grouping of samples in time; Choice of analysis windows; Overlap factoring
• CPC Class Codes: G10L 19/025 Detection of transients or attacks for time/frequency resolution switching
• CPC Class Codes: G10L 19/03 Spectral prediction for preventing pre-echo; Temporary noise shaping [TNS], e.g. in MPEG2 or MPEG4
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
• CPC Class Codes: G10L 21/0388 Details of processing therefor
• CPC Class Codes: G10L 25/06 the extracted parameters being correlation coefficients
• CPC Class Codes: G10L 25/18 the extracted parameters being spectral information of each sub-band
• CPC Class Codes: G10L 25/21 the extracted parameters being power information
• CPC Class Codes: H04S 1/007 in which the audio signals are in digital form data reduction aspects thereof based on psychoacoustics G10L19/02

Abstract

An apparatus for decoding an encoded audio signal having an encoded representation of a first set of first spectral portions and an encoded representation of parametric data indicating spectral energies for a second set of second spectral portions, has: an audio decoder for decoding the encoded representation of the first set of the first spectral portions to obtain a first set of first spectral portions and for decoding the encoded representation of the parametric data to obtain a decoded parametric data for the second set of second spectral portions indicating, for individual reconstruction bands, individual energies; a frequency regenerator for reconstructing spectral values in a reconstruction band having a second spectral portion using a first spectral portion of the first set of the first spectral portions and an individual energy for the reconstruction band, the reconstruction band having a first spectral portion and the second spectral portion.

Claims

1. An audio encoder for generating an encoded audio signal from an audio signal, the audio encoder comprising:

a time-spectrum converter configured for converting the audio signal into a spectral representation;

a spectral analyzer configured for analyzing the spectral representation of the audio signal in order to determine a first set of first spectral portions to be encoded with a first spectral resolution and a second set of second spectral portions to be encoded with a second spectral resolution, the second spectral resolution being lower than the first spectral resolution;

a parameter calculator configured for providing an energy information for a reconstruction band, wherein the reconstruction band comprises spectral values of a first spectral portion of the first set of first spectral portions and additionally comprises a second spectral portion of the second set of second spectral portions; and

an audio representation encoder configured for generating a first encoded representation of the first set of the first spectral portions including the first spectral portion, the first encoded representation comprising one or more encoded spectral values representing the first spectral resolution, wherein the audio representation encoder is configured for providing scale factors for scale factor bands, wherein the first encoded representation additionally comprises the scale factors;

wherein the parameter calculator is configured for generating a second encoded representation of the second set of second spectral portions including the second spectral portion, wherein the second encoded representation comprises the energy information for the reconstruction band, wherein the reconstruction band coincides with a scale factor band or a group of scale factor bands,

wherein the audio representation encoder is configured to provide the scale factor or the group of scale factors for the scale factor band or the group of scale factor bands coinciding with the reconstruction band first encoded representation,

wherein the encoded audio signal comprises the first encoded representation and the second encoded representation,

wherein the reconstruction band is represented, in the encoded audio signal, at least by the energy information in the second encoded representation, by the scale factor or the group of scale factors in the first encoded representation, and by the one or more encoded spectral values of the first spectral portion in the reconstruction band, and

wherein one or more of the time-spectrum converter, the spectral analyzer, the parameter calculator, and the audio representation encoder, is implemented, at least in part, by one or more hardware elements of the apparatus.

2. The audio encoder of claim 1, wherein the audio representation encoder is configured to calculate the one scale factor or the group of scale factors for the scale factor band or the group of scale factor bands in the reconstruction band using a psychoacoustic masking threshold.

3. The audio encoder of claim 1,

wherein the parameter calculator is configured to normalize an energy in the scale factor band or the group of scale factor bands in the reconstruction band by a number of spectral values located within the scale factor band or the group of scale factor bands in the reconstruction band, and wherein different reconstruction bands of a plurality of different reconstruction bands comprise different numbers of spectral values.

4. The audio encoder of claim 1,

wherein the audio representation encoder is configured to switch between long blocks and short blocks and to perform a block grouping in the calculation of transmitted scale factors, and wherein the parameter calculator is configured to perform an identical grouping of the energy information as done by the audio representation encoder.

5. The audio encoder of claim 1,

wherein the parameter calculator is configured to use reconstruction bands comprising frequency borders coinciding with frequency borders of the scale factor bands.

6. The audio encoder in accordance with claim 1, wherein the reconstruction band extends over two or more scale factor bands and wherein the parameter calculator is configured to calculate the energy information for the two or more scale factor bands as a grouped energy information for the two or more scale factor bands.

7. The audio encoder in accordance with claim 1,

wherein the parameter calculator is configured to calculate the energy information for the reconstruction band using the information on the energy of the reconstruction band and additionally using information on an energy of a source range associated to the reconstruction band for reconstructing the reconstruction band.

8. The audio encoder of claim 7, wherein the parameter calculator is configured to calculate an energy information for the reconstruction band of a complex spectrum of the audio signal, to calculate a further energy information for a source range of a real valued part of the complex spectrum of the audio signal associated to the reconstruction band for reconstructing the reconstruction band, and wherein the parameter calculator is configured to calculate the energy information for the reconstruction band using the energy information and the further energy information.

9. The audio encoder in accordance with claim 1,

wherein the parameter calculator is configured

for determining a first energy information on a scale factor band within the reconstruction band of a complex spectrum of the audio signal,

for determining a second energy information on a source range of the complex spectrum of the audio signal associated to the reconstruction band for reconstructing the reconstruction band,

or determining a third energy information on a source range of a real valued part of the complex spectrum of the audio signal associated to the reconstruction band for reconstructing the reconstruction band,

for determining a weighting information based on a relation between at least two of the first energy information, the second energy information, and the third energy information, and

for weighting one of the first energy information and the third energy information using the weighting information to acquire a weighted energy information and for using the weighted energy information as the energy information for the reconstruction band.

10. An audio encoding method of encoding an audio signal to generate an encoded audio signal, the method comprising:

converting the audio signal into a spectral representation;

analyzing the spectral representation of the audio signal in order to determine a first set of first spectral portions to be encoded with a first spectral resolution and a second set of second spectral portions to be encoded with a second spectral resolution, the second spectral resolution being lower than the first spectral resolution;

providing an energy information for a reconstruction band, wherein the reconstruction band comprises spectral values of a first spectral portion of the first set of first spectral portions and additionally comprises a second spectral portion of the second set of second spectral portions; and

generating a first encoded representation of the first set of the first spectral portions including the first spectral portion, the first encoded representation comprising one or more encoded spectral values representing the first spectral resolution, wherein the generating the first encoded representation comprises providing scale factors for scale factor bands, wherein the first encoded representation additionally comprises the scale factors;

wherein the providing the enemy information for the reconstruction band comprises generating a second encoded representation of the second set of second spectral portions including the second spectral portion, wherein the second encoded representation comprises the energy information for the reconstruction band,

wherein the generating the first encoded representation comprises providing the scale factor or the group of scale factors for the scale factor band or the group of scale factor bands coinciding with the reconstruction band,

wherein the encoded audio signal comprises the first encoded representation and the second encoded representation,

wherein the reconstruction band is represented, in the encoded audio signal, at least by the energy information in the second encoded representation, by the scale factor or the group of scale factors in the first encoded representation, and by the one or more encoded spectral values of the first spectral portion in the reconstruction band, and

wherein one or more of the converting, the analyzing, the providing the enemy information, and the generating the first encoded representation is implemented, at least in part, by one or more hardware elements of an audio signal processing device.

11. A non-transitory digital storage medium having stored thereon a computer program with program code for performing, when running on a computer or processor, a method of encoding an audio signal to generate an encoded audio signal, the method comprising:

converting the audio signal into a spectral representation;

analyzing the spectral representation of the audio signal in order to determine a first set of first spectral portions to be encoded with a first spectral resolution and a second set of second spectral portions to be encoded with a second spectral resolution, the second spectral resolution being lower than the first spectral resolution;

providing an energy information for a reconstruction band, wherein the reconstruction band comprises spectral values of a first spectral portion of the first set of first spectral portions and additionally comprises a second spectral portion of the second set of second spectral portions; and

generating a first encoded representation of the first set of the first spectral portions including the first spectral portion, the first encoded representation comprising one or more encoded spectral values representing the first spectral resolution, wherein the generating the first encoded representation comprises providing scale factors for scale factor bands, wherein the first encoded representation additionally comprises the scale factors;

wherein the providing the energy information for the reconstruction band comprises generating a second encoded representation of the second set of second spectral portions including the second spectral portion, wherein the second encoded representation comprises the energy information for the reconstruction band,

wherein the generating the first encoded representation comprises providing the scale factor or the group of scale factors for the scale factor band or the group of scale factor bands coinciding with the reconstruction band,

wherein the encoded audio signal comprises the first encoded representation and the second encoded representation,

wherein the reconstruction band is represented, in the encoded audio signal, at least by the energy information in the second encoded representation, by the scale factor or the group of scale factors in the first encoded representation, and by the encoded one or more spectral values of the first spectral portion in the reconstruction band, and

wherein one or more of the converting, the analyzing, the providing the energy information, and the generating the first encoded representation is implemented, at least in part, by one or more hardware elements of an audio signal processing device.