APPARATUS AND METHOD FOR DECODING OR ENCODING AN AUDIO SIGNAL USING ENERGY INFORMATION VALUES FOR A RECONSTRUCTION BAND

• US 20180144760A1
• Filed: 01/18/2018
• Published: 05/24/2018
• 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
• Granted Patent: US 10,332,531 B2
• Time in Patent Office: 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, comprising:

a time-spectrum converter configured for converting an 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 comprising spectral values of a first spectral portion and comprising a second spectral portion; and

an audio encoder configured for generating a first encoded representation of the first set of the first spectral portions comprising the first spectral resolution, wherein the audio encoder is configured for providing scale factors for scale factor bands, wherein the first encoded representation comprises the scale factors; and

wherein the parameter calculator is configured for generating a second encoded representation of the second set of second spectral portions, the second encoded representation comprising the energy information for the reconstruction band, wherein the reconstruction band coincides with a scale factor band or a group of scale factor bands, and wherein the first encoded representation comprises a scale factor for the scale factor band comprised in the reconstruction band.

2. The audio encoder of claim 1, wherein the audio encoder is configured to calculate the one or more scale factors for the one or more 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 one or more scale factor bands in the reconstruction band by a number of spectral values located within the one or more 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 encoder is configured to switch between long blocks and short blocks and to perform a block grouping in the calculation of transmitted scale factors, wherein the parameter calculator is configured to perform an identical grouping of the energy information as done by the audio 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 parameter encoder is configured to use the reconstruction band extending over two or more scale factor bands and 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 within an apparatus for decoding the encoded audio signal.

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

for determining a third energy information on a source range of a real valued part of the complex spectrum of the original signal associated to the reconstruction band for reconstructing the reconstruction band within an apparatus for decoding the encoded audio signal,

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. A method of generating an encoded audio signal, comprising:

converting an 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 comprising spectral values of a first spectral portion and comprising a second spectral portion; and

generating a first encoded representation of the first set of the first spectral portions comprising the first spectral resolution, wherein the audio encoder is configured for providing scale factors for scale factor bands, wherein the first encoded representation comprises the scale factors; and

wherein the providing comprises generating a second encoded representation of the second set of second spectral portions, the second encoded representation comprising the energy information for the reconstruction band, wherein the reconstruction band coincides with a scale factor band or a group of scale factor bands, and wherein the first encoded representation comprises a scale factor for the scale factor band comprised in the reconstruction band.

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, the method of claim 10.