Apparatus and method for encoding and decoding an encoded audio signal using temporal noise/patch shaping

• US 10,332,539 B2
• Filed: 04/07/2015
• 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: Disch, Sascha, Nagel, Frederik, Geiger, Ralf, Thoshkahna, Balaji Nagendran, Schmidt, Konstantin, Bayer, Stefan, Neukam, Christian, Edler, Bernd, Helmrich, Christian
• Primary Examiner(s): Opsasnick, Michael N
• Application Number:
  US14/680,743
• Publication Number:
  US 20150287417A1
• Time in Patent Office: 1,540 Days
• Field of Search: 704207, 704500-504
• 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, includes: a spectral domain audio decoder for generating a first decoded representation of a first set of first spectral portions being spectral prediction residual values; a frequency regenerator for generating a reconstructed second spectral portion using a first spectral portion of the first set of first spectral portions, wherein the reconstructed second spectral portion additionally includes spectral prediction residual values; and an inverse prediction filter for performing an inverse prediction over frequency using the spectral residual values for the first set of first spectral portions and the reconstructed second spectral portion using prediction filter information included in the encoded audio signal.

Claims

1. Audio decoder for decoding an encoded audio signal, the audio decoder comprising:

a spectral domain audio decoder configured for generating a first decoded representation of a first set of first audio spectral portions, the first decoded representation comprising spectral prediction residual values;

a frequency regenerator configured for generating a reconstructed second audio spectral portion using a first audio spectral portion of the first set of first audio spectral portions, wherein the reconstructed second audio spectral portion and the first set of first audio spectral portions comprise spectral prediction residual values, wherein the frequency regenerator is configured for

spectral patching or transposing the spectral prediction residual values in the first audio spectral portion to obtain the reconstructed second audio spectral portion, or

using the spectral prediction residual values in the first audio spectral portion within an intelligent clap filling operation to obtain the reconstructed second audio spectral portion, or

using the spectral prediction residual values in the first audio spectral portion within a spectral band replication operation to obtain the reconstructed second audio spectral portion; and

an inverse prediction filter configured for performing an inverse prediction over frequency using the spectral prediction residual values for the first set of first audio spectral portions and the spectral prediction residual values for the reconstructed second audio spectral portion using prediction filter information comprised in the encoded audio signal, wherein a spectral representation of a decoded audio signal comprising the first set of first audio spectral portions and the reconstructed second audio spectral portion is obtained,

wherein at least one of the spectral domain audio decoder, the frequency regenerator, and the inverse prediction filter comprises a hardware implementation.

2. Audio decoder of claim 1,

further comprising a spectral envelope shaper configured for shaping a spectral envelope of an input signal or an output signal of the inverse prediction filter.

3. Audio decoder of claim 2,

wherein the encoded audio signal comprises spectral envelope information for the second audio spectral portion, the spectral envelope information comprising a second spectral resolution, the second spectral resolution being lower than a first spectral resolution associated with the first decoded representation,

wherein the spectral envelope shaper is configured to apply a spectral envelope shaping operation on the output of the inverse prediction filter, wherein the prediction filter information has been determined by using an audio signal before prediction filtering, or

wherein the spectral envelope shaper is configured to apply a spectral envelope shaping operation on the input of the inverse prediction filter, wherein the prediction filter information has been determined by using an audio signal subsequent to a prediction filtering in an encoder.

4. Audio decoder of claim 1,

further comprising a frequency time converter configured for converting an output of the inverse prediction filter or an envelope shaped output of the inverse prediction filter into a time representation.

5. Audio decoder in accordance with claim 1,

wherein the inverse prediction filter is a complex filter defined by the prediction filter information.

6. Audio decoder in accordance with claim 1,

wherein the spectral domain audio decoder is configured to generate the first decoded representation so that the first decoded representation comprises an Nyquist frequency equal to a sampling rate of a time domain signal generated by a frequency-to-time conversion of an output of the inverse prediction filter.

7. Audio decoder of claim 1,

wherein the spectral domain audio decoder is configured so that a maximum frequency represented by a spectral value for the maximum frequency in the first decoded representation is equal to a maximum frequency comprised in a time representation generated by a frequency-to-time conversion of an output of the inverse prediction filter, wherein the spectral value for the maximum frequency in the first decoded representation is zero or different from zero.

8. Audio decoder of claim 1,

wherein the first decoded representation of a first set of first audio spectral portions comprises real spectral values,

wherein the audio decoder further comprises an estimator configured for estimating imaginary values for the first set of first audio spectral portions from the real-valued first set of first audio spectral portions, and wherein the inverse prediction filter is a complex inverse prediction filter defined by complex-valued prediction filter information, and wherein the audio decoder further comprises a frequency-time converter configured for performing a conversion of a complex-valued spectrum into a time domain audio signal.

9. Audio decoder of claim 1,

wherein the inverse prediction filter is configured to apply a plurality of subfilters, wherein a frequency border of each subfilter coincides with a frequency border of a reconstruction band coinciding with a frequency tile.

13. Audio decoder of claim 1, wherein the inverse prediction filter is a shaping filter controlled by filter coefficients included in the prediction filter information comprised in the encoded audio signal.

14. Audio decoder of claim 1, wherein the inverse prediction filter configured for performing an inverse prediction over frequency is adapted to perform the prediction over frequency along a frequency direction.

10. Method of audio decoding an encoded audio signal, comprising:

generating, by a spectral domain audio decoder, a first decoded representation of a first set of first audio spectral portions, the first decoded representation comprising spectral prediction residual values;

regenerating, by a frequency regenerator, a reconstructed second audio spectral portion using a first audio spectral portion of the first set of first audio spectral portions, wherein the reconstructed second audio spectral portion and the first set of first audio spectral portions comprise spectral prediction residual values, wherein the generating the reconstructed second audio spectral portion using a first audio spectral portion of the first set of first audio spectral portions comprises

spectral patching or transposing the spectral prediction residual values in the first audio spectral portion to obtain the reconstructed second audio spectral portion, or

using the spectral prediction residual values in the first audio spectral portion within an intelligent gap filling operation to obtain the reconstructed second audio spectral portion, or

using the spectral prediction residual values in the first audio spectral portion within a spectral band replication operation to obtain the reconstructed second audio spectral portion; and

performing, by an inverse prediction filter, an inverse prediction over frequency using the spectral prediction residual values for the first set of first audio spectral portions and the spectral prediction residual values for the reconstructed second audio spectral portion using prediction filter information comprised in the encoded audio signal, wherein a spectral representation of a decoded audio signal is obtained comprising the first set of first audio spectral portions and the reconstructed second audio spectral portion,

wherein at least one of the spectral domain audio decoder, the frequency regenerator, and the inverse prediction filter comprises a hardware implementation.

11. Method of claim 10,

wherein the encoded audio signal comprises spectral envelope information for the second audio spectral portion, the spectral envelope information comprising a second spectral resolution, the second spectral resolution being lower than a first spectral resolution associated with the first decoded representation,

wherein the regenerating comprises a spectral envelope shaping comprising applying a spectral envelope shaping operation on an output of the step of performing an inverse prediction over frequency, wherein the prediction filter information has been determined by using an audio signal before prediction filtering, or

wherein the regenerating comprises a spectral envelope shaping comprising applying a spectral envelope shaping operation on an input of the step of performing an inverse prediction over frequency, wherein the prediction filter information has been determined by using an audio signal subsequent to a prediction filtering in an encoder.

12. A non-transitory storage medium having stored thereon a computer program for performing, when running on a computer or a processor, a method of decoding an encoded audio signal, comprising:

generating a first decoded representation of a first set of first audio spectral portions, the first decoded representation comprising spectral prediction residual values;

regenerating a reconstructed second audio spectral portion using a first audio spectral portion of the first set of first audio spectral portions, wherein the reconstructed second audio spectral portion and the first set of first audio spectral portions comprise spectral prediction residual values, wherein the generating the reconstructed second audio spectral portion using a first audio spectral portion of the first set of first audio spectral portions comprises

spectral patching or transposing the spectral prediction residual values in the first audio spectral portion to obtain the reconstructed second audio spectral portion, or

using the spectral prediction residual values in the first audio spectral portion within an intelligent gap filling operation to obtain the reconstructed second audio spectral portion, or

using the spectral prediction residual values in the first audio spectral portion within a spectral band replication operation to obtain the reconstructed second audio spectral portion; and

performing an inverse prediction over frequency using the spectral prediction residual values for the first set of first audio spectral portions and the spectral prediction residual values for the reconstructed second audio spectral portion using prediction filter information comprised in the encoded audio signal, wherein a spectral representation of a decoded audio signal comprising the first set of first audio spectral portions and the reconstructed second audio spectral portion is obtained.