Apparatus for decoding an encoded audio signal with frequency tile adaption

• US 10,593,345 B2
• Filed: 01/20/2016
• Issued: 03/17/2020
• 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, Geiger, Ralf, Helmrich, Christian, Nagel, Frederik, Neukam, Christian, Schmidt, Konstantin, Fischer, Michael
• Primary Examiner(s): Serrou, Abdelali
• Application Number:
  US15/002,350
• Publication Number:
  US 20160140980A1
• Time in Patent Office: 1,518 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

Apparatus for decoding an encoded audio signal including an encoded core signal and parametric data, including: a core decoder for decoding the encoded core signal to obtain a decoded core signal; an analyzer for analyzing the decoded core signal before or after performing a frequency regeneration operation to provide an analysis result; and a frequency regenerator for regenerating spectral portions not included in the decoded core signal using a spectral portion of the decoded core signal, the parametric data, and the analysis result.

Claims

1. Audio decoder for decoding an encoded audio signal comprising an encoded core audio signal and parametric data, comprising:

a core decoder configured for decoding the encoded core audio signal to acquire a decoded core audio signal;

an analyzer configured for analyzing the decoded core audio signal to provide an analysis result; and

a frequency regenerator configured for regenerating spectral portions not comprised in the decoded core audio signal using a spectral portion of the decoded core audio signal, the parametric data, and the analysis result, to obtain a regenerated audio signal, wherein the regenerated audio signal and the decoded core audio signal represent a decoded audio signal,

wherein the analyzer is configured for detecting a splitting of a peak portion in the spectral portion of the decoded core audio signal or to locate one or more local spectral minima in the decoded core audio signal,

wherein the frequency regenerator is configured to changing a frequency border between the decoded core audio signal and the regenerated signal so that the splitting is reduced or eliminated, or to regenerating the spectral portion, wherein one or more frequency tile borders in the spectral portion of the decoded core audio signal or in the regenerated spectral portion are set at the one or more spectral minima, and

wherein one of more of the analyzer, the core decoder, and the frequency regenerator is implemented, at least in part, by one of more hardware elements of the audio decoder.

2. Audio decoder of claim 1,

wherein the analyzer is configured for detecting tonal signal portions positioned in a frequency detection range,

wherein the frequency detection range extends from a frequency border of a reconstruction range by a predetermined detection bandwidth, or

wherein the frequency detection range extends between adjacent frequency tiles within the reconstruction range by a predetermined detection bandwidth,

wherein the predetermined detection bandwidth is less than 20% of the bandwidth of a source frequency range, or wherein the predetermined detection bandwidth is less than 20% of the bandwidth of the reconstruction frequency range, or wherein the predetermined detection bandwidth is equal to one Bark.

3. Audio decoder of claim 1, wherein the frequency regenerator comprises a tile generator, wherein the tile generator is configured to generate a first frequency tile for a first regenerated spectral portion and a second frequency tile for a second regenerated spectral portion using the same or different spectral portions of the decoded core audio signal,

wherein a lower frequency border of the second frequency tile coincides with an upper frequency border of the first frequency tile,

wherein the analyzer is configured to detect, whether a peak spectral portion is clipped by the lower frequency border of the second frequency tile or whether a peak spectral portion is clipped by the upper frequency border of the first frequency tile or whether a peak spectral portion is clipped by a lower frequency border of the first frequency tile, or whether a peak spectral portion is clipped by a predetermined gap filling start frequency of the decoded core audio signal, and

wherein the frequency regenerator further comprises a manipulator being configured to control the tile generator so that the tile generator generates modified frequency tiles comprising modified start or stop frequency borders that are modified so that the clipping is reduced or eliminated.

4. Audio decoder of claim 1,

wherein the core decoder is configured to acquire frequency domain decoded spectral portions comprising a first set of first spectral portions being represented by spectral values different from a zero representation and wherein a second set of second spectral portions is represented by the zero representation for spectral values,

wherein the parametric information is provided for the second set of the second spectral portions, wherein the frequency regenerator is configured to use decoded spectral portions from the first set of first spectral portions to regenerate the spectral portions within a reconstruction band that are not comprised in the first set of first spectral portions, and

wherein the audio decoder further comprises a frequency-time converter for converting the regenerated spectral portions and the spectral portions of the decoded core audio signal into a time representation.

5. Audio decoder of claim 1,

wherein the core decoder is configured to output modified discrete cosine transform (MDCT) spectral values, and

wherein the frequency-time converter comprises a processor for performing an inverse MDCT transform applying an overlap-add processing to subsequently acquired MDCT frames.

6. Method of decoding an encoded audio signal comprising an encoded core audio signal and parametric data, comprising:

decoding the encoded core audio signal to acquire a decoded core audio signal;

analyzing the decoded core audio signal to provide an analysis result; and

regenerating spectral portions not comprised in the decoded core audio signal using a spectral portion of the decoded core audio signal, the parametric data, and the analysis result, to obtain a regenerated audio signal, wherein the regenerated audio signal and the decoded core audio signal represent a decoded audio signal,

wherein the analyzing comprises detecting a splitting of a peak portion in the spectral portion of the decoded core audio signal or to locate one or more local spectral minima in the decoded core audio signal,

wherein the regenerating comprises changing a frequency border between the decoded core audio signal and the regenerated signal so that the splitting is reduced or eliminated, or regenerating the spectral portion, wherein one or more frequency tile borders in the spectral portion of the decoded core audio signal or in the regenerated spectral portion are set at the one or more spectral minima, and

wherein one or more of the decoding the encoded core audio signal, the regenerating spectral portions, and the analyzing the preliminary regenerated signal is implemented, at least in part, by one or more hardware elements of an audio signal processing device.

7. A non-transitory computer readable medium comprising a computer program for performing, when running on a computer or a processor, a method of decoding an encoded audio signal comprising an encoded core audio signal and parametric data, the method comprising:

decoding the encoded core audio signal to acquire a decoded core audio signal;

analyzing the decoded core audio signal to provide an analysis result; and

regenerating spectral portions not comprised in the decoded core audio signal using a spectral portion of the decoded core audio signal, the parametric data, and the analysis result, to obtain a regenerated audio signal, wherein the regenerated audio signal and the decoded core audio signal represent a decoded audio signal,

wherein the analyzing comprises detecting a splitting of a peak portion in the spectral portion of the decoded core audio signal, and

wherein the regenerating comprises changing a frequency border between the decoded core audio signal and the regenerated signal so that the splitting is reduced or eliminated, or regenerating the spectral portion, wherein one or more frequency tile borders in the spectral portion of the decoded core audio signal or in the regenerated spectral portion are set at the one or more spectral minima.

8. Audio decoder for decoding an encoded audio signal comprising an encoded core audio signal and parametric data, comprising:

a core decoder configured for decoding the encoded core audio signal to obtain a decoded core audio signal;

a frequency regenerator configured for regenerating spectral portions not included in the decoded core audio signal using a spectral portion of the decoded core audio signal and the parametric data to obtain a preliminary regenerated signal; and

an analyzer configured for analyzing the preliminary regenerated signal;

wherein the analyzer is configured for detecting a splitting of a peak portion in the preliminary regenerated signal at a frequency border of the decoded core audio signal or at a frequency border between two regenerated spectral portions of the preliminary regenerated signal generated by using the same or different spectral portions of the decoded core audio signal or at a maximum frequency border of the regenerated signal,

wherein the frequency regenerator is configured to changing the frequency border between the decoded core audio signal and the preliminary regenerated signal or changing the frequency border between two regenerated spectral portions of the preliminary regenerated signal generated by using the same or different spectral portions of the decoded core audio signal or changing the maximum frequency border of the preliminary regenerated signal to obtain a regenerated audio signal in which the splitting is reduced or eliminated, wherein the regenerated audio signal and the decoded core audio signal represent a decoded audio signal, and

wherein one of more of the analyzer, the core decoder, and the frequency regenerator is implemented, at least in part, by one of more hardware elements of the audio decoder.

9. Audio decoder of claim 8,

wherein the frequency regenerator is configured for generating the preliminary regenerated signal using control data,

wherein the analyzer is configured for detecting artifact creating signal portions near the frequency border between the decoded core audio signal and a regenerated spectral portion of the preliminary regenerated signal or near the frequency border between the two regenerated spectral portions of the preliminary regenerated signal generated by using the same or different spectral portions of the decoded core audio signal;

and

wherein the frequency regenerator further comprises a manipulator configured for manipulating the preliminary regenerated signal or configured for manipulating the control data in order to generate the regenerated audio signal using manipulated control data being different from the control data used for generating the preliminary regenerated signal.

10. Audio decoder of claim 9,

wherein the frequency regenerator comprises a tile generator being configured to derive the spectral portions using the one or more spectral portions of the decoded core audio signal to acquire spectral portions of the preliminary regenerated signal,

wherein the manipulator is configured to manipulate the spectral portions of the preliminary regenerated signal or to manipulate the frequency tile generator to acquire manipulated spectral portions, and

wherein the frequency regenerator further comprises a spectral envelope adjuster configured for performing an envelope adjustment of the manipulated spectral portions using the parametric data.

11. Audio decoder of claim 8,

wherein the analyzer is configured to detect tonal signal portions positioned in a frequency detection range, the frequency detection range extending from a frequency border of a reconstruction range or between adjacent frequency tiles within the reconstruction range by a predetermined detection bandwidth being less than 20% of the bandwidth of a source frequency range or the reconstruction frequency range or a predetermined detection bandwidth being one Bark.

12. Audio decoder of claim 11,

wherein the manipulator is configured to attenuate or remove spectral parts comprising tonal portions in the regenerated signal in the predetermined detection bandwidth.

13. Audio decoder of claim 12,

wherein the manipulator is configured to determine a start spectral portion located in frequency at a start frequency of a tonal signal portion and an end spectral portion located in frequency at an end frequency of the tonal signal portion, and to interpolate of the preliminary regenerated signal between the start frequency and the end frequency to acquire an interpolated signal portion, and to replace the tonal signal portion between the start frequency and the end frequency by the interpolated signal portion.

14. Audio decoder of claim 12,

wherein the manipulator is configured to generate spectral lines with an energy determined by a non-tonal signal portion of the decoded core audio signal or a non-tonal signal portion of the regenerated spectral portions.

15. Audio decoder of claim 8,

wherein the frequency regenerator comprises a tile generator controlled by the control data, and

wherein the manipulator is configured to control the tile generator using the manipulated control data so that the tile generator is configured to change a frequency border of the spectral portion of the decoded core audio signal or a frequency border of the regenerated spectral portion.

16. Audio decoder of claim 8,

wherein the frequency regenerator is configured for detecting tonal components in the preliminary regenerated signal;

wherein the frequency regenerator is configured to adjust transition frequencies between a source range and a reconstruction range or between adjacent frequency tiles in the reconstruction range based on a result of the detecting to generate a regenerated signal,

wherein the frequency regenerator is furthermore configured for removing tonal components located in a detection range around the transition frequencies;

wherein the frequency regenerator further comprises a cross-over filter for cross-over filtering a signal with removed tonal components in a cross-over range around the transition frequencies; and

wherein the frequency regenerator further comprises a spectral envelope shaper for spectral envelope shaping a result of the cross-filter using the parametric data.

17. Method of decoding an encoded audio signal comprising an encoded core audio signal and parametric data, comprising:

decoding the encoded core audio signal to obtain a decoded core audio signal;

regenerating spectral portions not included in the decoded core audio signal using a spectral portion of the decoded core audio signal and the parametric data to obtain a preliminary regenerated signal; and

analyzing the preliminary regenerated signal;

wherein the analyzing comprises detecting a splitting of a peak portion in the preliminary regenerated signal at a frequency border of the decoded core audio signal or at a frequency border between two regenerated spectral portions of the preliminary regenerated signal generated by using the same or different spectral portions of the decoded core audio signal or at a maximum frequency border of the regenerated signal,

wherein the regenerating comprises changing the frequency border between the decoded core audio signal and the preliminary regenerated signal or changing the frequency border between two regenerated spectral portions of the preliminary regenerated signal generated by using the same or different spectral portions of the decoded core audio signal or changing the maximum frequency border of the preliminary regenerated signal to obtain a regenerated audio signal in which the splitting is reduced or eliminated, wherein the regenerated audio signal and the decoded core audio signal represent a decoded audio signal, and

wherein one or more of the decoding the encoded core audio signal, the regenerating spectral portions, and the analyzing the preliminary regenerated signal is implemented, at least in part, by one or more hardware elements of an audio signal processing device.

18. A non-transitory computer readable medium comprising a computer program for performing, when running on a computer or a processor, a method of decoding an encoded audio signal comprising an encoded core audio signal and parametric data, comprising:

decoding the encoded core audio signal to obtain a decoded core audio signal;

regenerating spectral portions not included in the decoded core audio signal using a spectral portion of the decoded core audio signal and the parametric data to obtain a preliminary regenerated signal; and

analyzing the preliminary regenerated signal;

wherein the analyzing comprises detecting a splitting of a peak portion in the preliminary regenerated signal at a frequency border of the decoded core audio signal or at a frequency border between two regenerated spectral portions of the preliminary regenerated signal generated by using the same or different spectral portions of the decoded core audio signal or at a maximum frequency border of the regenerated signal, and

wherein the regenerating comprises changing the frequency border between the decoded core audio signal and the preliminary regenerated signal or changing the frequency border between two regenerated spectral portions of the preliminary regenerated signal generated by using the same or different spectral portions of the decoded core audio signal or changing the maximum frequency border of the preliminary regenerated signal to obtain a regenerated audio signal in which the splitting is reduced or eliminated, wherein the regenerated audio signal and the decoded core audio signal represent a decoded audio signal.