High frequency regeneration of an audio signal by copying in a circular manner

• US 9,412,383 B1
• Filed: 04/14/2016
• Issued: 08/09/2016
• Est. Priority Date: 03/28/2002
• Status: Expired due to Term

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Truman, Michael M., Vinton, Mark S.
• Primary Examiner(s): Yen, Eric
• Application Number:
  US15/098,472
• Publication Number:
  US 20160232904A1
• Time in Patent Office: 117 Days
• US Class Current: 1/1
• CPC Class Codes: G10L 19/0017 Lossless audio signal coding; Perfect reconstruction of coded audio signal by transmission of coding error G10L19/24 takes precedence
• CPC Class Codes: G10L 19/002 Dynamic bit allocation for perceptual audio coders G10L19/032
• CPC Class Codes: G10L 19/012 Comfort noise or silence coding
• 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 19/028 Noise substitution, i.e. substituting non-tonal spectral components by noisy source comfort noise for discontinuous speech transmission G10L19/012
• CPC Class Codes: G10L 19/03 Spectral prediction for preventing pre-echo; Temporary noise shaping [TNS], e.g. in MPEG2 or MPEG4
• 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 19/16 Vocoder architecture
• CPC Class Codes: G10L 19/167 Audio streaming, i.e. formatting and decoding of an encoded audio signal representation into a data stream for transmission or storage purposes
• CPC Class Codes: G10L 19/173 Transcoding, i.e. converting between two coded representations avoiding cascaded coding-decoding
• CPC Class Codes: G10L 19/26 Pre-filtering or post-filtering
• CPC Class Codes: G10L 19/265 Pre-filtering, e.g. high frequency emphasis prior to encoding
• CPC Class Codes: G10L 21/00 Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility G10L19/00 takes precedence
• CPC Class Codes: G10L 21/038 using band spreading techniques
• CPC Class Codes: G10L 21/0388 Details of processing therefor

Abstract

A method for generating a reconstructed audio signal having a baseband portion and a highband portion is disclosed. The method includes deformatting an encoded audio signal into a first part and a second part and obtaining a decoded baseband audio signal by decoding the first part. The method also includes extracting, from the second part, a noise parameter and an estimated spectral envelope of the highband portion and obtaining a plurality of subband signals by filtering the decoded baseband audio signal. The method further includes generating a high-frequency reconstructed signal by copying in a circular manner a number of consecutive subband signals of the plurality of subband signals and obtaining an envelope adjusted high-frequency signal by adjusting, based on the estimated spectral envelope of the highband portion, a spectral envelope of the high-frequency reconstructed signal. The method also includes generating a noise component based on the noise parameter and obtaining a combined high-frequency signal by adding the noise component to the envelope adjusted high-frequency signal. Finally, the method includes obtaining a time-domain reconstructed audio signal by combining the decoded baseband audio signal and the combined high-frequency signal. The method may be implemented by an audio decoding device comprising one or more hardware elements.

Claims

1. A method for generating a reconstructed audio signal having a baseband portion and a highband portion, the method comprising:

deformatting an encoded audio signal into a first part and a second part;

obtaining a decoded baseband audio signal by decoding the first part, wherein the first part includes spectral components of the baseband portion and does not include spectral components of the highband portion, wherein the number of the spectral components of the baseband portion may vary dynamically;

extracting, from the second part, a noise parameter and an estimated spectral envelope of the highband portion;

obtaining a plurality of subband signals by filtering the decoded baseband audio signal;

generating a high-frequency reconstructed signal by copying in a circular manner a number of consecutive subband signals of the plurality of subband signals;

obtaining an envelope adjusted high-frequency signal by adjusting, based on the estimated spectral envelope of the highband portion, a spectral envelope of the high-frequency reconstructed signal, wherein a frequency resolution of the estimated spectral envelope is adaptive;

generating a noise component based on the noise parameter, wherein the noise parameter indicates a level of noise contained in the highband portion;

obtaining a combined high-frequency signal by adding the noise component to the envelope adjusted high-frequency signal; and

obtaining a time-domain reconstructed audio signal by combining the decoded baseband audio signal and the combined high-frequency signal;

wherein the method is implemented by an audio decoding device comprising one or more hardware elements.

2. The method of claim 1 wherein the plurality of subband signals is generated with one or more Quadrature Mirror Filters (QMF).

3. The method of claim 1 wherein the encoded audio signal is decoded using an inverse modified Discrete Cosine Transform (DCT).

4. The method of claim 1 wherein the noise parameter is represented in a form of a normalized ratio.

5. The method of claim 4 further comprising converting the normalized ratio to an amplitude value.

6. The method of claim 1 further comprising limiting an amount of envelope adjustment of the high-frequency reconstructed signal.

7. The method of claim 6 further comprising compensating for the limiting by boosting the combined high-frequency signal.

8. The method of claim 1 further comprising smoothing, based on a parameter extracted from the encoded audio signal, an amount of envelope adjustment of the high-frequency reconstructed signal.

9. An audio decoding device comprising one or more hardware elements that implement the method of claim 1 by executing a sequence of instructions.

10. A non-transitory computer-readable medium containing instructions that when executed by an audio decoding device comprising one or more hardware elements, cause the audio decoding device to implement the method of claim 1.

11. An audio decoder generating a reconstructed audio signal having a baseband portion and a highband portion, the audio decoder comprising:

a deformatter for extracting a first part and a second part from an encoded audio signal;

a decoder for obtaining a decoded baseband audio signal from the first part, wherein the first part includes spectral components of the baseband portion and does not include spectral components of the highband portion, wherein the number of the spectral components of the baseband portion may vary dynamically;

an extractor for obtaining, from the second part, a noise parameter and an estimated spectral envelope of the highband portion;

a filter for obtaining a plurality of subband signals from the decoded baseband audio signal;

a generator for creating a high-frequency reconstructed signal by copying in a circular manner a number of consecutive subband signals of the plurality of subband signals;

an envelope adjuster for obtaining an envelope adjusted high-frequency signal by adjusting, based on the estimated spectral envelope of the highband portion, a spectral envelope of the high-frequency reconstructed signal, wherein a frequency resolution of the estimated spectral envelope is adaptive;

a noise generator for generating a noise component based on the noise parameter, wherein the noise parameter indicates a level of noise contained in the highband portion;

a combiner for obtaining a combined high-frequency signal by adding the noise component to the envelope adjusted high-frequency signal; and

a synthesizer for obtaining a time-domain reconstructed audio signal by combining the decoded baseband audio signal and the combined high-frequency signal;

wherein the audio decoder comprises one or more hardware elements.