# US 2019/0172472 A1 · Methods, Apparatus and Systems for Determining Reconstructed Audio Signal

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- Number: US 2019/0172472 A1
- Document ID: US20190172472A1
- Status: Published application
- Kind: A1
- Application number: 16/268,448
- Filed: 2019-02-05
- Published: 2019-06-06
- Earliest claimed: 2002-03-28
- Assignees: Dolby Laboratories Licensing Corporation
- Applicants: Dolby Laboratories Licensing Corporation
- Inventors: Michael M. Truman; Mark S. Vinton
- Web page: https://patentgrep.com/patent/US20190172472A1

## CPC

- G10L 19/0208: {Subband vocoders}
- G10L 19/0017: {Lossless audio signal coding; Perfect reconstruction of coded audio signal by transmission of coding error (G10L19/24 takes precedence)}
- G10L 19/002: Dynamic bit allocation (for perceptual audio coders G10L19/032)
- G10L 19/012: Comfort noise or silence coding
- G10L 19/02: using spectral analysis, e.g. transform vocoders or subband vocoders
- G10L 19/0204: {using subband decomposition}
- G10L 19/028: Noise substitution, i.e. substituting non-tonal spectral components by noisy source (comfort noise for discontinuous speech transmission G10L19/012)
- G10L 19/03: Spectral prediction for preventing pre-echo; Temporary noise shaping [TNS], e.g. in MPEG2 or MPEG4
- G10L 19/06: Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
- G10L 19/16: Vocoder architecture
- 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}
- G10L 19/173: {Transcoding, i.e. converting between two coded representations avoiding cascaded coding-decoding}
- G10L 19/26: Pre-filtering or post-filtering
- G10L 19/265: {Pre-filtering, e.g. high frequency emphasis prior to encoding}
- 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)
- G10L 21/038: using band spreading techniques
- G10L 21/0388: Details of processing therefor
- G10L 19/0212: {using orthogonal transformation}
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING

## Abstract

According to an aspect of the present invention, a method for reconstructing an audio signal having a baseband portion and a highband portion is disclosed. The method includes obtaining a decoded baseband audio signal by decoding an encoded audio signal 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 a number of consecutive subband signals of the plurality of subband signals and obtaining an envelope adjusted high-frequency signal. The method further includes generating a noise component based on a noise parameter. Finally, the method includes adjusting a phase of the high-frequency reconstructed signal and obtaining a time-domain reconstructed audio signal by combining the decoded baseband audio signal and the combined high-frequency signal to obtain a time-domain reconstructed audio signal.

## Claims

### Claim 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;
extracting, from the first part, temporal envelope information;
extracting, from the first part, spectral components of the baseband portion, wherein the spectral components of the baseband portion do not include spectral components of the highband portion and the number of the spectral components of the baseband portion may vary dynamically;
decoding the first part to obtain a decoded baseband audio signal, wherein the decoding includes filtering in a frequency domain at least some of the spectral components of the baseband portion based on the temporal envelope information to shape a temporal envelope of the baseband portion;
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, wherein the plurality of subband signals are generated with one or more Quadrature Mirror Filters (QMF);
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, and wherein the obtaining the envelope adjusted high-frequency signal includes determining and applying a gain;
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.

### Claim 2 (depends on 1)

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

### Claim 3 (depends on 1)

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

### Claim 4 (depends on 3)

The method of claim 3, further comprising converting the normalized ratio to an amplitude value.

### Claim 5 (depends on 1)

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

### Claim 6 (depends on 5)

The method of claim 5, further comprising compensating for the limiting by boosting the combined high-frequency signal.

### Claim 7 (depends on 1)

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.

### Claim 8

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;
an extractor for obtaining, from the first part, temporal envelope information;
an extractor for obtaining, from the first part, spectral components of the baseband portion, wherein the spectral components of the baseband portion do not include spectral components of the highband portion and the number of the spectral components of the baseband portion may vary dynamically;
a decoder for obtaining a decoded baseband audio signal from the first part, wherein the decoder includes a frequency-domain filter for processing at least some of the spectral components of the baseband portion based on the temporal envelope information to shape a temporal envelope of the baseband portion;
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, wherein the plurality of subband signals are generated with one or more Quadrature Mirror Filters (QMF);
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 and wherein the obtaining the envelope adjusted high-frequency signal includes determining and applying a gain;
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.

### Claim 9 (depends on 8)

The apparatus of claim 8, wherein the encoded audio signal is decoded using an inverse modified Discrete Cosine Transform (DCT).

### Claim 10 (depends on 8)

The apparatus of claim 8, wherein the noise parameter is represented in a form of a normalized ratio.

### Claim 11 (depends on 10)

The apparatus of claim 10, further comprising converting the normalized ratio to an amplitude value.

### Claim 12 (depends on 8)

The apparatus of claim 8, further comprising limiting an amount of envelope adjustment of the high-frequency reconstructed signal.

### Claim 13 (depends on 12)

The apparatus of claim 12, further comprising compensating for the limiting by boosting the combined high-frequency signal.