NZ793664B2 - Backward-compatible integration of harmonic transposer for high frequency reconstruction of audio signals - Google Patents
Backward-compatible integration of harmonic transposer for high frequency reconstruction of audio signals Download PDFInfo
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- NZ793664B2 NZ793664B2 NZ793664A NZ79366418A NZ793664B2 NZ 793664 B2 NZ793664 B2 NZ 793664B2 NZ 793664 A NZ793664 A NZ 793664A NZ 79366418 A NZ79366418 A NZ 79366418A NZ 793664 B2 NZ793664 B2 NZ 793664B2
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- New Zealand
- Prior art keywords
- audio signal
- spectral band
- data
- band replication
- lowband
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- G—PHYSICS
- G06—COMPUTING OR CALCULATING; COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
- G06F17/10—Complex mathematical operations
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
- G10L19/008—Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
- G10L19/02—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis using spectral analysis, e.g. transform vocoders or subband vocoders
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
- G10L19/04—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis using predictive techniques
- G10L19/16—Vocoder architecture
- G10L19/18—Vocoders using multiple modes
- G10L19/22—Mode decision, i.e. based on audio signal content versus external parameters
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
- G10L19/04—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis using predictive techniques
- G10L19/16—Vocoder architecture
- G10L19/18—Vocoders using multiple modes
- G10L19/24—Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
- G10L19/04—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis using predictive techniques
- G10L19/26—Pre-filtering or post-filtering
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10L21/00—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
- G10L21/02—Speech enhancement, e.g. noise reduction or echo cancellation
- G10L21/038—Speech enhancement, e.g. noise reduction or echo cancellation using band spreading techniques
Abstract
method for decoding an encoded audio bitstream is disclosed. The method includes receiving the encoded audio bitstream and decoding the audio data to generate a decoded lowband audio signal. The method further includes extracting high frequency reconstruction metadata and filtering the decoded lowband audio signal with an analysis filterbank to generate a filtered lowband audio signal. The method also includes extracting a flag indicating whether either linear translation or harmonic transposition is to be performed on the audio data and regenerating a highband portion of the audio signal using the filtered lowband audio signal and the high frequency reconstruction metadata.
Claims (15)
1. A method for decoding an encoded audio bitstream, the method comprising: 5 receiving the encoded audio bitstream, the encoded audio bitstream including audio data representing a lowband portion of an audio signal; decoding the audio data to generate a decoded lowband audio signal; extracting from the encoded audio bitstream high frequency reconstruction metadata, the high frequency reconstruction metadata including linear translation 10 operating parameters tuned for a high frequency reconstruction process that linearly translates a consecutive number of subbands from a lowband portion of the audio signal to a highband portion of the audio signal, the linear translation operating parameters including envelope scale factors, noise floor scale factors, sinusoid addition information, time/frequency grid information, crossover frequency and 15 inverse filtering mode; filtering the decoded lowband audio signal with an analysis filterbank to generate a filtered lowband audio signal; extracting from the encoded audio bitstream a flag indicating whether either linear translation or harmonic transposition is to be performed on the audio data; if 20 the flag indicates that harmonic transposition is to be performed on the audio data: regenerating a highband portion of the audio signal by performing harmonic transposition using the filtered lowband audio signal and the high frequency reconstruction metadata, including the linear translation operating parameters; and combining the filtered lowband audio signal and the regenerated highband 25 portion to form a wideband audio signal, wherein the analysis filterbank includes analysis filters, h (n), that are modulated versions of a prototype filter, p (n), according to: ? 1 ? ( ) ( ) h ? = ? ? exp {? (? + ) (? - )}, 0 = ? = ? ; 0 = ? < ? ? 2 2 where p (n) is a real-valued symmetric or asymmetric prototype filter, M is a number 30 of channels in the analysis filterbank and N is the prototype filter order.
2. The method of claim 1 wherein the encoded audio bitstream further includes a fill element with an identifier indicating a start of the fill element and fill data after the identifier, wherein the fill data includes the flag. 5
3. The method of claim 2 wherein the identifier is a three bit unsigned integer transmitted most significant bit first and having a value of 0x6.
4. The method of claim 2, wherein the fill data includes an extension payload, the extension payload includes spectral band replication extension data, and the 10 extension payload is identified with a four bit unsigned integer transmitted most significant bit first and having a value of ‘1101’ or ‘1110’.
5. The method of claim 4, wherein the spectral band replication extension data includes: 15 a spectral band replication header, spectral band replication data after the spectral band replication header, an spectral band replication extension element after the spectral band replication data, and wherein the flag is included in the spectral band replication extension element.
6. The method of any one of claims 1-4 wherein the prototype filter, p0(n), is defined by the coefficients of Table 4.
7. The method of any one of claims 1-4 wherein the prototype filter, p0(n), is 25 derived from the coefficients of Table 4 by one or more mathematical operations selected from the group consisting of rounding, subsampling, interpolation, or decimation.
8. A computer program having instructions that when executed by a processor 30 cause said processor to perform the method of any one of claims 1-7.
9. A decoder for decoding an encoded audio bitstream, the decoder comprising: an input interface for receiving the encoded audio bitstream, the encoded audio bitstream including audio data representing a lowband portion of an audio signal; 5 a core decoder for decoding the audio data to generate a decoded lowband audio signal; a deformatter for extracting from the encoded audio bitstream high frequency reconstruction metadata, the high frequency reconstruction metadata including linear translation operating parameters tuned for a high frequency reconstruction process 10 that linearly translates a consecutive number of subbands from a lowband portion of the audio signal to a highband portion of the audio signal, the linear translation operating parameters including envelope scale factors, noise floor scale factors, sinusoid addition information, time/frequency grid information, crossover frequency and inverse filtering mode; 15 an analysis filterbank for filtering the decoded lowband audio signal to generate a filtered lowband audio signal; the deformatter for extracting from the encoded audio bitstream a flag indicating whether either linear translation or harmonic transposition is to be performed on the audio data; 20 a high frequency regenerator for regenerating, if the flag indicates that harmonic transposition is to be performed on the audio data, a highband portion of the audio signal by performing harmonic transposition using the filtered lowband audio signal and the high frequency reconstruction metadata, including the linear translation operating parameters; and 25 a synthesis filterbank for combining the filtered lowband audio signal and the regenerated highband portion to form a wideband audio signal, wherein the analysis filterbank includes analysis filters, h (n), that are modulated versions of a prototype filter, p0(n), according to: ? 1 ? h (? ) = ? (? ) exp {? (? + ) (? - )}, 0 = ? = ? ; 0 = ? < ? ? 2 2 30 where p (n) is a real-valued symmetric or asymmetric prototype filter, M is a number of channels in the analysis filterbank and N is the prototype filter order.
10. The decoder of claim 9 wherein the encoded audio bitstream further includes a fill element with an identifier indicating a start of the fill element and fill data after the identifier, wherein the fill data includes the flag. 5
11. The decoder of claim 10 wherein the identifier is a three bit unsigned integer transmitted most significant bit first and having a value of 0x6.
12. The decoder of claim 10, wherein the fill data includes an extension payload, the extension payload includes spectral band replication extension data, and the 10 extension payload is identified with a four bit unsigned integer transmitted most significant bit first and having a value of ‘1101’ or ‘1110’.
13. The decoder of claim 12, wherein the spectral band replication extension data includes: 15 a spectral band replication header, spectral band replication data after the spectral band replication header, an spectral band replication extension element after the spectral band replication data, and wherein the flag is included in the spectral band replication extension element.
14. The decoder of any one of claims 9-12 wherein the prototype filter, p0(n), is defined by the coefficients of Table 4.
15. The decoder of any one of claims 9-12 wherein the prototype filter, p0(n), is 25 derived from the coefficients of Table 4 by one or more mathematical operations selected from the group consisting of rounding, subsampling, interpolation, and decimation.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US201762475619P | 2017-03-23 | 2017-03-23 | |
| NZ777923A NZ777923B2 (en) | 2018-03-19 | Backward-compatible integration of harmonic transposer for high frequency reconstruction of audio signals |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| NZ793664A NZ793664A (en) | 2024-07-05 |
| NZ793664B2 true NZ793664B2 (en) | 2024-10-08 |
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