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NZ794714B2 - Backward-compatible integration of harmonic transposer for high frequency reconstruction of audio signals - Google Patents
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NZ794714B2 - 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 PDF

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Publication number
NZ794714B2
NZ794714B2 NZ794714A NZ79471418A NZ794714B2 NZ 794714 B2 NZ794714 B2 NZ 794714B2 NZ 794714 A NZ794714 A NZ 794714A NZ 79471418 A NZ79471418 A NZ 79471418A NZ 794714 B2 NZ794714 B2 NZ 794714B2
Authority
NZ
New Zealand
Prior art keywords
audio signal
high frequency
lowband
audio
frequency reconstruction
Prior art date
Application number
NZ794714A
Other versions
NZ794714A (en
Inventor
Per Ekstrand
Heiko Purnhagen
Lars Villemoes
Original Assignee
Dolby International Ab
Filing date
Publication date
Application filed by Dolby International Ab filed Critical Dolby International Ab
Publication of NZ794714A publication Critical patent/NZ794714A/en
Publication of NZ794714B2 publication Critical patent/NZ794714B2/en

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Classifications

    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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 in accordance with the flag.

Claims (6)

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, 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, and wherein the fill data includes an extension payload, the extension payload includes spectral band replication 10 extension data, and the extension payload is identified with a four bit unsigned integer transmitted most significant bit first and having a value of ‘1101’ or ‘1110’; 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 operating 15 parameters 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; filtering the decoded lowband audio signal with an analysis filterbank to generate a filtered lowband audio signal; 20 extracting from the encoded audio bitstream a flag indicating whether either linear translation or harmonic transposition is to be performed on the audio data, wherein the fill data includes the flag; and regenerating a highband portion of the audio signal using the filtered lowband audio signal and the high frequency reconstruction metadata in accordance with the 25 flag, 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 high frequency reconstruction metadata includes an operating parameter selected from the group consisting of envelope scalefactors, noise floor scale factors, sinusoid addition information, time/frequency grid information, crossover frequency, and inverse filtering mode.
3. The method of claim 1 or claim 2, wherein the prototype filter, p (n), is derived from coefficients of Table 4.
4. The method of claim 1 or claim 2, wherein the prototype filter, p (n), is derived 10 from coefficients of Table 4 by one or more mathematical operations selected from the group consisting of rounding, subsampling, interpolation, or decimation.
5. A non-transitory computer readable medium containing instructions that when executed by a processor perform the method of any one of claims 1 to 4.
6. 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, wherein the encoded audio bitstream further includes a fill element with an 20 identifier indicating a start of the fill element and fill data after the identifier, and wherein the fill data includes an extension payload, the extension payload includes spectral band replication extension data, and the extension payload is identified with a four bit unsigned integer transmitted most significant bit first and having a value of ‘1101’ or ‘1110’; 25 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 operating parameters for a high frequency reconstruction process that linearly 30 translates a consecutive number of subbands from a lowband portion of the audio signal to a highband portion of the audio signal; an analysis filterbank for filtering the decoded lowband audio signal to generate a filtered lowband audio signal; a 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, wherein the fill data includes the flag; and a high frequency regenerator for regenerating a highband portion of the audio 5 signal using the filtered lowband audio signal and the high frequency reconstruction metadata in accordance with the flag, 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 10 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.
NZ794714A 2018-03-19 Backward-compatible integration of harmonic transposer for high frequency reconstruction of audio signals NZ794714B2 (en)

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
NZ794714A NZ794714A (en) 2024-07-26
NZ794714B2 true NZ794714B2 (en) 2024-10-30

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