WO2009066869A1 - Procédé de détermination de la bande de fréquence pour la mise en forme de la distorsion de la quantification et procédé de mise en forme du bruit transitoire l'utilisant - Google Patents

Procédé de détermination de la bande de fréquence pour la mise en forme de la distorsion de la quantification et procédé de mise en forme du bruit transitoire l'utilisant Download PDF

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Publication number
WO2009066869A1
WO2009066869A1 PCT/KR2008/005918 KR2008005918W WO2009066869A1 WO 2009066869 A1 WO2009066869 A1 WO 2009066869A1 KR 2008005918 W KR2008005918 W KR 2008005918W WO 2009066869 A1 WO2009066869 A1 WO 2009066869A1
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WO
WIPO (PCT)
Prior art keywords
frequency band
transient
tns
noise shaping
quantization noise
Prior art date
Application number
PCT/KR2008/005918
Other languages
English (en)
Inventor
Taejin Lee
Minje Kim
Seungkwon Beack
Dae-Young Jang
Kyeongok Kang
Jeong-Il Seo
Jinwoo Hong
Hochong Park
Rin-Chul Kim
Jeong-Geun Kim
Youngcheol Park
Original Assignee
Electronics And Telecommunications Research Institute
Kwangwoon University Industry-Academic Collaboration Foundation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from KR1020080048837A external-priority patent/KR100938282B1/ko
Application filed by Electronics And Telecommunications Research Institute, Kwangwoon University Industry-Academic Collaboration Foundation filed Critical Electronics And Telecommunications Research Institute
Priority to DE112008003153.3T priority Critical patent/DE112008003153B4/de
Publication of WO2009066869A1 publication Critical patent/WO2009066869A1/fr

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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; 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
    • G10L19/022—Blocking, i.e. grouping of samples in time; Choice of analysis windows; Overlap factoring
    • G10L19/025—Detection of transients or attacks for time/frequency resolution switching

Definitions

  • the present invention relates to a frequency band determining method for quantization noise shaping and a transient noise shaping method using the same. More particularly, the method shapes the noise using a long block and reduces pre-echo and musical noise by figuring out whether an applied frequency band is a general frequency band and an extended frequency band based on whether audio signals are transient.
  • TNS Shaping
  • the quantization noise should not exceed a masking threshold value.
  • the quantization noise is coded and then widely spread in the time domain. Thus, at low bit rates, it is hard to satisfy a condition that the quantization noise does not exceed the masking threshold value in the time domain.
  • Discrete Cosine Transform (MDCT) coefficients
  • quantization noise with a 48kMz sampling rate is distributed over 40 ms. This distribution may cause audible artifacts when the signals are transient.
  • the quantization noise can be percep- tionally detected before the transient signals are generated. This quantization noise is called pre-echo phenomenon.
  • the TNS algorithm uses a Linear Predictive Coding (LPC) based on a duality between the time domain and a frequency domain.
  • LPC Linear Predictive Coding Table 1 explains an optimal coding method for tone signals and transient signals in consideration of the duality.
  • the optional coding method for the tone signals with a certain frequency is a direct coding method using a frequency coefficient coding.
  • the optimal coding method for the tone signals with a certain frequency is a predictive coding method using an LPC coding.
  • the optimal coding method for the transient signals is the predictive coding method using the frequency coefficient predictive coding.
  • the optional coding method for the transient signals is the direct coding method using the time sample coding.
  • the TNS algorithm is applied based on the predictive coding method in the frequency domain.
  • Table 2 shows the frequency band applying the TNS algorithm. [16] Table 2 [Table 2] [Table ]
  • the TNS frequency range (band) is classified according to block length into a long block and a short block.
  • the frequency band applying the TNS algorithm is over 1,275 Hz for the long block, and over 2,750 Hz for the short block.
  • the TNS algorithm is applied to a frequency range from a frequency band of 1,800 Hz to a boundary frequency where a Spectrum Band Replication (SBR) starts.
  • SBR Spectrum Band Replication
  • the TNS algorithm is applied to a frequency range from a frequency band of 2,750 Hz to the boundary frequency where the SBR begins. In a band lower than the above frequency bands, the pre-echo occurs frequently.
  • a block switching is performed.
  • the block switching indicates the method of replacing a long window having one-frame length with a short window having 1/8 frame length.
  • the block switching between the long block and the short block is for perceptionally improving the pre-echo by applying the quantization noise effect only in the short block.
  • the short window may cause an opposite effect. Since the bit is insufficient in the low bit rate, frequency components lost in each short block are shown as spectral holes.
  • the spectral holes are discontinuously connected on a time axis in a corresponding frame to cause the musical noise. That is, in the low bit rate with insufficient bit, when the long block is used instead of the short block, the pre-echo occurs. Also, in the low bit rate with insufficient bit, when the short block is overly used, the musical noise occurs.
  • An embodiment of the present invention is directed to providing a frequency band determining method for quantization noise shaping and transient noise shaping method using the same.
  • this invention provides a method for determining frequency range for quantization noise shaping by using a long block according to an applied frequency band is classified into a general frequency band and an extension frequency band according to whether audio signals are transient to effectively reduce the pre-echo and the musical noise, and transient noise shaping method using the same.
  • a frequency band determining method for quantization noise shaping including checking whether audio signals obtained from low-pass filtering are transient, determining a predetermined frequency band to be applied as a frequency band to be applied for quantization noise shaping when the audio signals are not transient, and determining an extended frequency band extended more than the predetermined frequency band to be applied as a frequency band to be applied when the audio signals are transient.
  • This invention shapes quantization noise of audio signals using a long block according to frequency band for applying a Temporal Noise Shaping (TNS) algorithm and classifies the frequency band into a general frequency band and an extension frequency band according to whether the audio signals are transient. Thus, pre-echo and musical noise can be easily reduced.
  • TMS Temporal Noise Shaping
  • the short block is not overly used to thereby reduce the musical noise.
  • Fig. 1 is a block view showing a Temporal Noise Shaping (TNS) processing apparatus in accordance with an embodiment of the present invention.
  • Figs. 2 and 3 show the pre-echo according to the transient index.
  • FIG. 4 is a flowchart describing a method for shaping quantization noise in a low frequency band by using a long block in accordance with an embodiment of the present invention.
  • Fig. 1 is a block view showing a Temporal Noise Shaping (TNS) processing apparatus in accordance with an embodiment of the present invention.
  • TMS Temporal Noise Shaping
  • a TNS processing apparatus 100 includes a TNS determiner 110 and a TNS coder 120.
  • the TNS processing apparatus 100 properly reshapes the quantization noise in a time domain in a filter bank window to make the noise imperceptible.
  • the TNS processing apparatus 100 in a general HE-ACC coding apparatus is described.
  • the TNS determiner 110 determines whether a TNS process is applied or not.
  • the TNS determiner 110 multiplies weight as shown in Eq. 1 to calculate Linear Predictive Coding (LPC) of pre-calculated Modified Discrete Cosine Transform (MDCT) spectrum.
  • LPC Linear Predictive Coding
  • MDCT Modified Discrete Cosine Transform
  • the Eq. 1 normalizes into energy of a corresponding scale band.
  • the MDCT spectrum range is applied to a predetermined range.
  • the TNS determiner 110 determines a frequency range (band) for applying the LPC.
  • the TNS determiner 110 applies a smoothing filter to the normalized spectrum. This is for the LPC analysis.
  • the smooth filtering indicates filtering down in a frequency band range from an LPC interruption frequency to an LPC operation frequency through the process as shown in Eq. 2.
  • k and n respectively represent MDCT coefficient unit and scale factor unit.
  • the TNS determiner 110 calculates an auto-correlation function and the LPC using a
  • the TNS determiner 110 acquires a Partial Autocorrelation Coefficient (PARCOR) and calculates prediction gain based on the calculation result using the Levinson-Durbin algorithm.
  • PARCOR Partial Autocorrelation Coefficient
  • the TNS coder 120 carries out a quantization simulation in order of high to low
  • the TNS coder 120 passes through an LPC filter with the determined order and coefficient and applies the TNS algorithm to the MDCT spectrum coefficient to perform coding.
  • the ACC coding is carried out using the applied MDCT spectrum coefficient.
  • This invention extends and applies the TNS algorithm down to low frequency as low as 100 Hz.
  • the pre-echo is decreased.
  • the tone components of the frequency applying the TNS algorithm i.e., the low frequency, may be distorted.
  • this invention simultaneously uses the general TNS algorithm and the extension TNS algorithm. That is, this invention determines whether it applies the general TNS algorithm or the extension TNS algorithm, and then performs the TNS algorithm based on the determination result.
  • a reference for the determination is extension range of the extended low frequency.
  • the TNS determiner 110 determines if the general TNS algorithm can be applied or not. When the block switching result only in the low frequency band is transient, the TNS determiner 110 applies the extension TNS algorithm.
  • the TNS determiner 110 applies the extension TNS algorithm when the prediction gain in the frequency band extensively applying the TNS algorithm up to 100 Hz exceeds the threshold value and the transient signals with increased energy are located between fourth and seventh frames among eight frames.
  • the TNS determiner 110 applies the general TNS algorithm when the transient signals with decreased energy are located in between zeroth to third frames among eight frames.
  • the transient index of the transient signals 0 to 7 indicates the transient index determined by the block switching between the short block and long block. Each block indicates each point where the corresponding frame is divided into eight. This transient index is used for the effective coding for the HE-ACC and referred when eight short blocks are bound up into four groups for applying the short blocks.
  • the reference value for the TNS algorithm is the transient index of the signals passed and filtered through the low frequency.
  • the pre-echo occurs in a narrower range.
  • the transient portion with increased energy is located in an end portion of the corresponding frame.
  • Figs. 2 and 3 show the pre-echo according to the transient index.
  • a first transient index 101 indicates a transient signal in an end portion of the frame.
  • first pre-echo 102 since first pre-echo 102 is located in the end portion of the frame, the first pre-echo 102 occurs in larger range.
  • a second transient index 103 indicates a transient signal in a front portion of the frame.
  • the second pre-echo 104 affects more than the first pre-echo 102 shown in Fig. 2.
  • the TNS determiner 110 determines that the extension TNS algorithm is applied.
  • FIG. 4 is a flowchart describing a method for shaping quantization noise in a low frequency band by using a long block in accordance with an embodiment of the present invention.
  • a TNS determiner 110 calculates prediction gain of audio signals by using a long block in step S302. That is, the TNS determiner 110 calculates the auto-correlation function and LPC by using a Levinson-Durbin algorithm and acquires a PARCOR based on the calculation result, and calculates prediction gain.
  • the TNS determiner 110 determines whether the calculated prediction gain exceeds the threshold value in step S304.
  • the TNS determiner 110 separately performs low-pass filtering by using the low- pass filter to determine frequency components in an extension band. This is for using only the long block.
  • An example of the low pass filter function is shown in Eq. 4.
  • H(z) indicates the low-pass filter function.
  • Various low-pass filer functions can be applied to the H(z). There is no big difference in a low-pass filtering ability of various low-pass filer functions.
  • the TNS determiner 110 uses the low-pass filter to acquire the signal in a low frequency band under 1 kHz.
  • the TNS determiner 110 checks the signals passed and filtered through the low frequency are transient in step S306. That is, the TNS determiner 110 determines the frequency band applied for shaping the quantization noise according to the check result in step S306. On the other hand, when the prediction gain does not exceed the threshold value, the TNS determiner 110 calculates the prediction gain of the extension band and checks the prediction gain of the extension band exceeds the threshold value in step S314. Herein, it is checked that the signals passed and filtered through the low frequency pass are transient by using the block switching algorithm in the AAC apparatus.
  • the TNS determiner 110 determines that the general TNS algorithm in applied in step 312.
  • the TNS determiner 110 does not re-adjust the masking threshold value and extends the frequency band applying the TNS algorithm down to the frequency as low as 100 Hz in step S310.
  • the TNS coder 120 re-calculates the coefficient based on the TNS algorithm extensively applied to the low frequency band, and then performs the TNS coding.
  • the TNS determiner 110 analyzes kind and index of transient signal passed and filtered through the low frequency and checks the effect of the pre-echo exceeds a reference value in step S316. That is, the TNS determiner 110 determines if the quantization noise is shaped or not based on the analysis result in step 316. For instance, the TNS determiner 110 determines that the effect of the pre-echo exceeds the reference value and applies the TNS algorithm when the kind and the index of the transient with increased energy is located in the end portion of the corresponding frame or when the kind and the index of the transient with decreased energy is located in the front portion of the corresponding frame.
  • the TNS determiner 110 does not apply the TNS in step S318.
  • the technology of the present invention can be realized as a program.
  • a code and a code segment forming the program can be easily inferred from a computer programmer of the related field.
  • the realized program is stored in a computer-readable recording medium, i.e., information storing media, and is read and operated by the computer, thereby realizing the method of the present invention.
  • the recording medium includes all types of recording media which can be read by the computer.

Abstract

La présente invention concerne un procédé de détermination de la bande de fréquence pour la mise en forme de la distorsion de la quantification qui comprend les étapes consistant à vérifier si les signaux audio obtenus à partir du filtrage passe-bas sont transitoires, à déterminer une bande de fréquence prédéterminée à appliquer en tant que bande de fréquence à appliquer pour la mise en forme de la distorsion de la quantification lorsque les signaux audio ne sont pas transitoires, et à déterminer une bande de fréquence étendue s'étendant plus que la bande de fréquence prédéterminée à appliquer comme bande de fréquence à appliquer lorsque les signaux audio sont transitoires.
PCT/KR2008/005918 2007-11-21 2008-10-09 Procédé de détermination de la bande de fréquence pour la mise en forme de la distorsion de la quantification et procédé de mise en forme du bruit transitoire l'utilisant WO2009066869A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE112008003153.3T DE112008003153B4 (de) 2007-11-21 2008-10-09 Frequenzband-Bestimmungsverfahren zum Formen von Quantisierungsrauschen

Applications Claiming Priority (4)

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KR10-2007-0119413 2007-11-21
KR20070119413 2007-11-21
KR10-2008-0048837 2008-05-26
KR1020080048837A KR100938282B1 (ko) 2007-11-21 2008-05-26 양자화 잡음 처리를 위한 적용 주파수 대역 결정 방법과,그를 이용한 양자화 잡음 처리 방법

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9173025B2 (en) 2012-02-08 2015-10-27 Dolby Laboratories Licensing Corporation Combined suppression of noise, echo, and out-of-location signals
JP2021502597A (ja) * 2017-11-10 2021-01-28 フラウンホーファー−ゲゼルシャフト・ツール・フェルデルング・デル・アンゲヴァンテン・フォルシュング・アインゲトラーゲネル・フェライン 一時的ノイズシェーピング
US11217261B2 (en) 2017-11-10 2022-01-04 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Encoding and decoding audio signals
US11315580B2 (en) 2017-11-10 2022-04-26 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Audio decoder supporting a set of different loss concealment tools
US11315583B2 (en) 2017-11-10 2022-04-26 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Audio encoders, audio decoders, methods and computer programs adapting an encoding and decoding of least significant bits
US11380341B2 (en) 2017-11-10 2022-07-05 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Selecting pitch lag
US11462226B2 (en) 2017-11-10 2022-10-04 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Controlling bandwidth in encoders and/or decoders
US11545167B2 (en) 2017-11-10 2023-01-03 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Signal filtering
US11562754B2 (en) 2017-11-10 2023-01-24 Fraunhofer-Gesellschaft Zur F Rderung Der Angewandten Forschung E.V. Analysis/synthesis windowing function for modulated lapped transformation

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US6266644B1 (en) * 1998-09-26 2001-07-24 Liquid Audio, Inc. Audio encoding apparatus and methods
KR20070109982A (ko) * 2004-11-09 2007-11-15 코닌클리케 필립스 일렉트로닉스 엔.브이. 오디오 코딩 및 디코딩

Patent Citations (3)

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US5886276A (en) * 1997-01-16 1999-03-23 The Board Of Trustees Of The Leland Stanford Junior University System and method for multiresolution scalable audio signal encoding
US6266644B1 (en) * 1998-09-26 2001-07-24 Liquid Audio, Inc. Audio encoding apparatus and methods
KR20070109982A (ko) * 2004-11-09 2007-11-15 코닌클리케 필립스 일렉트로닉스 엔.브이. 오디오 코딩 및 디코딩

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9173025B2 (en) 2012-02-08 2015-10-27 Dolby Laboratories Licensing Corporation Combined suppression of noise, echo, and out-of-location signals
JP2021502597A (ja) * 2017-11-10 2021-01-28 フラウンホーファー−ゲゼルシャフト・ツール・フェルデルング・デル・アンゲヴァンテン・フォルシュング・アインゲトラーゲネル・フェライン 一時的ノイズシェーピング
US11127408B2 (en) 2017-11-10 2021-09-21 Fraunhofer—Gesellschaft zur F rderung der angewandten Forschung e.V. Temporal noise shaping
US11217261B2 (en) 2017-11-10 2022-01-04 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Encoding and decoding audio signals
JP6990306B2 (ja) 2017-11-10 2022-01-12 フラウンホーファー－ゲゼルシャフト・ツール・フェルデルング・デル・アンゲヴァンテン・フォルシュング・アインゲトラーゲネル・フェライン 一時的ノイズシェーピング
US11315580B2 (en) 2017-11-10 2022-04-26 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Audio decoder supporting a set of different loss concealment tools
US11315583B2 (en) 2017-11-10 2022-04-26 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Audio encoders, audio decoders, methods and computer programs adapting an encoding and decoding of least significant bits
US11380339B2 (en) 2017-11-10 2022-07-05 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Audio encoders, audio decoders, methods and computer programs adapting an encoding and decoding of least significant bits
US11380341B2 (en) 2017-11-10 2022-07-05 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Selecting pitch lag
US11386909B2 (en) 2017-11-10 2022-07-12 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Audio encoders, audio decoders, methods and computer programs adapting an encoding and decoding of least significant bits
US11462226B2 (en) 2017-11-10 2022-10-04 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Controlling bandwidth in encoders and/or decoders
US11545167B2 (en) 2017-11-10 2023-01-03 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Signal filtering
US11562754B2 (en) 2017-11-10 2023-01-24 Fraunhofer-Gesellschaft Zur F Rderung Der Angewandten Forschung E.V. Analysis/synthesis windowing function for modulated lapped transformation

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