WO2001039174A1 - Effets audionumeriques, necessitant peu de memoire, utilisant une technique d'echantillonnages montant et descendant - Google Patents

Effets audionumeriques, necessitant peu de memoire, utilisant une technique d'echantillonnages montant et descendant Download PDF

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Publication number
WO2001039174A1
WO2001039174A1 PCT/SG1999/000133 SG9900133W WO0139174A1 WO 2001039174 A1 WO2001039174 A1 WO 2001039174A1 SG 9900133 W SG9900133 W SG 9900133W WO 0139174 A1 WO0139174 A1 WO 0139174A1
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WO
WIPO (PCT)
Prior art keywords
sampling
sample data
selected number
input
aliasing filter
Prior art date
Application number
PCT/SG1999/000133
Other languages
English (en)
Inventor
Mohammed Javed Absar
Sapna George
Original Assignee
Stmicroelectronics Asia Pacific Pte Ltd.
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
Application filed by Stmicroelectronics Asia Pacific Pte Ltd. filed Critical Stmicroelectronics Asia Pacific Pte Ltd.
Priority to PCT/SG1999/000133 priority Critical patent/WO2001039174A1/fr
Publication of WO2001039174A1 publication Critical patent/WO2001039174A1/fr

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Classifications

    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K15/00—Acoustics not otherwise provided for
    • G10K15/08—Arrangements for producing a reverberation or echo sound
    • G10K15/12—Arrangements for producing a reverberation or echo sound using electronic time-delay networks

Definitions

  • This invention is applicable in the field of Digital Audio Effects Algorithms (e.g. echo, chorus, reverberation, flanging) implemented on a DSP with reduced memory usage requirement.
  • Digital Audio Effects Algorithms e.g. echo, chorus, reverberation, flanging
  • Audio effects such as echo, chorus, reverberation and flanging are indispensable in systems such as music production, home entertainment (Hi-Fi), car audio and Karaoke Systems. Often these effects are implemented using digital signal processors, with associated memory, input-output peripherals, analogue-to-digital and digital-to-analogue converters.
  • the processor takes in the "dry” input, produced by an instrument such as a keyboard or previously recorded on some analogue medium, and samples it at an appropriate rate. It is also possible that the input comes from a digitally recorded source (e.g. 44.1 kHz. sampled Audio CD) , in which case no additional sampling is required. Whatever the source, the fmal input stream is in digital form so that it can be subjected to DSP effects algorithm. The resulting "wet" stream is reconstructed to analogue form, to be sent to the next unit in the audio chain, such as speaker system, a recording channel, a mixer, or another effects processor .
  • a digitally recorded source e.g. 44.1 kHz. sampled Audio CD
  • the basic element is the delay-buffer, several of which may be combined to form complicated effects such as reverberation.
  • the delay buffer stores data at the same rate as the input sampling rate. Therefore the delay buffer size is a function of not only of the maximum delay allowed in the system but also of the sampling frequency.
  • Delay Buffer Size (words) Max. Delay (ms.) x Sampling Frequency (kHz.)
  • words Max. Delay (ms.) x Sampling Frequency (kHz.)
  • the memory requirement can be prohibitive when it comes to implementing effects such as reverb where delays of over 200 ms. are often desired.
  • This invention attempts to decrease memory requirements for effects algorithm without affecting quality appreciably.
  • a method of introducing digital audio effects in an audio signal including: receiving an input stream at an input sampling frequency; down-sampling the input stream so that a selected number of sample data are retained; applying a digital audio effect to the selected number of sample data; and up-sampling the sample data to a predetermined output frequency.
  • a digital signal processor including an audio effect engine for introducing a digital audio effect in an audio signal, including: a down-sampler for down-sampling an input signal to a selected number of sample data; an audio effects engine for applying the digital audio effect to the sample data; and an up-sampler for up-sampling the sample data, to which the audio effect has been applied, to a predetermined output frequency.
  • the input data may be converted to a lower sampling frequency at, for example, a ratio of 4: 1.
  • the amount of data is lesser, for the same duration of the signal.
  • the algorithm introduces effect at this frequency.
  • For generating the output the effect added samples are reconvened to the desired output frequency.
  • Figure 2 illustrates a down-sampling/up-sampling technique to decrease delay-buffer size.
  • Delay Buffer Size Max. Delay (ms.)
  • x Sampling Frequency (kHz.) 200 ms.
  • x 44.1 kHz. 8820 words
  • the buffer size above can also be decreased if the amount of data necessary for representing the signal for same duration (Max. Delay) is decreased. This can be realised by perforrning sampling rate conversion. At a lower sampling rate the same duration of the signal can be represented using fewer samples. High frequency contents of the signals will have to be discarded, but this may be acceptable in cases where listening and singing environment (microphone, analogue-to-digital converters etc.) are of commercial level quality only.
  • Figure 2 shows the Down-Sampling Up-Sampling Technique for reducing buffer size.
  • the input stream Prior to storage or any action by the audio effects engine, the input stream passes through an anti-aliasing filter +decimator.
  • the anti-aliasing filter removes frequency components above ⁇ /N, where N is the decimation factor. Decimation by N means that one out of every N sample data is retained, the rest are thrown away. Decimation causes the high frequency components (above sampling_frequency/(2* ⁇ )), to wrap around and appear as ghost frequency components at lower frequency. To avoid these ghost components, the high frequencies are suppressed so that the wrap around is not audible.
  • 16-bit pcm pulse code modulated
  • the output from the effects' engine has to be re-converted to the desired output frequency through an up-sampling process.
  • Up-sampling consists of two steps, the first being the expansion stage wherein each data is preceded by N-l zeros, where N is the up-sampling ratio.
  • Zeros insertion causes the spectrum to shrink by N. Therefore frequency images at 2 ⁇ intervals (created due to sampling process) come within the 0 ⁇ / ⁇ boundary. They are removed by an anti-aliasing filter with cut-off at ⁇ /N. Looking equivalently at the time domain behaviours of the filtering process, the inserted zeros are changed to new values, obtained by interpolation behaviour of the filter.
  • the same filter may be used for both decimation and expansion steps.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)

Abstract

La présente invention concerne un procédé, destiné à introduire des effets audionumériques dans un signal audio, qui consiste à recevoir un flux entrant à une fréquence d'échantillonnage d'entrée, à effectuer un échantillonnage descendant sur le flux entrant de façon à ce qu'un nombre sélectionné de données échantillons soient retenues, à appliquer un effet audionumérique à ce nombre sélectionné de données échantillons, et à effectuer un échantillonnage montant sur ces données échantillons à une fréquence de sortie prédéterminée.
PCT/SG1999/000133 1999-11-25 1999-11-25 Effets audionumeriques, necessitant peu de memoire, utilisant une technique d'echantillonnages montant et descendant WO2001039174A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/SG1999/000133 WO2001039174A1 (fr) 1999-11-25 1999-11-25 Effets audionumeriques, necessitant peu de memoire, utilisant une technique d'echantillonnages montant et descendant

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/SG1999/000133 WO2001039174A1 (fr) 1999-11-25 1999-11-25 Effets audionumeriques, necessitant peu de memoire, utilisant une technique d'echantillonnages montant et descendant

Publications (1)

Publication Number Publication Date
WO2001039174A1 true WO2001039174A1 (fr) 2001-05-31

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SG1999/000133 WO2001039174A1 (fr) 1999-11-25 1999-11-25 Effets audionumeriques, necessitant peu de memoire, utilisant une technique d'echantillonnages montant et descendant

Country Status (1)

Country Link
WO (1) WO2001039174A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6949880B1 (en) 1999-12-17 2005-09-27 Osram Opto Semiconductors Gmbh Encapsulation for organic LED device
US6952078B1 (en) 1999-12-17 2005-10-04 Osram Opto Semiconductord Gmbh Encapsulation for organic LED device
US7166007B2 (en) 1999-12-17 2007-01-23 Osram Opto Semiconductors Gmbh Encapsulation of electronic devices
CN111801727A (zh) * 2018-02-01 2020-10-20 思睿逻辑国际半导体有限公司 具有可选择采样率的主动噪声消除（anc）系统

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5123050A (en) * 1989-10-12 1992-06-16 Matsushita Electric Industrial Co., Ltd. Sound field control system
US5917917A (en) * 1996-09-13 1999-06-29 Crystal Semiconductor Corporation Reduced-memory reverberation simulator in a sound synthesizer

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5123050A (en) * 1989-10-12 1992-06-16 Matsushita Electric Industrial Co., Ltd. Sound field control system
US5917917A (en) * 1996-09-13 1999-06-29 Crystal Semiconductor Corporation Reduced-memory reverberation simulator in a sound synthesizer

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6949880B1 (en) 1999-12-17 2005-09-27 Osram Opto Semiconductors Gmbh Encapsulation for organic LED device
US6952078B1 (en) 1999-12-17 2005-10-04 Osram Opto Semiconductord Gmbh Encapsulation for organic LED device
US7166007B2 (en) 1999-12-17 2007-01-23 Osram Opto Semiconductors Gmbh Encapsulation of electronic devices
US7394153B2 (en) 1999-12-17 2008-07-01 Osram Opto Semiconductors Gmbh Encapsulation of electronic devices
US7419842B2 (en) 1999-12-17 2008-09-02 Osram Gmbh Encapsulation of electroluminescent devices with shaped spacers
US7432533B2 (en) 1999-12-17 2008-10-07 Osram Gmbh Encapsulation of electronic devices with shaped spacers
US8344360B2 (en) 1999-12-17 2013-01-01 Osram Opto Semiconductor Gmbh Organic electronic devices with an encapsulation
CN111801727A (zh) * 2018-02-01 2020-10-20 思睿逻辑国际半导体有限公司 具有可选择采样率的主动噪声消除（anc）系统

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