168:
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98:. When resampling audio to a notably lower pitch, it may be preferred that the source audio is of a higher sample rate, as slowing down the playback rate will reproduce an audio signal of a lower resolution, and therefore reduce the perceived clarity of the sound. On the contrary, when resampling audio to a notably higher pitch, it may be preferred to incorporate an interpolation filter, as frequencies that surpass the
1490:
94:. When using this method, the frequencies in the recording are always scaled at the same ratio as the speed, transposing its perceived pitch up or down in the process. Slowing down the recording to increase duration also lowers the pitch, while speeding it up for a shorter duration respectively raises the pitch, creating the so-called
464:
is the representation of verbal text in compressed time. While one might expect speeding up to reduce comprehension, Herb
Friedman says that "Experiments have shown that the brain works most efficiently if the information rate through the ears—via speech—is the 'average' reading rate, which is about
198:
of the signal, and sinusoidal "tracks" are created by connecting peaks in adjacent frames. The tracks are then re-synthesized at a new time scale. This method can yield good results on both polyphonic and percussive material, especially when the signal is separated into sub-bands. However, this
306:
In order to preserve an audio signal's pitch when stretching or compressing its duration, many time-scale modification (TSM) procedures follow a frame-based approach. Given an original discrete-time audio signal, this strategy's first step is to split the signal into short
282:
This is much more limited in scope than the phase vocoder based processing, but can be made much less processor intensive, for real-time applications. It provides the most coherent results for single-pitched sounds like voice or musically monophonic instrument recordings.
161:("beat") waveforms at all non-integer compression/expansion rates, which renders the results phasey and diffuse. Recent improvements allow better quality results at all compression/expansion ratios but a residual smearing effect still remains.
554:
For example, one could move the pitch of every note up by a perfect fifth, keeping the tempo the same. One can view this transposition as "pitch shifting", "shifting" each note up 7 keys on a piano keyboard, or adding a fixed amount on the
439:. However, simply superimposing the unmodified analysis frames typically results in undesired artifacts such as phase discontinuities or amplitude fluctuations. To prevent these kinds of artifacts, the analysis frames are adapted to form
264:
or the synchronized overlap-add method (SOLA) and performs somewhat faster than the phase vocoder on slower machines but fails when the autocorrelation mis-estimates the period of a signal with complicated harmonics (such as
530:
an audio sample while holding speed or duration constant. This may be accomplished by time stretching and then resampling back to the original length. Alternatively, the frequency of the sinusoids in a
164:
The phase vocoder technique can also be used to perform pitch shifting, chorusing, timbre manipulation, harmonizing, and other unusual modifications, all of which can be changed as a function of time.
286:
High-end commercial audio processing packages either combine the two techniques (for example by separating the signal into sinusoid and transient waveforms), or use other techniques based on the
70:
These processes are often used to match the pitches and tempos of two pre-recorded clips for mixing when the clips cannot be reperformed or resampled. Time stretching is often used to adjust
275:(formerly Cool Edit Pro) seems to solve this by looking for the period closest to a center period that the user specifies, which should be an integer multiple of the tempo, and between 30
385:
347:
437:
102:(determined by the sampling rate of the audio reproduction software or device) will create usually undesired sound distortions, a phenomenon that is also known as
773:
1013:
149:
perform an inverse STFT by taking the inverse
Fourier transform on each chunk and adding the resulting waveform chunks, also called overlap and add (OLA).
597:-like effect, which may be desirable or undesirable. A process that preserves the formants and character of a voice involves analyzing the signal with a
78:
to fit exactly into the 30 or 60 seconds available. It can be used to conform longer material to a designated time slot, such as a 1-hour broadcast.
973:
871:
696:
978:
1063:
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103:
446:
The strategy of how to derive the synthesis frames from the analysis frames is a key difference among different TSM procedures.
17:
563:. One can view the same transposition as "frequency scaling", "scaling" (multiplying) the frequency of every note by 3/2.
811:
David Malah (April 1979). "Time-domain algorithms for harmonic bandwidth reduction and time scaling of speech signals".
1519:
788:
753:
Jont B. Allen (June 1977). "Short Time
Spectral Analysis, Synthesis, and Modification by Discrete Fourier Transform".
589:
Time domain processing works much better here, as smearing is less noticeable, but scaling vocal samples distorts the
1311:
613:
95:
914:
992:
Free and commercial versions of a popular 3rd party time stretching library for iOS, Linux, Windows and Mac OS X
1056:
67:
is a simpler process which affects pitch and speed simultaneously by slowing down or speeding up a recording.
86:
The simplest way to change the duration or pitch of an audio recording is to change the playback speed. For a
1445:
1098:
582:, which adds a fixed frequency offset to the frequency of every note. (In theory one could perform a literal
349:. To achieve the actual time-scale modification, the analysis frames are then temporally relocated to have a
167:
896:
355:
317:
261:
195:
191:
136:
953:
875:
632:
standard for media playback. Similar controls are ubiquitous in media applications and frameworks such as
146:
apply some processing to the
Fourier transform magnitudes and phases (like resampling the FFT blocks); and
1465:
394:
185:
1514:
735:
465:
200–300 wpm (words per minute), yet the average rate of speech is in the neighborhood of 100–150 wpm."
140:
858:
700:
1219:
1204:
1195:
1049:
986:
Theory, equations, figures and performances of a real-time guitar pitch shifter running on a DSP chip
606:
242:
721:
586:
in which the musical pitch space location is scaled , but that is highly unusual, and not musical.)
1494:
602:
290:
transform, or artificial neural network processing, producing the highest-quality time stretching.
254:
75:
1170:
947:
594:
485:
44:
1524:
1306:
708:
612:
A detailed description of older analog recording techniques for pitch shifting can be found at
461:
91:
1007:
206:
Modelling a monophonic sound as observation along a helix of a function with a cylinder domain
1130:
1020: (archived 2023-02-02), a well-known algorithm for extreme (>10×) time stretching
944:
A comprehensive overview of current time and pitch modification techniques by
Stephan Bernsee
527:
238:
158:
995:
1230:
1200:
968:
579:
8:
1145:
941:
637:
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of fixed length. The analysis frames are spaced by a fixed number of samples, called the
31:
1296:
1210:
769:
124:
One way of stretching the length of a signal without affecting the pitch is to build a
1103:
1093:
969:
New Phase-Vocoder
Techniques for Pitch-Shifting, Harmonizing and Other Exotic Effects
672:
535:
may be altered directly, and the signal reconstructed at the appropriate time scale.
99:
1407:
1316:
1235:
839:
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135:
compute the instantaneous frequency/amplitude relationship of the signal using the
71:
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1155:
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662:
246:
234:
387:. This frame relocation results in a modification of the signal's duration by a
55:
is the opposite: the process of changing the pitch without affecting the speed.
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1080:
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components well, but early implementations introduced considerable smearing on
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125:
119:
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48:
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Changing the speed or duration of an audio signal without affecting its pitch
957:
956:
A Javascript pitchshifter based on smbPitchShift code, from the open source
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1392:
1387:
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60:
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commercial cross-platform library, mainly used by DJ and DAW manufacturers
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Free MATLAB implementations of various Time-Scale
Modification procedures
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560:
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512:
230:
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of the signal. In this method, peaks are identified in frames using the
56:
1029:
454:
For the specific case of speech, time stretching can be performed using
443:, prior to the reconstruction of the time-scale modified output signal.
1372:
1331:
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1135:
844:
827:
505:
495:
1023:
229:
and
Schafer in 1978 put forth an alternate solution that works in the
1185:
1160:
1038:— open-source library for changing the tempo, pitch and playback rate
1035:
677:
633:
556:
540:
266:
154:
983:
825:
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1041:
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open source and commercial libraries for real time audio stretching
567:
250:
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and then resynthesizing it at a different fundamental frequency.
598:
590:
468:
Listening to time-compressed speech is seen as the equivalent of
287:
226:
1004:
from Qneo - specialized synthesizer for creative voice sculpting
900:
989:
571:
143:
of a short, overlapping and smoothly windowed block of samples;
1475:
813:
IEEE Transactions on
Acoustics, Speech, and Signal Processing
755:
IEEE Transactions on
Acoustics, Speech, and Signal Processing
455:
276:
221:
199:
method is more computationally demanding than other methods.
1032:— open source library for time stretching and pitch shifting
1001:
974:
A new Approach to Transient Processing in the Phase Vocoder
950:
C source code for doing frequency domain pitch manipulation
629:
624:
Pitch-corrected audio timestretch is found in every modern
1377:
861:, Creative Computing Vol. 9, No. 7 / July 1983 / p. 122
43:
is the process of changing the speed or duration of an
828:"A Review of Time-Scale Modification of Music Signals"
397:
358:
320:
614:Alvin and the Chipmunks § Recording technique
566:Musical transposition preserves the ratios of the
491:Pitch shifting (frequency scaling) is provided on
449:
431:
379:
341:
30:"Timestretch" redirects here. For the album, see
1506:
774:"Speech Processing Based on a Sinusoidal Model"
767:
190:Another method for time stretching relies on a
179:
172:
171:Sinusoidal analysis/synthesis system (based on
1057:
948:Stephan Bernsee's smbPitchShift C source code
826:Jonathan Driedger and Meinard Müller (2016).
752:
241:) of a given section of the wave using some
90:recording, this can be accomplished through
942:Time Stretching and Pitch Shifting Overview
810:
302:Frame-based approach of many TSM procedures
1064:
1050:
915:"HTMLMediaElement.playbackRate - Web APIs"
1471:Music technology (electronic and digital)
965:- A good description of the phase vocoder
843:
373:
335:
297:
201:
166:
619:
570:frequencies that determine the sound's
293:
14:
1507:
128:after Flanagan, Golden, and Portnoff.
1045:
872:"Listen to podcasts in half the time"
559:, or adding a fixed amount in linear
526:These techniques can also be used to
380:{\displaystyle H_{s}\in \mathbb {N} }
342:{\displaystyle H_{a}\in \mathbb {N} }
1071:
432:{\displaystyle \alpha =H_{s}/H_{a}}
245:(commonly the peak of the signal's
108:
63:and intended for live performance.
59:is pitch scaling implemented in an
24:
697:"Dolby, The Chipmunks And NAB2004"
25:
1536:
1312:Recording studio as an instrument
935:
519:keep frequency ratio and harmony.
1488:
511:Frequency shifting provided by
504:
484:
475:
113:
907:
450:Speed hearing and speed talking
279:and the lowest bass frequency.
889:
864:
852:
819:
804:
781:The Lincoln Laboratory Journal
761:
746:
728:
689:
210:
13:
1:
963:The Phase Vocoder: A Tutorial
683:
81:
1495:Record production portal
984:How to build a pitch shifter
787:(2): 153–167, archived from
605:vocoder plus any of several
551:, depending on perspective.
262:time-domain harmonic scaling
180:Sinusoidal spectral modeling
7:
1466:Music technology (electric)
990:ZTX Time Stretching Library
643:
186:Spectral modeling synthesis
173:McAulay & Quatieri 1988
10:
1541:
607:pitch detection algorithms
538:Transposing can be called
219:
183:
153:The phase vocoder handles
141:discrete Fourier transform
117:
29:
1520:Digital signal processing
1484:
1433:
1340:
1279:
1169:
1079:
954:pitchshift.js from KievII
257:one period into another.
243:pitch detection algorithm
76:television advertisements
815:. ASSP-27 (2): 121–133.
757:. ASSP-25 (3): 235–238.
716:Cite magazine requires
657:— real-time changes of
595:Alvin and the Chipmunks
215:
740:www.atarimagazines.com
462:Time-compressed speech
433:
381:
343:
303:
233:: attempt to find the
207:
176:
92:sample rate conversion
47:without affecting its
1383:Ghostwriters in music
434:
382:
344:
301:
239:fundamental frequency
237:(or equivalently the
205:
170:
18:Audio time stretching
620:In consumer software
580:amplitude modulation
395:
356:
318:
294:Frame-based approach
996:Elastique by zplane
1297:Hip hop production
845:10.3390/app6020057
515:Frequency Shifter
429:
377:
339:
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208:
177:
1515:Audio engineering
1502:
1501:
1104:Critical distance
736:"Variable speech"
673:Scrubbing (audio)
389:stretching factor
351:synthesis hopsize
253:processing), and
100:Nyquist frequency
74:and the audio of
72:radio commercials
16:(Redirected from
1532:
1493:
1492:
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1408:Session musician
1073:Music production
1066:
1059:
1052:
1043:
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930:
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925:
911:
905:
904:
899:. Archived from
897:"Speeding iPods"
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874:. Archived from
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832:Applied Sciences
823:
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799:
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768:McAulay, R. J.;
765:
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719:
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704:
699:. Archived from
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668:Pitch correction
655:Dynamic tonality
533:sinusoidal model
508:
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441:synthesis frames
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313:analysis hopsize
109:Frequency domain
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1398:Record producer
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1216:Double tracking
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1156:Sound recording
1094:Audio mastering
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1018:Wayback Machine
979:PICOLA and TDHS
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859:Variable Speech
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770:Quatieri, T. F.
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718:|magazine=
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628:as part of the
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593:into a sort of
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260:This is called
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139:, which is the
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96:Chipmunk effect
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41:Time stretching
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958:KievII library
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936:External links
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903:on 2006-09-02.
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703:on 2008-05-27.
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118:Main article:
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878:on 2011-08-29
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794:on 2012-05-21
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584:pitch scaling
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476:Pitch scaling
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131:Basic steps:
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126:phase vocoder
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120:Phase vocoder
114:Phase vocoder
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88:digital audio
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65:Pitch control
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1486:
1451:Loudness war
1418:Ghost singer
1393:Orchestrator
1388:Horn section
1271:Reverse echo
1231:Equalization
1201:Delay effect
1180:
1151:Punch in/out
1146:Ping-ponging
1114:Effects unit
1109:Effects loop
1099:Audio mixing
1089:Audio filter
922:. Retrieved
918:
909:
901:the original
891:
880:. Retrieved
876:the original
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789:the original
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1441:Click track
1425:Vocal coach
1368:Backup band
1348:professions
1322:Turntablism
1196:Compression
1181:Pitch shift
1141:Overdubbing
1081:Engineering
1030:Rubber Band
1014:PaulStretch
1008:TSM toolbox
1002:Voice Synth
924:1 September
626:web browser
561:pitch space
231:time domain
211:Time domain
57:Pitch shift
33:Timestretch
1509:Categories
1373:Bandleader
1332:Xenochrony
1287:aesthetics
1251:Noise gate
1211:Distortion
1173:processing
1136:Microphone
1036:SoundTouch
882:2008-07-24
798:2014-09-07
684:References
496:Harmonizer
267:orchestral
220:See also:
184:See also:
82:Resampling
1283:Practices
1186:Auto-Tune
1161:Tape loop
1131:Diffusion
838:(2): 57.
678:Nightcore
634:GStreamer
557:Mel scale
541:frequency
528:transpose
399:α
370:∈
332:∈
269:pieces).
255:crossfade
159:transient
104:aliasing.
1358:Arranger
1317:Sampling
1241:Flanging
1119:Talk box
772:(1988),
644:See also
591:formants
568:harmonic
517:does not
493:Eventide
251:cepstral
155:sinusoid
1261:Pumping
1226:Ducking
1171:Signal
1016:at the
543:scaling
288:wavelet
227:Rabiner
35:(album)
1461:Medley
1456:Mashup
1266:Reverb
1256:Phaser
1024:Bungee
663:timbre
659:tuning
572:timbre
235:period
1476:Remix
1434:Other
1344:Roles
1302:Lo-fi
1205:STEED
792:(PDF)
777:(PDF)
638:Unity
456:PSOLA
222:PSOLA
49:pitch
926:2021
722:help
661:and
636:and
630:HTML
513:Bode
216:SOLA
196:STFT
137:STFT
1220:ADT
919:MDN
840:doi
603:LPC
601:or
545:or
391:of
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1378:DJ
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374:N
365:s
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336:N
327:a
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
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