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US5973252A
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Pitch detection and intonation correction apparatus and method
Assignee: Antares Audio Technologies LLC
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Filing: 1998-10-15
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Granted: 1999-10-26
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Expires: 2018-10-15
Abstract
Abstract A device and method is disclosed to correct intonation errors and generate vibrato in solo instruments and vocal performances in real time. The device determines the pitch of a musical note produced by voice or instrument and shifts the pitch of that note to produce a very high quality, high fidelity output. The device includes a pitch detector that automatically recognizes the pitch of musical notes quickly. The detected pitch is then used as an input to a pitch corrector that converts the pitch of the input to an output with a desired pitch. The corrected musical note is then in tune with the pitch standard. The device and method employ a microprocessor that samples the signal from a musical instrument or voice at regular intervals using an analog-to-digital converter and then utilizes data derived from an auto-correlation function of the waveform to continuously determine the period of the waveform. The period of the waveform is then compared to a desired period or periods (such as found in a scale). The ratio of the waveform period and the desired period is computed to re-sample the waveform. This ratio is smoothed over time to remove instantaneous output pitch changes. The ratio is used to resample the input waveform. The resulting output waveform is processed through a digital-to-analog converter and output through audio interfaces.
Inventors
- 👤 Harold A. Hildebrand
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 15:46
CPC Classifications
G; G10; G10H; G10H3/00; G10H3/12; G10H3/125; G10H1/00; G10H1/02; G10H1/36; G10H1/361; G10H1/366; G10H1/44; G10H7/00; G10H7/002; G10H2210/00; G10H2210/031; G10H2210/066; G10H2210/155; G10H2210/195; G10H2210/201; G10H2210/211; G10H2210/325; G10H2210/331; G10H2240/00; G10H2240/171; G10H2240/281; G10H2240/311; G10H2250/00; G10H2250/131; G10H2250/135; G10H2250/541; G10H2250/621; G10H2250/631
Claims Analysis
Total Claims: 42
Claim 1
Independent Claim
115 words
A method for processing a music waveform comprising the steps of: sampling said music waveform at intervals of time to produce a music waveform sequence of numerical representations of the waveform, {x.sub.j } for j=0, . . . i, where i represents the current sample of the waveform and 0, 1, 2 . . . represent previous time samples of the waveform, determining the auto-correlation values of said sequence {x j } at lag values zero and L, and determining the smallest value of L which minimizes the difference between the auto-correlation at lag zero and the auto-correlation at lag L, whereby said smallest value of L represents the measured period of said music waveform.
Claim 2
Independent Claim
115 words
A method for processing a music waveform comprising the steps of: sampling said music waveform at intervals of time to produce a music waveform sequence of numerical representations of the waveform, {x.sub.j } for j=0, . . . i, where i represents the current sample of the waveform and 0, 1, 2 . . . represent previous time samples of the waveform, determining the auto-correlation values of said sequence {x j } at lag values zero and L, and determining the smallest value of L which minimizes the difference between the auto-correlation at lag zero and the auto-correlation at lag L, whereby said smallest value of L represents the measured period of said music waveform.
Claim 3
Dependent Claim
58 words
The method of claim 1 further comprising the step of retuning said music waveform sequence by changing its period by an amount equal to the difference between said measured period of said music waveform and the period of a note from a musical scale that is closest to said measured period to produce a retuned music waveform sequence.
Claim 4
Dependent Claim
48 words
The method of claim 2 further comprising the step of retuning said music waveform sequence by changing its period by an amount equal to the difference between said measured period of said music waveform and the period from a MIDI interface to produce a retuned music waveform sequence.
Claim 5
Dependent Claim
29 words
The method of claim 1 further comprising the step of determining said auto-correlation value by E and H functions, ##EQU5## which are determined within two cycles of said waveform.
Claim 6
Independent Claim
141 words
A method for processing a music waveform comprising the steps of, sampling said music waveform at intervals of time to produce a sequence of musical representations at a sample rate of the waveform, {x j } for j=0, 1, 2, . . . i, where i represents the current sample at a current sample rate of the waveform and j=1, j=2 . . . represent prior time samples of the waveform, providing an estimate of lag value L est of the period of the music waveform, updating two functions representative of the accumulated energy of the waveform over two periods 2L of the waveform, using E.sub.i (L)=E.sub.i-1 (L)+x.sup.2.sub.i -x.sub.i-2L.sup.2, H.sub.i (L)=H.sub.i-1 (L)+x.sub.i x.sub.i-L -x.sub.i-L x.sub.i-2L, and selecting that lag value of L as the period of the music waveform that minimizes the difference between E i (L) and 2H i (L).
Claim 7
Independent Claim
141 words
A method for processing a music waveform comprising the steps of, sampling said music waveform at intervals of time to produce a sequence of musical representations at a sample rate of the waveform, {x j } for j=0, 1, 2, . . . i, where i represents the current sample at a current sample rate of the waveform and j=1, j=2 . . . represent prior time samples of the waveform, providing an estimate of lag value L est of the period of the music waveform, updating two functions representative of the accumulated energy of the waveform over two periods 2L of the waveform, using E.sub.i (L)=E.sub.i-1 (L)+x.sup.2.sub.i -x.sub.i-2L.sup.2, H.sub.i (L)=H.sub.i-1 (L)+x.sub.i x.sub.i-L -x.sub.i-L x.sub.i-2L, and selecting that lag value of L as the period of the music waveform that minimizes the difference between E i (L) and 2H i (L).
Claim 8
Dependent Claim
103 words
The method of claim 5 wherein said value of L which minimizes the function V=E i (L)-2H i (L) is defined as L min est, and said method further comprising the steps of, determining three values, V 1 , V 2 , V 3 of said function about L min est, V.sub.1 =E(L.sub.min est -1)-2H(L.sub.min est -1), V.sub.2 =E(L.sub.min)-2H(L.sub.min est), and V.sub.3 =E(L.sub.min est +1)-2H(L.sub.min est +1), fitting a quadratic curve to said values V 1 , V 2 , V 3 as a function of L min est, and determining a value L min est at a minimum of said quadratic curve.
Claim 9
Dependent Claim
58 words
The method of claim 5 further comprising the step of retuning said music waveform sequence by changing its period by an amount equal to the difference between said measured period of said music waveform and the period of a note from a musical scale that is closest to said measured period to produce a retuned music waveform sequence.
Claim 10
Dependent Claim
48 words
The method of claim 5 further comprising the step of retuning said music waveform sequence by changing its period by an amount equal to the difference between said measured period of said music waveform and the period from a MIDI interface to produce a retuned music waveform sequence.
Claim 11
Dependent Claim
42 words
The method of claim 8 further comprising the step of retuning said music waveform sequence by gradually changing said sample rate to a new sample rate which will convert the period L to said period of a note from a musical scale.
Claim 12
Dependent Claim
39 words
The method of claim 8 further comprising the step of, retuning said music waveform sequence by gradually changing said sample rate to a new sample rate which will convert the period L to said period from said MIDI interface.
Claim 13
Dependent Claim
21 words
The method of claim 7 further comprising the step of converting said returned waveform sequence into a retuned analog music signal.
Claim 14
Dependent Claim
21 words
The method of claim 8 further comprising the step of converting said returned waveform sequence into a retuned analog music signal.
Claim 15
Dependent Claim
37 words
The method of claim 5 further comprising the step of, first applying said sequence {x j } for j=0, 1, 2 . . . i, to an 8 to 1 anti-aliasing filter, and then downsampling said sequence.
Claim 16
Dependent Claim
18 words
The method of claim 5 wherein, the variable L est is computed from N to 1 downsampled data.
Claim 17
Dependent Claim
11 words
The method of claim 14 wherein, N is the number 8.
Claim 18
Dependent Claim
32 words
The method of claim 5 wherein, the variable L est is computed from E i (L) and H i (L) over a wide range of the lag variable L using downsampled data.
Claim 19
Dependent Claim
80 words
The method of claim 5 wherein, said sequence is downsampled by a rate of eight to one to produce a downsampled sequence, providing said lag value estimate L est of the period of said downsampled sequence, and wherein periodicity of said waveform is determined by the step of, varying the parameter L, and selecting a particular value of L as the period of said waveform which minimizes the relationship, E.sub.i (L)-2H.sub.i (L)≦eps E.sub.i (L), where eps is a small number.
Claim 20
Dependent Claim
36 words
The method of claim 17 further comprising the step of, determining a second value of L which minimizes said function, E.sub.i (L)-2H.sub.i (L)≦eps E.sub.i (L) so as to identify a missing fundamental frequency of said waveform.
Claim 21
Dependent Claim
30 words
The method of claim 5 wherein, said steps for processing a music waveform to determine the period of said waveform are performed in a programmed digital processor during background processing.
Claim 22
Dependent Claim
115 words
Apparatus for processing a music waveform comprising, means for sampling said music waveform at intervals of time to produce a music waveform sequence of numerical representations of the waveform, {x.sub.j } for j=0, . . . i, where i represents the current sample of the waveform and 0,1,2 . . . represent previous time samples of the waveform, means for determining the auto-correlation values of said sequence {x j } at lag values zero and L, and means for determining the smallest value of L which minimizes the difference between the auto-correlation at lag zero and the auto-correlation at lag L, whereby said smallest value of L represents the measured period of said music waveform.
Claim 23
Dependent Claim
115 words
Apparatus for processing a music waveform comprising, means for sampling said music waveform at intervals of time to produce a music waveform sequence of numerical representations of the waveform, {x.sub.j } for j=0, . . . i, where i represents the current sample of the waveform and 0,1,2 . . . represent previous time samples of the waveform, means for determining the auto-correlation values of said sequence {x j } at lag values zero and L, and means for determining the smallest value of L which minimizes the difference between the auto-correlation at lag zero and the auto-correlation at lag L, whereby said smallest value of L represents the measured period of said music waveform.
Claim 24
Dependent Claim
57 words
The apparatus of claim 20 further comprising, means for retuning said music waveform sequence by changing its period by an amount equal to the difference between said measured period of said music waveform and the period of a note from a musical scale that is closest to said measured period to produce a returned music waveform sequence.
Claim 25
Dependent Claim
47 words
The apparatus of claim 21 further comprising, means for retuning said music waveform sequence by changing its period by an amount equal to the difference between said measured period of said music waveform and the period from a MIDI interface to produce a retuned music waveform sequence.
Claim 26
Dependent Claim
28 words
The apparatus of claim 20 further comprising, means for determining said auto-correlation value by E and H functions, ##EQU6## which are determined within two cycles of said waveform.
Claim 27
Dependent Claim
145 words
Apparatus for processing a music waveform comprising, means for sampling said music waveform at intervals of time to produce a sequence of musical representations at a sample rate of the waveform, {x j } for j=0, 1, 2, . . . i, where i represents the current sample at a current sample rate of the waveform and j=1, j=2 . . . represent prior time samples of the waveform, means for providing an estimate of lag value L est of the period of the music waveform, means for updating two functions representative of the accumulated energy of the waveform over two periods 2L of the waveform, using E.sub.i (L)=E.sub.i-1 (L)+x.sup.2.sub.i x.sub.i-2L.sup.2, H.sub.i (L)=H.sub.i-1 (L)+x.sub.i x.sub.i-L -x.sub.i-L x.sub.i-2L, and means for selecting that lag value of L as the period of the music waveform that minimizes the difference between E i (L) and 2H i (L).
Claim 28
Dependent Claim
145 words
Apparatus for processing a music waveform comprising, means for sampling said music waveform at intervals of time to produce a sequence of musical representations at a sample rate of the waveform, {x j } for j=0, 1, 2, . . . i, where i represents the current sample at a current sample rate of the waveform and j=1, j=2 . . . represent prior time samples of the waveform, means for providing an estimate of lag value L est of the period of the music waveform, means for updating two functions representative of the accumulated energy of the waveform over two periods 2L of the waveform, using E.sub.i (L)=E.sub.i-1 (L)+x.sup.2.sub.i x.sub.i-2L.sup.2, H.sub.i (L)=H.sub.i-1 (L)+x.sub.i x.sub.i-L -x.sub.i-L x.sub.i-2L, and means for selecting that lag value of L as the period of the music waveform that minimizes the difference between E i (L) and 2H i (L).
Claim 29
Dependent Claim
107 words
The apparatus of claim 24 wherein, said value of L which minimizes the function V=E i (L)-2H i (L) is defined as L min est, and said apparatus further includes, means for determining three values, V 1 , V 2 , V 3 of said function about L min est, V.sub.1 =E(L.sub.min est -1)-2H(L.sub.min est -1), V.sub.2 =E(L.sub.min est)-2H(L.sub.min est), and V.sub.3 =E(L.sub.min est +1)-2H(L.sub.min est +1), means for fitting a quadratic curve to said values V 1 , V 2 , V 3 as a function of L min est, and means for determining a value L min est at a minimum of said quadratic curve.
Claim 30
Dependent Claim
57 words
The apparatus of claim 24 further comprising, means for retuning said music waveform sequence by changing its period by an amount equal to the difference between said measured period of said music waveform and the period of a note from a musical scale that is closest to said measured period to produce a retuned music waveform sequence.
Claim 31
Dependent Claim
47 words
The apparatus of claim 24 further comprising, means for retuning said music waveform sequence by changing its period by an amount equal to the difference between said measured period of said music waveform and the period from a MIDI interface to produce a retuned music waveform sequence.
Claim 32
Dependent Claim
41 words
The apparatus of claim 27 further comprising, means for retuning said music waveform sequence by gradually changing said sample rate to a new sample rate which will convert the period L to said period of a note from a musical scale.
Claim 33
Dependent Claim
38 words
The apparatus of claim 27 further comprising, means for retuning said music waveform sequence by gradually changing said sample rate to a new sample rate which will convert the period L to said period from said MIDI interface.
Claim 34
Dependent Claim
20 words
The apparatus of claim 26 further comprising, means for converting said returned waveform sequence into a retuned analog music signal.
Claim 35
Dependent Claim
20 words
The apparatus of claim 27 further comprising, means for converting said retuned waveform sequence into a retuned analog music signal.
Claim 36
Dependent Claim
36 words
The apparatus of claim 24 further comprising, means for first applying said sequence {x} for j=0, 1, 2 . . . i, to an 8 to 1 anti-aliasing filter, and means for subsequently downsampling said sequence.
Claim 37
Dependent Claim
18 words
The apparatus of claim 24 wherein, the variable L est is computed from N to 1 downsampled data.
Claim 38
Dependent Claim
11 words
The apparatus of claim 33 wherein, N is the number 8.
Claim 39
Dependent Claim
32 words
The apparatus of claim 24 wherein, the variable L est is computed from E i (L) and H i (L) over a wide range of the lag variable L using downsampled data.
Claim 40
Dependent Claim
24 words
The apparatus of claim 24 further comprising, means for downsampling said sequence by a rate of eight to one to produce a downsampled sequence.
Claim 41
Dependent Claim
35 words
The apparatus of claim 36 further comprising, means for determining a second value of L which minimizes said function, E.sub.i (L)-2H.sub.i (L)≦eps E.sub.i (L) so as to identify a missing fundamental frequency of said waveform.
Claim 42
Dependent Claim
28 words
The apparatus of claim 24 further comprising, means for processing said music waveform to determine the period of said waveform in a programmed digital processor during background processing.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2002-10-25 | 2003-04-26 | 2003-10-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2006-10-25 | 2007-04-26 | 2007-10-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2010-10-25 | 2011-04-26 | 2011-10-26 | $7700.00 | Window Closed / Lapsed |