US5127053A
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Low-complexity method for improving the performance of autocorrelation-based pitch detectors
Assignee: L3 Technologies Inc
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Filing: 1990-12-24
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Granted: 1992-06-30
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Expires: 2010-12-24
Abstract
Abstract A method of operating an autocorrelation pitch detector for use in a vocoder overcomes the pitch doubling and tripling problem using a heuristic rather than an analytic approach. The process tracks the times of occurrence of a highest and a second-highest autocorrelation peak. The amplitudes of the highest and the second-highest autocorrelation peaks are compared and, when these peaks are within a predetermined percentage difference in amplitude, the ratio of the time position (IPITCH2) of the second-highest peak to the time position (IPITCH) of the highest peak is checked to determine if that ratio is 1/31/2 or 2/3, within a predetermined error limit epsilon . If so and if the ratio is either 1/2 or 1/3, then IPITCH is set equal to IPITCH2 as reepresentative of the pitch period while, if the ratio is 2/3, then IPITCH is divided by three in order to represent the pitch period.
Inventors
- 👤 Steven R. Koch
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 06:59
CPC Classifications
G; G10; G10L; G10L25/00; G10L25/90; G10L19/00; G10L19/04; G10L19/08; G10L19/09; G10L2019/0001; G10L2019/0011; G10L25/03; G10L25/06; G10L25/09; G10L25/93
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
125 words
A method of operating an autocorrelation pitch detector for use in a vocoder comprising the steps of: tracking times of occurrence of a highest and a second-highest autocorrelation peak in an input signal; comparing amplitudes of said highest and second-highest autocorrelation peaks; identifying said times of occurrence to determine if the time position of said highest autocorrelation peak and the time position of said second-highest autocorrelation peak are in a predetermined ratio when said highest and second-highest autocorrelation peaks are within a predetermined percentage difference in amplitude; and selecting as a true autocorrelation peak one of said highest or second-highest autocorrelation peaks when said predetermined ratio exists between said time position of said highest autocorrelation peak and said time position of said second-highest autocorrelation peak.
Claim 2
Independent Claim
125 words
A method of operating an autocorrelation pitch detector for use in a vocoder comprising the steps of: tracking times of occurrence of a highest and a second-highest autocorrelation peak in an input signal; comparing amplitudes of said highest and second-highest autocorrelation peaks; identifying said times of occurrence to determine if the time position of said highest autocorrelation peak and the time position of said second-highest autocorrelation peak are in a predetermined ratio when said highest and second-highest autocorrelation peaks are within a predetermined percentage difference in amplitude; and selecting as a true autocorrelation peak one of said highest or second-highest autocorrelation peaks when said predetermined ratio exists between said time position of said highest autocorrelation peak and said time position of said second-highest autocorrelation peak.
Claim 3
Dependent Claim
22 words
The method of operating an autocorrelation pitch detector as recited in claim 1 wherein said predetermined ratio is approximately 2:1 or 3:1.
Claim 4
Dependent Claim
92 words
The method of operating an autocorrelation pitch detector as recited in claim 1 further comprising the steps of: checking said times of occurrence to determine if the time position of said highest autocorrelation peak and the time position of said second-highest autocorrelation peak are in a ratio of approximately 3:2 when said highest and second-highest autocorrelation peaks are within said predetermined percentage difference in amplitude; and dividing said time position of said highest autocorrelation peak by three when said 3:2 ratio exists to provide a resulting output signal representing true pitch period.
Claim 5
Dependent Claim
91 words
The method of operating an autocorrelation pitch detector as recited in claim 2 further comprising the steps of: checking said times of occurrence to determine if the ratio of the time position of said highest autocorrelation peak to the time position of said second-highest autocorrelation peak is approximately 3:2 when said highest and second-highest autocorrelation peaks are within said predetermined percentage difference in amplitude; and dividing said time position of said highest autocorrelation peak by three when said 3:2 ratio exists to provide a resulting output signal representing true pitch period.
Claim 6
Dependent Claim
58 words
The method of operating an autocorrelation pitch detector as recited in claim 2 further comprising the step of selecting as a true autocorrelation peak one of said highest autocorrelation peaks whenever the ratio of the time position of said highest autocorrelation peak to the time position of said second-highest autocorrelation peak is other than 2:1, 3:1 or 3:2.
Claim 7
Independent Claim
115 words
A method of operating an autocorrelation pitch detector for use in a vocoder comprising the steps of: tracking times of occurrence of a highest and a second-highest autocorrelation peak in an input signal; comparing amplitudes of said highest and second-highest autocorrelation peaks; checking said times of occurrence to determine if the ratio of the time position of said highest autocorrelation peak to the time position of said second-highest autocorrelation peak is approximately 3:2 when said highest and second-highest autocorrelation peaks are within said predetermined percentage difference in amplitude; and dividing said time position of said highest autocorrelation peak by three when said 3:2 ratio exists to provide a resulting output signal representing true pitch period.
Claim 8
Independent Claim
115 words
A method of operating an autocorrelation pitch detector for use in a vocoder comprising the steps of: tracking times of occurrence of a highest and a second-highest autocorrelation peak in an input signal; comparing amplitudes of said highest and second-highest autocorrelation peaks; checking said times of occurrence to determine if the ratio of the time position of said highest autocorrelation peak to the time position of said second-highest autocorrelation peak is approximately 3:2 when said highest and second-highest autocorrelation peaks are within said predetermined percentage difference in amplitude; and dividing said time position of said highest autocorrelation peak by three when said 3:2 ratio exists to provide a resulting output signal representing true pitch period.
Claim 9
Dependent Claim
154 words
An autocorrelation pitch detector for use in a vocoder comprising: autocorrelation means for autocorrelating an input signal and generating an output signal having a plurality of peaks; first analyzer means for tracking times of occurrence of a highest and a second-highest autocorrelation peak from said autocorrelation means; and second analyzer means responsive to said first analyzer means for comparing amplitudes of said highest and second-highest autocorrelation peaks, checking said positions to determine if the ratio of the time position of said highest autocorrelation peak to the time position of said second-highest autocorrelation peak is approximately 2:1 or 3:1 when said highest and second-highest autocorrelation peaks are within a predetermined percentage difference in amplitude, and selecting as a true autocorrelation peak one of said highest or second-highest autocorrelation peaks when said approximately 2:1 or 3:1 ratio exists between said time position of said highest autocorrelation peak and said time position of said second-highest autocorrelation peak.
Claim 10
Dependent Claim
154 words
An autocorrelation pitch detector for use in a vocoder comprising: autocorrelation means for autocorrelating an input signal and generating an output signal having a plurality of peaks; first analyzer means for tracking times of occurrence of a highest and a second-highest autocorrelation peak from said autocorrelation means; and second analyzer means responsive to said first analyzer means for comparing amplitudes of said highest and second-highest autocorrelation peaks, checking said positions to determine if the ratio of the time position of said highest autocorrelation peak to the time position of said second-highest autocorrelation peak is approximately 2:1 or 3:1 when said highest and second-highest autocorrelation peaks are within a predetermined percentage difference in amplitude, and selecting as a true autocorrelation peak one of said highest or second-highest autocorrelation peaks when said approximately 2:1 or 3:1 ratio exists between said time position of said highest autocorrelation peak and said time position of said second-highest autocorrelation peak.
Claim 11
Dependent Claim
138 words
An autocorrelation pitch detector for use in a vocoder comprising: autocorrelation means for autocorrelating an input signal and generating an output signal having a plurality of peaks; first analyzer means for tracking times of occurrence of a highest and a second-highest autocorrelation peak from said autocorrelation means; and second analyzer means responsive to said first analyzer means for comparing amplitudes of said highest and second-highest autocorrelation peaks, checking said positions to determine if the ratio of the time position of said highest autocorrelation peak to the time position of said second-highest autocorrelation peak is approximately 3:2 when said highest and second-highest autocorrelation peaks are within said predetermined percentage difference in amplitude, and dividing said time position of said highest autocorrelation peak by three when said 3:2 ratio exists to provide a resulting output signal representing true pitch period.
Claim 12
Dependent Claim
138 words
An autocorrelation pitch detector for use in a vocoder comprising: autocorrelation means for autocorrelating an input signal and generating an output signal having a plurality of peaks; first analyzer means for tracking times of occurrence of a highest and a second-highest autocorrelation peak from said autocorrelation means; and second analyzer means responsive to said first analyzer means for comparing amplitudes of said highest and second-highest autocorrelation peaks, checking said positions to determine if the ratio of the time position of said highest autocorrelation peak to the time position of said second-highest autocorrelation peak is approximately 3:2 when said highest and second-highest autocorrelation peaks are within said predetermined percentage difference in amplitude, and dividing said time position of said highest autocorrelation peak by three when said 3:2 ratio exists to provide a resulting output signal representing true pitch period.
References Cited (Backward Citations)
US4360708A
Cited
US4184049A
Cited
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