Low-complexity method for improving the performance of autocorrelation-based pitch detectors

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.

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.

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.