Methods and apparatus for pitch determination
First Claim
1. A method for determining the pitch of a sampled digitized speech signal, comprising the steps of:
 embedding a portion of the sampled digitized speech signal into an mdimensional state space to obtain a sequence of mdimensional vectors;
selecting closest pairs of vectors in state space from a plurality of possible pairs of mdimensional vectors in said sequence of mdimensional vectors;
accumulating a total number of the selected closest pairs of vectors for each of a plurality of time separation values to produce a histogram of accumulated numbers; and
locating at least a highest peak in a portion of said histogram to obtain a pitch period value for said portion of the sampled digitized speech signal.
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Abstract
Methods and apparatus for detecting periodicity and/or for determining the fundamental period of a signal such as speech. The methods include embedding a portion of a sampled digitized signal into an mdimensional state space to obtain a sequence of mdimensional vectors, selecting closest pairs of vectors in state space from a plurality of possible pairs of mdimensional vectors in said sequence of mdimensional vectors, accumulating total numbers of selected closest pairs of vectors having the same time separation values to produce a histogram of accumulated numbers, and locating at least a highest peak in a portion of said histogram to obtain a value indicating the fundamental period of the signal. Various embodiments are directed to speech and audio signal processing and other speech related applications. However, the methods have a general nature and can be applied to other types of periodic or quasiperiodic signals as well.
39 Citations
62 Claims

1. A method for determining the pitch of a sampled digitized speech signal, comprising the steps of:

embedding a portion of the sampled digitized speech signal into an mdimensional state space to obtain a sequence of mdimensional vectors; selecting closest pairs of vectors in state space from a plurality of possible pairs of mdimensional vectors in said sequence of mdimensional vectors; accumulating a total number of the selected closest pairs of vectors for each of a plurality of time separation values to produce a histogram of accumulated numbers; and locating at least a highest peak in a portion of said histogram to obtain a pitch period value for said portion of the sampled digitized speech signal.  View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)


27. A method for determining if a portion of a signal is periodic, comprising:

transforming said portion of said signal into a sequence of mdimensional vectors; selecting closest pairs of vectors from a plurality of possible pairs of mdimensional vectors in said sequence of mdimensional vectors; accumulating total numbers of the selected closest pairs of vectors having same time separation values to produce a histogram of accumulated numbers; identifying highest peaks in a predetermined interval of said histogram, each identified highest peak having a corresponding position value; and determining said portion of said signal to be periodic when the position values of the identified highest peaks in said histogram are integer multiples or approximately integer multiples of the position value of the identified peak with the lowest position value.  View Dependent Claims (28, 29, 30, 31)


32. A method for estimating a fundamental period of a signal having periodicity, comprising the steps of:

transforming a sequence of signal samples into a sequence of mdimensional vectors; selecting closest pairs of vectors in a plurality of possible pairs of mdimensional vectors in said sequence of mdimensional vectors; accumulating a total number of the selected closest pairs of vectors for each of a plurality of time separation values to produce a histogram of accumulated numbers; and locating at least a highest peak in a portion of said histogram to obtain the fundamental period value for said sequence of said signal samples.  View Dependent Claims (33, 34, 35, 36, 37)


38. In a speech processing system, a pitch detector comprising:

a transformer module for transforming a sequence of input signal samples into a sequence of mdimensional vectors; a selector module for selecting closest pairs of vectors in a plurality of possible pairs of vectors in said sequence of mdimensional vectors; an accumulator module for accumulating total numbers of the selected closest pairs of vectors with same time separations between vectors to obtain an array of accumulated numbers; and a maxima locator module for locating at least one maximum in a distribution described by a portion of said array of accumulated numbers, wherein a position of the located maximum in said array provides an estimate of a pitch period.  View Dependent Claims (39, 40, 41, 42, 43)


44. An apparatus for determining the fundamental period of a sampled digitized signal, comprising:

means for embedding a portion of the sampled digitized signal into an mdimensional state space to obtain a sequence of mdimensional vectors; means for selecting closest pairs of vectors in state space from a plurality of possible pairs of mdimensional vectors in said sequence of mdimensional vectors; means for accumulating a total number of the selected closest pairs of vectors for each of a plurality of time separation values to generate a histogram of accumulated numbers; and means for locating at least a highest peak in a portion of said histogram to produce a fundamental period value for said portion of the sampled digitized signal.  View Dependent Claims (45)


46. A machine readable medium comprising computer executable instructions for controlling a computer to perform the steps of:

embedding a portion of a sampled digitized signal into an mdimensional state space to obtain a sequence of mdimensional vectors; selecting closest pairs of vectors in state space from a plurality of possible pairs of mdimensional vectors in said sequence of mdimensional vectors; accumulating a total number of the selected closest pairs of vectors for each of a plurality of time separation values to generate a histogram of accumulated numbers; and locating at least a highest peak in a portion of said histogram to produce a fundamental period value for said portion of the sampled digitized signal.


47. A method for estimating a fundamental frequency of a signal including a plurality of samples, comprising the steps of:

transforming a sequence of said signal samples into a sequence of mdimensional vectors; selecting closest pairs of vectors in a plurality of possible pairs of mdimensional vectors in said sequence or mdimensional vectors; generating an array of accumulated numbers by calculating total numbers of the selected closest pairs of vectors with same time separations between vectors in samples; identifying at least one maximum in a distribution described by said array of accumulated numbers; and determining the fundamental frequency of said signal from at least said identified one maximum.  View Dependent Claims (48, 49, 50)


51. A method for determining a fundamental period of a portion of a signal, comprising the steps of:

forming mdimensional vectors x(i) from a sequence of signal samples, where i is an integer index; selecting pairs of vectors {x(i),x(i+k)} with smallest distances D[x(i),x(i+k)] between vectors from a plurality of possible pairs of said mdimensional vectors, where k is an integer time separation value; computing a histogram of the distribution of the time separation values k for the selected pairs of vectors; and searching said histogram for at least one peak to determine the fundamental period of said portion of said signal.  View Dependent Claims (52, 53, 54, 55, 56, 57)


58. A method for determining a fundamental period of a portion of a signal, comprising the steps of:

selecting pairs of signal samples {s(i), s(i+k)} with smallest absolute differences s(i)−
s(i+k) from a plurality of possible pairs of samples of said portion of said signal, where i is an integer index and k is an integer time separation value;computing a histogram of the distribution of the time separation values k for the selected pairs of samples; and searching said histogram for at least one peak to determine the fundamental period of said portion of said signal.  View Dependent Claims (59, 60, 61, 62)

1 Specification