# US 7,612,275 B2 · Method, apparatus and computer program product for providing rhythm information from an audio signal > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,612,275 B2 - Document ID: US7612275B2 - Status: Granted - Kind: B2 - Application number: 11/405,890 - Filed: 2006-04-18 - Published: 2007-10-18 - Granted: 2009-11-03 - Earliest claimed: 2006-04-18 - Assignees: Nokia Corporation - Inventors: Jarno Seppänen; Antti Eronen; Jarmo Hiipakka - Web page: https://patentgrep.com/patent/US7612275B2 ## CPC - G10H 1/40: Rhythm - G10H 2210/076: for extraction of timing, tempo; Beat detection - G10H 2220/081: Beat indicator, e.g. marks or flashing LEDs to indicate tempo or beat positions - G10H 2250/105: Comb filters - G10H 2250/135: Autocorrelation - G10H 2250/221: Cosine transform; DCT [discrete cosine transform], e.g. for use in lossy audio compression such as MP3 - G10H 2250/235: Fourier transform; Discrete Fourier Transform [DFT]; Fast Fourier Transform [FFT] - G10H: ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE ## Abstract An apparatus for providing a beat and tatum tracker includes an accent filter bank, a periodicity estimator, a period estimator and a phase estimator. The accent filter bank is configured to downsample an input audio signal. The periodicity estimator is configured to determine a periodicity based on the downsampled signal. The period estimator is configured to determine a period based on the periodicity. The phase estimator is configured to estimate a phase based on the period for determining beat and tatum times of the input audio signal. ## Claims ### Claim 1 A method comprising: employing downsampling to preprocess an input audio signal; determining a periodicity and period based on the downsampled signal; performing, via a processor, a phase estimation based on the period to determine a score comprising an average of filter outputs at intervals defined by the period; and determining beat information based on the period and the score associated with the phase estimation. ### Claim 2 (depends on 1) A method according to claim 1, further comprising an initial operation of resampling the input audio signal. ### Claim 3 (depends on 1) A method according to claim 1, wherein employing downsampling comprises performing a data reduction using a decimating sub-band filter bank. ### Claim 4 (depends on 1) A method according to claim 1, wherein employing downsampling comprises performing a data reduction using a quadrature mirror filter. ### Claim 5 (depends on 1) A method according to claim 1, wherein determining the periodicity comprises transforming a signal derived from the input audio signal using a discrete cosine transform. ### Claim 6 (depends on 1) A method according to claim 1, wherein determining the period comprises determining the period based on the periodicity. ### Claim 7 (depends on 1) A method according to claim 1, wherein performing the phase estimation comprises selectively employing comb filters to filter accent information. ### Claim 8 (depends on 7) A method according to claim 7, wherein performing the phase estimation comprises performing the phase estimation based on the accent information and the period. ### Claim 9 (depends on 1) A method according to claim 1, wherein employing downsampling further comprises extracting accent information from the input audio signal. ### Claim 10 (depends on 1) A method according to claim 1, wherein determining the periodicity comprises transforming a signal derived from the input audio signal using a chirp z-transform. ### Claim 11 (depends on 1) A method according to claim 1, further comprising calculating one of beat times or tatum times based on corresponding one of beat period information or tatum period information. ### Claim 12 A computer program product comprising at least one computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable program code portions comprising: a first executable portion for employing downsampling to preprocess an input audio signal; a second executable portion for determining a periodicity and period based on the downsampled signal; a third executable portion for performing a phase estimation based on the period to determine a score comprising an average of filter outputs at intervals defined by the period; and a fourth executable portion for determining beat information based on the period and the score associated with the phase estimation. ### Claim 13 (depends on 12) A computer program product according to claim 12, further comprising a fifth executable portion for an initial operation of resampling the input audio signal. ### Claim 14 (depends on 12) A computer program product according to claim 12, wherein the first executable portion includes instructions for performing a data reduction using a decimating sub-band filter bank. ### Claim 15 (depends on 12) A computer program product according to claim 12, wherein the first executable portion includes instructions for performing a data reduction using a quadrature mirror filter. ### Claim 16 (depends on 12) A computer program product according to claim 12, wherein the second executable portion includes instructions for transforming a signal derived from the input audio signal using one of a discrete cosine transform or a chirp z-transform. ### Claim 17 (depends on 12) A computer program product according to claim 12, wherein the second executable portion includes instructions for determining the period based on the periodicity. ### Claim 18 (depends on 12) A computer program product according to claim 12, wherein the third executable portion includes instructions for selectively employing comb filters to filter accent information. ### Claim 19 (depends on 18) A computer program product according to claim 18, wherein the third executable portion includes instructions for performing the phase estimation based on the accent information and the period. ### Claim 20 (depends on 12) A computer program product according to claim 12, wherein the first executable portion includes instructions for employing downsampling further comprises extracting accent information from the input audio signal. ### Claim 21 (depends on 12) A computer program product according to claim 12, further comprising a fifth executable portion for calculating one of beat times or tatum times based on corresponding one of beat period information or tatum period information. ### Claim 22 An apparatus comprising: an accent filter bank configured to downsample an input audio signal; a periodicity estimator configured to determine a periodicity based on the downsampled signal; a period estimator configured to determine a period based on the periodicity; and a phase estimator configured to estimate a phase based on the period to determine a score comprising an average of filter outputs at intervals defined by the period for determining beat and tatum times of the input audio signal based on the period and the score associated with the phase estimation. ### Claim 23 (depends on 22) An apparatus according to claim 22, further comprising a resampler configured to resample the input audio signal. ### Claim 24 (depends on 22) An apparatus according to claim 22, wherein the accent filter bank comprises a decimating sub-band filter bank. ### Claim 25 (depends on 22) An apparatus according to claim 22, wherein the accent filter bank comprises a quadrature mirror filter. ### Claim 26 (depends on 22) An apparatus according to claim 22, wherein the accent filter bank comprises a power estimation element. ### Claim 27 (depends on 22) An apparatus according to claim 22, wherein the accent filter bank comprises an accent computation element. ### Claim 28 (depends on 27) An apparatus according to claim 27, wherein the accent computation element is configured to extract accent information from the input audio signal. ### Claim 29 (depends on 28) An apparatus according to claim 28, wherein the phase estimator includes a selectively determined number of comb filters configured to filter the accent information. ### Claim 30 (depends on 28) An apparatus according to claim 28, wherein the phase estimator is configured to perform the phase estimation based on the accent information and the period. ### Claim 31 (depends on 22) An apparatus according to claim 22, wherein the periodicity estimator is configured to transform a signal derived from the input audio signal using one of a discrete cosine transform or a chirp z-transform. ### Claim 32 (depends on 22) An apparatus according to claim 22, wherein the period estimator is configured to determine the period based on the periodicity. ### Claim 33 (depends on 22) An apparatus according to claim 22, wherein the apparatus is embodied in a mobile terminal. ### Claim 34 (depends on 22) An apparatus according to claim 22, wherein the phase estimator is configured to calculate one of beat times or tatum times based on corresponding one of beat period information or tatum period information. ### Claim 35 An apparatus comprising: means for employing downsampling to preprocess an input audio signal; means for determining a periodicity and period based on the downsampled signal; means for performing a phase estimation based on the period to determine a score comprising an average of filter outputs at intervals defined by the period; and means for determining beat information based on the period and the score associated with the phase estimation. ### Claim 36 An apparatus comprising a processor configured to: employ downsampling to preprocess an input audio signal; determine a periodicity and period based on the downsampled signal; perform a phase estimation based on the period to determine a score comprising an average of filter outputs at intervals defined by the period; and determine beat information based on the period and the score associated with the phase estimation.