Patent Document ID: 9653056
Application ID: 14397826
Patent Flag: 1

Claim One:
1. An apparatus, the apparatus having at least one processor and at least one memory having computer-readable code stored thereon which when executed causes the at least one processor to: identify beat time instants (t i ) in an audio signal; determine a chord change likelihood from the audio signal at or between the beat time instants by using a predefined algorithm that takes as input a value of pitch chroma at or between the current beat time instant (t i ) and one or more values of pitch chroma at or between preceding and/or succeeding beat time instants, wherein the predefined algorithm is defined as: Chord_change ⁢ ( t i ) = ∑ j = 1 x ⁢ ∑ k = 1 y ⁢  c _ j ⁡ ( t i ⁢ ) - c _ j ⁡ ( t i - k )  - ∑ j = 1 x ⁢ ∑ k = 1 z ⁢  c _ j ⁡ ( t i ) - c _ j ⁡ ( t i + k )  where x is a number of chroma or pitch classes, y is a number of preceding beat time instants and z is a number of succeeding beat time instants; determine a first accent-based downbeat likelihood from the audio signal at or between the beat time instants (t i ); determine a second, different, accent-based downbeat likelihood from the audio signal at or between the beat time instants (ti); normalize the determined chord change likelihood and the first and second accent based downbeat likelihoods; identify downbeats by generating, for each of a set of beat time instances, a score representing or including a summation of the chord change likelihood, the first accent-based downbeat likelihood, and the second accent-based downbeat likelihood; and identify a downbeat from a highest resulting likelihood value over the set of beat time instances.