Audio analysis method and audio analysis device

1. An audio analysis method comprising:

calculating, from an audio signal, a sound generation probability distribution which is a distribution of probabilities that sound representing the audio signal is generated at each position in a music piece;

estimating, from the sound generation probability distribution, a sound generation position of the sound in the music piece so as to synchronize automatic performance of the music piece with progress of the sound generation position;

calculating, from the sound generation probability distribution, an index of validity of the sound generation probability distribution, the index being calculated in accordance with a difference between a local maximum value at a maximum peak of the sound generation probability distribution and a local maximum value at a different peak of the sound generation probability distribution, which is different from the maximum peak;

determining a presence/absence of validity of the sound generation probability distribution based on the index; and

notifying a user of the absence of validity of the sound generation probability distribution in response to determining that the sound generation probability distribution is not valid.

2. The audio analysis method according to claim 1 , wherein

the sound generation probability distribution is determined as being not valid in response to the index being lower than a prescribed value.

3. The audio analysis method according to claim 1 , further comprising

executing the automatic performance of the music piece so as to be synchronized with the progression of the sound generation position that has been estimated.

4. An audio analysis method comprising:

calculating, from an audio signal, a sound generation probability distribution which is a distribution of probabilities that sound representing the audio signal is generated at each position in a music piece;

estimating, from the sound generation probability distribution, a sound generation position of the sound in the music piece;

calculating, from the sound generation probability distribution, an index of validity of the sound generation probability distribution;

determining a presence/absence of validity of the sound generation probability distribution based on the index;

executing automatic performance of the music piece so as to be synchronized with progression of the sound generation position that has been estimated; and

cancelling control to synchronize the automatic performance with the progression of the sound generation position in response to determining that the sound generation probability distribution is not valid.

5. The audio analysis method according to claim 4 , wherein

the index is calculated in accordance with a degree of dispersion at a peak of the sound generation probability distribution.

6. The audio analysis method according to claim 5 , wherein

the sound generation probability distribution is determined as being not valid in response to the index being higher than a prescribed value.

7. The audio analysis method according to claim 4 , further comprising

notifying a user in response to determining that the sound generation probability distribution is not valid.

8. An audio analysis device comprising:

an electronic controller including at least one processor, the electronic controller being configured to execute a plurality of modules including

a distribution calculation module that calculates, from an audio signal, a sound generation probability distribution which is a distribution of probabilities that sound representing the audio signal is generated at each position in a music piece;

a position estimation module that estimates a sound generation position of the sound in the music piece from the sound generation probability distribution so as to synchronize automatic performance of the music piece with progress of the sound generation position;

an index calculation module that calculates an index of validity of the sound generation probability distribution from the sound generation probability distribution, the index calculation module calculating the index in accordance with a difference between a local maximum value at a maximum peak of the sound generation probability distribution and a local maximum value at a different peak of the sound generation probability distribution, which is different from the maximum peak;

a validity determination module that determines a presence/absence of validity of the sound generation probability distribution based on the index; and

an operation control module that notifies a user of the absence of validity of the sound generation probability distribution in response to the validity determination module determining that the sound generation probability distribution is not valid.

9. The audio analysis device according to claim 8 , wherein

the validity determination module determines that the sound generation probability distribution is not valid in response to the index being lower than a prescribed value.

10. The audio analysis device according to claim 8 , wherein

the electronic controller further includes a performance control module that executes the automatic performance of the music piece so as to be synchronized with the progression of the sound generation position that has been estimated.

11. An audio analysis device comprising:

an electronic controller including at least one processor, the electronic controller being configured to execute a plurality of modules including

a distribution calculation module that calculates, from an audio signal, a sound generation probability distribution which is a distribution of probabilities that sound representing the audio signal is generated at each position in a music piece;

a position estimation module that estimates a sound generation position of the sound in the music piece from the sound generation probability distribution;

an index calculation module that calculates an index of validity of the sound generation probability distribution from the sound generation probability distribution;

a validity determination module that determines a presence/absence of validity of the sound generation probability distribution based on the index;

a performance control module that executes automatic performance of the music piece so as to be synchronized with progression of the sound generation position that has been estimated; and

an operation control module that cancels control of the performance control module to synchronize the automatic performance with the progression of the sound generation position in response to the validity determination module determining that the sound generation probability distribution is not valid.

12. The audio analysis device according to claim 11 , wherein

the index calculation module calculates the index in accordance with a degree of dispersion at a peak of the sound generation probability distribution.

13. The audio analysis device according to claim 12 , wherein

the validity determination module determines that the sound generation probability distribution is not valid in response to the index being higher than a prescribed value.

14. The audio analysis device according to claim 11 , wherein

the electronic controller further includes an operation control module that notifies a user in response to the validity determination module determining that the sound generation probability distribution is not valid.