Signal processing apparatus and signal processing method, program, and recording medium
A signal processing apparatus and method is disclosed by which a feature value of an audio signal such as the tempo can be detected with a high degree of accuracy. A level calculation section produces a level signal representative of a transition of the level of an audio signal. A frequency analysis section frequency analyzes the level signal. A feature value extraction section determines a tempo, a speed feeling and a tempo fluctuation of the audio signal based on a result of the frequency analysis of the level signal. The invention can be applied to an apparatus which determines, for example, a tempo from an audio signal.
1. A signal processing apparatus for processing an audio signal, comprising:
a production section configured to produce a representative signal of a transition of a level of the audio signal;
a frequency analysis section configured to analyze a frequency of the representative signal, said frequency analysis section including,
a frequency conversion section configured to convert the representative signal from the time domain to the frequency domain to produce initial frequency components, and
a frequency component processing section configured to produce sum values by adding, to respective initial frequency components of the representative signal, frequency components that are harmonics to the respective initial frequency components, and outputting the sum values as new frequency components; and
a feature value calculation section configured to determine at least one feature value of the audio signal based on the new frequency components received from the frequency analysis section, said feature value corresponding to a quantified value of a characteristic of said audio signal.
2. A signal processing apparatus according to claim 1 , wherein said feature value calculation section determines a tempo of the audio signal as the at least one feature value.
3. A signal processing apparatus according to claim 1 , wherein said feature value calculation section determines a value of the audio signal corresponding to a location of high peaks of the new frequency components in the frequency domain as the at least one feature value.
4. A signal processing apparatus according to claim 1 , wherein said feature value calculation section determines a fluctuation of a tempo of the audio signal as the at least one feature value.
5. A signal processing apparatus according to claim 1 , wherein said feature value calculation section determines a tempo and a value of the audio signal corresponding to a location of high peaks of the new frequency components in the frequency domain as feature values, and corrects the tempo based on the value to determine a final tempo.
6. A signal processing apparatus according to claim 1 , further comprising a statistic processing section configured to add the new frequency components of the representative signal for one tune supplied by said frequency analysis section, said feature value calculation section determining the at least one feature value based on the added new frequency components from said statistic processing section.
7. A signal processing method for a signal processing apparatus which processes an audio signal, comprising:
producing a representative signal of a transition of a level of the audio signal;
analyzing a frequency of the representative signal;
converting the representative signal from the time domain to the frequency domain to produce initial frequency components, and
producing sum values by adding, to respective initial frequency components of the representative signal, frequency components that are harmonics to the respective initial frequency components, and outputting the sum values as new frequency components; and
determining at least one feature value of the audio signal based on the new frequency components, said feature value corresponding to a quantified value of a characteristic of said audio signal.
8. A computer-readable storage medium encoded with computer executable instructions, which when executed by a computer, cause the computer to perform a method of processing of an audio signal, the method comprising:
producing a representative signal of a transition of a level of the audio signal;
analyzing a frequency of the representative signal;
converting the representative signal from the time domain to the frequency domain to produce initial frequency components, and
producing sum values by adding, to respective initial frequency components of the representative signal, frequency components that are harmonics to the respective initial frequency components, and outputting the sum values as new frequency components; and
determining at least one feature value of the audio signal based on the new frequency components, said feature value corresponding to a quantified value of a characteristic of said audio signal.