Abstract: A method for defining an index of a match between a content of two audio sources, comprising: sampling audio from a first source and a second source generating a first and second set of samples; selecting a sequential number of samples N belonging to the first set of samples and N samples belonging to the second set; transferring the first and second sequences of N samples to the frequency domain, generating a first and second sequences of N/2 frequency intervals; for the first sequence, calculating the sign of the derivative; for the second sequence, calculating the sign and the absolute value of the derivative, and a total sum of the absolute values of the derivative and a partial sum of the absolute values of the derivative; the ratio between the partial sum and the total sum being an index of the match of the audio sources.

Abstract: An audio tagging method adapted to insert, in audio generated by an audio source and represented in the frequency domain, an identification code which comprises a predefined number of bits, associating with each bit of the code a corresponding frequency interval and applying a bandpass filter centered on each of the frequency intervals associated with one of the bits of the code, such that: if the bit has the value 1, the value of the corresponding frequency interval is amplified; if the bit has the value 0, the value of the corresponding frequency interval is attenuated.

Abstract: A method for defining an index of a match between a content of two audio sources, comprising: sampling audio from a first source and a second source generating a first and second set of samples; selecting a sequential number of samples N belonging to the first set of samples and N samples belonging to the second set; transferring the first and second sequences of N samples to the frequency domain, generating a first and second sequences of N/2 frequency intervals; for the first sequence, calculating the sign of the derivative; for the second sequence, calculating the sign and the absolute value of the derivative, and a total sum of the absolute values of the derivative and a partial sum of the absolute values of the derivative; the ratio between the partial sum and the total sum being an index of the match of the audio sources.