Method and apparatus for adjusting the cadence of music on a personal audio device
Disclosed is an audio device that adjusts the cadence of played songs. All songs in a playlist may be adjusted to match the cadence of a particular song. First, the desired cadence of a reference song is determined by low pass filtering a digital representation of the reference song and determining the period (T) of the back beat of the reference song. The cadence of subsequent songs is then determined by low pass filtering digital representations of the subsequent songs and determining the period (T) of the back beat of the subsequent songs. An adjustment of the period (T) of the subsequent songs is then determined such that the adjustment of the period (T) of the subsequent songs results in the subsequent songs having the desired cadence (i.e., the cadence of the reference song). The period (T) of the back beat of the subsequent songs are then adjusted.
1. An apparatus for adjusting cadences of played songs, the apparatus comprising:
a period determination circuit for determining a period of a back beat of at least one song;
a period adjustment circuit for receiving said period of the back beat of said at least one song and determining a period adjustment signal based on the period of the back beat of said at least one song and a period of a back beat of a reference song; and
a CODEC for receiving said period adjustment signal and said digital representation of said at least one song and adjusting a cadence of said at least one song based on said period adjustment signal;
wherein the cadence is adjusted by an amount determined as a function of the period of the back beat of said at least one song, the period of the back beat of said reference song, and a clock rate of the CODEC.
2. The apparatus of claim 1 wherein said period adjustment signal specifies interpolation of a digital representation of said at least one song in order to increase said period of the back beat of said at least one song.
3. The apparatus of claim 1 wherein said period adjustment signal specifies decimation of a digital representation of said at least one song in order to decrease said period of the back beat of said at least one song.
4. The apparatus of claim 1 wherein said amount is calculated at least in part by dividing a difference between the period of the back beat of said at least one song and the period of the back beat of said reference song by a reciprocal of said clock rate.
5. The apparatus of claim 1 further comprising a memory for storing digital representations of songs.
6. The apparatus of claim 1 further comprising a low pass filter for receiving a digital representation of at least one song and generating a signal received by said period determination circuit.
7. The apparatus of claim 1 wherein said reference song is a song currently being played.
8. A personal audio device comprising the apparatus of claim 1 .
9. A method for adjusting cadences of played songs, the method comprising the steps of:
determining a period adjustment signal based on a period of a back beat of at least one song and a period of a back beat of a reference song; and
adjusting a cadence of said at least one song based on said period adjustment signal;
wherein the cadence is adjusted by an amount determined as a function of the period of the back beat of said at least one song, the period of the back beat of the reference song, and a clock rate of a CODEC.
10. The method of claim 9 wherein said reference song is a song currently being played.
11. The method of claim 9 , wherein the adjusting step is performed by the CODEC.
12. The method of claim 9 , wherein said period adjustment signal specifies interpolation of a digital representation of said at least one song in order to increase said period of the back beat of said at least one song.
13. The method of claim 9 , wherein said period adjustment signal specifies decimation of a digital representation of said at least one song in order to decrease said period of the back beat of said at least one song.
14. The method of claim 9 , wherein said amount is calculated at least in part by dividing a difference between the period of the back beat of said at least one song and the period of the back beat of said reference song by a reciprocal of said clock rate.