public class BeatDetect
extends java.lang.Object
The human listening system determines the rhythm of music by detecting a pseudo periodical succession of beats. The signal which is intercepted by the ear contains a certain energy, this energy is converted into an electrical signal which the brain interprets. Obviously, The more energy the sound transports, the louder the sound will seem. But a sound will be heard as a beat only if his energy is largely superior to the sound's energy history, that is to say if the brain detects a brutal variation in sound energy. Therefore if the ear intercepts a monotonous sound with sometimes big energy peaks it will detect beats, however, if you play a continuous loud sound you will not perceive any beats. Thus, the beats are big variations of sound energy.In fact, the two algorithms in this class are based on two algorithms described in that paper.
To use this class, inside of draw() you must first call
detect(), passing the AudioBuffer you want to
analyze. You may then use the isXXX functions to find out what
beats have occurred in that frame. For example, you might use
isKick() to cause a circle to pulse.
BeatDetect has two modes: sound energy tracking and frequency energy
tracking. In sound energy mode, the level of the buffer, as returned by
level(), is used as the instant energy in each frame. Beats,
then, are spikes in this value, relative to the previous one second of sound.
In frequency energy mode, the same process is used but instead of tracking
the level of the buffer, an FFT is used to obtain a spectrum, which is then
divided into average bands using logAverages(), and each of
these bands is tracked individually. The result is that it is possible to
track sounds that occur in different parts of the frequency spectrum
independently (like the kick drum and snare drum).
In sound energy mode you use isOnset() to query the algorithm
and in frequency energy mode you use isOnset(int i),
isKick(), isSnare(), and
isRange() to query particular frequnecy bands or ranges of
frequency bands. It should be noted that isKick(),
isSnare(), and isHat() merely call
isRange() with values determined by testing the algorithm
against music with a heavy beat and they may not be appropriate for all kinds
of music. If you find they are performing poorly with your music, you should
use isRange() directly to locate the bands that provide the
most meaningful information for you.
| Modifier and Type | Field and Description |
|---|---|
static int |
FREQ_ENERGY
Constant used to request frequency energy tracking mode.
|
static int |
SOUND_ENERGY
Constant used to request sound energy tracking mode.
|
| Constructor and Description |
|---|
BeatDetect()
Create a BeatDetect object that is in SOUND_ENERGY mode.
|
BeatDetect(int timeSize,
float sampleRate)
Create a BeatDetect object that is in FREQ_ENERGY mode and expects a
sample buffer with the requested attributes.
|
| Modifier and Type | Method and Description |
|---|---|
int |
dectectSize()
Deprecated.
|
void |
detect(AudioBuffer buffer)
Analyze the samples in
buffer. |
void |
detect(float[] buffer)
Analyze the samples in
buffer. |
void |
detectMode(int algo)
Set the object to use the requested algorithm.
|
int |
detectSize()
In frequency energy mode this returns the number of frequency bands
currently being used.
|
float |
getDetectCenterFrequency(int i)
Returns the center frequency of the ith frequency band.
|
boolean |
isHat()
In frequency energy mode this returns true if a beat corresponding to the
frequency range of a hi hat has been detected.
|
boolean |
isKick()
In frequency energy mode this returns true if a beat corresponding to the
frequency range of a kick drum has been detected.
|
boolean |
isOnset()
In sound energy mode this returns true when a beat has been detected.
|
boolean |
isOnset(int i)
In frequency energy mode this returns true when a beat has been detect in
the
ith frequency band. |
boolean |
isRange(int low,
int high,
int threshold)
In frequency energy mode this returns true if at least
threshold bands of the bands included in the range
[low, high] have registered a beat. |
boolean |
isSnare()
In frequency energy mode this returns true if a beat corresponding to the
frequency range of a snare drum has been detected.
|
void |
setSensitivity(int millis)
Sets the sensitivity of the algorithm.
|
public static final int FREQ_ENERGY
public static final int SOUND_ENERGY
public BeatDetect()
timeSize and sampleRate will be set to 1024
and 44100, respectively, so that it is possible to switch into FREQ_ENERGY
mode with meaningful values.public BeatDetect(int timeSize,
float sampleRate)
timeSize - int: the size of the buffersampleRate - float: the sample rate of the samples in the bufferpublic void detectMode(int algo)
algo - int: either BeatDetect.SOUND_ENERGY or BeatDetect.FREQ_ENERGYpublic void detect(AudioBuffer buffer)
buffer.
This is a cumulative process, so you must call this function every frame.buffer - AudioBuffer: the buffer to analyze.public void detect(float[] buffer)
buffer. This is a cumulative
process, so you must call this function every frame.buffer - float[]: the buffer to analyzepublic int detectSize()
@Deprecated public int dectectSize()
public float getDetectCenterFrequency(int i)
i - int: which detect band you want the center frequency of.public void setSensitivity(int millis)
millis milliseconds before allowing
another beat to be reported. You can use this to dampen the algorithm if
it is giving too many false-positives. The default value is 10, which is
essentially no damping. If you try to set the sensitivity to a negative
value, an error will be reported and it will be set to 10 instead.millis - int: the sensitivity in millisecondspublic boolean isOnset()
public boolean isOnset(int i)
ith frequency band. In sound energy mode
this always returns false.i - int: the frequency band to querypublic boolean isKick()
public boolean isSnare()
public boolean isHat()
public boolean isRange(int low,
int high,
int threshold)
threshold bands of the bands included in the range
[low, high] have registered a beat. In sound energy mode
this always returns false.low - int: the index of the lower bandhigh - int: the index of the higher bandthreshold - int: the smallest number of bands in the range
[low, high] that need to have registered a beat
for this to return truethreshold bands of the bands
included in the range [low, high] have registered a
beat