org.openimaj.audio.analysis

Class BeatDetector

java.lang.Object

org.openimaj.audio.Audio

org.openimaj.audio.AudioStream

org.openimaj.audio.processor.AudioProcessor

org.openimaj.audio.analysis.BeatDetector

All Implemented Interfaces:

Iterable<SampleChunk>

public class BeatDetector
extends AudioProcessor

A beat detector that uses a 2nd order LP filter, followed by an envelope detector (thanks Bram), feeding a Schmitt trigger. The rising edge detector provides a 1-sample pulse each time a beat is detected. The class also provides beat detection per sample chunk.

Author:

David Dupplaw (dpd@ecs.soton.ac.uk)

See Also:

"http://www.musicdsp.org/showArchiveComment.php?ArchiveID=200"

Created:

30 Nov 2011

Field Summary

Fields

Modifier and Type	Field and Description
static float	BEAT_RTIME Release time of envelope detector in seconds
static float	FREQ_LP_BEAT Low Pass filter frequency
static float	T_FILTER Low Pass filter time constant

Fields inherited from class org.openimaj.audio.Audio

format

Constructor Summary

Constructors

Modifier	Constructor and Description
	BeatDetector(AudioFormat af) Default constructor
	BeatDetector(AudioStream as) Chainable constructor
protected	BeatDetector(AudioStream as, AudioFormat af) Chainable constructor.

Method Summary

Modifier and Type	Method and Description
boolean	beatDetected() Returns whether a beat was detected within this sample chunk.
AudioTimecode	getBeatTimecode() Returns the timecode at which the first beat in this sample chunk was detected.
SampleChunk	process(SampleChunk samples) Function that takes a sample chunk and processes the chunk.

Methods inherited from class org.openimaj.audio.processor.AudioProcessor

getLength, getUnderlyingStream, nextSampleChunk, process, processingComplete, reset, setUnderlyingStream

Methods inherited from class org.openimaj.audio.AudioStream

iterator, seek

Methods inherited from class org.openimaj.audio.Audio

getFormat, setFormat

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Field Detail

FREQ_LP_BEAT

public static final float FREQ_LP_BEAT

Low Pass filter frequency

See Also:

Constant Field Values

T_FILTER

public static final float T_FILTER

Low Pass filter time constant

See Also:

Constant Field Values

BEAT_RTIME

public static final float BEAT_RTIME

Release time of envelope detector in seconds

See Also:

Constant Field Values

Constructor Detail

BeatDetector

public BeatDetector(AudioFormat af)

Default constructor

Parameters:

af - The format of the incoming data.

BeatDetector

public BeatDetector(AudioStream as)

Chainable constructor

Parameters:

as - The audio stream to process

BeatDetector

protected BeatDetector(AudioStream as,
                       AudioFormat af)

Chainable constructor.

Parameters:

as - The audio stream to process

af - The format to process.

Method Detail

process

public SampleChunk process(SampleChunk samples)

Function that takes a sample chunk and processes the chunk. It should also return a sample chunk containing the processed data. If wished, the chunk may be side-affected and the input chunk returned. It should not be assumed that the input chunk will be side-affected, but it must be noted that it is possible that it could be. This process function may also return null. If null is returned it means that the rest of the audio stream is not required to be processed by this processing function. Whether the rest of the sample chunks are copied or ignored is up to the caller.

Specified by:

process in class AudioProcessor

Parameters:

samples - The sample chunk to process.

Returns:

A sample chunk containing processed data.

See Also:

AudioProcessor.process(org.openimaj.audio.SampleChunk)

beatDetected

public boolean beatDetected()

Returns whether a beat was detected within this sample chunk.

Returns:

TRUE if a beat was detected

getBeatTimecode

public AudioTimecode getBeatTimecode()

Returns the timecode at which the first beat in this sample chunk was detected. Note that this class reuses this timecode class, so if you wish to use it afterwards you should clone it immediately after calling this function.

Returns:

The beat timecode.