Detailed Description

Detects downbeats (first beat of each measure) in music.

The Downbeat analyzes beat patterns to identify the first beat of each musical measure. It detects metric groupings (time signatures) and tracks measure position.

Features:

Downbeat detection with confidence
Time signature detection (4/4, 3/4, 6/8, etc.)
Beat numbering within measures
Measure phase tracking (0-1 within measure)
Adaptive meter detection

Dependencies:

Requires Beat for rhythm analysis
Uses FFT for accent detection
Analyzes beat interval patterns

Definition at line 33 of file downbeat.h.

#include <downbeat.h>

Inheritance diagram for fl::audio::detector::Downbeat:

Collaboration diagram for fl::audio::detector::Downbeat:

Public Member Functions
	Downbeat () FL_NOEXCEPT
	Construct with standalone Beat.

	Downbeat (shared_ptr< Beat > beatDetector)
	Construct with shared Beat (recommended)

	~Downbeat () FL_NOEXCEPT override

void	fireCallbacks () override

u8	getBeatsPerMeasure () const
	Returns detected beats per measure (time signature numerator)

float	getConfidence () const
	Returns downbeat detection confidence (0-1)

u8	getCurrentBeat () const
	Returns current beat number within measure (1-based, 1 = downbeat)

float	getMeasurePhase () const
	Returns measure phase (0-1, 0 = downbeat)

const char *	getName () const override

bool	isDownbeat () const
	Returns true if downbeat was detected this frame.

bool	needsFFT () const override

bool	needsFFTHistory () const override

void	reset () override

void	setAccentThreshold (float threshold)
	Set accent detection threshold (default: 1.2)

void	setAutoMeterDetection (bool enable)
	Enable/disable automatic meter detection (default: true)

void	setBeatDetector (shared_ptr< Beat > beatDetector)
	Share an external Beat instance.

void	setConfidenceThreshold (float threshold)
	Set minimum confidence for downbeat detection (default: 0.6)

void	setTimeSignature (u8 beatsPerMeasure)
	Manually set time signature (disables auto-detection)

void	update (shared_ptr< Context > context) override

Public Member Functions inherited from fl::audio::Detector
virtual	~Detector () FL_NOEXCEPT=default

virtual void	setSampleRate (int) FL_NOEXCEPT

Public Attributes
function_list< void()>	onDownbeat
	Fires on detected downbeat (first beat of measure)

function_list< void(u8 beatNumber)>	onMeasureBeat
	Fires on each beat with beat number (1-based, downbeat = 1)

function_list< void(float phase)>	onMeasurePhase
	Fires with measure phase each frame (0-1 range)

function_list< void(u8 beatsPerMeasure)>	onMeterChange
	Fires when time signature changes.

Private Member Functions
float	calculateBeatAccent (const fft::Bins &fft, float bassEnergy)

bool	detectDownbeat (u32 timestamp, float accent)

void	detectMeter ()

u8	findMostCommonMeter () const

void	updateBeatDetector (shared_ptr< Context > context)

void	updateMeasurePhase (u32 timestamp)

Private Attributes
float	mAccentThreshold

bool	mAutoMeterDetection

deque< float >	mBeatAccents

shared_ptr< Beat >	mBeatDetector

u8	mBeatsPerMeasure

u8	mBeatsSinceDownbeat

float	mConfidence

float	mConfidenceThreshold

u8	mCurrentBeat

bool	mDownbeatDetected

bool	mFireDownbeat = false

bool	mFireMeasureBeat = false

bool	mFireMeterChange = false

u32	mLastBeatTime

u32	mLastDownbeatTime

bool	mManualMeter

float	mMeasurePhase

deque< u8 >	mMeterCandidates

bool	mOwnsBeatDetector

u8	mPendingBeatNumber = 0

u8	mPendingMeter = 0

float	mPreviousEnergy

shared_ptr< const fft::Bins >	mRetainedFFT

Static Private Attributes
static constexpr size	MAX_BEAT_HISTORY = 32

static constexpr size	METER_HISTORY_SIZE = 8

The documentation for this class was generated from the following files:

fl/audio/detector/downbeat.h
fl/audio/detector/downbeat.cpp.hpp

Detailed Description

Public Member Functions

Public Attributes

Private Member Functions

Private Attributes

Static Private Attributes