fl::audio::FrequencyBinMapper Class Reference

Detailed Description

FrequencyBinMapper maps FFT output bins to perceptually-spaced frequency channels.

This class converts the linear FFT spectrum into logarithmically-spaced frequency bands that better match human hearing. It supports both 16-bin (WLED-compatible) and 32-bin (higher resolution) modes with pre-calculated bin boundaries for efficient real-time processing.

Frequency ranges (16-bin mode, log spacing 20-16000 Hz):

• Bass: bins 0-1 (20-80 Hz)
• Mid: bins 6-7 (320-640 Hz)
• Treble: bins 14-15 (5120-16000 Hz)

Usage:

FrequencyBinMapper mapper;
FrequencyBinMapperConfig config;
config.mode = FrequencyBinMode::Bins16;
config.sampleRate = 22050;
config.fftBinCount = 256;  // 512-sample FFT / 2
mapper.configure(config);
 
// Map FFT output to frequency bins
Bins fftOutput = ...;  // From FFT
vector<float> frequencyBins(16);
mapper.mapBins(fftOutput.raw(), frequencyBins);
 
// Access specific ranges
float bassEnergy = mapper.getBassEnergy(frequencyBins);
float midEnergy = mapper.getMidEnergy(frequencyBins);
float trebleEnergy = mapper.getTrebleEnergy(frequencyBins);

Definition at line 71 of file frequency_bin_mapper.h.

#include <frequency_bin_mapper.h>

Collaboration diagram for fl::audio::FrequencyBinMapper:

Classes
struct	BinMapping
	Mapping from output bins to FFT bin ranges Each entry contains (startBin, endBin) for averaging. More...
struct	FrequencyRange
	Get frequency boundaries for a specific output bin. More...
struct	Stats
	Get statistics (for debugging/monitoring) More...

Public Member Functions
	FrequencyBinMapper () FL_NOEXCEPT
	FrequencyBinMapper (const FrequencyBinMapperConfig &config)
	~FrequencyBinMapper () FL_NOEXCEPT
void	configure (const FrequencyBinMapperConfig &config)
	Configure the frequency bin mapper This calculates bin boundaries and FFT-to-frequency bin mappings.
float	getBassEnergy (span< const float > frequencyBins) const
	Get bass energy (average of bins 0-1 in 16-bin mode)
FrequencyRange	getBinFrequencyRange (size binIndex) const
const FrequencyBinMapperConfig &	getConfig () const
	Get current configuration.
float	getMidEnergy (span< const float > frequencyBins) const
	Get mid energy (average of bins 6-7 in 16-bin mode)
size	getNumBins () const
	Get number of output bins (16 or 32)
const Stats &	getStats () const
float	getTrebleEnergy (span< const float > frequencyBins) const
	Get treble energy (average of bins 14-15 in 16-bin mode)
void	mapBins (span< const float > fftBins, span< float > outputBins) const
	Map FFT bins to frequency channels.

Private Member Functions
void	calculateBinBoundaries ()
	Calculate frequency bin boundaries (linear or logarithmic spacing)
void	calculateBinMappings ()
	Calculate FFT bin to frequency bin mappings Pre-calculates which FFT bins contribute to each frequency bin.
void	calculateLinearFrequencies ()
	Calculate linearly-spaced frequency boundaries.
void	calculateLogFrequencies ()
	Calculate logarithmically-spaced frequency boundaries.
float	frequencyToFFTBin (float frequency) const
	Convert frequency (Hz) to FFT bin index.

Private Attributes
vector< float >	mBinFrequencies
	Pre-calculated frequency boundaries for each output bin Size: numBins + 1 (includes both lower and upper edges)
vector< BinMapping >	mBinMappings
FrequencyBinMapperConfig	mConfig
Stats	mStats

Static Private Attributes
static constexpr size	BASS_BIN_END = 2
static constexpr size	BASS_BIN_START = 0
	Bass/mid/treble bin indices (for 16-bin mode) These are pre-calculated based on the bin count.
static constexpr size	MID_BIN_END = 8
static constexpr size	MID_BIN_START = 6
static constexpr size	TREBLE_BIN_END = 16
static constexpr size	TREBLE_BIN_START = 14

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

• fl/audio/frequency_bin_mapper.h
• fl/audio/frequency_bin_mapper.cpp.hpp