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

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