A parallel bank of resonant band-pass sections for fixed source-filter colour. More...

#include <formant_filter_bank.hpp>

Classes
struct	FormantSpec
struct	Recipe

Public Member Functions
bool	prepare (double sample_rate, std::size_t capacity=MaxFormants) noexcept
bool	prepared () const noexcept
std::size_t	capacity () const noexcept
double	sample_rate () const noexcept
void	set_transition_samples (std::size_t samples) noexcept
std::size_t	transition_samples () const noexcept
bool	transition_active () const noexcept
FormantConfigureStatus	configure (std::span< const FormantSpec > formants, double headroom_db=3.0) noexcept
FormantConfigureStatus	configure (const Recipe &recipe) noexcept
FormantConfigureStatus	configure_vowel_morph (FormantVowel from, FormantVowel to, double amount, double headroom_db=3.0) noexcept
const Recipe &	requested_recipe () const noexcept
SampleType	process (SampleType input) noexcept
bool	process_block (const SampleType input, SampleType output, std::size_t frames) noexcept
bool	process_block (SampleType *samples, std::size_t frames) noexcept
void	reset () noexcept
double	tail_seconds () const noexcept
BiquadCoefficientsT< SampleType >	coefficients (std::size_t index) const noexcept
double	magnitude (double frequency_hz) const noexcept
	Exact complex-sum magnitude of the requested endpoint.
double	magnitude_db (double frequency_hz) const noexcept
void	response_curve_db (double min_hz, double max_hz, std::span< SampleType > output) const noexcept

Static Public Member Functions
static constexpr int	latency_samples () noexcept
static constexpr Recipe	vowel_recipe (FormantVowel vowel) noexcept
static Recipe	interpolate (const Recipe &from, const Recipe &to, double amount) noexcept

Static Public Attributes
static constexpr std::size_t	storage_capacity = MaxFormants
static constexpr double	min_frequency_hz = 40.0
static constexpr double	min_bandwidth_hz = 20.0
static constexpr double	min_q = 0.5
static constexpr double	max_q = 50.0
static constexpr double	min_gain_db = -60.0
static constexpr double	max_gain_db = 24.0
static constexpr double	min_headroom_db = 0.0
static constexpr double	max_headroom_db = 24.0
static constexpr std::size_t	default_transition_samples = 64

Detailed Description

template<typename SampleType = float, std::size_t MaxFormants = 5>
class pulp::signal::FormantFilterBankT< SampleType, MaxFormants >

A parallel bank of resonant band-pass sections for fixed source-filter colour.

This is an audio filter, not a formant tracker and not an STFT envelope shifter. Frequencies and bandwidths are supplied explicitly. A complete recipe is validated before any active or requested state changes. Retunes crossfade two complete stable banks; recursive coefficients are never interpolated.

Headroom policy: each band's linear weight is divided by the sum of all absolute weights and by the requested headroom gain. Since an RBJ band-pass section has at most unity steady-state magnitude, the summed response is bounded by that headroom gain. This intentionally normalizes level rather than adding a limiter or nonlinear recovery stage.

RT contract: all storage is fixed. prepare(), configure(), process(), reset(), and response inspection allocate no memory, take no locks, perform no I/O, and throw no exceptions. Configure at a block boundary. One instance owns one recursive signal path; use one instance per channel.