Brickworks > API documentation > bw_satur
Antialiased tanh-based saturation with parametric bias and gain (compensation) and output bias removal.
In other words this implements (approximately)
y(n) = tanh(gain * x(n) + bias) - tanh(bias)
with antialiasing and optionally dividing the output by gain.
As a side effect, antialiasing causes attenuation at higher frequencies (about 3 dB at 0.5 × Nyquist frequency and rapidly increasing at higher frequencies).
The antialiasing technique used here is described in
J. D. Parker, V. Zavalishin, and E. Le Bivic, "Reducing the Aliasing of Nonlinear Waveshaping Using Continuous-Time Convolution", Proc. 19th Intl. Conf. Digital Audio Effects (DAFx-16), pp. 137-144, Brno, Czech Republic, September 2016.
Module type: dsp
Version: 1.1.0
Requires:
typedef struct bw_satur_coeffs bw_satur_coeffs;
Coefficients and related.
typedef struct bw_satur_state bw_satur_state;
Internal state and related.
static inline void bw_satur_init(
bw_satur_coeffs * BW_RESTRICT coeffs);
Initializes input parameter values in coeffs.
static inline void bw_satur_set_sample_rate(
bw_satur_coeffs * BW_RESTRICT coeffs,
float sample_rate);
Sets the sample_rate (Hz) value in coeffs.
static inline void bw_satur_reset_coeffs(
bw_satur_coeffs * BW_RESTRICT coeffs);
Resets coefficients in coeffs to assume their target values.
static inline float bw_satur_reset_state(
const bw_satur_coeffs * BW_RESTRICT coeffs,
bw_satur_state * BW_RESTRICT state,
float x_0);
Resets the given state to its initial values using the given coeffs and the initial input value x_0.
Returns the corresponding initial output value.
static inline void bw_satur_reset_state_multi(
const bw_satur_coeffs * BW_RESTRICT coeffs,
bw_satur_state * BW_RESTRICT const * BW_RESTRICT state,
const float * x_0,
float * y_0,
size_t n_channels);
Resets each of the n_channels states to its initial values using the given coeffs and the corresponding initial input value in the x_0 array.
The corresponding initial output values are written into the y_0 array, if not BW_NULL.
static inline void bw_satur_update_coeffs_ctrl(
bw_satur_coeffs * BW_RESTRICT coeffs);
Triggers control-rate update of coefficients in coeffs.
static inline void bw_satur_update_coeffs_audio(
bw_satur_coeffs * BW_RESTRICT coeffs);
Triggers audio-rate update of coefficients in coeffs.
static inline float bw_satur_process1(
const bw_satur_coeffs * BW_RESTRICT coeffs,
bw_satur_state * BW_RESTRICT state,
float x);
static inline float bw_satur_process1_comp(
const bw_satur_coeffs * BW_RESTRICT coeffs,
bw_satur_state * BW_RESTRICT state,
float x);
These function process one input sample x using coeffs, while using and updating state. They return the corresponding output sample.
In particular:
bw_satur_process1() assumes that gain compensation is disabled;bw_satur_process1_comp() assumes that gain compensation is enabled.The actual gain compensation parameter value is ignored.
static inline void bw_satur_process(
bw_satur_coeffs * BW_RESTRICT coeffs,
bw_satur_state * BW_RESTRICT state,
const float * x,
float * y,
size_t n_samples);
Processes the first n_samples of the input buffer x and fills the first n_samples of the output buffer y, while using and updating both coeffs and state (control and audio rate).
static inline void bw_satur_process_multi(
bw_satur_coeffs * BW_RESTRICT coeffs,
bw_satur_state * BW_RESTRICT const * BW_RESTRICT state,
const float * const * x,
float * const * y,
size_t n_channels,
size_t n_samples);
Processes the first n_samples of the n_channels input buffers x and fills the first n_samples of the n_channels output buffers y, while using and updating both the common coeffs and each of the n_channels states (control and audio rate).
static inline void bw_satur_set_bias(
bw_satur_coeffs * BW_RESTRICT coeffs,
float value);
Sets the input bias value in coeffs.
Valid range: [-1e12f, 1e12f].
Default value: 0.f.
static inline void bw_satur_set_gain(
bw_satur_coeffs * BW_RESTRICT coeffs,
float value);
Sets the gain value in coeffs.
Valid range: [1e-12f, 1e12f].
Default value: 1.f.
static inline void bw_satur_set_gain_compensation(
bw_satur_coeffs * BW_RESTRICT coeffs,
char value);
Sets whether the output should be divided by gain (value non-0) or not (0).
Default value: 0 (off).
static inline char bw_satur_coeffs_is_valid(
const bw_satur_coeffs * BW_RESTRICT coeffs);
Tries to determine whether coeffs is valid and returns non-0 if it seems to be the case and 0 if it is certainly not. False positives are possible, false negatives are not.
coeffs must at least point to a readable memory block of size greater than or equal to that of bw_satur_coeffs.
static inline char bw_satur_state_is_valid(
const bw_satur_coeffs * BW_RESTRICT coeffs,
const bw_satur_state * BW_RESTRICT state);
Tries to determine whether state is valid and returns non-0 if it seems to be the case and 0 if it is certainly not. False positives are possible, false negatives are not.
If coeffs is not BW_NULL extra cross-checks might be performed (state is supposed to be associated to coeffs).
state must at least point to a readable memory block of size greater than or equal to that of bw_satur_state.
template<size_t N_CHANNELS>
class Satur {
public:
Satur();
void setSampleRate(
float sampleRate);
void reset(
float x0 = 0.f,
float * BW_RESTRICT y0 = nullptr);
#ifndef BW_CXX_NO_ARRAY
void reset(
float x0,
std::array<float, N_CHANNELS> * BW_RESTRICT y0);
#endif
void reset(
const float * x0,
float * y0 = nullptr);
#ifndef BW_CXX_NO_ARRAY
void reset(
std::array<float, N_CHANNELS> x0,
std::array<float, N_CHANNELS> * BW_RESTRICT y0 = nullptr);
#endif
void process(
const float * const * x,
float * const * y,
size_t nSamples);
#ifndef BW_CXX_NO_ARRAY
void process(
std::array<const float *, N_CHANNELS> x,
std::array<float *, N_CHANNELS> y,
size_t nSamples);
#endif
void setBias(
float value);
void setGain(
float value);
void setGainCompensation(
bool value);
...
}
bw_satur_process_multi().BW_NULL and BW_CXX_NO_ARRAY.bw_satur_reset_state().bw_satur_reset_state_multi() and updated C++ API in this regard.bw_satur_reset_state() returns the initial output value.reset() functions taking arrays as arguments.bw_satur_process() and bw_satur_process_multi() now use size_t to count samples and channels.const and BW_RESTRICT specifiers to input arguments and implementation.process() function taking C-style arrays as arguments.bw_satur_process_multi().