Brickworks > API documentation > bw_ls2
Second-order low shelf filter (12 dB/oct) with gain asymptotically approaching unity as frequency increases.
Module type: dsp
Version: 1.1.0
Requires:
typedef struct bw_ls2_coeffs bw_ls2_coeffs;
Coefficients and related.
typedef struct bw_ls2_state bw_ls2_state;
Internal state and related.
static inline void bw_ls2_init(
bw_ls2_coeffs * BW_RESTRICT coeffs);
Initializes input parameter values in coeffs.
static inline void bw_ls2_set_sample_rate(
bw_ls2_coeffs * BW_RESTRICT coeffs,
float sample_rate);
Sets the sample_rate (Hz) value in coeffs.
static inline void bw_ls2_reset_coeffs(
bw_ls2_coeffs * BW_RESTRICT coeffs);
Resets coefficients in coeffs to assume their target values.
static inline float bw_ls2_reset_state(
const bw_ls2_coeffs * BW_RESTRICT coeffs,
bw_ls2_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_ls2_reset_state_multi(
const bw_ls2_coeffs * BW_RESTRICT coeffs,
bw_ls2_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_ls2_update_coeffs_ctrl(
bw_ls2_coeffs * BW_RESTRICT coeffs);
Triggers control-rate update of coefficients in coeffs.
static inline void bw_ls2_update_coeffs_audio(
bw_ls2_coeffs * BW_RESTRICT coeffs);
Triggers audio-rate update of coefficients in coeffs.
static inline float bw_ls2_process1(
const bw_ls2_coeffs * BW_RESTRICT coeffs,
bw_ls2_state * BW_RESTRICT state,
float x);
Processes one input sample x using coeffs, while using and updating state. Returns the corresponding output sample.
static inline void bw_ls2_process(
bw_ls2_coeffs * BW_RESTRICT coeffs,
bw_ls2_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_ls2_process_multi(
bw_ls2_coeffs * BW_RESTRICT coeffs,
bw_ls2_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_ls2_set_cutoff(
bw_ls2_coeffs * BW_RESTRICT coeffs,
float value);
Sets the cutoff frequency value (Hz) in coeffs.
value must be finite and positive.
By the time bw_ls2_reset_coeffs(), bw_ls2_update_coeffs_ctrl(), bw_ls2_update_coeffs_audio(), bw_ls2_process1(), bw_ls2_process(), or bw_ls2_process_multi() is called, cutoff * bw_rcpf(bw_sqrtf(bw_sqrtf(dc_gain))) must be in [1e-6f, 1e12f].
Default value: 1e3f.
static inline void bw_ls2_set_Q(
bw_ls2_coeffs * BW_RESTRICT coeffs,
float value);
Sets the quality factor to the given value in coeffs.
Valid range: [1e-6f, 1e6f].
Default value: 0.5f.
static inline void bw_ls2_set_prewarp_at_cutoff(
bw_ls2_coeffs * BW_RESTRICT coeffs,
char value);
Sets whether bilinear transform prewarping frequency should match the cutoff frequency (non-0) or not (0).
Default value: non-0 (on).
static inline void bw_ls2_set_prewarp_freq(
bw_ls2_coeffs * BW_RESTRICT coeffs,
float value);
Sets the prewarping frequency value (Hz) in coeffs.
Only used when the prewarp_at_cutoff parameter is off and however internally limited to avoid instability.
Valid range: [1e-6f, 1e12f].
Default value: 1e3f.
static inline void bw_ls2_set_dc_gain_lin(
bw_ls2_coeffs * BW_RESTRICT coeffs,
float value);
Sets the dc gain parameter to the given value (linear gain) in coeffs.
Valid range: [1e-30f, 1e30f].
By the time bw_ls2_reset_coeffs(), bw_ls2_update_coeffs_ctrl(), bw_ls2_update_coeffs_audio(), bw_ls2_process1(), bw_ls2_process(), or bw_ls2_process_multi() is called, cutoff * bw_rcpf(bw_sqrtf(bw_sqrtf(dc_gain))) must be in [1e-6f, 1e12f].
Default value: 1.f.
static inline void bw_ls2_set_dc_gain_dB(
bw_ls2_coeffs * BW_RESTRICT coeffs,
float value);
Sets the dc gain parameter to the given value (dB) in coeffs.
Valid range: [-600.f, 600.f].
By the time bw_ls2_reset_coeffs(), bw_ls2_update_coeffs_ctrl(), bw_ls2_update_coeffs_audio(), bw_ls2_process1(), bw_ls2_process(), or bw_ls2_process_multi() is called, cutoff * bw_rcpf(bw_sqrtf(bw_sqrtf(dc_gain))) must be in [1e-6f, 1e12f].
Default value: 0.f.
static inline char bw_ls2_coeffs_is_valid(
const bw_ls2_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_ls2_coeffs.
static inline char bw_ls2_state_is_valid(
const bw_ls2_coeffs * BW_RESTRICT coeffs,
const bw_ls2_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_ls2_state.
template<size_t N_CHANNELS>
class LS2 {
public:
LS2();
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 setCutoff(
float value);
void setQ(
float value);
void setPrewarpAtCutoff(
bool value);
void setPrewarpFreq(
float value);
void setDcGainLin(
float value);
void setDcGainDB(
float value);
...
}
BW_NULL and BW_CXX_NO_ARRAY.bw_ls2_set_cutoff(), bw_ls2_set_dc_gain_lin(), and bw_ls2_set_dc_gain_dB().bw_ls2_reset_state_multi() and updated C++ API in this regard.bw_ls2_reset_state() returns the initial output value.reset() functions taking arrays as arguments.bw_ls2_process() and bw_ls2_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_ls2_process_multi().bw_ls2_reset_state().