Triangle oscillator waveshaper with variable slope (increasing time over period) and PolyBLEP antialiasing.
It turns a normalized phase signal, such as that geneated by bw_phase_gen, into a triangle wave.
The antialiasing algorithm is based on
V. Valimaki and A. Huovilainen, "Antialiasing Oscillators in Subtractive Synthesis", IEEE Signal Processing Magazine, vol. 24, no. 2, pp. 116-125, March 2007.
Version: 1.2.0
License:
Requires:
Included in Brickworks, which is:
Module type: DSP
typedef struct bw_osc_tri_coeffs bw_osc_tri_coeffs;
Coefficients and related.
static inline void bw_osc_tri_init(
bw_osc_tri_coeffs * BW_RESTRICT coeffs);
Initializes input parameter values in coeffs.
static inline void bw_osc_tri_set_sample_rate(
bw_osc_tri_coeffs * BW_RESTRICT coeffs,
float sample_rate);
Sets the sample_rate (Hz) value in coeffs.
static inline void bw_osc_tri_reset_coeffs(
bw_osc_tri_coeffs * BW_RESTRICT coeffs);
Resets coefficients in coeffs to assume their target values.
static inline void bw_osc_tri_update_coeffs_ctrl(
bw_osc_tri_coeffs * BW_RESTRICT coeffs);
Triggers control-rate update of coefficients in coeffs.
static inline void bw_osc_tri_update_coeffs_audio(
bw_osc_tri_coeffs * BW_RESTRICT coeffs);
Triggers audio-rate update of coefficients in coeffs.
static inline float bw_osc_tri_process1(
const bw_osc_tri_coeffs * BW_RESTRICT coeffs,
float x);
static inline float bw_osc_tri_process1_antialias(
const bw_osc_tri_coeffs * BW_RESTRICT coeffs,
float x,
float x_inc);
These function process one input sample x, representing the normalized phase, using coeffs. They return the corresponding output sample.
In particular:
bw_osc_tri_process1() assumes that antialiasing is disabled;bw_osc_tri_process1_antialias() assumes that antialiasing is enabled and requires the corresponding phase increment value to be passed via x_inc.Whether antialiasing is enabled or not is unchecked even for debugging purposes.
x must be in [0.f, 1.f).
x_inc must be in [-0.5f, 0.5f].
static inline void bw_osc_tri_process(
bw_osc_tri_coeffs * BW_RESTRICT coeffs,
const float * x,
const float * x_inc,
float * y,
size_t n_samples);
Processes the first n_samples of the input buffer x, containing the normalized phase signal, and fills the first n_samples of the output buffer y, while using and updating coeffs.
If antialiasing is enabled, x_inc must contain phase increment values, otherwise it is ignored and can be BW_NULL.
All samples in x must be in [0.f, 1.f).
All samples is x_inc, if not ignored, must be in [-0.5f, 0.5f].
static inline void bw_osc_tri_process_multi(
bw_osc_tri_coeffs * BW_RESTRICT coeffs,
const float * const * x,
const float * const * x_inc,
float * const * y,
size_t n_channels,
size_t n_samples);
Processes the first n_samples of the n_channels input buffers x, containing the normalized phase signals, and fills the first n_samples of the n_channels output buffers y, while using and updating the common coeffs (control and audio rate).
If antialiasing is enabled, x_inc must contain n_channels buffers of phase increment values, otherwise it is ignored and can be BW_NULL.
All samples in x must be in [0.f, 1.f).
All samples is x_inc, if not ignored, must be in [-0.5f, 0.5f].
static inline void bw_osc_tri_set_antialiasing(
bw_osc_tri_coeffs * BW_RESTRICT coeffs,
char value);
Sets whether the antialiasing is on (value non-0) or off (0) in coeffs.
Default value: 0 (off).
static inline void bw_osc_tri_set_slope(
bw_osc_tri_coeffs * BW_RESTRICT coeffs,
float value);
Sets the slope (increasing time over period) to value in coeffs.
Valid range: [0.001f, 0.999f].
Default value: 0.5f.
static inline char bw_osc_tri_coeffs_is_valid(
const bw_osc_tri_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_osc_tri_coeffs.
template<size_t N_CHANNELS>
class OscTri {
public:
OscTri();
void setSampleRate(
float sampleRate);
void reset();
void process(
const float * const * x,
const float * const * xInc,
float * const * y,
size_t nSamples);
# ifndef BW_CXX_NO_ARRAY
void process(
std::array<const float *, N_CHANNELS> x,
std::array<const float *, N_CHANNELS> xInc,
std::array<float *, N_CHANNELS> y,
size_t nSamples);
# endif
void setAntialiasing(
bool value);
void setSlope(
float value);
...
}
BW_INCLUDE_WITH_QUOTES, BW_NO_CXX, and BW_CXX_NO_EXTERN_C.bw_osc_tri_process() to bw_osc_tri_process_multi().bw_osc_tri_process_multi() to ensure that x_inc is not BW_NULL when antialiasing is on and that buffers used for both input and output appear at the same channel indices.bw_osc_tri_coeffs_is_valid().BW_NULL and BW_CXX_NO_ARRAY.bw_osc_tri_process() and bw_osc_tri_process_multi() now use size_t to count samples and channels.const specifiers to input arguments.process() function taking C-style arrays as arguments.bw_osc_tri_process_multi().bw_osc_tri_process1\*() documentation.