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Diffstat (limited to 'src/include/wavedata.h')
| -rw-r--r-- | src/include/wavedata.h | 192 |
1 files changed, 192 insertions, 0 deletions
diff --git a/src/include/wavedata.h b/src/include/wavedata.h new file mode 100644 index 0000000..82bc70f --- /dev/null +++ b/src/include/wavedata.h @@ -0,0 +1,192 @@ +/* + Structures to represent a set of wavetables. + Copyright 2011 David Robillard + Copyright 2003 Mike Rawes + + This is free software: you can redistribute it and/or modify it + under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This software is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this software. If not, see <http://www.gnu.org/licenses/>. +*/ + +#ifndef blip_wavedata_h +#define blip_wavedata_h + +#include "lv2/lv2plug.in/ns/lv2core/lv2.h" +#include <config.h> +#include "math_func.h" +#include "interpolate.h" +#include "common.h" + +/* Functions identifying wavedata dlls */ +#define BLOP_DLSYM_SAWTOOTH "blip_get_sawtooth" +#define BLOP_DLSYM_SQUARE "blip_get_square" +#define BLOP_DLSYM_PARABOLA "blip_get_parabola" + +/* + * Structure holding a single segment of sample data + * along with information relating to playback. + */ +typedef struct { + unsigned long sample_count; /* Sample count */ + float* samples_lf; /* Sample data played back at amplitude + inversely proportional to frequency */ + float* samples_hf; /* Sample data played back at amplitude + proportional to frequency */ + unsigned long harmonics; /* Max harmonic content of sample data */ + + float phase_scale_factor; /* Phase scale factor for playback */ + float min_frequency; /* Minimum playback frequency */ + float max_frequency; /* Maximum playback frequency */ + float range_scale_factor; /* Blend scale factor for cross fading */ +} Wavetable; + +/* + * Structure holding the wavetable data and playback state + */ +typedef struct { + void* data_handle; /* Data DLL handle */ + unsigned long table_count; /* Number of wavetables in wavedata */ + Wavetable** tables; /* One or more wavetables, plus pair of + extra tables for frequency extremes */ + unsigned long* lookup; /* Wavetable lookup vector */ + unsigned long lookup_max; /* For clipping lookup indices */ + + float sample_rate; /* Sample rate */ + float nyquist; /* Nyquist rate (sample_rate / 2) */ + + /* Playback state */ + float frequency; /* Current playback frequency */ + float abs_freq; /* Absolute playback frequency */ + float xfade; /* Crossfade factor for fading */ + Wavetable* table; /* Wavetable to playback */ +} Wavedata; + +#ifdef __cplusplus +extern "C" { +#endif + +int wavedata_load(Wavedata* w, + const char* wdat_descriptor_name, + unsigned long sample_rate); + +void wavedata_unload(Wavedata* w); + +/***************************************************************************** + * Description: Get interpolated sample from current wavetable in wavedata + * at given phase offset + * + * Arguments: w Wavedata containing playback state and data + * phase Phase offset [0.0, sample_rate] + * + * Returns: Interpolated sample + * + * Notes: Cubic (or quintic) interpolation requires four consecutive + * samples for operation: + * + * phase + * : + * p1 p0 : n0 n1 + * | | x | | + * : : + * <-o-> + * : + * interval + * + * Phase values less than one make p0 the first sample in + * the table - p1 will be the last sample, as a previous + * sample does not exist. To avoid checking for this case, + * a copy of the last sample is stored before the first + * sample in each table. + * Likewise, if the phase means p0 is the last sample, n0 + * and n1 will be the first and second samples respectively. + * Copies of these samples are stored after the last sample + * in each table. + * + *****************************************************************************/ +static inline float +wavedata_get_sample(Wavedata* w, + float phase) +{ + float* samples_hf = w->table->samples_hf; + float* samples_lf = w->table->samples_lf; + float p1, p0, n0, n1; + float phase_f; + long int index; + + /* Scale phase to map to position in wavetable */ + phase *= w->table->phase_scale_factor; + + /* Get position of first contributing sample (p1) */ + index = LRINTF((float)phase - 0.5f); + phase_f = (float)index; + + index %= w->table->sample_count; + + /* Cross-fade table pairs */ + /* Previous two samples */ + p1 = w->xfade * (samples_lf[index] - samples_hf[index]) + samples_hf[index]; + index++; + p0 = w->xfade * (samples_lf[index] - samples_hf[index]) + samples_hf[index]; + index++; + /* Next two samples */ + n0 = w->xfade * (samples_lf[index] - samples_hf[index]) + samples_hf[index]; + index++; + n1 = w->xfade * (samples_lf[index] - samples_hf[index]) + samples_hf[index]; + + /* Return interpolated sample */ + return interpolate_cubic(phase - phase_f, p1, p0, n0, n1); +} + +/***************************************************************************** + * Description: Get wavetable to use for playback frequency. + * + * Arguments: w Wavedata object (contains all table info) + * frequency Playback frequency + * + * Notes: The lookup vector used to determine the wavetable + * is indexed by harmonic number. + * + * The maximum playback frequency for a wavetable is + * determined by its harmonic content and the sample rate, + * and equals sample_rate / 2 / max_harmonic_in_table. + * + *****************************************************************************/ +static inline void +wavedata_get_table(Wavedata* w, + float frequency) +{ + unsigned long harmonic; + + w->frequency = frequency; + w->abs_freq = (float)FABSF((float)frequency); + + /* Get highest harmonic possible in frequency */ + harmonic = LRINTF(w->nyquist / w->abs_freq - 0.5f); + + /* Clip so lookup is within bounds */ + if (harmonic > w->lookup_max) { + harmonic = w->lookup_max; + } + + /* Set playback table */ + w->table = w->tables[w->lookup[harmonic]]; + + /* Get cross fade factor */ + w->xfade = f_max(w->table->max_frequency - w->abs_freq, 0.0f) * w->table->range_scale_factor; + w->xfade = f_min(w->xfade, 1.0f); +} + +#ifdef __cplusplus +} /* extern "C" { */ +#endif + +#endif /* blip_wavedata_h */ |