590 lines
22 KiB
C
590 lines
22 KiB
C
/*
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* This file is part of the MicroPython project, http://micropython.org/
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2021 Artyom Skrobov
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* Copyright (c) 2023 Jeff Epler for Adafruit Industries
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include "shared-module/synthio/__init__.h"
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#include "shared-bindings/synthio/__init__.h"
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#include "shared-module/synthio/Note.h"
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#include "py/runtime.h"
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#include <math.h>
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#include <stdlib.h>
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STATIC const int16_t square_wave[] = {-32768, 32767};
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STATIC const uint16_t notes[] = {8372, 8870, 9397, 9956, 10548, 11175, 11840,
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12544, 13290, 14080, 14917, 15804}; // 9th octave
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STATIC int32_t round_float_to_int(mp_float_t f) {
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return (int32_t)(f + MICROPY_FLOAT_CONST(0.5));
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}
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STATIC int64_t round_float_to_int64(mp_float_t f) {
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return (int64_t)(f + MICROPY_FLOAT_CONST(0.5));
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}
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mp_float_t common_hal_synthio_midi_to_hz_float(mp_float_t arg) {
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return common_hal_synthio_onevo_to_hz_float(arg / 12.);
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}
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mp_float_t common_hal_synthio_onevo_to_hz_float(mp_float_t octave) {
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return notes[0] * MICROPY_FLOAT_C_FUN(pow)(2., octave - 10);
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}
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STATIC int16_t convert_time_to_rate(uint32_t sample_rate, mp_obj_t time_in, int16_t difference) {
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mp_float_t time = mp_obj_get_float(time_in);
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int num_samples = (int)MICROPY_FLOAT_C_FUN(round)(time * sample_rate);
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if (num_samples == 0) {
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return 32767;
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}
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int16_t result = MIN(32767, MAX(1, abs(difference * SYNTHIO_MAX_DUR) / num_samples));
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return (difference < 0) ? -result : result;
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}
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void synthio_envelope_definition_set(synthio_envelope_definition_t *envelope, mp_obj_t obj, uint32_t sample_rate) {
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if (obj == mp_const_none) {
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envelope->attack_level = 32767;
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envelope->sustain_level = 32767;
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envelope->attack_step = 32767;
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envelope->decay_step = -32767;
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envelope->release_step = -32767;
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return;
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}
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mp_arg_validate_type(obj, (mp_obj_type_t *)&synthio_envelope_type_obj, MP_QSTR_envelope);
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size_t len;
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mp_obj_t *fields;
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mp_obj_tuple_get(obj, &len, &fields);
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envelope->attack_level = (int)(32767 * mp_obj_get_float(fields[3]));
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envelope->sustain_level = (int)(32767 * mp_obj_get_float(fields[4]) * mp_obj_get_float(fields[3]));
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envelope->attack_step = convert_time_to_rate(
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sample_rate, fields[0], envelope->attack_level);
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envelope->decay_step = -convert_time_to_rate(
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sample_rate, fields[1], envelope->attack_level - envelope->sustain_level);
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envelope->release_step = -convert_time_to_rate(
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sample_rate, fields[2],
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envelope->sustain_level
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? envelope->sustain_level
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: envelope->attack_level);
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}
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STATIC void synthio_envelope_state_step(synthio_envelope_state_t *state, synthio_envelope_definition_t *def, size_t n_steps) {
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state->substep += n_steps;
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while (state->substep >= SYNTHIO_MAX_DUR) {
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// max n_steps should be SYNTHIO_MAX_DUR so this loop executes at most
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// once
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state->substep -= SYNTHIO_MAX_DUR;
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switch (state->state) {
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case SYNTHIO_ENVELOPE_STATE_SUSTAIN:
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break;
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case SYNTHIO_ENVELOPE_STATE_ATTACK:
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state->level = MIN(state->level + def->attack_step, def->attack_level);
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if (state->level == def->attack_level) {
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state->state = SYNTHIO_ENVELOPE_STATE_DECAY;
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}
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break;
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case SYNTHIO_ENVELOPE_STATE_DECAY:
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state->level = MAX(state->level + def->decay_step, def->sustain_level);
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if (state->level == def->sustain_level) {
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state->state = SYNTHIO_ENVELOPE_STATE_SUSTAIN;
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}
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break;
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case SYNTHIO_ENVELOPE_STATE_RELEASE:
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state->level = MAX(state->level + def->release_step, 0);
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}
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}
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}
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STATIC void synthio_envelope_state_init(synthio_envelope_state_t *state, synthio_envelope_definition_t *def) {
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state->level = 0;
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state->substep = 0;
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state->state = SYNTHIO_ENVELOPE_STATE_ATTACK;
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synthio_envelope_state_step(state, def, SYNTHIO_MAX_DUR);
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}
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STATIC void synthio_envelope_state_release(synthio_envelope_state_t *state, synthio_envelope_definition_t *def) {
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state->state = SYNTHIO_ENVELOPE_STATE_RELEASE;
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}
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STATIC synthio_envelope_definition_t *synthio_synth_get_note_envelope(synthio_synth_t *synth, mp_obj_t note_obj) {
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synthio_envelope_definition_t *def = &synth->global_envelope_definition;
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if (!mp_obj_is_small_int(note_obj)) {
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synthio_note_obj_t *note = MP_OBJ_TO_PTR(note_obj);
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if (note->envelope_obj != mp_const_none) {
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def = ¬e->envelope_def;
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}
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}
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return def;
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}
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#define RANGE_LOW (-28000)
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#define RANGE_HIGH (28000)
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#define RANGE_SHIFT (16)
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#define RANGE_SCALE (0xfffffff / (32768 * CIRCUITPY_SYNTHIO_MAX_CHANNELS - RANGE_HIGH))
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// dynamic range compression via a downward compressor with hard knee
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//
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// When the output value is within the range +-28000 (about 85% of full scale),
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// it is unchanged. Otherwise, it undergoes a gain reduction so that the
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// largest possible values, (+32768,-32767) * CIRCUITPY_SYNTHIO_MAX_CHANNELS,
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// still fit within the output range
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//
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// This produces a much louder overall volume with multiple voices, without
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// much additional processing.
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//
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// https://en.wikipedia.org/wiki/Dynamic_range_compression
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STATIC
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int16_t mix_down_sample(int32_t sample) {
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if (sample < RANGE_LOW) {
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sample = (((sample - RANGE_LOW) * RANGE_SCALE) >> RANGE_SHIFT) + RANGE_LOW;
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} else if (sample > RANGE_HIGH) {
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sample = (((sample - RANGE_HIGH) * RANGE_SCALE) >> RANGE_SHIFT) + RANGE_HIGH;
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}
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return sample;
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}
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static void synth_note_into_buffer(synthio_synth_t *synth, int chan, int32_t *out_buffer32, int16_t dur) {
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mp_obj_t note_obj = synth->span.note_obj[chan];
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if (note_obj == SYNTHIO_SILENCE) {
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synth->accum[chan] = 0;
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return;
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}
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if (synth->envelope_state[chan].level == 0) {
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// note is truly finished, but we only just noticed
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synth->span.note_obj[chan] = SYNTHIO_SILENCE;
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return;
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}
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int32_t sample_rate = synth->sample_rate;
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// adjust loudness by envelope
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uint16_t loudness[2] = {synth->envelope_state[chan].level,synth->envelope_state[chan].level};
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uint32_t dds_rate;
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const int16_t *waveform = synth->waveform_bufinfo.buf;
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uint32_t waveform_length = synth->waveform_bufinfo.len / sizeof(int16_t);
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uint32_t ring_dds_rate = 0;
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const int16_t *ring_waveform = NULL;
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uint32_t ring_waveform_length = 0;
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if (mp_obj_is_small_int(note_obj)) {
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uint8_t note = mp_obj_get_int(note_obj);
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uint8_t octave = note / 12;
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uint16_t base_freq = notes[note % 12];
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// rate = base_freq * waveform_length
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// den = sample_rate * 2 ^ (10 - octave)
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// den = sample_rate * 2 ^ 10 / 2^octave
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// dds_rate = 2^SHIFT * rate / den
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// dds_rate = 2^(SHIFT-10+octave) * base_freq * waveform_length / sample_rate
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dds_rate = (sample_rate / 2 + ((uint64_t)(base_freq * waveform_length) << (SYNTHIO_FREQUENCY_SHIFT - 10 + octave))) / sample_rate;
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} else {
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synthio_note_obj_t *note = MP_OBJ_TO_PTR(note_obj);
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int32_t frequency_scaled = synthio_note_step(note, sample_rate, dur, loudness);
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if (note->waveform_buf.buf) {
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waveform = note->waveform_buf.buf;
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waveform_length = note->waveform_buf.len / sizeof(int16_t);
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}
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dds_rate = synthio_frequency_convert_scaled_to_dds((uint64_t)frequency_scaled * waveform_length, sample_rate);
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if (note->ring_frequency_scaled != 0 && note->ring_waveform_buf.buf) {
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ring_waveform = note->ring_waveform_buf.buf;
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ring_waveform_length = note->ring_waveform_buf.len / sizeof(int16_t);
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ring_dds_rate = synthio_frequency_convert_scaled_to_dds((uint64_t)note->ring_frequency_scaled * ring_waveform_length, sample_rate);
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uint32_t lim = ring_waveform_length << SYNTHIO_FREQUENCY_SHIFT;
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if (ring_dds_rate > lim / sizeof(int16_t)) {
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ring_dds_rate = 0; // can't ring at that frequency
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}
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}
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}
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int synth_chan = synth->channel_count;
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if (ring_dds_rate) {
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uint32_t lim = waveform_length << SYNTHIO_FREQUENCY_SHIFT;
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uint32_t accum = synth->accum[chan];
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if (dds_rate > lim / 2) {
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// beyond nyquist, can't play note
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return;
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}
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// can happen if note waveform gets set mid-note, but the expensive modulo is usually avoided
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if (accum > lim) {
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accum %= lim;
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}
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int32_t ring_buffer[dur];
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// first, fill with waveform
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for (uint16_t i = 0; i < dur; i++) {
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accum += dds_rate;
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// because dds_rate is low enough, the subtraction is guaranteed to go back into range, no expensive modulo needed
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if (accum > lim) {
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accum -= lim;
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}
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int16_t idx = accum >> SYNTHIO_FREQUENCY_SHIFT;
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ring_buffer[i] = waveform[idx];
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}
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synth->accum[chan] = accum;
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// now modulate by ring and accumulate
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accum = synth->ring_accum[chan];
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lim = ring_waveform_length << SYNTHIO_FREQUENCY_SHIFT;
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// can happen if note waveform gets set mid-note, but the expensive modulo is usually avoided
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if (accum > lim) {
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accum %= lim;
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}
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for (uint16_t i = 0, j = 0; i < dur; i++) {
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accum += ring_dds_rate;
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// because dds_rate is low enough, the subtraction is guaranteed to go back into range, no expensive modulo needed
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if (accum > lim) {
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accum -= lim;
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}
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int16_t idx = accum >> SYNTHIO_FREQUENCY_SHIFT;
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int16_t wi = (ring_waveform[idx] * ring_buffer[i]) / 32768;
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for (int c = 0; c < synth_chan; c++) {
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out_buffer32[j] += (wi * loudness[c]) / 32768;
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j++;
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}
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}
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synth->ring_accum[chan] = accum;
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} else {
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uint32_t lim = waveform_length << SYNTHIO_FREQUENCY_SHIFT;
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uint32_t accum = synth->accum[chan];
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if (dds_rate > lim / 2) {
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// beyond nyquist, can't play note
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return;
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}
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// can happen if note waveform gets set mid-note, but the expensive modulo is usually avoided
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if (accum > lim) {
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accum %= lim;
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}
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for (uint16_t i = 0, j = 0; i < dur; i++) {
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accum += dds_rate;
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// because dds_rate is low enough, the subtraction is guaranteed to go back into range, no expensive modulo needed
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if (accum > lim) {
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accum -= lim;
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}
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int16_t idx = accum >> SYNTHIO_FREQUENCY_SHIFT;
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int16_t wi = waveform[idx];
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for (int c = 0; c < synth_chan; c++) {
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out_buffer32[j] += (wi * loudness[c]) / 65536;
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j++;
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}
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}
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synth->accum[chan] = accum;
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}
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}
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STATIC void run_fir(synthio_synth_t *synth, int32_t *out_buffer32, uint16_t dur) {
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int16_t *coeff = (int16_t *)synth->filter_bufinfo.buf;
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size_t fir_len = synth->filter_bufinfo.len / sizeof(int16_t);
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int32_t *in_buf = synth->filter_buffer;
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int synth_chan = synth->channel_count;
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// FIR and copy values to output buffer
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for (int16_t i = 0; i < dur * synth_chan; i++) {
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int32_t acc = 0;
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for (size_t j = 0; j < fir_len; j++) {
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// shift 5 here is good for up to 32 filtered voices, else might wrap
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acc = acc + (in_buf[j * synth_chan] * (coeff[j] >> 5));
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}
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*out_buffer32++ = acc >> 10;
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in_buf++;
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}
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// Move values down so that they get filtered next time
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memmove(synth->filter_buffer, &synth->filter_buffer[dur * synth_chan], fir_len * sizeof(int32_t) * synth_chan);
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}
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STATIC bool synthio_synth_get_note_filtered(mp_obj_t note_obj) {
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if (note_obj == mp_const_none) {
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return false;
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}
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if (!mp_obj_is_small_int(note_obj)) {
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synthio_note_obj_t *note = MP_OBJ_TO_PTR(note_obj);
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return note->filter;
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}
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return true;
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}
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void synthio_synth_synthesize(synthio_synth_t *synth, uint8_t **bufptr, uint32_t *buffer_length, uint8_t channel) {
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if (channel == synth->other_channel) {
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*buffer_length = synth->last_buffer_length;
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*bufptr = (uint8_t *)(synth->buffers[synth->other_buffer_index] + channel);
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return;
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}
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synth->buffer_index = !synth->buffer_index;
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synth->other_channel = 1 - channel;
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synth->other_buffer_index = synth->buffer_index;
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uint16_t dur = MIN(SYNTHIO_MAX_DUR, synth->span.dur);
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synth->span.dur -= dur;
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int32_t out_buffer32[dur * synth->channel_count];
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if (synth->filter_buffer) {
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int32_t *filter_start = &synth->filter_buffer[synth->filter_bufinfo.len * synth->channel_count / sizeof(int16_t)];
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memset(filter_start, 0, dur * synth->channel_count * sizeof(int32_t));
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for (int chan = 0; chan < CIRCUITPY_SYNTHIO_MAX_CHANNELS; chan++) {
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mp_obj_t note_obj = synth->span.note_obj[chan];
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if (!synthio_synth_get_note_filtered(note_obj)) {
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continue;
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}
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synth_note_into_buffer(synth, chan, filter_start, dur);
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}
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run_fir(synth, out_buffer32, dur);
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} else {
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memset(out_buffer32, 0, sizeof(out_buffer32));
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}
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for (int chan = 0; chan < CIRCUITPY_SYNTHIO_MAX_CHANNELS; chan++) {
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mp_obj_t note_obj = synth->span.note_obj[chan];
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if (synth->filter_buffer && synthio_synth_get_note_filtered(note_obj)) {
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continue;
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}
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synth_note_into_buffer(synth, chan, out_buffer32, dur);
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}
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int16_t *out_buffer16 = (int16_t *)(void *)synth->buffers[synth->buffer_index];
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// mix down audio
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for (size_t i = 0; i < MP_ARRAY_SIZE(out_buffer32); i++) {
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int32_t sample = out_buffer32[i];
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out_buffer16[i] = mix_down_sample(sample);
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}
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// advance envelope states
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for (int chan = 0; chan < CIRCUITPY_SYNTHIO_MAX_CHANNELS; chan++) {
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mp_obj_t note_obj = synth->span.note_obj[chan];
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if (note_obj == SYNTHIO_SILENCE) {
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continue;
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}
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synthio_envelope_state_step(&synth->envelope_state[chan], synthio_synth_get_note_envelope(synth, note_obj), dur);
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}
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*buffer_length = synth->last_buffer_length = dur * SYNTHIO_BYTES_PER_SAMPLE * synth->channel_count;
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*bufptr = (uint8_t *)out_buffer16;
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}
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void synthio_synth_reset_buffer(synthio_synth_t *synth, bool single_channel_output, uint8_t channel) {
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if (single_channel_output && channel == 1) {
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return;
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}
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synth->other_channel = -1;
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}
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bool synthio_synth_deinited(synthio_synth_t *synth) {
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return synth->buffers[0] == NULL;
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}
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void synthio_synth_deinit(synthio_synth_t *synth) {
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synth->filter_buffer = NULL;
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synth->buffers[0] = NULL;
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synth->buffers[1] = NULL;
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}
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void synthio_synth_envelope_set(synthio_synth_t *synth, mp_obj_t envelope_obj) {
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synthio_envelope_definition_set(&synth->global_envelope_definition, envelope_obj, synth->sample_rate);
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synth->envelope_obj = envelope_obj;
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}
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mp_obj_t synthio_synth_envelope_get(synthio_synth_t *synth) {
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return synth->envelope_obj;
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}
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void synthio_synth_init(synthio_synth_t *synth, uint32_t sample_rate, int channel_count, mp_obj_t waveform_obj, mp_obj_t filter_obj, mp_obj_t envelope_obj) {
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synthio_synth_parse_waveform(&synth->waveform_bufinfo, waveform_obj);
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synthio_synth_parse_filter(&synth->filter_bufinfo, filter_obj);
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mp_arg_validate_int_range(channel_count, 1, 2, MP_QSTR_channel_count);
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synth->buffer_length = SYNTHIO_MAX_DUR * SYNTHIO_BYTES_PER_SAMPLE * channel_count;
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synth->buffers[0] = m_malloc(synth->buffer_length, false);
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synth->buffers[1] = m_malloc(synth->buffer_length, false);
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if (synth->filter_bufinfo.len) {
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synth->filter_buffer_length = (synth->filter_bufinfo.len / 2 + SYNTHIO_MAX_DUR) * channel_count * sizeof(int32_t);
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synth->filter_buffer = m_malloc(synth->filter_buffer_length, false);
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}
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synth->channel_count = channel_count;
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synth->other_channel = -1;
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synth->waveform_obj = waveform_obj;
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synth->sample_rate = sample_rate;
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synthio_synth_envelope_set(synth, envelope_obj);
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|
|
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for (size_t i = 0; i < CIRCUITPY_SYNTHIO_MAX_CHANNELS; i++) {
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synth->span.note_obj[i] = SYNTHIO_SILENCE;
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}
|
|
}
|
|
|
|
void synthio_synth_get_buffer_structure(synthio_synth_t *synth, bool single_channel_output,
|
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bool *single_buffer, bool *samples_signed, uint32_t *max_buffer_length, uint8_t *spacing) {
|
|
*single_buffer = false;
|
|
*samples_signed = true;
|
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*max_buffer_length = synth->buffer_length;
|
|
if (single_channel_output) {
|
|
*spacing = synth->channel_count;
|
|
} else {
|
|
*spacing = 1;
|
|
}
|
|
}
|
|
|
|
STATIC void parse_common(mp_buffer_info_t *bufinfo, mp_obj_t o, int16_t what, mp_int_t max_len) {
|
|
if (o != mp_const_none) {
|
|
mp_get_buffer_raise(o, bufinfo, MP_BUFFER_READ);
|
|
if (bufinfo->typecode != 'h') {
|
|
mp_raise_ValueError_varg(translate("%q must be array of type 'h'"), what);
|
|
}
|
|
mp_arg_validate_length_range(bufinfo->len / sizeof(int16_t), 2, max_len, what);
|
|
}
|
|
}
|
|
|
|
void synthio_synth_parse_waveform(mp_buffer_info_t *bufinfo_waveform, mp_obj_t waveform_obj) {
|
|
*bufinfo_waveform = ((mp_buffer_info_t) { .buf = (void *)square_wave, .len = 4 });
|
|
parse_common(bufinfo_waveform, waveform_obj, MP_QSTR_waveform, 16384);
|
|
}
|
|
|
|
void synthio_synth_parse_filter(mp_buffer_info_t *bufinfo_filter, mp_obj_t filter_obj) {
|
|
*bufinfo_filter = ((mp_buffer_info_t) { .buf = NULL, .len = 0 });
|
|
parse_common(bufinfo_filter, filter_obj, MP_QSTR_filter, 128);
|
|
}
|
|
|
|
STATIC int find_channel_with_note(synthio_synth_t *synth, mp_obj_t note) {
|
|
for (int i = 0; i < CIRCUITPY_SYNTHIO_MAX_CHANNELS; i++) {
|
|
if (synth->span.note_obj[i] == note) {
|
|
return i;
|
|
}
|
|
}
|
|
int result = -1;
|
|
if (note == SYNTHIO_SILENCE) {
|
|
// replace the releasing note with lowest volume level
|
|
int level = 32768;
|
|
for (int chan = 0; chan < CIRCUITPY_SYNTHIO_MAX_CHANNELS; chan++) {
|
|
if (!SYNTHIO_NOTE_IS_PLAYING(synth, chan)) {
|
|
synthio_envelope_state_t *state = &synth->envelope_state[chan];
|
|
if (state->level < level) {
|
|
result = chan;
|
|
level = state->level;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
return result;
|
|
}
|
|
|
|
bool synthio_span_change_note(synthio_synth_t *synth, mp_obj_t old_note, mp_obj_t new_note) {
|
|
int channel;
|
|
if (new_note != SYNTHIO_SILENCE && (channel = find_channel_with_note(synth, new_note)) != -1) {
|
|
// note already playing, re-enter attack phase
|
|
synth->envelope_state[channel].state = SYNTHIO_ENVELOPE_STATE_ATTACK;
|
|
return true;
|
|
}
|
|
channel = find_channel_with_note(synth, old_note);
|
|
if (channel != -1) {
|
|
if (new_note == SYNTHIO_SILENCE) {
|
|
synthio_envelope_state_release(&synth->envelope_state[channel], synthio_synth_get_note_envelope(synth, old_note));
|
|
} else {
|
|
synth->span.note_obj[channel] = new_note;
|
|
synthio_envelope_state_init(&synth->envelope_state[channel], synthio_synth_get_note_envelope(synth, new_note));
|
|
synth->accum[channel] = 0;
|
|
}
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
uint64_t synthio_frequency_convert_float_to_scaled(mp_float_t val) {
|
|
return round_float_to_int64(val * (1 << SYNTHIO_FREQUENCY_SHIFT));
|
|
}
|
|
|
|
uint32_t synthio_frequency_convert_float_to_dds(mp_float_t frequency_hz, int32_t sample_rate) {
|
|
return synthio_frequency_convert_scaled_to_dds(synthio_frequency_convert_float_to_scaled(frequency_hz), sample_rate);
|
|
}
|
|
|
|
uint32_t synthio_frequency_convert_scaled_to_dds(uint64_t frequency_scaled, int32_t sample_rate) {
|
|
return (sample_rate / 2 + frequency_scaled) / sample_rate;
|
|
}
|
|
|
|
void synthio_lfo_set(synthio_lfo_state_t *state, const synthio_lfo_descr_t *descr, uint32_t sample_rate) {
|
|
state->amplitude_scaled = round_float_to_int(descr->amplitude * 32768);
|
|
state->dds = synthio_frequency_convert_float_to_dds(descr->frequency * 65536, sample_rate);
|
|
}
|
|
|
|
STATIC int synthio_lfo_step_common(synthio_lfo_state_t *state, uint16_t dur) {
|
|
uint32_t phase = state->phase;
|
|
uint16_t whole_phase = phase >> 16;
|
|
|
|
// advance the phase accumulator
|
|
state->phase = phase + state->dds * dur;
|
|
|
|
return whole_phase;
|
|
}
|
|
STATIC int synthio_lfo_sweep_common(synthio_lfo_state_t *state, uint16_t dur) {
|
|
uint32_t old_phase = state->phase;
|
|
uint16_t whole_phase = synthio_lfo_step_common(state, dur);
|
|
if (state->phase < old_phase) {
|
|
state->phase = 0xffffffff;
|
|
}
|
|
return whole_phase;
|
|
}
|
|
|
|
int synthio_sweep_step(synthio_lfo_state_t *state, uint16_t dur) {
|
|
uint16_t whole_phase = synthio_lfo_sweep_common(state, dur);
|
|
return (state->amplitude_scaled * whole_phase) / 65536 + state->offset_scaled;
|
|
}
|
|
|
|
int synthio_sweep_in_step(synthio_lfo_state_t *state, uint16_t dur) {
|
|
uint16_t whole_phase = 65535 - synthio_lfo_sweep_common(state, dur);
|
|
return (state->amplitude_scaled * whole_phase) / 65536 + state->offset_scaled;
|
|
}
|
|
|
|
int synthio_lfo_step(synthio_lfo_state_t *state, uint16_t dur) {
|
|
uint16_t whole_phase = synthio_lfo_step_common(state, dur);
|
|
// create a triangle wave, it's quick and easy
|
|
int v;
|
|
if (whole_phase < 16384) { // ramp from 0 to amplitude
|
|
v = (state->amplitude_scaled * whole_phase);
|
|
} else if (whole_phase < 49152) { // ramp from +amplitude to -amplitude
|
|
v = (state->amplitude_scaled * (32768 - whole_phase));
|
|
} else { // from -amplitude to 0
|
|
v = (state->amplitude_scaled * (whole_phase - 65536));
|
|
}
|
|
return v / 16384 + state->offset_scaled;
|
|
}
|