MicroMDAEPiano/effect_modulated_delay.cpp

/* Audio Library for Teensy 3.X
   Copyright (c) 2014, Pete (El Supremo)
   Copyright (c) 2019, Holger Wirtz

   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files (the "Software"), to deal
   in the Software without restriction, including without limitation the rights
   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   copies of the Software, and to permit persons to whom the Software is
   furnished to do so, subject to the following conditions:

   The above copyright notice and this permission notice shall be included in
   all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   THE SOFTWARE.
*/

#include <Arduino.h>
#include <Audio.h>
#include "arm_math.h"
#include "effect_modulated_delay.h"
#include "config.h"

/******************************************************************/

// Based on;      A u d i o E f f e c t D e l a y
// Written by Pete (El Supremo) Jan 2014
// 140529 - change to handle mono stream - change modify() to voices()
// 140219 - correct storage class (not static)
// 190527 - added modulation input (by Holger Wirtz)

boolean AudioEffectModulatedDelay::begin(short *delayline, int d_length)
{
#if 0
  Serial.print(F("AudioEffectModulatedDelay.begin(Chorus delay line length = "));
  Serial.print(d_length);
  Serial.println(F(")"));
#endif

  _delayline = NULL;
  _delay_length = 0;
  _delay_offset = 0.0;
  _circ_idx = 0;

  if (delayline == NULL) {
    return (false);
  }
  if (d_length < 10) {
    return (false);
  }

  _delayline = delayline;
  _delay_length = d_length;

#ifdef CHORUS_MODULATOR_BIQUAD
  mod_lp_coeffs[0] = -1.98982427; // https://arachnoid.com/BiQuadDesigner/ Lopass Fc=50Hz, Q=0.7
  mod_lp_coeffs[1] = 0.98987476;
  mod_lp_coeffs[2] = 1.26228228e-5;
  mod_lp_coeffs[3] = 2.52456456e-5;
  mod_lp_coeffs[4] = 1.26228228e-5;
  biquad_mod = {1, mod_lp_state, mod_lp_coeffs};
#endif
#ifdef CHORUS_OUTUT_BIQUAD // https://web.fhnw.ch/technik/projekte/eit/Fruehling2016/MuelZum/html/parametric__equalizer__example_8c_source.html
  out_lp_coeffs[0] = -0.10987036; // https://arachnoid.com/BiQuadDesigner/ Lopass Fc=10000Hz, Q=0.3
  out_lp_coeffs[1] = -0.24497694;
  out_lp_coeffs[2] = 0.16128817;
  out_lp_coeffs[3] = 0.32257635;
  out_lp_coeffs[4] = 0.16128817;
  biquad_out = {1, out_lp_state, out_lp_coeffs, 0};
#endif
  return (true);
}

void AudioEffectModulatedDelay::update(void)
{
  audio_block_t *block;
  audio_block_t *modulation;

  if (_delayline == NULL)
    return;

  block = receiveWritable(0);
  modulation = receiveReadOnly(1);

  if (block && modulation)
  {
    int16_t *bp;
    float *mp;
    float mod_idx;
    float mod_number;
    float mod_fraction;
    float mod_float[AUDIO_BLOCK_SAMPLES];

    bp = block->data;
    arm_q15_to_float(modulation->data, mod_float, AUDIO_BLOCK_SAMPLES);
    mp = mod_float;
#ifdef CHORUS_MODULATOR_BIQUAD
    arm_biquad_cascade_df1_f32(&biquad_mod, mod_float, mod_float, AUDIO_BLOCK_SAMPLES);
#endif

    for (uint16_t i = 0; i < AUDIO_BLOCK_SAMPLES; i++)
    {
      // write data into circular buffer (delayline)
      if (_circ_idx >= _delay_length)
        _circ_idx = 0;
      _delayline[_circ_idx] = *bp;

      // Calculate the modulation-index as a floating point number for interpolation
      mod_idx = *mp * (1 - MODULATION_MAX_FACTOR) * _delay_length;
      mod_fraction = modff(mod_idx, &mod_number);

      // calculate modulation index into circular buffer
      c_mod_idx = (_circ_idx - _delay_offset - int(mod_number)) % _delay_length;
      if (c_mod_idx < 0) // check for negative offsets and correct them
        c_mod_idx += _delay_length;

      // linear interpolation
      if (c_mod_idx < 1)
      {
        idx[0] = _delay_length - 1;
        idx[1] = 0;
      }
      else if (c_mod_idx + 1 >= _delay_length)
      {
        idx[0] = 0;
        idx[1] = c_mod_idx;
      }
      else
      {
        idx[0] = c_mod_idx + 1;
        idx[1] = c_mod_idx;
      }
      if (mod_idx < 0.0)
        *bp = round(float(_delayline[idx[0]]) * (mod_fraction) + float(_delayline[idx[1]]) * (1.0 - mod_fraction));
      else
        *bp = round(float(_delayline[idx[0]]) * (1.0 - mod_fraction) + float(_delayline[idx[1]]) * mod_fraction);


      // push the pointers forward
      bp++; // next audio data
      mp++; // next modulation data
      _circ_idx++; // next circular buffer index
    }
  }

  if (modulation)
    release(modulation);

  if (block)
  {
#ifdef CHORUS_OUTPUT_BIQUAD
    arm_biquad_cascade_df1_fast_q15(&biquad_out, (q15_t*)block, (q15_t*)block, AUDIO_BLOCK_SAMPLES);
#endif
    transmit(block, 0);
    release(block);
  }
}

float AudioEffectModulatedDelay::offset(float offset_value) // in ms
{
  uint16_t offset_frames = (offset_value / 1000) * AUDIO_SAMPLE_RATE;
  if (offset_frames > _delay_length * MODULATION_MAX_FACTOR)
    _delay_offset = _delay_length * MODULATION_MAX_FACTOR;
  else if (offset_frames <= _delay_length * (1 - MODULATION_MAX_FACTOR))
    _delay_offset = _delay_length * (1 - MODULATION_MAX_FACTOR);
  else
    _delay_offset = offset_frames;

  return (offset_frames / AUDIO_SAMPLE_RATE * 1000);
}