mod-delay-gain.cpp

/* Modulated delay line

   Inspired by;
   http://musicdsp.org/showArchiveComment.php?ArchiveID=154

   But details changed for Teensy Audio.
   No feedback within the class, just done externally
   so we can add filters and stuff to the loop.

   Delay time is a signal input to the block, and functions from 0 to 0x7fff,
   scaling the delay time accordingly.
*/
/*
   Copyright (c) 2016, Byron Jacquot, SparkFun Electronics
   SparkFun code, firmware, and software is released under
   the MIT License(http://opensource.org/licenses/MIT).

   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, development funding 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 "mod-delay-gain.h"

#define INTERPOLATE (1)

void AudioEffectModDelayGain::update(void)
{
  audio_block_t *audioblock, *controlblockDelay, *controlblockGain;
  int16_t *data, *end, *ctrlDelay, *ctrlGain;

  int32_t extract_index;
  int32_t temp;

#ifdef INTERPOLATE
  int32_t interp_delta;
  int32_t next;
  int16_t calc;
#endif

  if (buffer_length == 0)
    return;

  audioblock = receiveWritable(0);
  if (!audioblock) return;

  controlblockDelay = receiveReadOnly(1);
  if (!controlblockDelay) {
    release(audioblock);
    return;
  }

  controlblockGain = receiveReadOnly(2);
  if (!controlblockGain) {
    release(audioblock);
    release(controlblockDelay);
    return;
  }

  data = audioblock->data;
  end = audioblock->data + AUDIO_BLOCK_SAMPLES;

  ctrlDelay = controlblockDelay->data;

  ctrlGain = controlblockGain->data;

  do
  {
    delayline_p[insert_index] = *data;
    insert_index++;
    if (insert_index >= buffer_length)
    {
      insert_index = 0;
    }

#ifdef INTERPOLATE
    //
    interp_delta =  (buffer_length * (*ctrlDelay));
    delay_delta = interp_delta >> 15;   // MSB's for delay len
    interp_delta &= 0x7fff;             //LSBs for interp distance
#else
    delay_delta = (buffer_length * (*ctrlDelay)) >> 15;
#endif

    extract_index = insert_index - delay_delta;

    if (extract_index < 0)
    {
      extract_index = buffer_length + extract_index;
    }

#ifdef INTERPOLATE
    // Use the fractional part to interpolate between samples
    next = extract_index + 1;
    if (next >= buffer_length)
    {
      next = 0;
    }

    calc = delayline_p[next] -  delayline_p[extract_index];

    calc = (calc * interp_delta ) >> 15;
    calc += delayline_p[extract_index];

    //*data = calc;
    temp = (int32_t)calc * (*ctrlGain);
    *data = temp >> 15;
#else
    //data = delayline_p[extract_index];
    temp = (int32_t)delayline_p[extract_index] * (*ctrlGain);
    *data = temp >> 15;
#endif

    data++;
    ctrlDelay++;
    ctrlGain++;
  } while (data < end);
  transmit(audioblock);
  release(audioblock);
  release(controlblockDelay);
  release(controlblockGain);
}