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delay.cpp
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delay.cpp
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/**
******************************************************************************
* File Name : delay.c
* Author : Xavier Halgand
* Date :
* Description : simple delay/echo effect with low pass filter in the feedback loop
******************************************************************************
*/
/*
* This program 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 2 of the License, or
* (at your option) any later version.
*
* This program 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 program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include "delay.h"
/*-------------------------------------------------------------------------------------------*/
/* Delay effect variables */
static float delayline[DELAYLINE_LEN + 2];
static float *readpos; // output pointer of delay line
static float *writepos; // input pointer of delay line
static uint32_t shift;
static float coeff_a1 = 0.6f; // coeff for the one pole low-pass filter in the feedback loop
// coeff_a1 is between 0 and 1
// 0 : no filtering ; 1 : heavy filtering
static float old_dy; //previous delayed sample
static float fdb = INIT_FEEDB;
static float wet = INIT_WET;
/*-------------------------------------------------------------------------------------------*/
void Delay_init(void) {
/* initialize pointers positions for delay effect */
shift = DELAY;
readpos = delayline;
writepos = delayline + DELAY;
}
/*-------------------------------------------------------------------------------------------*/
void Delay_clean(void) {
for (int i = 0; i < DELAYLINE_LEN + 2; i++)
delayline[i] = 0;
}
/*-------------------------------------------------------------------------------------------*/
void Delay_time_inc(uint8_t val) {
if (val == MIDI_MAXi) {
float *pos;
if (shift < (DELAYLINE_LEN - DELTA_DELAY))
shift += DELTA_DELAY; //
pos = writepos - shift;
if (pos >= delayline)
readpos = pos;
else
readpos = pos + DELAYLINE_LEN - 1;
}
}
/*-------------------------------------------------------------------------------------------*/
void Delay_time_dec(uint8_t val) {
if (val == MIDI_MAXi) {
float *pos;
if (shift > (MIN_DELAY + DELTA_DELAY))
shift -= DELTA_DELAY; //
pos = writepos - shift;
if (pos >= delayline)
readpos = pos;
else
readpos = pos + DELAYLINE_LEN - 1;
}
}
/*-------------------------------------------------------------------------------------------*/
void Delay_time_set(uint8_t val) {
float *pos;
shift = (uint32_t) lrintf(
(DELAYLINE_LEN - 1 - MIN_DELAY) / MIDI_MAX * val + MIN_DELAY);
pos = writepos - shift;
if (pos >= delayline)
readpos = pos;
else
readpos = pos + DELAYLINE_LEN - 1;
}
/*-------------------------------------------------------------------------------------------*/
void Delay_feedback_inc(void) {
/* increment feedback delay */
fdb *= 1.05f; //
}
/*-------------------------------------------------------------------------------------------*/
void Delay_feedback_dec(void) {
/* decrement feedback delay */
fdb *= 0.95f; //
}
/*-------------------------------------------------------------------------------------------*/
void DelayFeedback_set(uint8_t val) {
fdb = val / MIDI_MAX;
}
/*-------------------------------------------------------------------------------------------*/
void DelayWet_set(uint8_t val) {
wet = val / MIDI_MAX;
}
/*-------------------------------------------------------------------------------------------*/
float Delay_compute(float x) {
float y, dy;
// (*readpos) : delayed sample read at the output of the delay line
dy = (1.f - coeff_a1) * (*readpos) + coeff_a1 * old_dy; // apply lowpass filter in the loop
old_dy = dy;
y = x + fdb * dy;
y = (y > 1.0f) ? 1.0f : y; //clip too loud samples
y = (y < -1.0f) ? -1.0f : y;
*writepos = y; // write new computed sample at the input of the delay line
/* update the delay line pointers : */
writepos++;
readpos++;
if ((writepos - delayline) >= DELAYLINE_LEN)
writepos = delayline; // wrap pointer
if ((readpos - delayline) >= DELAYLINE_LEN)
readpos = delayline; // wrap pointer
return (wet * y + (1 - wet) * x);
}
/************************************************** EOF ****************************************************/