src/calf/delay.h

   1 /* Calf DSP Library
   2  * Reusable audio effect classes.
   3  *
   4  * Copyright (C) 2001-2007 Krzysztof Foltman
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2 of the License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General
  17  * Public License along with this program; if not, write to the
  18  * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  19  * Boston, MA  02110-1301  USA
  20  */
  21 #ifndef __CALF_DELAY_H
  22 #define __CALF_DELAY_H
  23
  24 #include "primitives.h"
  25 #include "buffer.h"
  26 #include "onepole.h"
  27
  28 namespace dsp {
  29
  30 /**
  31  * Delay primitive. Can be used for most delay stuff, including
  32  * variable (modulated) delays like chorus/flanger. Note that
  33  * for modulated delay effects use of GetInterp is preferred,
  34  * because it handles fractional positions and uses linear
  35  * interpolation, which sounds better most of the time.
  36  *
  37  * @param N maximum length
  38  * @param C number of channels read/written for each sample (1 mono, 2 stereo etc)
  39  */
  40 template<int N, class T>
  41 struct simple_delay {
  42     auto_buffer<N, T> data;
  43     int pos;
  44
  45     simple_delay() {
  46         reset();
  47     }
  48     void reset() {
  49         pos = 0;
  50         for (int i=0; i<N; i++)
  51             zero(data[i]);
  52     }
  53     /** Write one C-channel sample from idata[0], idata[1] etc into buffer */
  54     inline void put(T idata) {
  55         data[pos] = idata;
  56         pos = wrap_around<N>(pos+1);
  57     }
  58
  59     /**
  60      * Read one C-channel sample into odata[0], odata[1] etc into buffer.
  61      * Don't use for modulated delays (chorus/flanger etc) unless you
  62      * want them to crackle and generally sound ugly
  63      * @param odata pointer to write into
  64      * @param delay delay relative to current writing pos
  65      */
  66     template<class U>
  67     inline void get(U &odata, int delay) {
  68         assert(delay >= 0 && delay < N);
  69         int ppos = wrap_around<N>(pos + N - delay);
  70         odata = data[ppos];
  71     }
  72
  73     /**
  74      * Read and write during the same function call
  75      */
  76     inline T process(T idata, int delay)
  77     {
  78         assert(delay >= 0 && delay < N);
  79         int ppos = wrap_around<N>(pos + N - delay);
  80         T odata = data[ppos];
  81         data[pos] = idata;
  82         pos = wrap_around<N>(pos+1);
  83         return odata;
  84     }
  85
  86     /** Read one C-channel sample at fractional position.
  87      * This version can be used for modulated delays, because
  88      * it uses linear interpolation.
  89      * @param odata value to write into
  90      * @param delay delay relative to current writing pos
  91      * @param udelay fractional delay (0..1)
  92      */
  93     template<class U>
  94     inline void get_interp(U &odata, int delay, float udelay) {
  95 //        assert(delay >= 0 && delay <= N-1);
  96         int ppos = wrap_around<N>(pos + N - delay);
  97         int pppos = wrap_around<N>(ppos + N - 1);
  98         odata = lerp(data[ppos], data[pppos], udelay);
  99     }
 100
 101     /** Read one C-channel sample at fractional position.
 102      * This version can be used for modulated delays, because
 103      * it uses linear interpolation.
 104      * @param odata value to write into
 105      * @param delay delay relative to current writing pos
 106      * @param udelay fractional delay (0..1)
 107      */
 108     inline T get_interp_1616(unsigned int delay) {
 109         float udelay = (float)((delay & 0xFFFF) * (1.0 / 65536.0));
 110         delay = delay >> 16;
 111 //        assert(delay >= 0 && delay < N-1);
 112         int ppos = wrap_around<N>(pos + N - delay);
 113         int pppos = wrap_around<N>(ppos + N - 1);
 114         return lerp(data[ppos], data[pppos], udelay);
 115     }
 116
 117     /**
 118      * Comb filter. Feedback delay line with given delay and feedback values
 119      * @param in input signal
 120      * @param delay delay length (must be <N and integer)
 121      * @param fb feedback (must be <1 or it will be unstable)
 122      */
 123     inline T process_comb(T in, unsigned int delay, float fb)
 124     {
 125         T old, cur;
 126         get(old, delay);
 127         cur = in + fb*old;
 128         sanitize(cur);
 129         put(cur);
 130         return old;
 131     }
 132
 133     /**
 134      * Comb filter with linear interpolation. Feedback delay line with given delay and feedback values
 135      * Note that linear interpolation introduces some weird effects in frequency response.
 136      * @param in input signal
 137      * @param delay fractional delay length (must be < 65536 * N)
 138      * @param fb feedback (must be <1 or it will be unstable)
 139      */
 140     inline T process_comb_lerp16(T in, unsigned int delay, float udelay, float fb)
 141     {
 142         T old, cur;
 143         get_interp(old, delay>>16, dsp::fract16(delay));
 144         cur = in + fb*old;
 145         sanitize(cur);
 146         put(cur);
 147         return old;
 148     }
 149
 150     /**
 151      * Comb allpass filter. The comb filter with additional direct path, which is supposed to cancel the coloration.
 152      * @param in input signal
 153      * @param delay delay length (must be <N and integer)
 154      * @param fb feedback (must be <1 or it will be unstable)
 155      */
 156     inline T process_allpass_comb(T in, unsigned int delay, float fb)
 157     {
 158         T old, cur;
 159         get(old, delay);
 160         cur = in + fb*old;
 161         sanitize(cur);
 162         put(cur);
 163         return old - fb * cur;
 164     }
 165
 166         /**
 167      * Comb allpass filter. The comb filter with additional direct path, which is supposed to cancel the coloration.
 168      * @param in input signal
 169      * @param delay fractional delay length (must be < 65536 * N)
 170      * @param fb feedback (must be <1 or it will be unstable)
 171      */
 172     inline T process_allpass_comb_lerp16(T in, unsigned int delay, float fb)
 173     {
 174         T old, cur;
 175         get_interp(old, delay>>16, dsp::fract16(delay));
 176         cur = in + fb*old;
 177         sanitize(cur);
 178         put(cur);
 179         return old - fb * cur;
 180     }
 181 };
 182
 183 };
 184
 185 #endif