79 lines
2.5 KiB
C++
79 lines
2.5 KiB
C++
/*
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* Waveshaper for Teensy 3.X audio
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*
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* Copyright (c) 2017 Damien Clarke, http://damienclarke.me
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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 all
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* 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 THE
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* SOFTWARE.
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*/
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#include <Arduino.h>
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#include "effect_waveshaper.h"
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AudioEffectWaveshaper::~AudioEffectWaveshaper()
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{
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if(this->waveshape) {
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delete [] this->waveshape;
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}
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}
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void AudioEffectWaveshaper::shape(float* waveshape, int length)
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{
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// length must be bigger than 1 and equal to a power of two + 1
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// anything else means we don't continue
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if(!waveshape || length < 2 || length > 32769 || ((length - 1) & (length - 2))) return;
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if(this->waveshape) {
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delete [] this->waveshape;
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}
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this->waveshape = new int16_t[length];
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for(int i = 0; i < length; i++) {
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this->waveshape[i] = 32767 * waveshape[i];
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}
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// set lerpshift to the number of bits to shift while interpolating
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// to cover the entire waveshape over a uint16_t input range
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int index = length - 1;
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lerpshift = 16;
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while (index >>= 1) --lerpshift;
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}
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void AudioEffectWaveshaper::update(void)
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{
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if(!waveshape) return;
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audio_block_t *block;
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block = receiveWritable();
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if (!block) return;
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uint16_t x, xa;
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int16_t i, ya, yb;
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for (i = 0; i < AUDIO_BLOCK_SAMPLES; i++) {
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// bring int16_t data into uint16_t range
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x = block->data[i] + 32768;
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// lerp waveshape (from http://coranac.com/tonc/text/fixed.htm)
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xa = x >> lerpshift;
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ya = waveshape[xa];
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yb = waveshape[xa + 1];
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block->data[i] = ya + ((yb - ya) * (x - (xa << lerpshift)) >> lerpshift);
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}
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transmit(block);
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release(block);
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}
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