90 lines
2.6 KiB
C++
90 lines
2.6 KiB
C++
/* Audio Library for Teensy 3.X
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* Copyright (c) 2016, Paul Stoffregen, paul@pjrc.com
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*
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* Development of this audio library was funded by PJRC.COM, LLC by sales of
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* Teensy and Audio Adaptor boards. Please support PJRC's efforts to develop
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* open source software by purchasing Teensy or other PJRC products.
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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, development funding notice, and this permission
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* notice shall be included in all 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
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* THE SOFTWARE.
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*/
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#include <Arduino.h>
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#include "synth_karplusstrong.h"
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static uint32_t pseudorand(uint32_t lo)
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{
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uint32_t hi;
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hi = multiply_16bx16t(16807, lo); // 16807 * (lo >> 16)
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lo = 16807 * (lo & 0xFFFF);
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lo += (hi & 0x7FFF) << 16;
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lo += hi >> 15;
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lo = (lo & 0x7FFFFFFF) + (lo >> 31);
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return lo;
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}
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void AudioSynthKarplusStrong::update(void)
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{
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audio_block_t *block;
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if (state == 0) return;
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if (state == 1) {
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uint32_t lo = seed;
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for (int i=0; i < bufferLen; i++) {
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lo = pseudorand(lo);
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buffer[i] = signed_multiply_32x16b(magnitude, lo);
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}
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seed = lo;
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state = 2;
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}
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block = allocate();
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if (!block) {
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state = 0;
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return;
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}
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int16_t prior;
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if (bufferIndex > 0) {
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prior = buffer[bufferIndex - 1];
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} else {
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prior = buffer[bufferLen - 1];
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}
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int16_t *data = block->data;
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for (int i=0; i < AUDIO_BLOCK_SAMPLES; i++) {
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int16_t in = buffer[bufferIndex];
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//int16_t out = (in * 32604 + prior * 32604) >> 16;
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int16_t out = (in * 32686 + prior * 32686) >> 16;
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//int16_t out = (in * 32768 + prior * 32768) >> 16;
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*data++ = out;
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buffer[bufferIndex] = out;
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prior = in;
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if (++bufferIndex >= bufferLen) bufferIndex = 0;
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}
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transmit(block);
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release(block);
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}
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uint32_t AudioSynthKarplusStrong::seed = 1;
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