251 lines
11 KiB
C
251 lines
11 KiB
C
/*
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* vic20sound.c - Implementation of VIC20 sound code.
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*
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* Written by
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* Rami Rasanen <raipsu@users.sf.net>
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* Ville-Matias Heikkila <viznut@iki.fi>
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*
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* This file is part of VICE, the Versatile Commodore Emulator.
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* See README for copyright notice.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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* 02111-1307 USA.
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "vic20sound.h"
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/* ---------------------------------------------------------------------*/
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static float voltagefunction[] = {
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0.00f, 148.28f, 296.55f, 735.97f, 914.88f, 1126.89f, 1321.86f, 1503.07f, 1603.50f,
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1758.00f, 1913.98f, 2070.94f, 2220.36f, 2342.91f, 2488.07f, 3188.98f, 3285.76f, 3382.53f,
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3479.31f, 3576.08f, 3672.86f, 3769.63f, 3866.41f, 3963.18f, 4059.96f, 4248.10f, 4436.24f,
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4624.38f, 4812.53f, 5000.67f, 5188.81f, 5192.91f, 5197.00f, 5338.52f, 5480.04f, 5621.56f,
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5763.07f, 5904.59f, 6046.11f, 6187.62f, 6329.14f, 6609.31f, 6889.47f, 7169.64f, 7449.80f,
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7729.97f, 7809.36f, 7888.75f, 7968.13f, 8047.52f, 8126.91f, 8206.30f, 8285.69f, 8365.07f,
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8444.46f, 8523.85f, 8603.24f, 8905.93f, 9208.63f, 9511.32f, 9814.02f, 9832.86f, 9851.70f,
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9870.54f, 9889.38f, 9908.22f, 9927.07f, 9945.91f, 9964.75f, 9983.59f, 10002.43f, 10021.27f,
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10040.12f, 10787.23f, 11534.34f, 12281.45f, 12284.98f, 12288.50f, 12292.03f, 12295.56f, 12299.09f,
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12302.62f, 12306.15f, 12309.68f, 12313.21f, 12316.74f, 12320.26f, 12323.79f, 12327.32f, 13113.05f,
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13898.78f, 13910.58f, 13922.39f, 13934.19f, 13945.99f, 13957.80f, 13969.60f, 13981.40f, 13993.21f,
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14005.01f, 14016.81f, 14028.62f, 14040.42f, 14052.22f, 14064.03f, 16926.31f, 16987.04f, 17047.77f,
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17108.50f, 17169.23f, 17229.96f, 17290.69f, 17351.42f, 17412.15f, 17472.88f, 17533.61f, 17594.34f,
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17655.07f, 17715.80f, 17776.53f, 17837.26f, 18041.51f, 18245.77f, 18450.02f, 18654.28f, 18858.53f,
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19062.78f, 19267.04f, 19471.29f, 19675.55f, 19879.80f, 20084.05f, 20288.31f, 20417.74f, 20547.17f,
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20676.61f, 20774.26f, 20871.91f, 20969.55f, 21067.20f, 21164.85f, 21262.50f, 21360.15f, 21457.80f,
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21555.45f, 21653.09f, 21750.74f, 21848.39f, 21946.04f, 22043.69f, 22141.34f, 22212.33f, 22283.33f,
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22354.33f, 22425.33f, 22496.32f, 22567.32f, 22638.32f, 22709.32f, 22780.31f, 22851.31f, 22922.31f,
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22993.31f, 23064.30f, 23135.30f, 23206.30f, 23255.45f, 23304.60f, 23353.75f, 23402.91f, 23452.06f,
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23501.21f, 23550.36f, 23599.51f, 23648.67f, 23768.81f, 23888.96f, 24009.11f, 24129.26f, 24249.41f,
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24369.56f, 24451.92f, 24534.28f, 24616.63f, 24698.99f, 24781.35f, 24863.70f, 24946.06f, 25028.42f,
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25110.77f, 25193.13f, 25275.49f, 25357.84f, 25440.20f, 25522.56f, 25604.92f, 25658.87f, 25712.83f,
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25766.79f, 25820.75f, 25874.71f, 25928.66f, 25982.62f, 26036.58f, 26090.54f, 26144.49f, 26198.45f,
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26252.41f, 26306.37f, 26360.33f, 26414.28f, 26501.23f, 26588.17f, 26675.12f, 26762.06f, 26849.01f,
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26935.95f, 27022.90f, 27109.84f, 27196.78f, 27283.73f, 27370.67f, 27457.62f, 27544.56f, 27631.51f,
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27718.45f, 27726.89f, 27735.33f, 27743.78f, 27752.22f, 27760.66f, 27769.10f, 27777.54f, 27785.98f,
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27794.43f, 27802.87f, 27811.31f, 27819.75f, 27828.19f, 27836.63f, 27845.08f, 27853.52f, 27861.96f,
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27870.40f, 27878.84f, 27887.28f, 27895.73f, 27904.17f, 27912.61f, 27921.05f, 27929.49f, 27937.93f,
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27946.38f, 27954.82f, 27963.26f, 27971.70f, 27980.14f, 27988.58f, 27997.03f, 28005.47f, 28013.91f,
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28022.35f, 28030.79f, 28039.23f, 28047.68f, 28056.12f, 28064.56f, 28073.00f, 28081.44f, 28089.88f,
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28098.33f, 28106.77f, 28115.21f, 28123.65f, 28132.09f, 28140.53f, 28148.98f, 28157.42f, 28165.86f,
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28174.30f, 28182.74f, 28191.18f, 28199.63f, 28208.07f, 28216.51f, 28224.95f, 28233.39f, 28241.83f,
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28250.28f, 28258.72f, 28267.16f, 28275.60f, 28284.04f, 28292.48f, 28300.93f, 28309.37f, 28317.81f,
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28326.25f, 28334.69f, 28343.13f, 28351.58f, 28360.02f, 28368.46f, 28376.90f, 28385.34f, 28393.78f,
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28402.23f, 28410.67f, 28419.11f, 28427.55f, 28435.99f, 28444.43f, 28452.88f, 28461.32f, 28469.76f,
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28478.20f, 28486.64f, 28495.08f, 28503.53f, 28511.97f, 28520.41f, 28528.85f, 28537.29f, 28545.73f,
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28554.18f, 28562.62f, 28571.06f, 28579.50f, 28587.94f, 28596.38f, 28604.83f, 28613.27f, 28621.71f,
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28630.15f, 28638.59f, 28647.03f, 28655.48f, 28663.92f, 28672.36f, 28680.80f, 28689.24f, 28697.68f,
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28706.13f, 28714.57f, 28723.01f, 28731.45f, 28739.89f, 28748.33f, 28756.78f, 28765.22f, 28773.66f,
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28782.10f, 28790.54f, 28798.98f, 28807.43f, 28815.87f, 28824.31f, 28832.75f, 28841.19f, 28849.63f,
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28858.08f, 28866.52f, 28874.96f, 28883.40f, 28891.84f, 28900.28f, 28908.73f, 28917.17f, 28925.61f,
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28934.05f, 28942.49f, 28950.93f, 28959.38f, 28967.82f, 28976.26f, 28984.70f, 28993.14f, 29001.58f,
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29010.03f, 29018.47f, 29026.91f, 29035.35f, 29043.79f, 29052.23f, 29060.68f, 29069.12f, 29077.56f,
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29086.00f, 29094.44f, 29102.88f, 29111.33f, 29119.77f, 29128.21f, 29136.65f, 29145.09f, 29153.53f,
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29161.98f, 29170.42f, 29178.86f, 29187.30f, 29195.74f, 29204.18f, 29212.63f, 29221.07f, 29229.51f,
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29237.95f, 29246.39f, 29254.83f, 29263.28f, 29271.72f, 29280.16f, 29288.60f, 29297.04f, 29305.48f,
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29313.93f, 29322.37f, 29330.81f, 29339.25f, 29347.69f, 29356.13f, 29364.58f, 29373.02f, 29381.46f,
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29389.90f, 29398.34f, 29406.78f, 29415.23f, 29423.67f, 29432.11f, 29440.55f, 29448.99f, 29457.43f,
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29465.88f, 29474.32f, 29482.76f, 29491.20f
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};
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void vic_sound_clock(sound_vic20_t *snd, uint32_t cycles);
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int vic_sound_machine_calculate_samples(sound_vic20_t *snd, int16_t *pbuf, int nr, int soc, int scc, uint32_t delta_t)
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{
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int s = 0;
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int i;
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float o;
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int16_t vicbuf;
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int samples_to_do;
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while (s < nr && delta_t >= snd->cycles_per_sample - snd->leftover_cycles) {
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samples_to_do = (int)(snd->cycles_per_sample - snd->leftover_cycles);
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snd->leftover_cycles += samples_to_do - snd->cycles_per_sample;
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vic_sound_clock(snd, samples_to_do);
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o = snd->lowpassbuf - snd->highpassbuf;
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snd->highpassbuf += snd->highpassbeta * (snd->lowpassbuf - snd->highpassbuf);
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snd->lowpassbuf += snd->lowpassbeta * (voltagefunction[(((snd->accum * 7) / snd->accum_cycles) + 1) * snd->volume] - snd->lowpassbuf);
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if (o < -32768) {
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vicbuf = -32768;
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} else if (o > 32767) {
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vicbuf = 32767;
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} else {
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vicbuf = (int16_t)o;
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}
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for (i = 0; i < soc; i++) {
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pbuf[(s * soc) + i] = vicbuf;
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}
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s++;
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snd->accum = 0;
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snd->accum_cycles = 0;
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delta_t -= samples_to_do;
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}
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if (delta_t > 0) {
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snd->leftover_cycles += delta_t;
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vic_sound_clock(snd, delta_t);
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delta_t = 0;
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}
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return s;
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}
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void vic_sound_clock(sound_vic20_t *snd, uint32_t cycles)
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{
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uint32_t i;
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int j, enabled;
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if (cycles <= 0) {
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return;
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}
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for (j = 0; j < 4; j++) {
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int chspeed = "\4\3\2\1"[j];
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if (snd->ch[j].ctr > cycles) {
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snd->accum += snd->ch[j].out * cycles;
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snd->ch[j].ctr -= cycles;
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} else {
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for (i = cycles; i; i--) {
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snd->ch[j].ctr--;
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if (snd->ch[j].ctr <= 0) {
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int a = (~snd->ch[j].reg) & 127;
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int edge_trigger;
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a = a ? a : 128;
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snd->ch[j].ctr += a << chspeed;
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enabled = (snd->ch[j].reg & 128) >> 7;
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edge_trigger = (snd->noise_LFSR & 1) & !snd->noise_LFSR0_old;
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if((j != 3) || ((j == 3) && edge_trigger)) {
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uint8_t shift = snd->ch[j].shift;
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shift = ((shift << 1) | (((((shift & 128) >> 7)) ^ 1) & enabled));
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snd->ch[j].shift = shift;
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}
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if(j == 3) {
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int bit3 = (snd->noise_LFSR >> 3) & 1;
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int bit12 = (snd->noise_LFSR >> 12) & 1;
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int bit14 = (snd->noise_LFSR >> 14) & 1;
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int bit15 = (snd->noise_LFSR >> 15) & 1;
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int gate1 = bit3 ^ bit12;
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int gate2 = bit14 ^ bit15;
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int gate3 = (gate1 ^ gate2) ^ 1;
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int gate4 = (gate3 & enabled) ^ 1;
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snd->noise_LFSR0_old = snd->noise_LFSR & 1;
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snd->noise_LFSR = (snd->noise_LFSR << 1) | gate4;
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}
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snd->ch[j].out = snd->ch[j].shift & (j == 3 ? enabled : 1);
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}
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snd->accum += snd->ch[j].out; /* FIXME: doesn't take DC offset into account */
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}
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}
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}
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snd->accum_cycles += cycles;
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}
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void vic_sound_machine_store(sound_vic20_t *snd, uint16_t addr, uint8_t value)
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{
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switch (addr) {
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case 0xA:
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snd->ch[0].reg = value;
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break;
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case 0xB:
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snd->ch[1].reg = value;
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break;
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case 0xC:
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snd->ch[2].reg = value;
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break;
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case 0xD:
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snd->ch[3].reg = value;
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break;
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case 0xE:
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snd->volume = value & 0x0f;
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break;
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}
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}
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int vic_sound_machine_init(sound_vic20_t *snd, int speed, int cycles_per_sec)
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{
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uint32_t i;
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float dt;
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memset(snd, 0, sizeof(sound_vic20_t));
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snd->cycles_per_sample = (float)cycles_per_sec / speed;
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snd->leftover_cycles = 0.0f;
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snd->lowpassbuf = 0.0f;
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snd->highpassbuf = 0.0f;
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snd->speed = speed;
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dt = 1.f / speed;
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/*
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Audio output stage
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5V
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-----+
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audio| 1k |
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+---+---R---+--------(K) +-----
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out | | | | |audio
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-----+ C .01 C .1 | 1 uF |
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| uF | uF +-----C-----+ 1K
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GND GND R 470 | amp
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| +-----
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GND
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*/
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/* Low-pass: R = 1 kOhm, C = 100 nF; RC = 1e3*1e-7 = 1e-4 (1591 Hz) */
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snd->lowpassbeta = dt / ( dt + 1e-4f );
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/* High-pass: R = 1 kOhm, C = 1 uF; RC = 1e3*1e-6 = 1e-3 ( 159 Hz) */
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snd->highpassbeta = dt / ( dt + 1e-3f );
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for (i = 0; i < 16; i++) {
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vic_sound_machine_store(snd, (uint16_t)i, 0);
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}
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return 1;
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}
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