pmdwin: fmgen/psg.c comparison

comparison fmgen/psg.c @ 0:c55ea9478c80

Hello Gensokyo!

author	Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
date	Tue, 21 May 2013 10:29:21 +0200
parents
children	8ad174416431

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--1:000000000000
+:c55ea9478c80
+// FIXME: move ugly-ass legalese somewhere where it won't be seen
+// by anyone other than lawyers. (/dev/null would be ideal but sadly
+// we live in an imperfect world).
+/* Copyright (c) 2012/2013, Peter Barfuss
+All rights reserved.
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+1. Redistributions of source code must retain the above copyright notice, this
+list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright notice,
+this list of conditions and the following disclaimer in the documentation
+and/or other materials provided with the distribution.
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
+// Quick, somewhat hacky PSG implementation. Seems to work fine in most cases.
+// Known bugs: volume *may* still be off for a lot of samples. Importantly,
+// waveform volume is too quiet but setting it at the correct volume makes
+// the noise volume too loud and vice-versa. I *think* what I have currently
+// is mostly correct (I'm basing this mostly on how good Strawberry Crisis
+// sounds with the given settings), but it's possible that more fine-tuning
+// is needed. Apart from that, this is probably the sketchiest part of all
+// of my emulator code, but then again there's a bit-exact VHDL core of
+// the YM2149F/AY-3-8910, so while I do want to make this as good
+// as the code in opna.c, it's the lowest-priority of all of the code here.
+// --bofh
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include <unistd.h>
+#include "op.h"
+#include "psg.h"
+#define Max(a,b) ((a>b)?a:b)
+#define Min(a,b) ((a<b)?a:b)
+// ---------------------------------------------------------------------------
+//  テーブル
+//
+int     EmitTable[0x20] = { -1, };
+uint    enveloptable[16][64] = { 0, };
+// ---------------------------------------------------------------------------
+//  PSG reset to power-on defaults
+//
+void PSGReset(PSG *psg)
+{
+int i;
+for (i=0; i<14; i++)
+PSGSetReg(psg, i, 0);
+PSGSetReg(psg, 7, 0xff);
+PSGSetReg(psg, 14, 0xff);
+PSGSetReg(psg, 15, 0xff);
+}
+// ---------------------------------------------------------------------------
+// This code is strongly inspired by some random PSG emulator code I found,
+// and is probably not the optimal way to define periods. It *is* at least
+// among the fastest, given that it uses the hilarious hack of using the
+// integer overflow on a 32-bit unsigned integer to compute ""moduli"".
+//
+void PSGSetClock(PSG *psg, uint32_t clock, uint32_t rate)
+{
+psg->tperiodbase = (uint32_t)((1 << toneshift ) / 4.0f * clock / rate);
+psg->eperiodbase = (uint32_t)((1 << envshift  ) / 4.0f * clock / rate);
+// 各データの更新
+int tmp;
+tmp = ((psg->reg[0] + psg->reg[1] * 256) & 0xfff);
+psg->speriod[0] = tmp ? psg->tperiodbase / tmp : psg->tperiodbase;
+tmp = ((psg->reg[2] + psg->reg[3] * 256) & 0xfff);
+psg->speriod[1] = tmp ? psg->tperiodbase / tmp : psg->tperiodbase;
+tmp = ((psg->reg[4] + psg->reg[5] * 256) & 0xfff);
+psg->speriod[2] = tmp ? psg->tperiodbase / tmp : psg->tperiodbase;
+tmp = psg->reg[6] & 0x1f;
+psg->nperiod = tmp;
+tmp = ((psg->reg[11] + psg->reg[12] * 256) & 0xffff);
+psg->eperiod = tmp ? psg->eperiodbase / tmp : psg->eperiodbase * 2;
+}
+// ---------------------------------------------------------------------------
+//  エンベロープ波形テーブル
+//
+static uint8_t table3[4] = {  0,  1, -1,  0 };
+void MakeEnvelopTable(void)
+{
+// 0 lo  1 up 2 down 3 hi
+static uint8_t table1[16*2] =
+{
+2,0, 2,0, 2,0, 2,0, 1,0, 1,0, 1,0, 1,0,
+2,2, 2,0, 2,1, 2,3, 1,1, 1,3, 1,2, 1,0,
+};
+int i, j;
+if (!enveloptable[0][0])
+{
+uint* ptr = enveloptable[0];
+for (i=0; i<16*2; i++)
+{
+uint8_t v = ((table1[i] & 0x2) ? 31 : 0);
+for (j=0; j<32; j++)
+{
+*ptr++ = EmitTable[v];
+v += table3[table1[i]];
+}
+}
+}
+}
+// ---------------------------------------------------------------------------
+//  Sets the channel output mask for the PSG device.
+//  c is a bitvector where the 3 LSBs are set to 0 to disable a given
+//  PSG channel and 1 to enable it.
+//  TODO: Possibly allow enabling tone/noise output for each channel independently?
+//
+void PSGSetChannelMask(PSG *psg, int c)
+{
+int i;
+psg->mask = c;
+for (i=0; i<3; i++)
+psg->olevel[i] = psg->mask & (1 << i) ? EmitTable[(psg->reg[8+i] & 15) * 2 + 1] : 0;
+}
+// ---------------------------------------------------------------------------
+// Sets the PSG volume. It's a fairly standard dB -> internal linear scale
+// conversion, followed by generating a table with volume levels.
+// The "magic number" 1.189207115 is just sqrt(sqrt(2))
+// TODO: is this table really needed? We have fast floating-point now.
+//
+void SetVolumePSG(PSG *psg, int volume)
+{
+int i;
+float base = 0x4000 / 3.0f * expf((float)M_LN10*(volume / 40.0f));
+for (i=31; i>=2; i--)
+{
+EmitTable[i] = lrintf(base);
+base /= 1.189207115f;
+}
+EmitTable[1] = 0;
+EmitTable[0] = 0;
+MakeEnvelopTable();
+PSGSetChannelMask(psg, psg->mask);
+}
+// ---------------------------------------------------------------------------
+//  PSG register set routine. Mostly just what you'd expect from reading the manual.
+//  Fairly boring code overall. regnum can be 0 - 15, data can be 0x00 - 0xFF.
+//  (This should not be surprising - the YM2149F *did* use an 8-bit bus, after all).
+//  Interesting quirk: the task of register 7 (channel enable/disable) is basically
+//  entirely duplicated by other registers, to the point where you can basically
+//  just ignore any writes to register 7 entirely. I save it here in case some
+//  braindead routine wants to read its value and do something based on that
+//  (Another curiosity: register 7 on the PSG appears to be the only register
+//   between *both* the OPNA and the PSG which is actually *read from* by
+//   pmdwin.cpp and not just written to. Amusingly enough, the only reason
+//   that it is ever read is so that it can then OR something with what it just read
+//   and then write that back to register 7. Hilarity).
+//  HACK ALERT: The output levels for channels 0 and 1 are increased by a factor of 4
+//  to make them match the actual chip in loudness, but without causing the noise channel
+//  to overtake everything in intensity. This is almost certainly wrong, and moreover
+//  it assumes that channel 2 will be playing back Speak Board effects which usually means
+//  drum kit only (for the most part, at least), and not being used as a separate tonal
+//  channel in its own right. To the best of my knowledge, this does hold for all of ZUN's
+//  songs, however, once you step outside that set of music, it's trivial to find
+//  all sorts of counterexamples to that assumption. Therefore, this should be fixed ASAP.
+//
+void PSGSetReg(PSG *psg, uint8_t regnum, uint8_t data)
+{
+if (regnum < 0x10)
+{
+psg->reg[regnum] = data;
+switch (regnum)
+{
+int tmp;
+case 0:     // ChA Fine Tune
+case 1:     // ChA Coarse Tune
+tmp = ((psg->reg[0] + psg->reg[1] * 256) & 0xfff);
+psg->speriod[0] = tmp ? psg->tperiodbase / tmp : psg->tperiodbase;
+break;
+case 2:     // ChB Fine Tune
+case 3:     // ChB Coarse Tune
+tmp = ((psg->reg[2] + psg->reg[3] * 256) & 0xfff);
+psg->speriod[1] = tmp ? psg->tperiodbase / tmp : psg->tperiodbase;
+break;
+case 4:     // ChC Fine Tune
+case 5:     // ChC Coarse Tune
+tmp = ((psg->reg[4] + psg->reg[5] * 256) & 0xfff);
+psg->speriod[2] = tmp ? psg->tperiodbase / tmp : psg->tperiodbase;
+break;
+case 6:     // Noise generator control
+data &= 0x1f;
+psg->nperiod = data;
+break;
+case 8:
+psg->olevel[0] = psg->mask & 1 ? EmitTable[(data & 15) * 2 + 1] : 0;
+break;
+case 9:
+psg->olevel[1] = psg->mask & 2 ? EmitTable[(data & 15) * 2 + 1] : 0;
+break;
+case 10:
+psg->olevel[2] = psg->mask & 4 ? EmitTable[(data & 15) * 2 + 1] : 0;
+break;
+case 11:    // Envelope period
+case 12:
+tmp = ((psg->reg[11] + psg->reg[12] * 256) & 0xffff);
+psg->eperiod = tmp ? psg->eperiodbase / tmp : psg->eperiodbase * 2;
+break;
+case 13:    // Envelope shape
+psg->ecount = 0;
+psg->envelop = enveloptable[data & 15];
+break;
+}
+}
+}
+// ---------------------------------------------------------------------------
+// Init code. Set volume to 0, reset the chip, enable all channels, seed the RNG.
+// RNG seed lifted from MAME's YM2149F emulation routine, appears to be correct.
+//
+void PSGInit(PSG *psg)
+{
+SetVolumePSG(psg, 0);
+psg->rng = 14231;
+psg->ncount = 0;
+PSGReset(psg);
+psg->mask = 0x3f;
+}
+// ---------------------------------------------------------------------------
+// The main output routine for the PSG emulation.
+// dest should be an array of size nsamples, and of type Sample
+// (one of int16_t, int32_t or float - any will work here without causing
+//  clipping/precision problems).
+// Everything is implemented using some form of fixed-point arithmetic
+// that currently needs no more than 32-bits for its implementation,
+// but I'm pretty certain that you can get by with much less than that
+// and still have mostly correct-to-fully-correct emulation.
+//
+// TODO: In the future, test the veracity of the above statement. Moreover,
+// if it turns out to be correct, rewrite this routine to not use more than
+// the required precision. This is irrelevant for any PC newer than, well,
+// a 386DX/68040, but important for efficient hardware implementation.
+//
+void PSGMix(PSG *psg, Sample* dest, uint32_t nsamples)
+{
+uint8_t chenable[3];
+uint8_t r7 = ~psg->reg[7];
+int i;
+if ((r7 & 0x3f) | ((psg->reg[8] | psg->reg[9] | psg->reg[10]) & 0x1f)) {
+chenable[0] = (r7 & 0x01) && (psg->speriod[0] <= (1 << toneshift));
+chenable[1] = (r7 & 0x02) && (psg->speriod[1] <= (1 << toneshift));
+chenable[2] = (r7 & 0x04) && (psg->speriod[2] <= (1 << toneshift));
+int noise, sample;
+uint env;
+uint* p1 = ((psg->mask & 1) && (psg->reg[ 8] & 0x10)) ? &env : &psg->olevel[0];
+uint* p2 = ((psg->mask & 2) && (psg->reg[ 9] & 0x10)) ? &env : &psg->olevel[1];
+uint* p3 = ((psg->mask & 4) && (psg->reg[10] & 0x10)) ? &env : &psg->olevel[2];
+#define SCOUNT(ch)  (psg->scount[ch] >> toneshift)
+if (p1 != &env && p2 != &env && p3 != &env) {
+// ノイズ有り
+for (i=0; i<nsamples; i++) {
+psg->ncount++;
+if(psg->ncount >= psg->nperiod) {
+if(psg->rng & 1)
+psg->rng ^= 0x24000;
+psg->rng >>= 1;
+psg->ncount = 0;
+}
+noise = (psg->rng & 1);
+sample = 0;
+{
+int x, y, z;
+x = ((SCOUNT(0) & chenable[0]) | ((r7 >> 3) & noise)) - 1;     // 0 or -1
+sample += (psg->olevel[0] + x) ^ x;
+psg->scount[0] += psg->speriod[0];
+y = ((SCOUNT(1) & chenable[1]) | ((r7 >> 4) & noise)) - 1;
+sample += (psg->olevel[1] + y) ^ y;
+psg->scount[1] += psg->speriod[1];
+z = ((SCOUNT(2) & chenable[2]) | ((r7 >> 5) & noise)) - 1;
+sample += (psg->olevel[2] + z) ^ z;
+psg->scount[2] += psg->speriod[2];
+}
+dest[0] += sample;
+dest += 1;
+}
+// エンベロープの計算をさぼった帳尻あわせ
+psg->ecount = (psg->ecount >> 8) + (psg->eperiod >> 8) * nsamples;
+if (psg->ecount >= (1 << (envshift+6-8))) {
+if ((psg->reg[0x0d] & 0x0b) != 0x0a)
+psg->ecount |= (1 << (envshift+5-8));
+psg->ecount &= (1 << (envshift+6-8)) - 1;
+}
+psg->ecount <<= 8;
+} else {
+// エンベロープあり
+for (i=0; i<nsamples; i++) {
+psg->ncount++;
+if(psg->ncount >= psg->nperiod) {
+if(psg->rng & 1)
+psg->rng ^= 0x24000;
+psg->rng >>= 1;
+psg->ncount = 0;
+}
+noise = (psg->rng & 1);
+sample = 0;
+{
+env = psg->envelop[psg->ecount >> envshift];
+psg->ecount += psg->eperiod;
+if (psg->ecount >= (1 << (envshift+6))) {
+if ((psg->reg[0x0d] & 0x0b) != 0x0a)
+psg->ecount |= (1 << (envshift+5));
+psg->ecount &= (1 << (envshift+6)) - 1;
+}
+int x, y, z;
+x = ((SCOUNT(0) & chenable[0]) | ((r7 >> 3) & noise)) - 1;     // 0 or -1
+sample += (*p1 + x) ^ x;
+psg->scount[0] += psg->speriod[0];
+y = ((SCOUNT(1) & chenable[1]) | ((r7 >> 4) & noise)) - 1;
+sample += (*p2 + y) ^ y;
+psg->scount[1] += psg->speriod[1];
+z = ((SCOUNT(2) & chenable[2]) | ((r7 >> 5) & noise)) - 1;
+sample += (*p3 + z) ^ z;
+psg->scount[2] += psg->speriod[2];
+}
+dest[0] += sample;
+dest += 1;
+}
+}
+}
+}

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comparison fmgen/psg.c @ 0:c55ea9478c80