SDLPAL/adplug/emuopl.cpp

/*
 * AdPlug - Replayer for many OPL2/OPL3 audio file formats.
 * Copyright (C) 1999 - 2005 Simon Peter <dn.tlp@gmx.net>, et al.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * emuopl.cpp - Emulated OPL, by Simon Peter <dn.tlp@gmx.net>
 */

#include "emuopl.h"

CEmuopl::CEmuopl(int rate, bool bit16, bool usestereo)
      : use16bit(bit16), stereo(usestereo), mixbufSamples(0) {
   opl[0] = OPLCreate(OPL_TYPE_YM3812, 3579545, rate);
   opl[1] = OPLCreate(OPL_TYPE_YM3812, 3579545, rate);

   currType = TYPE_OPL2;

   init();
}

CEmuopl::~CEmuopl() {
   OPLDestroy(opl[0]);
   OPLDestroy(opl[1]);

   if (mixbufSamples) {
      delete [] mixbuf0;
      delete [] mixbuf1;
   }
}

void CEmuopl::update(short *buf, int samples) {
   int i;

   //ensure that our mix buffers are adequately sized
   if (mixbufSamples < samples) {
      if (mixbufSamples) {
         delete[] mixbuf0;
         delete[] mixbuf1;
      }
      mixbufSamples = samples;

      //*2 = make room for stereo, if we need it
      mixbuf0 = new short[samples*2];
      mixbuf1 = new short[samples*2];
   }

   //data should be rendered to outbuf
   //tempbuf should be used as a temporary buffer
   //if we are supposed to generate 16bit output,
   //then outbuf may point directly to the actual waveform output "buf"
   //if we are supposed to generate 8bit output,
   //then outbuf cannot point to "buf" (because there will not be enough room)
   //and so it must point to a mixbuf instead--
   //it will be reduced to 8bit and put in "buf" later
   short *outbuf;
   short *tempbuf=mixbuf0;
   short *tempbuf2=mixbuf1;
   if (use16bit) outbuf = buf;
   else outbuf = mixbuf1;
   //...there is a potentially confusing situation where mixbuf1 can be aliased.
   //beware. it is a little loony.

   //all of the following rendering code produces 16bit output

   switch (currType) {
   case TYPE_OPL2:
      //for opl2 mode:
      //render chip0 to the output buffer
      YM3812UpdateOne(opl[0],outbuf,samples);

      //if we are supposed to output stereo,
      //then we need to dup the mono channel
      if (stereo)
         for (i=samples-1;i>=0;i--) {
            outbuf[i*2] = outbuf[i];
            outbuf[i*2+1] = outbuf[i];
         }
      break;

   case TYPE_OPL3:	// unsupported
      break;

   case TYPE_DUAL_OPL2:
      //for dual opl2 mode:
      //render each chip to a different tempbuffer
      YM3812UpdateOne(opl[0],tempbuf2,samples);
      YM3812UpdateOne(opl[1],tempbuf,samples);

      //output stereo:
      //then we need to interleave the two buffers
      if (stereo) {
         //first, spread tempbuf's samples across left channel
         //left channel
         for (i=0;i<samples;i++)
            outbuf[i*2] = tempbuf2[i];
         //next, insert the samples from tempbuf2 into right channel
         for (i=0;i<samples;i++)
            outbuf[i*2+1] = tempbuf[i];
      } else
         //output mono:
         //then we need to mix the two buffers into buf
         for (i=0;i<samples;i++)
            outbuf[i] = (tempbuf[i]>>1) + (tempbuf2[i]>>1);
      break;
   }

   //now reduce to 8bit if we need to
   if (!use16bit)
      for (i=0;i<(stereo ? samples*2 : samples);i++)
         ((char *)buf)[i] = (outbuf[i] >> 8) ^ 0x80;
}

void CEmuopl::write(int reg, int val) {
   switch (currType) {
   case TYPE_OPL2:
   case TYPE_DUAL_OPL2:
      OPLWrite(opl[currChip], 0, reg);
      OPLWrite(opl[currChip], 1, val);
      break;
   case TYPE_OPL3:	// unsupported
      break;
   }
}

void CEmuopl::init() {
   OPLResetChip(opl[0]);
   OPLResetChip(opl[1]);
   currChip = 0;
}

void CEmuopl::settype(ChipType type) {
   currType = type;
}