Supermodel/Src/Model3/DSB.cpp

/**
 ** Supermodel
 ** A Sega Model 3 Arcade Emulator.
 ** Copyright 2011 Bart Trzynadlowski 
 **
 ** This file is part of Supermodel.
 **
 ** Supermodel is free software: you can redistribute it and/or modify it under
 ** the terms of the GNU General Public License as published by the Free 
 ** Software Foundation, either version 3 of the License, or (at your option)
 ** any later version.
 **
 ** Supermodel 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 General Public License for
 ** more details.
 **
 ** You should have received a copy of the GNU General Public License along
 ** with Supermodel.  If not, see <http://www.gnu.org/licenses/>.
 **/
 
/*
 * DSB.cpp
 * 
 * Sega Digital Sound Board (MPEG audio). Implementation of the CDSB1 and CDSB2
 * classes. Based on code donated by R. Belmont. Many Bothans died to bring us 
 * this emulation.
 *
 * TODO List
 * ---------
 * - Music looping on DSB2 does not work in Daytona 2 (will play next track).
 * - Check actual MPEG sample rate. So far, all games seem to use 32 KHz, which
 *   may be a hardware requirement, but if other sampling rates are allowable,
 *   the code here will fail (it is hard coded for 32 KHz).
 * - Should we do some bounds checking on the MPEG start/end points?
 */

#include "Supermodel.h"


/******************************************************************************
 Resampler
 
 MPEG Layer 2 audio can be 32, 44.1, or 48 KHz. Here, an up-sampling algorithm
 is provided, which should work for any frequency less than 44.1 KHz and an 
 output frequency of 44.1 KHz. Down-sampling is not yet implemented, but would 
 work in a similar fashion. The chief difference is that the input index would
 sometimes advance by more than one for a single output sample and the
 fractions, nFrac and pFrac, would sometimes exceed 1.0.
 
 Up-Sampling Description
 -----------------------
 
 Linear interpolation is used to up-sample. Not as accurate as the Shannon
 reconstruction equation but it seems to work quite well.
 
 1. Linear Interpolation
 
 Input samples for a given frame (here, this means 1/60Hz, not to be confused
 with an MPEG frame, which is shorter) are numbered 0 ... L-1 (L samples in 
 total). Output samples are 0 ... M-1.
 
 For two adjacent input samples at times p ("previous") and n ("next"), in[p]
 and in[n], and output out[t] at time t, linear interpolation yields:
 
 		out[t] = (n-t)/(n-p) * in[p] + (t-p)/(n-p) * in[n]
 
 Note that (n-p) = 1/fin (fin being the input sampling frequency).
 
 Let pFrac = (n-t)/(n-p) and nFrac = (t-p)/(n-p). As t moves from p to n, pFrac
 moves from 1 to 0 and nFrac from 0 to 1, as we expect.
 
 If we proceed one output sample at a time, we must add the time difference 
 between output samples, 1/fout, to t. Call this delta_t. If we divide delta_t
 by (n-p), we can add it directly to nFrac and subtract from pFrac. Therefore:
 
 	delta = (1/fout)/(n-p) = fin/fout
 	
 What happens when nFrac exceeds 1.0 or pFrac goes below 0.0? That can't
 be allowed to happen -- it means that we've actually moved along the line into
 the region between the next set of samples. We use pFrac < 0 as the condition
 to update the input samples.
 
 It so happens that when fin < fout, pFrac and nFrac will never exceed 1.0. So
 there is no need to check or mask the fixed point values when using them to
 interpolate samples.
 
 2. Input Buffer Overflows
 
 For some low sampling rates, particularly those that are a factor of 2 or 4
 smaller, it is possible that the very last sample or two needed from the input
 stream will be beyond the end. Fetching two extra samples (which can introduce
 an update lag of two samples -- imperceptible and inconsequential) fixes this,
 and so we do it.
 
 3. Continuity Between Frames
 
 The very last output sample will typically sit somewhere between two input
 samples. It is wrong to start the next frame by assuming everything is lined
 up again. The first sample of the next frame will often have to be interpol-
 ated with the last sample of the previous frame. To facilitate this, we check
 to see how many input samples remain unprocessed when up-sampling is finished,
 and then copy those to the beginning of the buffer. We then return the number
 of samples so that the buffer update function will know to skip them.
 
 We also must maintain the state of pFrac and nFrac to resume interpolation 
 correctly. Therefore, these variables are persistent.
 
 4. Fixed Point Arithmetic
 
 Fixed point arithmetic is used to track fractions. For such numbers, the low
 8 bits represent a fraction (0x100 would be 1.0, 0x080 would be 0.5, etc.)
 and the upper bits are the integral portion.
******************************************************************************/
 
void CDSBResampler::Reset(void)
{
	// Initial state of fractions (24.8 fixed point)
	nFrac = 0<<8;	// fraction of next sample to use (0->1.0 as x moves p->n)
 	pFrac = 1<<8;	// previous sample (1.0->0 as x moves p->n)
}

// Mixes 16-bit samples (sign extended in a and b)
static inline INT16 MixAndClip(INT32 a, INT32 b)
{
	a += b;
	if (a > 32767)
		a = 32767;
	else if (a < -32768)
		a = -32768;
	return (INT16) a;
}

// Mixes audio and returns number of samples copied back to start of buffer (ie. offset at which new samples should be written)
int CDSBResampler::UpSampleAndMix(INT16 *outL, INT16 *outR, INT16 *inL, INT16 *inR, int sizeOut, int sizeIn, int outRate, int inRate)
{
	int 	delta = (inRate<<8)/outRate;	// (1/fout)/(1/fin)=fin/fout, 24.8 fixed point
	int		outIdx = 0;
	int		inIdx = 0;
	INT16	leftSample, rightSample;
	
	while (outIdx < sizeOut)
	{
		// nFrac, pFrac will never exceed 1.0 (0x100) (only true if delta does not exceed 1)
		leftSample	= ((int)inL[inIdx]*pFrac+(int)inL[inIdx+1]*nFrac) >> 8;	// left channel
		rightSample	= ((int)inR[inIdx]*pFrac+(int)inR[inIdx+1]*nFrac) >> 8;	// right channel
		
		
		outL[outIdx] = MixAndClip(outL[outIdx], leftSample);
		outR[outIdx] = MixAndClip(outR[outIdx], rightSample);
		outIdx++;
		
		// Time step
		pFrac -= delta;
		nFrac += delta;
		
		// Time to move to next samples?
		if (pFrac <= 0)	// when pFrac becomes 0, advance samples, reset pFrac to 1
		{
			pFrac += (1<<8);
			nFrac -= (1<<8);
			inIdx++;	// advance samples (for upsampling only; downsampling may advance by more than one -- add delta every loop iteration)
			
		}
	}

	// Copy remaining "active" input samples to start of buffer
	int i = 0;
	int j = inIdx;
	while (j < sizeIn)
	{
		inL[i] = inL[j];
		inR[i] = inR[j];
		i++;
		j++;
	}
	return i;	// first free position in input buffer to copy next MPEG update to
}


/******************************************************************************
 Digital Sound Board Type 1: Z80 CPU
******************************************************************************/

UINT8 CDSB1::Read8(UINT32 addr)
{
	// ROM: 0x0000-0x7FFF
	if (addr < 0x8000)
		return progROM[addr];
	
	// RAM: 0x8000-0xFFFF
	return ram[addr&0x7FFF];
}

void CDSB1::Write8(UINT32 addr, UINT8 data)
{
	if (addr >= 0x8000)
		ram[addr&0x7FFF] = data;
}

void CDSB1::IOWrite8(UINT32 addr, UINT8 data)
{
	switch ((addr&0xFF))
	{
	case 0xE0:	// MPEG trigger
		mpegState = data;

		if (data == 0)	// stop
		{
			MPEG_StopPlaying();
			return;
		}

		if (data == 1)	// play without loop
		{
			MPEG_SetLoop(NULL, 0);
			//printf("====> Playing %06X\n", mpegStart);
			MPEG_PlayMemory((const char *) &mpegROM[mpegStart], mpegEnd-mpegStart);
			return;
		}

		if (data == 2)	// play with loop
		{
			//printf("====> Playing %06X\n", mpegStart);
			MPEG_PlayMemory((const char *) &mpegROM[mpegStart], mpegEnd-mpegStart);
			return;
		}
		break;
	
	case 0xE2:	// MPEG start, high byte
		startLatch &= 0x00FFFF;
		startLatch |= ((UINT32)data) << 16;
		break;
	
	case 0xE3:	// MPEG start, middle byte
		startLatch &= 0xFF00FF;
		startLatch |= ((UINT32)data) << 8;
		break;
		
	case 0xE4:	// MPEG start, low byte
		startLatch &= 0xFFFF00;
		startLatch |= data;

		if (mpegState == 0)
		{
			mpegStart = startLatch;
			//printf("mpegStart = %08X\n", mpegStart);
		}
		else
		{
			loopStart = startLatch;
			//printf("loopStart = %08X\n", loopStart);
			// SWA: if loop end is zero, it means "keep previous end marker"
			if (loopEnd == 0)
			{
				MPEG_SetLoop((const char *) &mpegROM[loopStart], mpegEnd-loopStart);
			}
			else
			{
				MPEG_SetLoop((const char *) &mpegROM[loopStart], loopEnd-loopStart);
			}
		}
			
		break;
		
	case 0xE5:	// MPEG end, high byte
		endLatch &= 0x00FFFF;
		endLatch |= ((UINT32)data) << 16;
		break;		
	
	case 0xE6:	// MPEG end, middle byte
		endLatch &= 0xFF00FF;
		endLatch |= ((UINT32)data) << 8;
		break;
		
	case 0xE7:	// MPEG end, low byte
		endLatch &= 0xFFFF00;
		endLatch |= data;

		if (mpegState == 0)
		{
			mpegEnd = endLatch;
			//printf("mpegEnd = %08X\n", mpegEnd);
		}
		else
		{
			loopEnd = endLatch;
			//printf("loopEnd = %08X\n", loopEnd);
			MPEG_SetLoop((const char *) &mpegROM[loopStart], loopEnd-loopStart);
		}
		break;		
		
	case 0xE8:	// MPEG volume
		break;
		
	case 0xE9:	// MPEG stereo
		break;
		
	case 0xF0:	// command echo back
		break;
	
	default:
		//printf("Z80 Port %02X=%08X\n", addr, data);
		break;
	}
}

UINT8 CDSB1::IORead8(UINT32 addr)
{
	int	progress;
	
	switch ((addr&0xFF))
	{
	case 0xE2:	// MPEG position, high byte
		progress = MPEG_GetProgress() + mpegStart;	// byte address currently playing
		return (progress>>16)&0xFF;
		
	case 0xE3:	// MPEG position, middle byte
		progress = MPEG_GetProgress() + mpegStart;
		return (progress>>8)&0xFF;
		
	case 0xE4:	// MPEG position, low byte
		progress = MPEG_GetProgress() + mpegStart;
		return progress&0xFF;
		
	case 0xF0:	// Latch
		UINT8 d;
		d = fifo[fifoIdxR];	// retrieve next command byte
		if (fifoIdxR != fifoIdxW)	// if these are equal, nothing has been written yet (don't advance)
		{
			fifoIdxR++;
			fifoIdxR &= 127;
		}
		
		if (fifoIdxR == fifoIdxW)	// FIFO empty?
			status &= ~2;			// yes, indicate no commands left
		else
			status |= 2;
			
		Z80.SetINT(FALSE);	// clear IRQ
		//printf("Z80: INT cleared, read from FIFO\n");
		return d;
		
	case 0xF1:	// Status
		/*
		 * Bit 0: Must be 1 for most games.
		 * Bit 1: Command pending (used by SWA instead of IRQ)
		 * SWA requires (status&0x38)==0 or else it loops endlessly
		 */
		return status;
	}
	
	//printf("Z80 Port Read %02X\n", addr);
	return 0;
}

static int Z80IRQCallback(CZ80 *Z80)
{
	return 0x38;
}	

void CDSB1::SendCommand(UINT8 data)
{
	/*
	 * Commands are buffered in a FIFO. This probably does not actually exist
	 * on the real DSB but is necessary because the Z80 is not really synced
	 * up with the other CPUs and must process all commands it has received
	 * over the course of a frame at once.
	 */
	fifo[fifoIdxW++] = data;
	fifoIdxW &= 127;
	//printf("Write FIFO: %02X\n", data);
	
	// Have we caught up to the read pointer?
#ifdef DEBUG
	if (fifoIdxW == fifoIdxR)
		printf("DSB1 FIFO overflow!\n");
#endif
}

void CDSB1::RunFrame(INT16 *audioL, INT16 *audioR)
{
#ifdef SUPERMODEL_SOUND
	int	cycles;
	
	// While FIFO not empty, fire interrupts, run for up to one frame
	for (cycles = (4000000/60)/4; (cycles > 0) && (fifoIdxR != fifoIdxW);  )
	{
		Z80.SetINT(TRUE);	// fire an IRQ to indicate pending command
		//printf("Z80 INT fired\n");
		cycles -= Z80.Run(500);
	}	
		
	// Run remaining cycles
	Z80.Run(cycles);
	
	// Decode MPEG for this frame
	INT16 *mpegFill[2] = { &mpegL[retainedSamples], &mpegR[retainedSamples] };
	MPEG_Decode(mpegFill, 32000/60-retainedSamples+2);
	retainedSamples = Resampler.UpSampleAndMix(audioL, audioR, mpegL, mpegR, 44100/60, 32000/60+2, 44100, 32000);
	
#endif
}

void CDSB1::Reset(void)
{
	MPEG_StopPlaying();
	Resampler.Reset();
	retainedSamples = 0;
	
	memset(fifo, 0, sizeof(fifo));
	fifoIdxW = fifoIdxR = 0;
	
	status = 1;
	mpegState = 0;	// why doesn't RB ever init this?
	
	Z80.Reset();
	DebugLog("DSB1 Reset\n");
}

// Offsets of memory regions within DSB2's pool
#define DSB1_OFFSET_RAM			0		// 32KB Z80 RAM
#define DSB1_OFFSET_MPEG_LEFT	0x8000	// 1604 bytes (48 KHz max., 1/60th second, 2 extra = 2*(48000/60+2)) left MPEG buffer
#define DSB1_OFFSET_MPEG_RIGHT	0x8644	// 1604 bytes right MPEG buffer
#define DSB1_MEMORY_POOL_SIZE	(0x8000 + 0x644 + 0x644)

BOOL CDSB1::Init(const UINT8 *progROMPtr, const UINT8 *mpegROMPtr)
{
	float	memSizeMB = (float)DSB1_MEMORY_POOL_SIZE/(float)0x100000;
	
	// Receive ROM
	progROM = progROMPtr;
	mpegROM = mpegROMPtr;
	
	// Allocate memory pool
	memoryPool = new(std::nothrow) UINT8[DSB1_MEMORY_POOL_SIZE];
	if (NULL == memoryPool)
		return ErrorLog("Insufficient memory for DSB1 board (needs %1.1f MB).", memSizeMB);
	memset(memoryPool, 0, DSB1_MEMORY_POOL_SIZE);
	
	// Set up memory pointers
	ram = &memoryPool[DSB1_OFFSET_RAM];
	mpegL = (INT16 *) &memoryPool[DSB1_OFFSET_MPEG_LEFT];
	mpegR = (INT16 *) &memoryPool[DSB1_OFFSET_MPEG_RIGHT];
	
	// Initialize Z80 CPU
	Z80.Init(this, Z80IRQCallback);
	
	// MPEG decoder
	if (OKAY != MPEG_Init())
		return ErrorLog("Insufficient memory to initialize MPEG decoder.");
	retainedSamples = 0;
		
	return OKAY;
}

CDSB1::CDSB1(void)
{
	progROM = NULL;
	mpegROM = NULL;
	memoryPool = NULL;
	ram = NULL;
	mpegL = NULL;
	mpegR = NULL;
	
	DebugLog("Built DSB1 Board\n");
}

CDSB1::~CDSB1(void)
{	
	MPEG_Shutdown();
	
	if (memoryPool != NULL)
	{
		delete [] memoryPool;
		memoryPool = NULL;
	}
	
	progROM = NULL;
	mpegROM = NULL;
	ram = NULL;
	mpegL = NULL;
	mpegR = NULL;
	
	DebugLog("Destroyed DSB1 Board\n");
}


/******************************************************************************
 Digital Sound Board Type 2: 68K CPU
******************************************************************************/

enum 
{
	ST_IDLE = 0,
	ST_GOT14,	// start/loop addr
	ST_14_0,
	ST_14_1,
	ST_GOT24,	// end addr
	ST_24_0,
	ST_24_1,
	ST_GOT74,
	ST_GOTA0,
	ST_GOTA1,
	ST_GOTA4,
	ST_GOTA5,
	ST_GOTB0,
	ST_GOTB1,
	ST_GOTB4,
	ST_GOTB5,
};

void CDSB2::WriteMPEGFIFO(UINT8 byte)
{
	//printf("fifo: %x (state %d)\n", byte, mpegState);
	switch (mpegState)
	{
		case ST_IDLE:
			if (byte == 0x14) mpegState = ST_GOT14;
			else if (byte == 0x15) mpegState = ST_GOT14;
			else if (byte == 0x24) mpegState = ST_GOT24;
			else if (byte == 0x25) mpegState = ST_GOT24;

			else if (byte == 0x74 || byte == 0x75)	// "start play"
			{
				MPEG_PlayMemory((const char *) &mpegROM[mpegStart], mpegEnd-mpegStart);
				mpegState = ST_IDLE;
				playing = 1;
			}

			else if (byte == 0x84 || byte == 0x85)
			{
				MPEG_StopPlaying();
				playing = 0;
			}

			else if (byte == 0xa0) mpegState = ST_GOTA0;
			else if (byte == 0xa1) mpegState = ST_GOTA1;
			else if (byte == 0xa4) mpegState = ST_GOTA4;
			else if (byte == 0xa5) mpegState = ST_GOTA5;

			else if (byte == 0xb0) mpegState = ST_GOTB0;
			else if (byte == 0xb1) mpegState = ST_GOTB1;
			else if (byte == 0xb4) mpegState = ST_GOTB4;
			else if (byte == 0xb5) mpegState = ST_GOTB5;

			break;

		case ST_GOT14:
			mpegStart &= ~0xff0000;
			mpegStart |= (byte<<16);
			mpegState++;
			break;
		case ST_14_0:
			mpegStart &= ~0xff00;
			mpegStart |= (byte<<8);
			mpegState++;
			break;
		case ST_14_1:
			mpegStart &= ~0xff;
			mpegStart |= (byte);
			mpegState = ST_IDLE;

			if (playing)
			{
				//printf("Setting loop point to %x\n", mpegStart);
				MPEG_PlayMemory((const char *) &mpegROM[mpegStart], mpegEnd-mpegStart);
			}

			//printf("mpegStart=%x\n", mpegStart);
			break;
		case ST_GOT24:
			mpegEnd &= ~0xff0000;
			mpegEnd |= (byte<<16);
			mpegState++;
			break;
		case ST_24_0:
			mpegEnd &= ~0xff00;
			mpegEnd |= (byte<<8);
			mpegState++;
			break;
		case ST_24_1:
			mpegEnd &= ~0xff;
			mpegEnd |= (byte);
			//printf("mpegEnd=%x\n", mpegEnd);

			// default to full stereo
//			mixer_set_stereo_volume(0, 255, 255);
//			mixer_set_stereo_pan(0, MIXER_PAN_RIGHT, MIXER_PAN_LEFT);
			mpegState = ST_IDLE;
			break;
		case ST_GOTA0:
			// ch 0 mono
//			mixer_set_stereo_volume(0, 0, 255);
//			printf("ch 0 mono\n");
//			mixer_set_stereo_pan(0, MIXER_PAN_CENTER, MIXER_PAN_CENTER);
			mpegState = ST_IDLE;
			break;
		case ST_GOTA1:
			mpegState = ST_IDLE;
			break;
		case ST_GOTA4:
			mpegState = ST_IDLE;
			break;
		case ST_GOTA5:
			mpegState = ST_IDLE;
			break;
		case ST_GOTB0:
			mpegState = ST_IDLE;
			break;
		case ST_GOTB1:
			// ch 1 mono
//			printf("ch 1 mono\n");
//			mixer_set_stereo_volume(0, 255, 0);
//			mixer_set_stereo_pan(0, MIXER_PAN_CENTER, MIXER_PAN_CENTER);
			mpegState = ST_IDLE;
			break;
		case ST_GOTB4:
			mpegState = ST_IDLE;
			break;
		case ST_GOTB5:
			mpegState = ST_IDLE;
			break;
		default:
			break;
	}
}

UINT8 CDSB2::Read8(UINT32 addr)
{
	if (addr < (128*1024))
		return progROM[addr^1];

	if (addr == 0xc00001)	
	{
		return cmdLatch;
	}
	if (addr == 0xc00003)	// bit 0 = command valid
	{
		return 1;
	}

	if (addr == 0xe80001)
	{
		return 0x01;	// MPEG busy status: bit 1 = busy
	}			// polled by irq2, stored | 0x10 at f01010

	if ((addr >= 0xf00000) && (addr < 0xf10000))
	{
		addr &= 0x1ffff;
		return ram[addr^1];
	}

//	printf("R8 @ %x\n", addr);
	return 0;
}

UINT16 CDSB2::Read16(UINT32 addr)
{
	if (addr < (128*1024))
	{
		return *(UINT16 *) &progROM[addr];
	}
	if ((addr >= 0xf00000) && (addr < 0xf20000))
	{
		addr &= 0x1ffff;
		return *(UINT16 *) &ram[addr];
	}

//	printf("R16 @ %x\n", addr);
	return 0;
}

UINT32 CDSB2::Read32(UINT32 addr)
{
	UINT32	hi, lo;
	
	if (addr < (128*1024))
	{
		hi = *(UINT16 *) &progROM[addr];
		lo = *(UINT16 *) &progROM[addr+2];
		return (hi<<16)|lo;
	}
	if ((addr >= 0xf00000) && (addr < 0xf20000))
	{
		addr &= 0x1ffff;
		hi = *(UINT16 *) &ram[addr];
		lo = *(UINT16 *) &ram[addr+2];
		return (hi<<16)|lo;
	}
//	printf("R32 @ %x\n", addr);
	return 0;
}

void CDSB2::Write8(UINT32 addr, UINT8 data)
{
	if ((addr >= 0xf00000) && (addr < 0xf20000))
	{
		addr &= 0x1ffff;
		ram[addr^1] = data;
		return;
	}
	
	if (addr == 0xd00001) return;

	if (addr == 0xe00003) 
	{
		WriteMPEGFIFO(data);
		return;
	}

//	printf("W8: %x @ %x (PC=%x)\n", data, addr, m68k_get_reg(NULL, M68K_REG_PC));
}

void CDSB2::Write16(UINT32 addr, UINT16 data)
{
	if ((addr >= 0xf00000) && (addr < 0xf20000))
	{
		addr &= 0x1ffff;
		*(UINT16 *) &ram[addr] = data;
		return;
	}
//	printf("W16: %x @ %x\n", data, addr);
}

void CDSB2::Write32(UINT32 addr, UINT32 data)
{
	if ((addr >= 0xf00000) && (addr < 0xf20000))
	{
		addr &= 0x1ffff;
		*(UINT16 *) &ram[addr+0] = (data>>16);
		*(UINT16 *) &ram[addr+2] = data&0xFFFF;
		return;
	}
//	printf("W32: %x @ %x\n", data, addr);
}

void CDSB2::SendCommand(UINT8 data)
{
	/*
	 * Commands are buffered in a FIFO. This probably does not actually exist
	 * on the real DSB but is necessary because the Z80 is not really synced
	 * up with the other CPUs and must process all commands it has received
	 * over the course of a frame at once.
	 */
	fifo[fifoIdxW++] = data;
	fifoIdxW &= 127;
	//printf("Write FIFO: %02X\n", data);
	
	// Have we caught up to the read pointer?
#ifdef DEBUG
	if (fifoIdxW == fifoIdxR)
		printf("DSB2 FIFO overflow!\n");
#endif
}
	

void CDSB2::RunFrame(INT16 *audioL, INT16 *audioR)
{
#ifdef SUPERMODEL_SOUND
	M68KSetContext(&M68K);
	
	// While FIFO not empty...
	while (fifoIdxR != fifoIdxW)
	{
		cmdLatch = fifo[fifoIdxR];	// retrieve next command byte
		fifoIdxR++;
		fifoIdxR &= 127;	
		
		M68KSetIRQ(1);	// indicate pending command
		//printf("68K INT fired\n");
		M68KRun(500);
	}	

	// Per-frame interrupt
	M68KSetIRQ(2);
	M68KRun(4000000/60);
	
	M68KGetContext(&M68K);
	
	// Decode MPEG for this frame
	INT16 *mpegFill[2] = { &mpegL[retainedSamples], &mpegR[retainedSamples] };
	MPEG_Decode(mpegFill, 32000/60-retainedSamples+2);
	retainedSamples = Resampler.UpSampleAndMix(audioL, audioR, mpegL, mpegR, 44100/60, 32000/60+2, 44100, 32000);

#endif
}

void CDSB2::Reset(void)
{
	MPEG_StopPlaying();
	Resampler.Reset();
	retainedSamples = 0;
	
	memset(fifo, 0, sizeof(fifo));
	fifoIdxW = fifoIdxR = 0;
	
	mpegState = ST_IDLE;
	playing = 0;
	
	M68KSetContext(&M68K);
	M68KReset();
	M68KGetContext(&M68K);
	
	DebugLog("DSB2 Reset\n");
}

// Offsets of memory regions within DSB2's pool
#define DSB2_OFFSET_RAM			0		// 128KB 68K RAM
#define DSB2_OFFSET_MPEG_LEFT	0x20000	// 1604 bytes (48 KHz max., 1/60th second, 2 extra = 2*(48000/60+2)) left MPEG buffer
#define DSB2_OFFSET_MPEG_RIGHT	0x20644	// 1604 bytes right MPEG buffer
#define DSB2_MEMORY_POOL_SIZE	(0x20000 + 0x644 + 0x644)

BOOL CDSB2::Init(const UINT8 *progROMPtr, const UINT8 *mpegROMPtr)
{
	float	memSizeMB = (float)DSB2_MEMORY_POOL_SIZE/(float)0x100000;
	
	// Receive ROM
	progROM = progROMPtr;
	mpegROM = mpegROMPtr;
	
	// Allocate memory pool
	memoryPool = new(std::nothrow) UINT8[DSB2_MEMORY_POOL_SIZE];
	if (NULL == memoryPool)
		return ErrorLog("Insufficient memory for DSB2 board (needs %1.1f MB).", memSizeMB);
	memset(memoryPool, 0, DSB2_MEMORY_POOL_SIZE);
	
	// Set up memory pointers
	ram = &memoryPool[DSB2_OFFSET_RAM];
	mpegL = (INT16 *) &memoryPool[DSB2_OFFSET_MPEG_LEFT];
	mpegR = (INT16 *) &memoryPool[DSB2_OFFSET_MPEG_RIGHT];
	
	// Initialize 68K CPU
	M68KSetContext(&M68K);
	M68KInit();
	M68KAttachBus(this);
	M68KSetIRQCallback(NULL);	// use default behavior (autovector, clear interrupt)
	M68KGetContext(&M68K);
	
	// MPEG decoder
	if (OKAY != MPEG_Init())
		return ErrorLog("Insufficient memory to initialize MPEG decoder.");
	retainedSamples = 0;
		
	return OKAY;
}

CDSB2::CDSB2(void)
{
	progROM = NULL;
	mpegROM = NULL;
	memoryPool = NULL;
	ram = NULL;
	mpegL = NULL;
	mpegR = NULL;

	DebugLog("Built DSB2 Board\n");
}

CDSB2::~CDSB2(void)
{	
	MPEG_Shutdown();
	
	if (memoryPool != NULL)
	{
		delete [] memoryPool;
		memoryPool = NULL;
	}
	
	progROM = NULL;
	mpegROM = NULL;
	ram = NULL;
	mpegL = NULL;
	mpegR = NULL;
	
	DebugLog("Destroyed DSB2 Board\n");
}