void TrashAudio(void)
{
/* If SoundBlaster was initialized... */
if(SndRate)
{
/* Reset DSP */
WriteDSP(0xD3);
WriteDSP(0xD0);
/* Disable DMA */
outp(0x0A,SBDMA|0x04);
/* Disable IRQ */
outp(0x21,inp(0x21)|(1<<SBIRQ));
}
/* If SB interrupt vector changed, restore it */
if(IRQ5Old) { _dos_setvect(SBIRQ+8,IRQ5Old);IRQ5Old=0; }
/* If low memory was allocated for DMA, free it */
if(SBSegment) { FreeSegment(SBSegment);SBSegment=0; }
/* Sound trashed */
SndRate=0;
}
/*
================
StartSB
================
*/
void StartSB(void)
{
int i;
// version 4.xx startup code
if (dsp_version >= 4)
{
Con_Printf("Version 4 SB startup\n");
WriteDSP(0xd1); // turn on speaker
WriteDSP(0x41);
WriteDSP(shm->speed>>8);
WriteDSP(shm->speed&0xff);
WriteDSP(0xb6); // 16-bit output
WriteDSP(0x30); // stereo
WriteDSP((shm->samples-1) & 0xff); // # of samples - 1
WriteDSP((shm->samples-1) >> 8);
}
unsigned int InitAudio(unsigned int Rate,unsigned int Latency)
{
static const int PagePort[8] = { 0x87,0x83,0x81,0x82,-1,0x8B,0x89,0x8A };
int J,TotalBuf;
char *P;
/* Disable audio if was initialized */
TrashAudio();
/* If turning audio off, drop out */
if(!Rate) return(1);
/* If Rate is out of range, fall out */
if((Rate<8192)||(Rate>44100)) return(0);
/* Default values */
SBPort = 0x220;
SBIRQ = 7;
SBDMA = 1;
SBIRQBusy = 0;
SBWrite = 0;
SBRead = 0;
/* Get SoundBlaster Port#,IRQ#,DMA# */
if(P=getenv("BLASTER"))
while(*P)
switch(toupper(*P++))
{
case 'A': SBPort=strtol(P,0,16);break;
case 'D': SBDMA=strtol(P,0,16);break;
case 'I': SBIRQ=strtol(P,0,16);break;
}
/* IRQ# = 0,1,2,3,4,5,6,7, DMA# = 0,1,2,3 */
if((SBIRQ>7)||(SBDMA>3)) return(0);
/* Reset DSP */
outp(SBPort+0x06,0x01); /* Set the reset flag */
delay(100); /* Wait for 100ms */
outp(SBPort+0x06,0x00); /* Clear the reset flag */
/* Wait for READY status */
for(J=100;J&&!(inp(SBPort+0x0E)&0x80);J--);
if(!J) return(0);
for(J=100;J&&(ReadDSP()!=0xAA);J--);
if(!J) return(0);
/* Allocate low memory for DMA buffer */
TotalBuf=(Rate*Latency/1000/SND_BUFSIZE)*SND_BUFSIZE;
if(TotalBuf<SND_BUFSIZE) TotalBuf=SND_BUFSIZE;
SBBuffers=TotalBuf/SND_BUFSIZE;
SBSegment=GetSegment(TotalBuf*sizeof(sample)*2/16+4);
if(!SBSegment) return(0);
J=SBSegment*16;
SBBuffer=(unsigned char *)J;
if((J>>16)!=((J+TotalBuf-1)>>16)) SBBuffer+=TotalBuf;
memset(SBBuffer,0,TotalBuf*sizeof(sample));
/* Interrupts off */
_disable();
/* Save old interrupt vector */
IRQ5Old=(void (interrupt *)())_dos_getvect(SBIRQ+8);
/* Install new interrupt vector */
_dos_setvect(SBIRQ+8,IRQ5Handler);
/* Enable the SoundBlaster IRQ */
outp(0x21,inp(0x21)&~(1<<SBIRQ));
/* Disable DMA channel */
outp(0x0A,SBDMA|0x04);
/* Clear byte pointer flip-flop */
outp(0x0C,0x00);
/* Auto-initialized playback mode */
outp(0x0B,SBDMA|0x58);
/* Write DMA offset and transfer length */
J=SBDMA<<1;
outp(J,(int)SBBuffer&0xFF);
outp(J,((int)SBBuffer>>8)&0xFF);
outp(J+1,(TotalBuf-1)&0xFF);
outp(J+1,((TotalBuf-1)>>8)&0xFF);
/* Write DMA page */
outp(PagePort[SBDMA],((int)SBBuffer>>16)&0xFF);
/* Enable DMA channel */
outp(0x0A,SBDMA);
/* Enable interrupts */
_enable();
/* Set sampling rate */
WriteDSP(0x40);
WriteDSP((65536L-(256000000L/Rate))/256);
/* Set DMA transfer size */
WriteDSP(0x48);
WriteDSP((SND_BUFSIZE-1)&0xFF);
WriteDSP((SND_BUFSIZE-1)>>8);
/* Run auto-initialized 8bit DMA */
WriteDSP(0x90);
/* Speaker enabled */
WriteDSP(0xD1);
/* Done */
return(SndRate=Rate);
}