mplayer.c

SDL_mixer 是一个基于 SDL 的混音器

			else if (a->notedelay)
				a->notedelay--;
			break;
		case 0xe: /* pattern delay */
			if (pf->vbtick) break;
			if (!pf->patdly2) pf->patdly=nib+1; /* only once, when vbtick=0 */
			break;
		case 0xf: /* invert loop, not supported  */
			break;
	}
}

static void DoVibrato(void)
{
	UBYTE q;
	UWORD temp=0;

	q=(a->vibpos>>2)&0x1f;

	switch (a->wavecontrol&3) {
		case 0: /* sine */
			temp=VibratoTable[q];
			break;
		case 1: /* ramp down */
			q<<=3;
			if (a->vibpos<0) q=255-q;
			temp=q;
			break;
		case 2: /* square wave */
			temp=255;
			break;
		case 3: /* random wave */
			temp=getrandom(256);
			break;
	}

	temp*=a->vibdepth;
	temp>>=7;temp<<=2;

	if (a->vibpos>=0)
		a->period=a->tmpperiod+temp;
	else
		a->period=a->tmpperiod-temp;

	if (pf->vbtick) a->vibpos+=a->vibspd;
}

static void DoTremolo(void)
{
	UBYTE q;
	UWORD temp=0;

	q=(a->trmpos>>2)&0x1f;

	switch ((a->wavecontrol>>4)&3) {
		case 0: /* sine */
			temp=VibratoTable[q];
			break;
		case 1: /* ramp down */
			q<<=3;
			if (a->trmpos<0) q=255-q;
			temp=q;
			break;
		case 2: /* square wave */
			temp=255;
			break;
		case 3: /* random wave */
			temp=getrandom(256);
			break;
	}
	temp*=a->trmdepth;
	temp>>=6;

	if (a->trmpos>=0) {
		a->volume=a->tmpvolume+temp;
		if (a->volume>64) a->volume=64;
	} else {
		a->volume=a->tmpvolume-temp;
		if (a->volume<0) a->volume=0;
	}

	if (pf->vbtick) a->trmpos+=a->trmspd;
}

static void DoVolSlide(UBYTE dat)
{
	if (!pf->vbtick) return;

	if (dat&0xf) {
		a->tmpvolume-=(dat&0x0f);
		if (a->tmpvolume<0) a->tmpvolume=0;
	} else {
		a->tmpvolume+=(dat>>4);
		if (a->tmpvolume>64) a->tmpvolume=64;
	}
}

static void DoToneSlide(void)
{
	if (pf->vbtick) {
		int dist;

		/* We have to slide a->period towards a->wantedperiod, so compute the
		   difference between those two values */
		dist=a->period-a->wantedperiod;

		/* if they are equal or if portamentospeed is too big ...*/
		if ((!dist)||a->portspeed>abs(dist))
			/* ...make tmpperiod equal tperiod */
			a->tmpperiod=a->period=a->wantedperiod;
		else if (dist>0) {
			a->tmpperiod-=a->portspeed;
			a->period-=a->portspeed; /* dist>0, slide up */
		} else {
			a->tmpperiod+=a->portspeed;
			a->period+=a->portspeed; /* dist<0, slide down */
		}
	} else
		a->tmpperiod=a->period;
}

static void DoArpeggio(UBYTE dat)
{
	UBYTE note=a->note;

	if (dat) {
		switch (pf->vbtick%3) {
			case 1:
				note+=(dat>>4);  break;
			case 2:
				note+=(dat&0xf); break;
		}
		a->period=GetPeriod((UWORD)note<<1,a->speed);
		a->ownper=1;
	}
}

/*========== Scream Tracker effects */

static void DoS3MVolSlide(UBYTE inf)
{
	UBYTE lo, hi;

	explicitslides=1;

	if (inf) a->s3mvolslide=inf;
	else inf=a->s3mvolslide;

	lo=inf&0xf;
	hi=inf>>4;

	if (!lo) {
		if ((pf->vbtick)||(pf->flags&UF_S3MSLIDES)) a->tmpvolume+=hi;
	} else
	  if (!hi) {
		if ((pf->vbtick)||(pf->flags&UF_S3MSLIDES)) a->tmpvolume-=lo;
	} else
	  if (lo==0xf) {
		if (!pf->vbtick) a->tmpvolume+=(hi?hi:0xf);
	} else
	  if (hi==0xf) {
		if (!pf->vbtick) a->tmpvolume-=(lo?lo:0xf);
	} else
	  return;

	if (a->tmpvolume<0) a->tmpvolume=0;
	else if (a->tmpvolume>64) a->tmpvolume=64;
}

static void DoS3MSlideDn(UBYTE inf)
{
	UBYTE hi,lo;

	if (inf) a->slidespeed=inf;
	else inf=a->slidespeed;

	hi=inf>>4;
	lo=inf&0xf;

	if (hi==0xf) {
		if (!pf->vbtick) a->tmpperiod+=(UWORD)lo<<2;
	} else
	  if (hi==0xe) {
		if (!pf->vbtick) a->tmpperiod+=lo;
	} else {
		if (pf->vbtick) a->tmpperiod+=(UWORD)inf<<2;
	}
}

static void DoS3MSlideUp(UBYTE inf)
{
	UBYTE hi,lo;

	if (inf) a->slidespeed=inf;
	else inf=a->slidespeed;

	hi=inf>>4;
	lo=inf&0xf;

	if (hi==0xf) {
		if (!pf->vbtick) a->tmpperiod-=(UWORD)lo<<2;
	} else
	  if (hi==0xe) {
		if (!pf->vbtick) a->tmpperiod-=lo;
	} else {
		if (pf->vbtick) a->tmpperiod-=(UWORD)inf<<2;
	}
}

static void DoS3MTremor(UBYTE inf)
{
	UBYTE on,off;

	if (inf)
		a->s3mtronof=inf;
	else {
		inf=a->s3mtronof;
		if (!inf) return;
	}

	if (!pf->vbtick) return;

	on=(inf>>4)+1;
	off=(inf&0xf)+1;
	a->s3mtremor%=(on+off);
	a->volume=(a->s3mtremor<on)?a->tmpvolume:0;
	a->s3mtremor++;
}

static void DoS3MRetrig(UBYTE inf)
{
	if (inf) {
		a->s3mrtgslide=inf>>4;
		a->s3mrtgspeed=inf&0xf;
	}

	/* only retrigger if low nibble > 0 */
	if ( a->s3mrtgspeed>0) {
		if (!a->retrig) {
			/* when retrig counter reaches 0, reset counter and restart the
			   sample */
			if (a->kick!=KICK_NOTE) a->kick=KICK_KEYOFF;
			a->retrig=a->s3mrtgspeed;

			if ((pf->vbtick)||(pf->flags&UF_S3MSLIDES)) {
				switch (a->s3mrtgslide) {
					case 1:
					case 2:
					case 3:
					case 4:
					case 5:
						a->tmpvolume-=(1<<(a->s3mrtgslide-1));
						break;
					case 6:
						a->tmpvolume=(2*a->tmpvolume)/3;
						break;
					case 7:
						a->tmpvolume>>=1;
						break;
					case 9:
					case 0xa:
					case 0xb:
					case 0xc:
					case 0xd:
						a->tmpvolume+=(1<<(a->s3mrtgslide-9));
						break;
					case 0xe:
						a->tmpvolume=(3*a->tmpvolume)>>1;
						break;
					case 0xf:
						a->tmpvolume=a->tmpvolume<<1;
						break;
				}
				if (a->tmpvolume<0) a->tmpvolume=0;
				else if (a->tmpvolume>64) a->tmpvolume=64;
			}
		}
		a->retrig--; /* countdown  */
	}
}

static void DoS3MSpeed(UBYTE speed)
{
	if (pf->vbtick||pf->patdly2) return;

	if (speed>128) speed-=128;
	if (speed) {
		pf->sngspd=speed;
		pf->vbtick=0;
	}
}

static void DoS3MTempo(UBYTE tempo)
{
	if (pf->vbtick||pf->patdly2) return;

	pf->bpm=(tempo<32)?32:tempo;
}

static void DoS3MFineVibrato(void)
{
	UBYTE q;
	UWORD temp=0;

	q=(a->vibpos>>2)&0x1f;

	switch (a->wavecontrol&3) {
		case 0: /* sine */
			temp=VibratoTable[q];
			break;
		case 1: /* ramp down */
			q<<=3;
			if (a->vibpos<0) q=255-q;
			temp=q;
			break;
		case 2: /* square wave */
			temp=255;
			break;
		case 3: /* random */
			temp=getrandom(256);
			break;
	}

	temp*=a->vibdepth;
	temp>>=8;

	if (a->vibpos>=0)
		a->period=a->tmpperiod+temp;
	else
		a->period=a->tmpperiod-temp;

	a->vibpos+=a->vibspd;
}

static void DoS3MTremolo(void)
{
	UBYTE q;
	UWORD temp=0;

	q=(a->trmpos>>2)&0x1f;

	switch ((a->wavecontrol>>4)&3) {
		case 0: /* sine */
			temp=VibratoTable[q];
			break;
		case 1: /* ramp down */
			q<<=3;
			if (a->trmpos<0) q=255-q;
			temp=q;
			break;
		case 2: /* square wave */
			temp=255;
			break;
		case 3: /* random */
			temp=getrandom(256);
			break;
	}

	temp*=a->trmdepth;
	temp>>=7;

	if (a->trmpos>=0) {
		a->volume=a->tmpvolume+temp;
		if (a->volume>64) a->volume=64;
	} else {
		a->volume=a->tmpvolume-temp;
		if (a->volume<0) a->volume=0;
	}

	if (pf->vbtick) a->trmpos+=a->trmspd;
}

/*========== Fast Tracker effects */

static void DoXMVolSlide(UBYTE inf)
{
	UBYTE lo,hi;

	explicitslides=2;

	if (inf) a->s3mvolslide=inf;
	else inf=a->s3mvolslide;

	if (!pf->vbtick) return;

	lo=inf&0xf;
	hi=inf>>4;

	if (!hi) {
		a->tmpvolume-=lo;
		if (a->tmpvolume<0) a->tmpvolume=0;
	} else {
		a->tmpvolume+=hi;
		if (a->tmpvolume>64) a->tmpvolume=64;
	}
}

static void DoXMGlobalSlide(UBYTE inf)
{
	if (pf->vbtick) {
		if (inf) pf->globalslide=inf;
		else inf=pf->globalslide;
		if (inf & 0xf0) inf&=0xf0;
		pf->volume=pf->volume+((inf>>4)-(inf&0xf))*2;

		if (pf->volume<0) pf->volume=0;
		else if (pf->volume>128) pf->volume=128;
	}
}

static void DoXMPanSlide(UBYTE inf)
{
	UBYTE lo,hi;
	SWORD pan;

	if (inf) a->pansspd=inf;
	else inf=a->pansspd;

	if (!pf->vbtick) return;

	lo=inf&0xf;
	hi=inf>>4;

	/* slide right has absolute priority */
	if (hi) lo=0;

	pan=((a->panning==PAN_SURROUND)?PAN_CENTER:a->panning)+hi-lo;

	a->panning=(pan<PAN_LEFT)?PAN_LEFT:(pan>PAN_RIGHT?PAN_RIGHT:pan);
}

static void DoXMExtraFineSlideUp(UBYTE inf)
{
	if (!pf->vbtick) {
		a->period-=inf;
		a->tmpperiod-=inf;
	}
}

static void DoXMExtraFineSlideDown(UBYTE inf)
{
	if (!pf->vbtick) {
		a->period+=inf;
		a->tmpperiod+=inf;
	}
}

/*========== Impulse Tracker effects */

static void DoITChanVolSlide(UBYTE inf)
{
	UBYTE lo, hi;

	if (inf) a->chanvolslide=inf;
	inf=a->chanvolslide;

	lo=inf&0xf;
	hi=inf>>4;

	if (!hi)
		a->chanvol-=lo;
	else
	  if (!lo) {
		a->chanvol+=hi;
	} else
	  if (hi==0xf) {
		if (!pf->vbtick) a->chanvol-=lo;
	} else
	  if (lo==0xf) {
		if (!pf->vbtick) a->chanvol+=hi;
	}

	if (a->chanvol<0) a->chanvol=0;
	if (a->chanvol>64) a->chanvol=64;
}

static void DoITGlobalSlide(UBYTE inf)
{
	UBYTE lo,hi;

	if (inf) pf->globalslide=inf;
	inf=pf->globalslide;

	lo=inf&0xf;
	hi=inf>>4;

	if (!lo) {
		if (pf->vbtick) pf->volume+=hi;
	} else
	  if (!hi) {
		if (pf->vbtick) pf->volume-=lo;
	} else
	  if (lo==0xf) {
		if (!pf->vbtick) pf->volume+=hi;
	} else
	  if (hi==0xf) {
		if (!pf->vbtick) pf->volume-=lo;
	}

	if (pf->volume<0)   pf->volume=0;
	if (pf->volume>128) pf->volume=128;
}

static void DoITPanSlide(UBYTE inf)
{
	UBYTE lo,hi;
	SWORD pan;

	if (inf) a->pansspd=inf;
	else inf=a->pansspd;

	lo=inf&0xf;
	hi=inf>>4;

	pan=(a->panning==PAN_SURROUND)?PAN_CENTER:a->panning;

	if (!hi)
		pan+=lo<<2;
	else
	  if (!lo) {
		pan-=hi<<2;
	} else
	  if (hi==0xf) {
		if (!pf->vbtick) pan+=lo<<2;
	} else
	  if (lo==0xf) {
		if (!pf->vbtick) pan-=hi<<2;
	}
	a->panning=/*pf->panning[mp_channel]=*/
	  (pan<PAN_LEFT)?PAN_LEFT:(pan>PAN_RIGHT?PAN_RIGHT:pan);
}

static void DoITTempo(UBYTE tempo)
{
	SWORD temp=pf->bpm;

	if (pf->vbtick||pf->patdly2) return;

	if (tempo&0x10)
		temp+=(tempo&0x0f);
	else
		temp-=tempo;

	pf->bpm=(temp>255)?255:(temp<1?1:temp);
}

static void DoITVibrato(void)
{