/*  CDVol controls output volume of CD player */

#include <stdio.h>
#include <stdlib.h>
#include <dos.h>
#include <string.h>
#include <alloc.h>

#define MULTIPLEX_INT   0x2f
#define INIT_MP_INT     0x1500
#define CDREQ_MP_INT    0x1510

#define STAT_HAS_AN_ERROR 0x8000
#define STAT_BUSY         0x0200
#define STAT_DONE         0x0100

int CDRomLoaded,CDRomDrive;

#define WRITE_IOCTL_COMMAND  12
#define AUDIO_CHANNEL_CTRL   3

typedef struct {
   unsigned char ParamLength;
   unsigned char SubUnit;
   unsigned char CommandCode;
   unsigned int  Status;
   unsigned long Reserved1;
   unsigned long Reserved2;

   unsigned char Meddescr;
   unsigned long Transfaddr;
   unsigned int  Numbytes;
   unsigned int  Startsec;
   unsigned long volID;
} IOCTLStruc;


typedef struct {
	unsigned char CntrlCode;
	unsigned char InputChan0;
	unsigned char VolChan0;
	unsigned char InputChan1;
	unsigned char VolChan1;
	unsigned char InputChan2;
	unsigned char VolChan2;
	unsigned char InputChan3;
	unsigned char VolChan3;
} AudCtrlStruc;


AudCtrlStruc AudCtrlBlock;
IOCTLStruc IOCTLBlock;

int CDRomLoaded,CDRomDrive;


main(int argc, char *argv[])
{
	if (!CheckCD2F()){
		printf("MSCDEX NOT LOADED\n");
		exit(1);
	}

	if(argc > 2)
	   SetVol( (unsigned char)atoi(argv[1]),(unsigned char)atoi(argv[2]) );
	else
	{
		printf("CDVOL Sets audio output volume of CD-ROM\n");
		printf("usage: cdvol <leftvol 0-255> <rightvol 0-255>\n");
	}
}

CheckCD2F()
{
union REGS regs;

	regs.x.ax = INIT_MP_INT;
	int86(MULTIPLEX_INT,&regs,&regs);
	CDRomLoaded = regs.x.bx;
	CDRomDrive = regs.x.cx;
}

SetVol(unsigned char Leftvol, unsigned char Rightvol)
{
union REGS regs;
struct SREGS sregs;

	AudCtrlBlock.CntrlCode = AUDIO_CHANNEL_CTRL;

	AudCtrlBlock.InputChan0 = 0;
	AudCtrlBlock.VolChan0 = Leftvol;
	AudCtrlBlock.InputChan1 = 1;
	AudCtrlBlock.VolChan1 = Rightvol;
	AudCtrlBlock.InputChan2 = 2;
	AudCtrlBlock.VolChan2 = 0;
	AudCtrlBlock.InputChan3 = 3;
	AudCtrlBlock.VolChan3 = 0;

	IOCTLBlock.ParamLength = 13;
	IOCTLBlock.SubUnit     = 0;
	IOCTLBlock.CommandCode = WRITE_IOCTL_COMMAND;
	IOCTLBlock.Status      = 0;

	IOCTLBlock.Meddescr = 0;
	IOCTLBlock.Transfaddr =  (unsigned long)&AudCtrlBlock;
	IOCTLBlock.Numbytes = 9;
	IOCTLBlock.Startsec = 0;
	IOCTLBlock.volID = 0;

	regs.x.ax = CDREQ_MP_INT;
	regs.x.bx = FP_OFF(&IOCTLBlock);
	regs.x.cx = CDRomDrive;
	sregs.es  = FP_SEG(&IOCTLBlock);

	int86x(MULTIPLEX_INT,&regs,&regs,&sregs);

	return(IOCTLBlock.Status);
}
.