// GC DVD ADPCM decoding algorithm 
// NOTE: the ADPCM format used by the dvd drive is *NOT* the same as the ADPCM format used by the DSP
// they are similiar but the dvd adpcm format requires less multiplies
// previous public decoder by Shinji Chiba is innacurate
// -Crazynation

#include <stdio.h>

int predL1,predL2,predR1,predR2;
int new_pred;

init_predictors()
{
	predL1=0;
	predL2=0;
	predR1=0;
	predR2=0;
}
int decode(int predictor1,int predictor2,int nibble,int index)
{
	int i,j,k;
	short  scalex,scaley;

	int data1,data2;


	switch(index>>4)
	{
		case 0:
			scalex=0;
			scaley=0;
			break;
		case 1:
			scalex=0x3C;
			scaley=0;
			break;
		case 2:
			scalex=0x73;
			scaley=0xFFCC;
			break;
		case 3:
			scalex=0x62;
			scaley=0xFFC9;
			break;
		default:
			break;
	}
	i=predictor1*scalex;
	j=predictor2*scaley;
	i=i+j+0x20;
	i=i>>6;
	if(i<(int)0xFFE00000)
		i=0xFFE00000;
	else if(i>0x1FFFFF)
		i=0x1FFFFF;

	data1=i;

	j=(nibble&0xF)<<12;
	j=(short)j>>(index&0xF);

	i=j<<6;
	i=i+data1;
	
	data2=i;
	new_pred=data2;

	j=data2>>6;
	if(j<(int)0xFFFF8000)
		j=0x8000;
	else if(j>0x7FFF)
		j=0x7FFF;

	return j;



	

}
char wav_header[]={0x52,0x49,0x46,0x46,0x26,0x40,0x21,0x00,0x57,0x41,0x56,0x45,0x66,0x6D,0x74,0x20,
0x10,0x00,0x00,0x00,0x01,0x00,0x02,0x00,0x80,0xBB,0x00,0x00,0x00,0xEE,0x02,0x00,
0x04,0x00,0x10,0x00,0x64,0x61,0x74,0x61,0x00,0x40,0x21,0x00};

int main(int argc, char *argv[])
{
	int i,j,k;
	int count,length,offset;
	int nibble_high,nibble_low;
	FILE *fin,*fout;
	unsigned char buffer[32];
	short wav[128];
	

	if(argc<3)
	{
		printf("decode <adpcm in file> <output wav file>\n");
		exit(1);
	}
	fin=fopen(argv[1],"rb");
	if(fin==0)
	{
		printf("cant open input file %s\n",argv[1]);
		exit(1);
	}

	fout=fopen(argv[2],"wb");
	if(fout==0)
	{
		printf("cant open output file %s\n",argv[2]);
		exit(1);
	}
	fseek(fin,0,SEEK_END);
	length=ftell(fin);
	fseek(fin,0,SEEK_SET);

	init_predictors();
	offset=0;
	fwrite(wav_header,44,1,fout);
//-----------------------------------------------------------------------------
decode:
	i=fread(buffer,32,1,fin);
	if(i==0)
		exit(1);

	if(buffer[0]!=buffer[2])
	{
		printf("invalid ADPCM file\n");
		exit(1);
	}

	if(buffer[1]!=buffer[3])
	{
		printf("invalid ADPCM file\n");
		exit(1);
	}
	count=0;
	do{

		nibble_high=buffer[count+4]>>4;
		nibble_low=buffer[count+4]&0xF;

		k=decode(predL1,predL2,nibble_low,buffer[0]);
		wav[count*2]=k;

		predL2=predL1;
		predL1=new_pred;

		k=decode(predR1,predR2,nibble_high,buffer[1]);
		wav[(count*2)+1]=k;

		predR2=predR1;
		predR1=new_pred;

	count++;
	}while(count<28);

	fwrite(wav,28*4,1,fout);
	
	offset+=32;
	if(offset<length)
		goto decode;

	length=ftell(fout);
	fseek(fout,4,SEEK_SET);
	i=length-0x6;
	fwrite(&i,4,1,fout);
	fseek(fout,0x28,SEEK_SET);
	i=length-0x2C;
	fwrite(&i,4,1,fout);

	


}