/*
 * mkcf.c
 *
 * @author Karen Orton
 * @copyright Karen Orton 2012
 *
 * This program is part of an article in CQ-TV 235 entitled:
 *  "A Compact Flash player for 405 Lines"
 *
 * To compile this program enter:
 * gcc -D_FILE_OFFSET_BITS=64 -Wall -o mkcf mkcf.c
 *
 **/

#include <stdio.h>
#include <string.h>

#define	HRES	501
#define	VRES	376
#define	SECSZ	512
#define	FLDSZ	256
#define	AUDSZ	1620
#define	VIDSTT	7
#define	UCHAR	unsigned char
#define	ULONG	unsigned long

typedef struct {
    UCHAR leftlo;
    UCHAR lefthi;
    UCHAR rightlo;
    UCHAR righthi;
} AUDREC;

typedef struct {
    UCHAR *plobyte;
    UCHAR *phibyte;
    int hinibble;
} AUDVEC;

AUDREC audbuf[AUDSZ];
AUDVEC audvector[AUDSZ];
UCHAR vidbuf[VRES][HRES];
UCHAR outbuf[2*FLDSZ][SECSZ];
FILE *vidfd, *audfd, *cffd;
void genvector();
int doproc();

int main (int argc, char *argv[])
{
    int nframes;

    if(argc!=4)
    {
	fprintf(stderr, "\n\nusage: mkcf <videofile> <audiofile> <cffile>\n");
	return 1;
    }
    if(!(vidfd=fopen(argv[1], "r")))
    {
	fprintf(stderr, "\n\nmkcf: cannot open video file\n");
	return 1;
    }
    if(!(audfd=fopen(argv[2], "r")))
    {
	fclose(vidfd);
	fprintf(stderr, "\n\nmkcf: cannot open audio file\n");
	return 1;
    }
    if(!(cffd=fopen(argv[3], "w")))
    {
	fclose(vidfd);
	fclose(audfd);
	fprintf(stderr, "\n\nmkcf: cannot open CF file\n");
	return 1;
    }
    genvector();
    nframes=doproc();
    fclose(vidfd);
    fclose(audfd);
    fclose(cffd);
    fprintf(stderr, "\n\nmkcf: total %d frames processed\n", nframes);
    return 0;
}

void genvector()
{
    int i, j;
    AUDVEC *p;

    p=audvector;
    for(i=0; i<(VRES/2); i++)
    {
	p->plobyte=&outbuf[i][0];
	p->phibyte=&outbuf[i][4];
	p->hinibble=0;
	p++;
	p->plobyte=&outbuf[i][1];
	p->phibyte=&outbuf[i][4];
	p->hinibble=1;
	p++;
	p->plobyte=&outbuf[i][2];
	p->phibyte=&outbuf[i][5];
	p->hinibble=0;
	p++;
	p->plobyte=&outbuf[i][3];
	p->phibyte=&outbuf[i][5];
	p->hinibble=1;
	p++;
    }
    for(i=0; i<60; i++)
    {
	j=(VRES/2)-1-(2*i);
	p->plobyte=&outbuf[j-1][6];
	p->phibyte=&outbuf[j][6];
	p->hinibble=0;
	p++;
    }
    for(i=0; i<(VRES/2); i++)
    {
	j=i+FLDSZ;
	p->plobyte=&outbuf[j][0];
	p->phibyte=&outbuf[j][4];
	p->hinibble=0;
	p++;
	p->plobyte=&outbuf[j][1];
	p->phibyte=&outbuf[j][4];
	p->hinibble=1;
	p++;
	p->plobyte=&outbuf[j][2];
	p->phibyte=&outbuf[j][5];
	p->hinibble=0;
	p++;
	p->plobyte=&outbuf[j][3];
	p->phibyte=&outbuf[j][5];
	p->hinibble=1;
	p++;
    }
    for(i=0; i<56; i++)
    {
	j=FLDSZ+(VRES/2)-1-(2*i);
	p->plobyte=&outbuf[j-1][6];
	p->phibyte=&outbuf[j][6];
	p->hinibble=0;
	p++;
    }
}

int doproc()
{
    int i, j, nframes, audexhausted;
    AUDREC *p;
    AUDVEC *q;
    ULONG audsmp;

    memset(outbuf, 0, sizeof(outbuf));
    nframes=0;
    audexhausted=0;
    while(fread(vidbuf, HRES, VRES, vidfd)==VRES)
    {
	for(i=0; i<(VRES/2); i++)
	{
	    j=i<<1;
	    memcpy(&outbuf[i][VIDSTT],       vidbuf[j], HRES);
	    memcpy(&outbuf[i+FLDSZ][VIDSTT], vidbuf[j+1], HRES);
	}
	if((i=fread(audbuf, sizeof(AUDREC), AUDSZ, audfd))<AUDSZ)
	{
	    memset(audbuf+i, 0, (AUDSZ-i)*sizeof(AUDREC));
	    if(!audexhausted)
		fprintf(stderr, "\n\nmkcf: audio file exhausted - padding with silence\n");
	    audexhausted=1;
	}
	p=audbuf;
	q=audvector;
	for(i=0; i<AUDSZ; i++)
	{
	    audsmp=((ULONG)p->leftlo)+(((ULONG)p->lefthi)<<8)+((ULONG)p->rightlo)+(((ULONG)p->righthi)<<8);
	    audsmp^=(((ULONG)(p->lefthi^p->righthi))<<9)&0x10000;
	    *(q->plobyte)=(UCHAR)(audsmp>>5);
	    if(q->hinibble)
		*(q->phibyte)|=(UCHAR)((audsmp>>9)&0xf0);
	    else
		*(q->phibyte)=(UCHAR)((audsmp>>13)&0x0f);
	    p++;
	    q++;
	}
	fwrite(outbuf, SECSZ, 2*FLDSZ, cffd);
	nframes++;
	if((nframes%100)==0)
	    fprintf(stderr, "mkcf: %d frames processed\n", nframes);
    }
    return nframes;
}