cd.c

来自「ESS3890+SL原代码（1*16内存）」· C语言 代码 · 共 160 行

/* Copyright 1996, ESS Technology, Inc.					*/
/* SCCSID @(#)cd.c	4.6 11/04/03 */

/*
 * $Log$
 */
#include "vcxi.h"
#include "const.h"
#include "constvar.h"
#include "util.h"
#include "cd.h"

#ifdef PLAY20
/************************************************************************
 * Utility routine to adjust the CD time.				*
 ************************************************************************/
/*------------------------------------------------------------------------
  Description:
      return (time1 - time0) / 9.
      This function is used for track digest.  
------------------------------------------------------------------------*/

unsigned int deltaCDtime(unsigned int time1, unsigned int time0)
{
    int delta;
    int mmss00 = 0xffff00;

    
    delta = msf2sectors(time1) - msf2sectors(time0);
    delta /= 9;

    mmss00 &= logical2physical(delta); /* remove frames info */
    
    return(mmss00);
}
#endif /* PLAY20 */

/* 
 * Translate sector number into mm:ss:ff. Since division and mod are
 * rather expensive in MIPS-X, we'll use multiplication instead.
 *
 * Input:	num is the sector number
 * Return:	MMSSFF in CD time format where each of MM/SS/FF is a BCD
 */
int logical2physical(int num)
{
    int min=0, sec=0;
    

    /* limit to max. CD time: 99:59:74 */
    if (num > 449999) return (xMAX_CDTIME);

    /* get minutes */
    while (num >= 4500) {
	num -= 4500;
	min++;
    }
    
    /* get seconds */
    while (num >= 75) {
	num -= 75;
	sec++;
    }
    /* "num" has frames now */

    return ( (hex2bcd[min]<<16) | (hex2bcd[sec]<<8) | hex2bcd[num] );
}

/*
 * This routine operates on 2 CD-format time and return the result.
 * CD-format time is MMSSFF where each of MM/SS/FF is in BCD
 *
 * Inputs:
 *	time:		CD format time to be adjusted
 *	amount:		Amount to adjust with in CD format time
 *	direction:  	1: to add the two numbers together
 *		    other: time - amount
 *
 * Return:
 *	result:		in CD format time
 *
 * I assume the sum and difference are all within CD range. I.e. this
 * routine is defined to do fine grain adjustment arount a given time.
 */
unsigned int adjCDtime(uint time, uint amount, int direction)
{
    int new_sector;
    

    new_sector = msf2sectors(time);
    if (direction > 0) {
	new_sector += msf2sectors(amount);
	/* check for overflow..
	 * limit to max. CD time: 99:59:74
	 */
	if (new_sector > 449999) return (xMAX_CDTIME);
    } else {
	new_sector -= msf2sectors(amount);
	/* check for underflow */
	if (new_sector < 0) return (0);
    }
    
    return (logical2physical(new_sector));
}


/* 
 * Translate mm:ss:ff into sector number.
 *
 * Input:	MMSSFF in CD time format where each of MM/SS/FF is a BCD
 * Return:	num is the sector number
 */
int msf2sectors(unsigned int msf)
{
    int time_in_frames;

    /* Translate BCD time to frames..75 frames/sec */
    time_in_frames = (int)bcd2hex[msf & 0xff]; /* frames */
    msf >>= 8;
    time_in_frames += (int)(75 * bcd2hex[msf & 0xff]); /* seconds */
    msf >>= 8;
    time_in_frames += (int)(4500 * bcd2hex[msf & 0xff]); /* minutes */    

    return (time_in_frames);
}


/*
 * Sanity check for valid BCD mm:ss:ff values in time_msf. 
 *
 * input: 
 *	time_msf - time in BCD mm:ss:ff format.
 *	           (examples of "bad" mm, ss, ff, are: 0xA7, 0x2B)
 *
 * output: 
 *	non-zero - invalid "time_msf", i.e. non-BCD msf.
 *	zero - valid BCD msf format.
 * 
 * NOTE: This function does not check if the time value is "correct".
 * It only determines if the values for mm, ss and ff are valid BCD
 * numbers. For severely scratched discs, we have found that
 * values like: 0xa02544, 0x092b32, were coming in for "currCDtime".
 */
int CDtime_check(uint time_msf) 
{
#ifdef CDTIME_FILTER
    unsigned int msf0,msf1;	
    
    msf0=time_msf;
    msf1=(hex2bcd[bcd2hex[(msf0>>16)&0xff]])<<16;
    msf1|=(hex2bcd[bcd2hex[(msf0>>8)&0xff]])<<8;
    msf1|=hex2bcd[bcd2hex[msf0&0xff]];

    return (msf0^msf1); /* 0: good, non-zero: bad */
#else

    return (0); /* "good"..no checking */
#endif
}