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/*
*
* uncouple.c Copyright (C) Aaron Holtzman - May 1999
*
* This file is part of libmpeg3
*
* libmpeg3 is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* libmpeg3 is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU Make; see the file COPYING. If not, write to
* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
*
*/
#include "../bitstream.h"
#include "mpeg3audio.h"
static unsigned char mpeg3_first_bit_lut[256] =
{
0, 8, 7, 7, 6, 6, 6, 6, 5, 5, 5, 5, 5, 5, 5, 5,
4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
};
/* Converts an unsigned exponent in the range of 0-24 and a 16 bit mantissa
* to an IEEE single precision floating point value */
static inline void mpeg3audio_ac3_convert_to_float(unsigned short exp,
unsigned short mantissa,
unsigned MPEG3_INT32 *dest)
{
int num;
short exponent;
int i;
/* If the mantissa is zero we can simply return zero */
if(mantissa == 0)
{
*dest = 0;
return;
}
/* Exponent is offset by 127 in IEEE format minus the shift to
* align the mantissa to 1.f (subtracted in the final result) */
exponent = 127 - exp;
/* Take care of the one asymmetric negative number */
if(mantissa == 0x8000)
mantissa++;
/* Extract the sign bit, invert the mantissa if it's negative, and
shift out the sign bit */
if(mantissa & 0x8000)
{
mantissa *= -1;
num = 0x80000000 + (exponent << 23);
}
else
{
mantissa *= 1;
num = exponent << 23;
}
/* Find the index of the most significant one bit */
i = mpeg3_first_bit_lut[mantissa >> 8];
if(i == 0)
i = mpeg3_first_bit_lut[mantissa & 0xff] + 8;
*dest = num - (i << 23) + (mantissa << (7 + i));
return;
}
int mpeg3audio_ac3_uncouple(mpeg3audio_t *audio,
mpeg3_ac3bsi_t *bsi,
mpeg3_ac3audblk_t *audblk,
mpeg3_stream_coeffs_t *coeffs)
{
int i, j;
for(i = 0; i < bsi->nfchans; i++)
{
for(j = 0; j < audblk->endmant[i]; j++)
mpeg3audio_ac3_convert_to_float(audblk->fbw_exp[i][j],
audblk->chmant[i][j],
(unsigned MPEG3_INT32*)&coeffs->fbw[i][j]);
}
if(audblk->cplinu)
{
for(i = 0; i < bsi->nfchans; i++)
{
if(audblk->chincpl[i])
{
mpeg3audio_ac3_uncouple_channel(audio,
coeffs,
audblk,
i);
}
}
}
if(bsi->lfeon)
{
/* There are always 7 mantissas for lfe */
for(j = 0; j < 7 ; j++)
mpeg3audio_ac3_convert_to_float(audblk->lfe_exp[j],
audblk->lfemant[j],
(unsigned MPEG3_INT32*)&coeffs->lfe[j]);
}
return 0;
}
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