kolibrios-fun/programs/media/ac97snd/trunk/mp3dec/l1dec.c

#include "bstream.h"
#include "mp3dec.h"

extern MPEG_DECODE_OPTION m_option;

extern float m_sample[2304];
extern int m_nsb_limit;
extern SBT_PROC	m_sbt_proc;

extern int m_max_sb;
extern int m_stereo_sb;
extern int m_bat[4][16];
extern int m_ballo[64];
extern unsigned int m_samp_dispatch[66];
extern float m_c_value[64];
extern unsigned int m_sf_dispatch[66];
extern float m_sf_table[64];
extern float m_cs_factor[3][64];

float m_look_c_valueL1[18];
float *m_cs_factorL1 = m_cs_factor[0];
int m_nbatL1;

int m_bit_skip;

static const int look_joint[16] =
{				/* lookup stereo sb's by mode+ext */
   64, 64, 64, 64,		/* stereo */
   2 * 4, 2 * 8, 2 * 12, 2 * 16,	/* joint */
   64, 64, 64, 64,		/* dual */
   32, 32, 32, 32,		/* mono */
};

static const int bat_bit_masterL1[] =
{
	0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16
};

void unpack_baL1();
void unpack_sfL1();
void unpack_sampL1();

void L1decode_frame(MPEG_HEADER* h, byte* mpeg, byte* pcm)
{
	int crc_size;

	crc_size = (h->error_prot) ? 2 : 0;
	bitget_init(mpeg + 4 + crc_size);

	m_stereo_sb = look_joint[(h->mode << 2) + h->mode_ext];
	unpack_baL1();		/* unpack bit allocation */
	unpack_sfL1();		/* unpack scale factor */
	unpack_sampL1();	/* unpack samples */

	m_sbt_proc(m_sample, pcm, 12);
}

void unpack_baL1()
{
	int j;
	int nstereo;

	m_bit_skip = 0;
	nstereo = m_stereo_sb;

	for (j = 0; j < m_nbatL1; j++)
	{
		bitget_check(4);
		m_ballo[j] = m_samp_dispatch[j] = mac_bitget(4);
		if (j >= m_nsb_limit)
			m_bit_skip += bat_bit_masterL1[m_samp_dispatch[j]];
		m_c_value[j] = m_look_c_valueL1[m_samp_dispatch[j]];
		if (--nstereo < 0)
		{
			m_ballo[j + 1] = m_ballo[j];
			// flag as joint
			m_samp_dispatch[j] += 15;
			// flag for sf
			m_samp_dispatch[j + 1] = m_samp_dispatch[j];
			m_c_value[j + 1] = m_c_value[j];
			j++;
		}
	}
// terminate with bit skip and end
	m_samp_dispatch[m_nsb_limit] = 31;
	m_samp_dispatch[j] = 30;
}

// unpack scale factor
// combine dequant and scale factors
void unpack_sfL1()
{
	int i;

	for (i = 0; i < m_nbatL1; i++)
	{
		if (m_ballo[i])
		{
			bitget_check(6);
			m_cs_factorL1[i] = m_c_value[i] * m_sf_table[mac_bitget(6)];
		}
	}
}

// unpack samples
#define UNPACKL1_N(n) \
	s[k] = m_cs_factorL1[k]*(bitget(n)-((1 << n-1) -1));     \
	goto dispatch;
#define UNPACKL1J_N(n) \
	tmp        =  (bitget(n)-((1 << n-1) -1));             \
	s[k]       =  m_cs_factorL1[k]*tmp;                      \
	s[k+1]     =  m_cs_factorL1[k+1]*tmp;                    \
	k++;                                                   \
	goto dispatch;

void unpack_sampL1()
{
   int j, k;
   float *s;
   long tmp;

   s = m_sample;
   for (j = 0; j < 12; j++)
   {
      k = -1;
    dispatch:
	  switch (m_samp_dispatch[++k])
      {
	 case 0:
	    s[k] = 0.0F;
	    goto dispatch;
	 case 1:
	    UNPACKL1_N(2)	/*  3 levels */
	 case 2:
	    UNPACKL1_N(3)	/*  7 levels */
	 case 3:
	    UNPACKL1_N(4)	/* 15 levels */
	 case 4:
	    UNPACKL1_N(5)	/* 31 levels */
	 case 5:
	    UNPACKL1_N(6)	/* 63 levels */
	 case 6:
	    UNPACKL1_N(7)	/* 127 levels */
	 case 7:
	    UNPACKL1_N(8)	/* 255 levels */
	 case 8:
	    UNPACKL1_N(9)	/* 511 levels */
	 case 9:
	    UNPACKL1_N(10)	/* 1023 levels */
	 case 10:
	    UNPACKL1_N(11)	/* 2047 levels */
	 case 11:
	    UNPACKL1_N(12)	/* 4095 levels */
	 case 12:
	    UNPACKL1_N(13)	/* 8191 levels */
	 case 13:
	    UNPACKL1_N(14)	/* 16383 levels */
	 case 14:
	    UNPACKL1_N(15)	/* 32767 levels */
/* -- joint ---- */
	 case 15 + 0:
	    s[k + 1] = s[k] = 0.0F;
	    k++;		/* skip right chan dispatch */
	    goto dispatch;
/* -- joint ---- */
	 case 15 + 1:
	    UNPACKL1J_N(2)	/*  3 levels */
	 case 15 + 2:
	    UNPACKL1J_N(3)	/*  7 levels */
	 case 15 + 3:
	    UNPACKL1J_N(4)	/* 15 levels */
	 case 15 + 4:
	    UNPACKL1J_N(5)	/* 31 levels */
	 case 15 + 5:
	    UNPACKL1J_N(6)	/* 63 levels */
	 case 15 + 6:
	    UNPACKL1J_N(7)	/* 127 levels */
	 case 15 + 7:
	    UNPACKL1J_N(8)	/* 255 levels */
	 case 15 + 8:
	    UNPACKL1J_N(9)	/* 511 levels */
	 case 15 + 9:
	    UNPACKL1J_N(10)	/* 1023 levels */
	 case 15 + 10:
	    UNPACKL1J_N(11)	/* 2047 levels */
	 case 15 + 11:
	    UNPACKL1J_N(12)	/* 4095 levels */
	 case 15 + 12:
	    UNPACKL1J_N(13)	/* 8191 levels */
	 case 15 + 13:
	    UNPACKL1J_N(14)	/* 16383 levels */
	 case 15 + 14:
	    UNPACKL1J_N(15)	/* 32767 levels */

/* -- end of dispatch -- */
	 case 31:
	    bitget_skip(m_bit_skip);
	 case 30:
	    s += 64;
      }				/* end switch */
   }				/* end j loop */
}