mpeg3dec.c

mp3解码源代码

						sfb--;
						index = band_l[sfb] - 1;
					}
					mps->sfb_nul_l[ch] = sfb;
				}
			}

		}
	} else {
		// Long Blocks
		sfb = 21;
		while ((band_l[sfb] >= nul_begin) && (sfb >= 0))
			sfb--;
		mps->sfb_nul_l[ch] = sfb + 1;
		mps->sfb_nul_s[0][ch] = mps->sfb_nul_s[1][ch] =
			mps->sfb_nul_s[2][ch] = 0;
		mps->sfb_nul_s_top[ch] = 0;
	}
	if ((mps->header.mode == MPA_MODE_JOINT_STEREO) && (ch > 0)) {
		mps->imdct_max[1] = mps->imdct_max[0];
	} else {
		mps->imdct_max[ch] = 1 + (INT16) (nul_begin +
			(MPA_SSLIMIT - 1)) / MPA_SSLIMIT;
		if (mps->imdct_max[ch] > mps->sb_max)
			mps->imdct_max[ch] = mps->sb_max;
		if (mps->imdct_max[ch] > MPA_SBLIMIT)
			mps->imdct_max[ch] = MPA_SBLIMIT;
	}

	return(MPEGDEC_ERR_NONE);
}

/****************************************************************************/

static const INT16 pretab[22] = {
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 3, 3, 3, 2, 0
};

#ifdef MPEGAUD_INT
#define POW_TYPE	INT32
#define POW_2_BITS	13
#define POW_4_3_BITS	MPEGTAB_POW_BITS	// 18 usually
#else
#define POW_TYPE REAL
#endif

/****************************************************************************/

/*
 *	Dequantize the current samples of MPEG III stream
 *	Return 0 if Ok
 */

static INT16 MPEG3_dequantize_samples(MPA_STREAM *mps, INT16 *is,
	MPEGAUD_FRACT_TYPE *xr, INT16 gr, INT16 ch)
{
	static BOOL init = FALSE;
#ifdef MPEGAUD_INT
	// Init for POW_2_BITS = 13 (rounded to lowest)
	static POW_TYPE pow_2[4] = { 8192, 4870, 5792, 6888 };
	INT16 sh, xrk_sh;
	POW_TYPE *pow4;
#ifdef SPLIT_TABLE
	static POW_TYPE *pow_4_3_t[4];
#endif
#else
	static POW_TYPE *pows = NULL;
	static POW_TYPE *pow_2;
#define POW_2_MAX   434		// 178+255+1
#endif

	static POW_TYPE *pow_4_3 = NULL;
#define POW_4_3_MAX 8192

	MPA_GRANULE_INFO *gi = &mps->side_info.ch[ch].gr[gr];
	MPA_SCALE_FAC3 *scf = &mps->scale_fac3[ch];
	const INT16 *band_l = sfBandIndex_l[mps->header.ID][mps->header.sampling_frequency];
	const INT16 *band_s = sfBandIndex_s[mps->header.ID][mps->header.sampling_frequency];
	INT16 sfb;
	INT16 k, window;
	INT16 gk;
	MPEGAUD_FRACT_TYPE *xrp;
	INT16 *isp;
	POW_TYPE xrk;

#ifdef MPEGAUD_INT
#define DEQ(sa) \
	if (sa >= 0) { \
		sh = xrk_sh + (MPT_pow_4_3[sa] & 0xFF); \
		if (sh < 32) \
			*xrp = pow4[sa] >> sh; \
		else \
			*xrp = 0; \
	} else { \
		sh = xrk_sh + (MPT_pow_4_3[-(sa)] & 0xFF); \
		if (sh < 32) \
			*xrp = -(pow4[-(sa)] >> sh); \
		else \
			*xrp = 0; \
	}
#else
#define DEQ(sa) \
	if (sa >= 0) { \
		*xrp = xrk * pow_4_3[sa]; \
	} else { \
		*xrp = -xrk * pow_4_3[-(sa)]; \
	}
#endif

	if (!init) {
		register INT16 i;
#ifdef MPEGAUD_INT
		// Pre calc 2^(1/4 * k) * 2^POW2_BITS
		// ie: Keep POW_2_BITS as mantissa
#ifdef SPLIT_TABLE
		pow_4_3_t[0] = (POW_TYPE *) malloc((POW_4_3_MAX * sizeof(POW_TYPE)));
		if (!pow_4_3_t[0])
			return(MPEGDEC_ERR_MEM);
		pow_4_3_t[1] = (POW_TYPE *) malloc((POW_4_3_MAX * sizeof(POW_TYPE)));
		if (!pow_4_3_t[1])
			return(MPEGDEC_ERR_MEM);
		pow_4_3_t[2] = (POW_TYPE *) malloc((POW_4_3_MAX * sizeof(POW_TYPE)));
		if (!pow_4_3_t[2])
			return(MPEGDEC_ERR_MEM);
		pow_4_3_t[3] = (POW_TYPE *) malloc((POW_4_3_MAX * sizeof(POW_TYPE)));
		if (!pow_4_3_t[3])
			return(MPEGDEC_ERR_MEM);

		for (k = 0; k < 4; k++) {
			pow4 = pow_4_3_t[k];
			xrk = pow_2[k];
			for (i = 0; i < POW_4_3_MAX; i++)
				pow4[i] = xrk * (MPT_pow_4_3[i] >> 8);
		}
#else

		pow_4_3 = (POW_TYPE *) malloc((POW_4_3_MAX * 4 * sizeof(POW_TYPE)) - 1);
		if (!pow_4_3)
			return(MPEGDEC_ERR_MEM);
		for (k = 0; k < 4; k++) {
			pow4 = &pow_4_3[k * POW_4_3_MAX];
			xrk = pow_2[k];
			for (i = 0; i < POW_4_3_MAX; i++)
				pow4[i] = xrk * (MPT_pow_4_3[i] >> 8);
		}
#endif

#else
		pows = (POW_TYPE *) malloc((POW_2_MAX + POW_4_3_MAX) *
			sizeof(POW_TYPE));
		if (!pows)
			return(MPEGDEC_ERR_MEM);
		pow_2 = pows;
		pow_4_3 = pow_2 + POW_2_MAX;
		for (i = 0; i < POW_2_MAX; i++)
			pow_2[i] = pow(2.0, 0.25 * (double) (i - 388));
		for (i = 0; i < POW_4_3_MAX; i++)
			pow_4_3[i] = pow((double) i, 4.0 / 3.0);
#endif
		init = TRUE;
	}

	isp = is;
	xrp = xr;
	gk = gi->global_gain + 178;

	if ((gi->window_switching_flag) && (gi->block_type == 2)) {
		// Short blocks
		sfb = 0;
		if (gi->mixed_block_flag) {
			// First 2 subbands are long blocks
			while (band_l[sfb + 1] < 36) {
				INT16 i = band_l[sfb + 1] - band_l[sfb];
				k = scf->l[sfb];
				if (gi->preflag)
					k += pretab[sfb];
				if (gi->scalefac_scale)
					k <<= 1;
#ifdef MPEGAUD_INT
#ifdef SPLIT_TABLE
				pow4 = pow_4_3_t[((gk - (k << 1)) & 3)];
#else
				pow4 = &pow_4_3[((gk - (k << 1)) & 3) * POW_4_3_MAX];
#endif
				xrk_sh = POW_2_BITS - MPEGAUD_FRACT_BITS -
					((gk - (k << 1) - 388 + 3) >> 2);
#else
				xrk = pow_2[gk - (k << 1)];
#endif
				while (i--) {
					if (*isp) {
						DEQ(*isp);
						xrp++;
					} else {
						*xrp++ = (MPEGAUD_FRACT_TYPE) 0;
					}
					isp++;
				}
				sfb++;
			}
			sfb = 3;
			// Start of short blocks now
		}
		// Short part
		while (sfb < mps->sfb_nul_s_top[ch]) {
			for (window = 0; window < 3; window++) {
				INT16 i = band_s[sfb + 1] - band_s[sfb];
				k = scf->s[window][sfb];
				if (gi->scalefac_scale)
					k <<= 1;
				k += (gi->subblock_gain[window] << 2);
#ifdef MPEGAUD_INT
#ifdef SPLIT_TABLE
				pow4 = pow_4_3_t[((gk - (k << 1)) & 3)];
#else
				pow4 = &pow_4_3[((gk - (k << 1)) & 3) * POW_4_3_MAX];
#endif
				xrk_sh = POW_2_BITS - MPEGAUD_FRACT_BITS -
					((gk - (k << 1) - 388 + 3) >> 2);
#else
				xrk = pow_2[gk - (k << 1)];
#endif
				while (i--) {
					if (*isp) {
						DEQ(*isp);
						xrp++;
					} else {
						*xrp++ = (MPEGAUD_FRACT_TYPE) 0;
					}
					isp++;
				}
			}
			sfb++;
		}

		{
			register INT16 i =
				MPA_GRANULE_SIZE - (band_s[sfb] * 3);
			if (i > 0) {
				while (i--)
					*xrp++ = (MPEGAUD_FRACT_TYPE) 0;
			}
		}
	} else {
		// Long blocks
		for (sfb = 0; sfb < mps->sfb_nul_l[ch]; sfb++) {
			register INT16 i = band_l[sfb + 1] - band_l[sfb];
			k = scf->l[sfb];
			if (gi->preflag)
				k += pretab[sfb];
			if (gi->scalefac_scale)
				k <<= 1;
#ifdef MPEGAUD_INT
			// #7 Begin
//         xrk = pow_2[ (gk - (k<<1)) & 3 ];
#ifdef SPLIT_TABLE
			pow4 = pow_4_3_t[((gk - (k << 1)) & 3)];
#else
			pow4 = &pow_4_3[((gk -
					  (k << 1)) & 3) * POW_4_3_MAX];
#endif
			xrk_sh = POW_2_BITS - MPEGAUD_FRACT_BITS -
				((gk - (k << 1) - 388 + 3) >> 2);
			// #7 End
#else
			xrk = pow_2[gk - (k << 1)];
#endif
			while (i--) {
				if (*isp) {
					DEQ(*isp);
					xrp++;
				} else {
					*xrp++ = (MPEGAUD_FRACT_TYPE) 0;
				}
				isp++;
			}
		}

		{
			INT16 i = MPA_GRANULE_SIZE - band_l[sfb];
			if (i > 0) {
				while (i--)
					*xrp++ = (MPEGAUD_FRACT_TYPE) 0;
			}
		}
	}

	return(MPEGDEC_ERR_NONE);
}

/****************************************************************************/

#define MAX_POS1	7
#define MAX_POS2	32

#ifdef MPEGAUD_INT
#define ST_TYPE		INT16
#define ST_BITS		14
#define ST_MULT(a, b)	(((ST_TYPE)(a) * (ST_TYPE)(b))>>ST_BITS)

/*
 *	 Precalc tables for ST_BITS = 14
 */
static const ST_TYPE tan_pos0[MAX_POS1] = {
	0x0000, 0x0D86, 0x176C, 0x2000, 0x2893, 0x3279, 0x4000
};

static const ST_TYPE tan_pos1[MAX_POS1] = {
	0x4000, 0x3279, 0x2893, 0x2000, 0x176C, 0x0D86, 0x0000
};

static const ST_TYPE pow_io0[2][MAX_POS2] = {
	0x4000, 0x35D1, 0x4000, 0x2D41, 0x4000, 0x260D, 0x4000, 0x2000,
	0x4000, 0x1AE8, 0x4000, 0x16A0, 0x4000, 0x1306, 0x4000, 0x1000,
	0x4000, 0x0D74, 0x4000, 0x0B50, 0x4000, 0x0983, 0x4000, 0x0800,
	0x4000, 0x06BA, 0x4000, 0x05A8, 0x4000, 0x04C1, 0x4000, 0x0400,
	0x4000, 0x2D41, 0x4000, 0x2000, 0x4000, 0x16A0, 0x4000, 0x1000,
	0x4000, 0x0B50, 0x4000, 0x0800, 0x4000, 0x05A8, 0x4000, 0x0400,
	0x4000, 0x02D4, 0x4000, 0x0200, 0x4000, 0x016A, 0x4000, 0x0100,
	0x4000, 0x00B5, 0x4000, 0x0080, 0x4000, 0x005A, 0x4000, 0x0040
};

static const ST_TYPE pow_io1[2][MAX_POS2] = {
	0x4000, 0x4000, 0x35D1, 0x4000, 0x2D41, 0x4000, 0x260D, 0x4000,
	0x2000, 0x4000, 0x1AE8, 0x4000, 0x16A0, 0x4000, 0x1306, 0x4000,
	0x1000, 0x4000, 0x0D74, 0x4000, 0x0B50, 0x4000, 0x0983, 0x4000,
	0x0800, 0x4000, 0x06BA, 0x4000, 0x05A8, 0x4000, 0x04C1, 0x4000,
	0x4000, 0x4000, 0x2D41, 0x4000, 0x2000, 0x4000, 0x16A0, 0x4000,
	0x1000, 0x4000, 0x0B50, 0x4000, 0x0800, 0x4000, 0x05A8, 0x4000,
	0x0400, 0x4000, 0x02D4, 0x4000, 0x0200, 0x4000, 0x016A, 0x4000,
	0x0100, 0x4000, 0x00B5, 0x4000, 0x0080, 0x4000, 0x005A, 0x4000
};

#else

#define ST_TYPE		REAL
#define ST_MULT(a, b)	((a) * (b))

static const ST_TYPE tan_pos0[MAX_POS1] = {
	0.0, 0.211324841, 0.366025358, 0.5, 0.633974493, 0.788674951, 1.0
};

static const ST_TYPE tan_pos1[MAX_POS1] = {
	1.0, 0.788674951, 0.633974493, 0.5, 0.366025358, 0.211324841, 0.0
};

static const ST_TYPE pow_io0[2][MAX_POS2] = {
	1.0, 0.840896368, 1.0, 0.707106769,
	1.0, 0.594603539, 1.0, 0.500000000,
	1.0, 0.420448184, 1.0, 0.353553385,
	1.0, 0.297301769, 1.0, 0.250000000,
	1.0, 0.210224092, 1.0, 0.176776692,
	1.0, 0.148650885, 1.0, 0.125000000,
	1.0, 0.105112046, 1.0, 0.088388346,
	1.0, 0.074325442, 1.0, 0.062500000,
	1.0, 0.707106769, 1.0, 0.500000000,
	1.0, 0.353553385, 1.0, 0.250000000,
	1.0, 0.176776692, 1.0, 0.125000000,
	1.0, 0.088388346, 1.0, 0.062500000,
	1.0, 0.044194173, 1.0, 0.031250000,
	1.0, 0.022097087, 1.0, 0.015625000,
	1.0, 0.011048543, 1.0, 0.007812500,
	1.0, 0.005524272, 1.0, 0.003906250,
};

static const ST_TYPE pow_io1[2][MAX_POS2] = {
	1.0, 1.0, 0.840896368, 1.0,
	0.707106769, 1.0, 0.594603539, 1.0,
	0.500000000, 1.0, 0.420448184, 1.0,
	 0.353553385, 1.0, 0.297301769, 1.0,
	0.250000000, 1.0, 0.210224092, 1.0,
	0.176776692, 1.0, 0.148650885, 1.0,
	0.125000000, 1.0, 0.105112046, 1.0,
	0.088388346, 1.0, 0.074325442, 1.0,
	1.0, 1.0, 0.707106769, 1.0,
	0.500000000, 1.0, 0.353553385, 1.0,
	0.250000000, 1.0, 0.176776692, 1.0,
	0.125000000, 1.0, 0.088388346, 1.0,
	0.062500000, 1.0, 0.044194173, 1.0,
	0.031250000, 1.0, 0.022097087, 1.0,
	0.015625000, 1.0, 0.011048543, 1.0,
	 0.007812500, 1.0, 0.005524272, 1.0,
};

#endif

/****************************************************************************/

/*
 *	Decode the stereo data of a granule
 *	Return 0 if Ok
 */

static int MPEG3_stereo(MPA_STREAM *mps, MPEGAUD_FRACT_TYPE *xr, INT16 gr)
{
	static int init = 0;
	static FILE *fquant;

	const INT16 *band_l = sfBandIndex_l[mps->header.ID][mps->header.sampling_frequency];
	const INT16 *band_s = sfBandIndex_s[mps->header.ID][mps->header.sampling_frequency];
	MPA_SCALE_FAC3 *sf = &mps->scale_fac3[1];
	MPA_GRANULE_INFO *gi = &mps->side_info.ch[0].gr[gr];

	BOOL ms_stereo = (mps->header.mode == MPA_MODE_JOINT_STEREO) &&
		(mps->header.mode_extension & 0x2);
	BOOL i_stereo = (mps->header.mode == MPA_MODE_JOINT_STEREO) &&
		(mps->header.mode_extension & 0x1);

	INT16 sfb;
	INT16 i, j, sb, sbmax;
	BOOL lsf = (mps->header.ID == MPA_ID_2);

#define MAX_POS1	7
#define MAX_POS2	32

	const ST_TYPE *pow_iok0;
	const ST_TYPE *pow_iok1;
	MPEGAUD_FRACT_TYPE *xrp0, *xrp1, temp;
#ifdef MPEGAUD_INT
	ST_TYPE sq2 = 0.7071067812 * (1 << ST_BITS);
#else
	REAL sq2 = 0.7071067812;
#endif

	if (lsf) {
		if (gi->scalefac_compress & 1) {
			pow_iok0 = pow_io0[1];
			pow_iok1 = pow_io1[1];
		} else {
			pow_iok0 = pow_io0[0];
			pow_iok1 = pow_io1[0];
		}
	} else {
		pow_iok0 = tan_pos0;
		pow_iok1 = tan_pos1;
	}

	if ((mps->stereo) && i_stereo) {
		ST_TYPE k0, k1;
		INT16 sfb_top;
		INT16 max_sfb = 0;
		INT16 ispos;
		INT16 is_illegal;

		if (gi->window_switching_flag && (gi->block_type == 2)) {
			sbmax = mps->sfb_nul_s_top[0];
			if (sbmax < mps->sfb_nul_s_top[1])
				sbmax = mps->sfb_nul_s_top[1];
			sbmax++;
			if (sbmax > 13)
				sbmax = 13;

			for (j = 0; j < 3; j++) {
				sfb_top = mps->sfb_nul_s[j][1];
				if ((gi->mixed_block_flag) && (sfb_top < 3))
					sfb_top = 3;	// Normaly not !!!
				if (sfb_top > max_sfb)
					max_sfb = sfb_top;

				is_illegal = (lsf) ? mps->is_max_s[j][0] : 7;
				// Implicit: ispos == is_illegal here (not nul bands)
				ispos = is_illegal;
				for (sfb = 0; sfb < sfb_top; sfb++) {
					sb = band_s[sfb + 1] - band_s[sfb];

					i = 3 * band_s[sfb] + j * sb;
					xrp0 = &xr[i];
					xrp1 = &xr[MPA_GRANULE_SIZE + i];

					if (ms_stereo)
						while (sb--) {
							temp = ST_MULT((*xrp0 + *xrp1), sq2);
							*xrp1 = ST_MULT((*xrp0 - *xrp1), sq2);
							*xrp0++ = temp;
							xrp1++;
						}
				}
				while (sfb < sbmax) {
					// #9: sbmax instead of 13
					sb = band_s[sfb + 1] - band_s[sfb];

					i = 3 * band_s[sfb] + j * sb;
					xrp0 = &xr[i];
					xrp1 = &xr[MPA_GRANULE_SIZE + i];

					if (sfb < 12) {
						// keep previous ispos for
						// last sfb
						ispos = sf->s[j][sfb];
						is_illegal = (lsf) ? mps->
							is_max_s[j][sfb] : 7;
					}
					if (ispos == is_illegal) {
						if (ms_stereo)
							while (sb--) {
								temp = ST_MULT((*xrp0 + *xrp1), sq2);
								*xrp1 = ST_MULT((*xrp0 - *xrp1), sq2);
								*xrp0++ =
									temp;
								xrp1++;
							}
					} else {
						// ispos != is_illegal
						k0 = pow_iok0[ispos];
						k1 = pow_iok1[ispos];
						while (sb--) {
							temp = ST_MULT(*xrp0, k0);
							*xrp1 = ST_MULT(*xrp0, k1);
							*xrp0++ = temp;
							xrp1++;
						}
					}
					sfb++;
				}
			}
			if (gi->mixed_block_flag) {
				INT16 sfb_max = (lsf) ? 6 : 8;
				xrp0 = xr;
				xrp1 = &xr[MPA_GRANULE_SIZE];

				if (max_sfb <= 3) {
					// Top of nul bands in long blocks
					sfb = mps->sfb_nul_l[1];
					// Begin of nul bands
				} else {
					sfb = sfb_max;
					// Begin of nul band not in long blocks
				}
				sb = band_l[sfb];
				// Implicit: ispos == is_illegal here (not nul bands)
				if (ms_stereo)
					while (sb--) {
						temp = ST_MULT((*xrp0 + *xrp1), sq2);
						*xrp1 = ST_MULT((*xrp0 - *xrp1), sq2);
						*xrp0++ = temp;
						xrp1++;
				} else {
					xrp0 += sb;
					xrp1 += sb;
				}
				for (; sfb < sfb_max; sfb++) {
					sb = band_l[sfb + 1] - band_l[sfb];
					ispos = sf->l[sfb];
					is_illegal = (lsf) ? mps->
						is_max_l[sfb] : 7;
					if (ispos == is_illegal) {
						if (ms_stereo)
							while (sb--) {
								temp = ST_MULT((*xrp0 + *xrp1), sq2);
								*xrp1 = ST_MULT((*xrp0 - *xrp1), sq2);
								*xrp0++ = temp;
								xrp1++;
						} else {
							xrp0 += sb;
							xrp1 += sb;
						}
					} else {
						// ispos != is_illegal
						k0 = pow_iok0[ispos];
						k1 = pow_iok1[ispos];
						while (sb--) {
							temp = ST_MULT(*xrp0, k0);
							*xrp1 = ST_MULT(*xrp0, k1);
							*xrp0++ = temp;
							xrp1++;
						}
					}
				}
			}
		} else {
			// Long blocks, intensity stereo
			sbmax = mps->sfb_nul_l[0];
			if (sbmax < mps->sfb_nul_l[1])
				sbmax = mps->sfb_nul_l[1];
			sbmax++;
			if (sbmax > 22)
				sbmax = 22;

			xrp0 = xr;
			xrp1 = &xr[MPA_GRANULE_SIZE];

			sfb = mps->sfb_nul_l[1];	// Begin of nul bands
			sb = band_l[sfb];
			is_illegal = (lsf) ? mps->is_max_l[0] : 7;
			// Implicit: ispos == is_illegal here (not nul bands)
			ispos = is_illegal;
			if (ms_stereo)