mpeg3dec.c

arm9开发板上的例子,可以学习一下有简单的c程序

	if (region1Start > region_stop)
		region1Start = region_stop;
	if (region2Start > region_stop)
		region2Start = region_stop;

	if (region_stop > 0) {
		huff_count = region1Start - i;
		if (huff_count > 0) {
			HUFF_decode_pair(h, gi->table_select[0],
				 (INT16) (huff_count >> 1), isp);
			isp += huff_count;
			i += huff_count;
		}
		huff_count = region2Start - i;
		if (huff_count > 0) {
			HUFF_decode_pair(h, gi->table_select[1],
				 (INT16) (huff_count >> 1), isp);
			isp += huff_count;
			i += huff_count;
		}
		huff_count = region_stop - i;
		if (huff_count > 0) {
			HUFF_decode_pair(h, gi->table_select[2],
				 (INT16) (huff_count >> 1), isp);
			isp += huff_count;
			i += huff_count;
		}
	}
	/* Read count1 area. */
	htable = gi->count1table_select;
	pos = HUFF_pos(h);
	count = HUFF_diff(part2_start, pos);	// bits already used
	region_stop = gi->part2_3_length - count;	// max bits to use
	HUFF_decode_quad(h, htable, region_stop, i, max_val, isp);

	return(MPEGDEC_ERR_NONE);
}

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

/*
 *	Get nul pos of the current samples of MPEG III stream
 *	Return 0 if Ok
 */

static INT16 MPEG3_get_nul_pos(MPA_STREAM *mps, INT16 *is, INT16 gr, INT16 ch)
{
	MPA_GRANULE_INFO *gi = &mps->side_info.ch[ch].gr[gr];
	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 nul_begin = mps->huffman->nul_begin;
	INT16 sfb;

	if ((gi->window_switching_flag) && (gi->block_type == 2)) {
		// Short blocks
		INT16 nul_s;

		nul_s = (INT16) (nul_begin + 2) / 3;
		if (gi->mixed_block_flag) {
			// First 2 subbands are long blocks
			if (nul_begin > 36) {
				// can be in short blocks
				sfb = 12;
				while ((band_s[sfb] >= nul_s) && (sfb >= 3))
					sfb--;
				mps->sfb_nul_s_top[ch] =
					mps->sfb_nul_s[0][ch] =
					mps->sfb_nul_s[1][ch] =
					mps->sfb_nul_s[2][ch] = sfb + 1;
				mps->sfb_nul_l[ch] = 8;
			} else {
				sfb = 7;
				while ((band_l[sfb] >= nul_begin) && (sfb >= 0))
					sfb--;
				mps->sfb_nul_l[ch] = sfb + 1;
				mps->sfb_nul_s_top[ch] =
					mps->sfb_nul_s[0][ch] =
					mps->sfb_nul_s[1][ch] =
					mps->sfb_nul_s[2][ch] = 3;
			}
		} else {
			sfb = 12;
			while ((band_s[sfb] >= nul_s) && (sfb >= 0))
				sfb--;
			mps->sfb_nul_s_top[ch] = mps->sfb_nul_s[0][ch] =
				mps->sfb_nul_s[1][ch] =
				mps->sfb_nul_s[2][ch] = sfb + 1;
			mps->sfb_nul_l[ch] = 0;
		}
		if (mps->header.ID == MPA_ID_2) {
			// Each null band should be evaluated for each window
			INT16 w;
			INT16 sfb_top = mps->sfb_nul_s[0][ch];
			INT16 sfb_min = (gi->mixed_block_flag) ? 3 : 0;

			mps->sfb_nul_s_top[ch] = 0;
			for (w = 0; w < 3; w++) {
				register INT16 index;
				register INT16 cnt;
				register INT16 *isp;

				sfb = sfb_top;
				index = (band_s[sfb - 1] * 3) + ((INT16)
					(band_s[sfb] - band_s[sfb - 1]) *
					(INT16) (w + 1)) - 1;
				if (nul_begin < index)
					index = nul_begin;
				while (sfb > sfb_min) {
					isp = &is[index];
					cnt = 1 + index -
						((band_s[sfb - 1] * 3) +
						((INT16) (band_s[sfb] -
						band_s[sfb - 1]) * w));
					while (cnt--)
						if (*isp--)
							break;
					if (cnt >= 0)
						break;
					sfb--;
					index = (band_s[sfb - 1] * 3) +
						((INT16) (band_s[sfb] -
						band_s[sfb - 1]) *
						(INT16) (w + 1)) - 1;
				}
				mps->sfb_nul_s[w][ch] = sfb;
				if (sfb > mps->sfb_nul_s_top[ch])
					mps->sfb_nul_s_top[ch] = sfb;
				if ((sfb == sfb_min) && (sfb_min > 0)) {
					// Find into long blocks now
					sfb = 6;
					index = band_l[sfb] - 1;
					if (nul_begin < index)
						index = nul_begin;
					while (sfb > 0) {
						isp = &is[index];
						cnt = 1 + index -
							band_l[sfb - 1];
						while (cnt--)
							if (*isp--)
								break;
						if (cnt >= 0)
							break;
						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);
}

/****************************************************************************/
#ifndef SRAM_OPT_TABLE
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
};
#else
extern INT16 *pretab;
#endif

#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
 */

#ifdef MOV_FUNC
void (*MPEGSUBB_antialias_cp)(MPEGAUD_FRACT_TYPE *xr, INT16 sblim );
#endif

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
/*
 *	 Precalc tables for ST_BITS = 14
 */
#ifndef SRAM_OPT_TABLE
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
};