FFmpeg/libavcodec/libac3/bit_allocate.c

/* 
 *  bit_allocate.c
 *
 *	Copyright (C) Aaron Holtzman - May 1999
 *
 *  This file is part of ac3dec, a free Dolby AC-3 stream decoder.
 *	
 *  ac3dec 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.
 *   
 *  ac3dec 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 "../common.h"
#include "ac3.h"
#include "ac3_internal.h"

static int hthtab[3][50] = {
    {0x730, 0x730, 0x7c0, 0x800, 0x820, 0x840, 0x850, 0x850, 0x860, 0x860,
     0x860, 0x860, 0x860, 0x870, 0x870, 0x870, 0x880, 0x880, 0x890, 0x890,
     0x8a0, 0x8a0, 0x8b0, 0x8b0, 0x8c0, 0x8c0, 0x8d0, 0x8e0, 0x8f0, 0x900,
     0x910, 0x910, 0x910, 0x910, 0x900, 0x8f0, 0x8c0, 0x870, 0x820, 0x7e0,
     0x7a0, 0x770, 0x760, 0x7a0, 0x7c0, 0x7c0, 0x6e0, 0x400, 0x3c0, 0x3c0},
    {0x710, 0x710, 0x7a0, 0x7f0, 0x820, 0x830, 0x840, 0x850, 0x850, 0x860,
     0x860, 0x860, 0x860, 0x860, 0x870, 0x870, 0x870, 0x880, 0x880, 0x880,
     0x890, 0x890, 0x8a0, 0x8a0, 0x8b0, 0x8b0, 0x8c0, 0x8c0, 0x8e0, 0x8f0,
     0x900, 0x910, 0x910, 0x910, 0x910, 0x900, 0x8e0, 0x8b0, 0x870, 0x820,
     0x7e0, 0x7b0, 0x760, 0x770, 0x7a0, 0x7c0, 0x780, 0x5d0, 0x3c0, 0x3c0},
    {0x680, 0x680, 0x750, 0x7b0, 0x7e0, 0x810, 0x820, 0x830, 0x840, 0x850,
     0x850, 0x850, 0x860, 0x860, 0x860, 0x860, 0x860, 0x860, 0x860, 0x860,
     0x870, 0x870, 0x870, 0x870, 0x880, 0x880, 0x880, 0x890, 0x8a0, 0x8b0,
     0x8c0, 0x8d0, 0x8e0, 0x8f0, 0x900, 0x910, 0x910, 0x910, 0x900, 0x8f0,
     0x8d0, 0x8b0, 0x840, 0x7f0, 0x790, 0x760, 0x7a0, 0x7c0, 0x7b0, 0x720}
};

static int8_t baptab[305] = {
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,	// 93 padding entries

    16, 16, 16, 16, 16, 16, 16, 16, 16, 14, 14, 14, 14, 14, 14, 14,
    14, 12, 12, 12, 12, 11, 11, 11, 11, 10, 10, 10, 10,  9,  9,  9,
     9,  8,  8,  8,  8,  7,  7,  7,  7,  6,  6,  6,  6,  5,  5,  5,
     5,  4,  4, -3, -3,  3,  3,  3, -2, -2, -1, -1, -1, -1, -1,  0,

     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
     0,  0,  0,  0					// 148 padding entries
};

static int bndtab[30] = {21, 22,  23,  24,  25,  26,  27,  28,  31,  34,
			 37, 40,  43,  46,  49,  55,  61,  67,  73,  79,
			 85, 97, 109, 121, 133, 157, 181, 205, 229, 253};

static int8_t latab[256] = {
    -64, -63, -62, -61, -60, -59, -58, -57, -56, -55, -54, -53,
    -52, -52, -51, -50, -49, -48, -47, -47, -46, -45, -44, -44,
    -43, -42, -41, -41, -40, -39, -38, -38, -37, -36, -36, -35,
    -35, -34, -33, -33, -32, -32, -31, -30, -30, -29, -29, -28,
    -28, -27, -27, -26, -26, -25, -25, -24, -24, -23, -23, -22,
    -22, -21, -21, -21, -20, -20, -19, -19, -19, -18, -18, -18,
    -17, -17, -17, -16, -16, -16, -15, -15, -15, -14, -14, -14,
    -13, -13, -13, -13, -12, -12, -12, -12, -11, -11, -11, -11,
    -10, -10, -10, -10, -10,  -9,  -9,  -9,  -9,  -9,  -8,  -8,
     -8,  -8,  -8,  -8,  -7,  -7,  -7,  -7,  -7,  -7,  -6,  -6,
     -6,  -6,  -6,  -6,  -6,  -6,  -5,  -5,  -5,  -5,  -5,  -5,
     -5,  -5,  -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,  -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,   0,   0,   0,   0,   0,   0,
      0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
      0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
      0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
      0,   0,   0,   0
};

#define UPDATE_LEAK() 		\
do {				\
    fastleak += fdecay;		\
    if (fastleak > psd + fgain)	\
	fastleak = psd + fgain;	\
    slowleak += sdecay;		\
    if (slowleak > psd + sgain)	\
	slowleak = psd + sgain;	\
} while (0)

#define COMPUTE_MASK()				\
do {						\
    if (psd > dbknee)				\
	mask -= (psd - dbknee) >> 2;		\
    if (mask > hth [i >> halfrate])		\
	mask = hth [i >> halfrate];		\
    mask -= snroffset + 128 * deltba[i];	\
    mask = (mask > 0) ? 0 : ((-mask) >> 5);	\
    mask -= floor;				\
} while (0)

void bit_allocate (ac3_state_t * state, ac3_ba_t * ba, int bndstart,
		   int start, int end, int fastleak, int slowleak,
		   uint8_t * exp, int8_t * bap)
{
    static int slowgain[4] = {0x540, 0x4d8, 0x478, 0x410};
    static int dbpbtab[4]  = {0xc00, 0x500, 0x300, 0x100};
    static int floortab[8] = {0x910, 0x950, 0x990, 0x9d0,
			      0xa10, 0xa90, 0xb10, 0x1400};

    int i, j;
    int fdecay, fgain, sdecay, sgain, dbknee, floor, snroffset;
    int psd, mask;
    int8_t * deltba;
    int * hth;
    int halfrate;

    halfrate = state->halfrate;
    fdecay = (63 + 20 * state->fdcycod) >> halfrate;
    fgain = 128 + 128 * ba->fgaincod;
    sdecay = (15 + 2 * state->sdcycod) >> halfrate;
    sgain = slowgain[state->sgaincod];
    dbknee = dbpbtab[state->dbpbcod];
    hth = hthtab[state->fscod];
    /*
     * if there is no delta bit allocation, make deltba point to an area
     * known to contain zeroes. baptab+156 here.
     */
    deltba = (ba->deltbae == DELTA_BIT_NONE) ? baptab + 156 : ba->deltba;
    floor = floortab[state->floorcod];
    snroffset = 960 - 64 * state->csnroffst - 4 * ba->fsnroffst + floor;
    floor >>= 5;

    i = bndstart;
    j = start;
    if (start == 0) {	// not the coupling channel
	int lowcomp;

	lowcomp = 0;
	j = end - 1;
	do {
	    if (i < j) {
		if (exp[i+1] == exp[i] - 2)
		    lowcomp = 384;
		else if (lowcomp && (exp[i+1] > exp[i]))
		    lowcomp -= 64;
	    }
	    psd = 128 * exp[i];
	    mask = psd + fgain + lowcomp;
	    COMPUTE_MASK ();
	    bap[i++] = (baptab+156)[mask + 4 * exp[i]];
	} while ((i < 3) || ((i < 7) && (exp[i] > exp[i-1])));
	fastleak = psd + fgain;
	slowleak = psd + sgain;

	while (i < 7) {
	    if (i < j) {
		if (exp[i+1] == exp[i] - 2)
		    lowcomp = 384;
		else if (lowcomp && (exp[i+1] > exp[i]))
		    lowcomp -= 64;
	    }
	    psd = 128 * exp[i];
	    UPDATE_LEAK ();
	    mask = ((fastleak + lowcomp < slowleak) ?
		    fastleak + lowcomp : slowleak);
	    COMPUTE_MASK ();
	    bap[i++] = (baptab+156)[mask + 4 * exp[i]];
	}

	if (end == 7)	// lfe channel
	    return;

	do {
	    if (exp[i+1] == exp[i] - 2)
		lowcomp = 320;
	    else if (lowcomp && (exp[i+1] > exp[i]))
		lowcomp -= 64;
	    psd = 128 * exp[i];
	    UPDATE_LEAK ();
	    mask = ((fastleak + lowcomp < slowleak) ?
		    fastleak + lowcomp : slowleak);
	    COMPUTE_MASK ();
	    bap[i++] = (baptab+156)[mask + 4 * exp[i]];
	} while (i < 20);

	while (lowcomp > 128) {		// two iterations maximum
	    lowcomp -= 128;
	    psd = 128 * exp[i];
	    UPDATE_LEAK ();
	    mask = ((fastleak + lowcomp < slowleak) ?
		    fastleak + lowcomp : slowleak);
	    COMPUTE_MASK ();
	    bap[i++] = (baptab+156)[mask + 4 * exp[i]];
	}
	j = i;
    }

    do {
	int startband, endband;

	startband = j;
	endband = ((bndtab-20)[i] < end) ? (bndtab-20)[i] : end;
	psd = 128 * exp[j++];
	while (j < endband) {
	    int next, delta;

	    next = 128 * exp[j++];
	    delta = next - psd;
	    switch (delta >> 9) {
	    case -6: case -5: case -4: case -3: case -2:
		psd = next;
		break;
	    case -1:
		psd = next + latab[(-delta) >> 1];
		break;
	    case 0:
		psd += latab[delta >> 1];
		break;
	    }
	}
	// minpsd = -289
	UPDATE_LEAK ();
	mask = (fastleak < slowleak) ? fastleak : slowleak;
	COMPUTE_MASK ();
	i++;
	j = startband;
	do {
	    // max(mask+4*exp)=147=-(minpsd+fgain-deltba-snroffset)>>5+4*exp
	    // min(mask+4*exp)=-156=-(sgain-deltba-snroffset)>>5
	    bap[j++] = (baptab+156)[mask + 4 * exp[j]];
	} while (j < endband);
    } while (j < end);
}