mpegaudiodec.c

/*
 * MPEG Audio decoder
 * Copyright (c) 2001, 2002 Fabrice Bellard.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/**
 * @file mpegaudiodec.c
 * MPEG Audio decoder.
 */ 

//#define DEBUG
#include "avcodec.h"
#include "mpegaudio.h"
#include "dsputil.h"

/*
 * TODO:
 *  - in low precision mode, use more 16 bit multiplies in synth filter
 *  - test lsf / mpeg25 extensively.
 */

/* define USE_HIGHPRECISION to have a bit exact (but slower) mpeg
   audio decoder */
#ifdef CONFIG_MPEGAUDIO_HP
#define USE_HIGHPRECISION
#endif

#ifdef USE_HIGHPRECISION
#define FRAC_BITS   23   /* fractional bits for sb_samples and dct */
#define WFRAC_BITS  16   /* fractional bits for window */
#else
#define FRAC_BITS   15   /* fractional bits for sb_samples and dct */
#define WFRAC_BITS  14   /* fractional bits for window */
#endif

#define FRAC_ONE    (1 << FRAC_BITS)

#define MULL(a,b) (((int64_t)(a) * (int64_t)(b)) >> FRAC_BITS)
#define MUL64(a,b) ((int64_t)(a) * (int64_t)(b))
#define FIX(a)   ((int)((a) * FRAC_ONE))
/* WARNING: only correct for posititive numbers */
#define FIXR(a)   ((int)((a) * FRAC_ONE + 0.5))
#define FRAC_RND(a) (((a) + (FRAC_ONE/2)) >> FRAC_BITS)

#if FRAC_BITS <= 15
typedef int16_t MPA_INT;
#else
typedef int32_t MPA_INT;
#endif

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

#define HEADER_SIZE 4
#define BACKSTEP_SIZE 512

struct GranuleDef;

typedef struct MPADecodeContext {
    uint8_t inbuf1[2][MPA_MAX_CODED_FRAME_SIZE + BACKSTEP_SIZE];	/* input buffer */
    int inbuf_index;
    uint8_t *inbuf_ptr, *inbuf;
    int frame_size;
    int free_format_frame_size; /* frame size in case of free format
                                   (zero if currently unknown) */
    /* next header (used in free format parsing) */
    uint32_t free_format_next_header; 
    int error_protection;
    int layer;
    int sample_rate;
    int sample_rate_index; /* between 0 and 8 */
    int bit_rate;
    int old_frame_size;
    GetBitContext gb;
    int nb_channels;
    int mode;
    int mode_ext;
    int lsf;
    MPA_INT synth_buf[MPA_MAX_CHANNELS][512 * 2] __attribute__((aligned(16)));
    int synth_buf_offset[MPA_MAX_CHANNELS];
    int32_t sb_samples[MPA_MAX_CHANNELS][36][SBLIMIT] __attribute__((aligned(16)));
    int32_t mdct_buf[MPA_MAX_CHANNELS][SBLIMIT * 18]; /* previous samples, for layer 3 MDCT */
#ifdef DEBUG
    int frame_count;
#endif
    void (*compute_antialias)(struct MPADecodeContext *s, struct GranuleDef *g);
} MPADecodeContext;

/* layer 3 "granule" */
typedef struct GranuleDef {
    uint8_t scfsi;
    int part2_3_length;
    int big_values;
    int global_gain;
    int scalefac_compress;
    uint8_t block_type;
    uint8_t switch_point;
    int table_select[3];
    int subblock_gain[3];
    uint8_t scalefac_scale;
    uint8_t count1table_select;
    int region_size[3]; /* number of huffman codes in each region */
    int preflag;
    int short_start, long_end; /* long/short band indexes */
    uint8_t scale_factors[40];
    int32_t sb_hybrid[SBLIMIT * 18]; /* 576 samples */
} GranuleDef;

#define MODE_EXT_MS_STEREO 2
#define MODE_EXT_I_STEREO  1

/* layer 3 huffman tables */
typedef struct HuffTable {
    int xsize;
    const uint8_t *bits;
    const uint16_t *codes;
} HuffTable;

#include "mpegaudiodectab.h"

static void compute_antialias_integer(MPADecodeContext *s, GranuleDef *g);
static void compute_antialias_float(MPADecodeContext *s, GranuleDef *g);

/* vlc structure for decoding layer 3 huffman tables */
static VLC huff_vlc[16]; 
static uint8_t *huff_code_table[16];
static VLC huff_quad_vlc[2];
/* computed from band_size_long */
static uint16_t band_index_long[9][23];
/* XXX: free when all decoders are closed */
#define TABLE_4_3_SIZE (8191 + 16)
static int8_t  *table_4_3_exp;
#if FRAC_BITS <= 15
static uint16_t *table_4_3_value;
#else
static uint32_t *table_4_3_value;
#endif
/* intensity stereo coef table */
static int32_t is_table[2][16];
static int32_t is_table_lsf[2][2][16];
static int32_t csa_table[8][4];
static float csa_table_float[8][4];
static int32_t mdct_win[8][36];

/* lower 2 bits: modulo 3, higher bits: shift */
static uint16_t scale_factor_modshift[64];
/* [i][j]:  2^(-j/3) * FRAC_ONE * 2^(i+2) / (2^(i+2) - 1) */
static int32_t scale_factor_mult[15][3];
/* mult table for layer 2 group quantization */

#define SCALE_GEN(v) \
{ FIXR(1.0 * (v)), FIXR(0.7937005259 * (v)), FIXR(0.6299605249 * (v)) }

static int32_t scale_factor_mult2[3][3] = {
    SCALE_GEN(4.0 / 3.0), /* 3 steps */
    SCALE_GEN(4.0 / 5.0), /* 5 steps */
    SCALE_GEN(4.0 / 9.0), /* 9 steps */
};

/* 2^(n/4) */
static uint32_t scale_factor_mult3[4] = {
    FIXR(1.0),
    FIXR(1.18920711500272106671),
    FIXR(1.41421356237309504880),
    FIXR(1.68179283050742908605),
};

static MPA_INT window[512] __attribute__((aligned(16)));
    
/* layer 1 unscaling */
/* n = number of bits of the mantissa minus 1 */
static inline int l1_unscale(int n, int mant, int scale_factor)
{
    int shift, mod;
    int64_t val;

    shift = scale_factor_modshift[scale_factor];
    mod = shift & 3;
    shift >>= 2;
    val = MUL64(mant + (-1 << n) + 1, scale_factor_mult[n-1][mod]);
    shift += n;
    /* NOTE: at this point, 1 <= shift >= 21 + 15 */
    return (int)((val + (1LL << (shift - 1))) >> shift);
}

static inline int l2_unscale_group(int steps, int mant, int scale_factor)
{
    int shift, mod, val;

    shift = scale_factor_modshift[scale_factor];
    mod = shift & 3;
    shift >>= 2;

    val = (mant - (steps >> 1)) * scale_factor_mult2[steps >> 2][mod];
    /* NOTE: at this point, 0 <= shift <= 21 */
    if (shift > 0)
        val = (val + (1 << (shift - 1))) >> shift;
    return val;
}

/* compute value^(4/3) * 2^(exponent/4). It normalized to FRAC_BITS */
static inline int l3_unscale(int value, int exponent)
{
#if FRAC_BITS <= 15    
    unsigned int m;
#else
    uint64_t m;
#endif
    int e;

    e = table_4_3_exp[value];
    e += (exponent >> 2);
    e = FRAC_BITS - e;
#if FRAC_BITS <= 15    
    if (e > 31)
        e = 31;
#endif
    m = table_4_3_value[value];
#if FRAC_BITS <= 15    
    m = (m * scale_factor_mult3[exponent & 3]);
    m = (m + (1 << (e-1))) >> e;
    return m;
#else
    m = MUL64(m, scale_factor_mult3[exponent & 3]);
    m = (m + (uint64_t_C(1) << (e-1))) >> e;
    return m;
#endif
}

/* all integer n^(4/3) computation code */
#define DEV_ORDER 13

#define POW_FRAC_BITS 24
#define POW_FRAC_ONE    (1 << POW_FRAC_BITS)
#define POW_FIX(a)   ((int)((a) * POW_FRAC_ONE))
#define POW_MULL(a,b) (((int64_t)(a) * (int64_t)(b)) >> POW_FRAC_BITS)

static int dev_4_3_coefs[DEV_ORDER];

static int pow_mult3[3] = {
    POW_FIX(1.0),
    POW_FIX(1.25992104989487316476),
    POW_FIX(1.58740105196819947474),
};

static void int_pow_init(void)
{
    int i, a;

    a = POW_FIX(1.0);
    for(i=0;i<DEV_ORDER;i++) {
        a = POW_MULL(a, POW_FIX(4.0 / 3.0) - i * POW_FIX(1.0)) / (i + 1);
        dev_4_3_coefs[i] = a;
    }
}

/* return the mantissa and the binary exponent */
static int int_pow(int i, int *exp_ptr)
{
    int e, er, eq, j;
    int a, a1;
    
    /* renormalize */
    a = i;
    e = POW_FRAC_BITS;
    while (a < (1 << (POW_FRAC_BITS - 1))) {
        a = a << 1;
        e--;
    }
    a -= (1 << POW_FRAC_BITS);
    a1 = 0;
    for(j = DEV_ORDER - 1; j >= 0; j--)
        a1 = POW_MULL(a, dev_4_3_coefs[j] + a1);
    a = (1 << POW_FRAC_BITS) + a1;
    /* exponent compute (exact) */
    e = e * 4;
    er = e % 3;
    eq = e / 3;
    a = POW_MULL(a, pow_mult3[er]);
    while (a >= 2 * POW_FRAC_ONE) {
        a = a >> 1;
        eq++;
    }
    /* convert to float */
    while (a < POW_FRAC_ONE) {
        a = a << 1;
        eq--;
    }
    /* now POW_FRAC_ONE <= a < 2 * POW_FRAC_ONE */
#if POW_FRAC_BITS > FRAC_BITS
    a = (a + (1 << (POW_FRAC_BITS - FRAC_BITS - 1))) >> (POW_FRAC_BITS - FRAC_BITS);
    /* correct overflow */
    if (a >= 2 * (1 << FRAC_BITS)) {
        a = a >> 1;
        eq++;
    }
#endif
    *exp_ptr = eq;
    return a;
}

static int decode_init(AVCodecContext * avctx)
{
    MPADecodeContext *s = avctx->priv_data;
    static int init=0;
    int i, j, k;

    if(avctx->antialias_algo == FF_AA_INT)
        s->compute_antialias= compute_antialias_integer;
    else
        s->compute_antialias= compute_antialias_float;

    if (!init && !avctx->parse_only) {
        /* scale factors table for layer 1/2 */
        for(i=0;i<64;i++) {
            int shift, mod;
            /* 1.0 (i = 3) is normalized to 2 ^ FRAC_BITS */
            shift = (i / 3);
            mod = i % 3;
            scale_factor_modshift[i] = mod | (shift << 2);
        }

        /* scale factor multiply for layer 1 */
        for(i=0;i<15;i++) {
            int n, norm;
            n = i + 2;
            norm = ((int64_t_C(1) << n) * FRAC_ONE) / ((1 << n) - 1);
            scale_factor_mult[i][0] = MULL(FIXR(1.0 * 2.0), norm);
            scale_factor_mult[i][1] = MULL(FIXR(0.7937005259 * 2.0), norm);
            scale_factor_mult[i][2] = MULL(FIXR(0.6299605249 * 2.0), norm);
            dprintf("%d: norm=%x s=%x %x %x\n",
                    i, norm, 
                    scale_factor_mult[i][0],
                    scale_factor_mult[i][1],
                    scale_factor_mult[i][2]);
        }
        
        /* window */
        /* max = 18760, max sum over all 16 coefs : 44736 */
        for(i=0;i<257;i++) {
            int v;
            v = mpa_enwindow[i];
#if WFRAC_BITS < 16
            v = (v + (1 << (16 - WFRAC_BITS - 1))) >> (16 - WFRAC_BITS);
#endif
            window[i] = v;
            if ((i & 63) != 0)
                v = -v;
            if (i != 0)
                window[512 - i] = v;
        }
        
        /* huffman decode tables */
        huff_code_table[0] = NULL;
        for(i=1;i<16;i++) {
            const HuffTable *h = &mpa_huff_tables[i];
	    int xsize, x, y;
            unsigned int n;
            uint8_t *code_table;

            xsize = h->xsize;
            n = xsize * xsize;
            /* XXX: fail test */
            init_vlc(&huff_vlc[i], 8, n, 
                     h->bits, 1, 1, h->codes, 2, 2);
            
            code_table = av_mallocz(n);
            j = 0;
            for(x=0;x<xsize;x++) {
                for(y=0;y<xsize;y++)
                    code_table[j++] = (x << 4) | y;
            }
            huff_code_table[i] = code_table;
        }
        for(i=0;i<2;i++) {
            init_vlc(&huff_quad_vlc[i], i == 0 ? 7 : 4, 16, 
                     mpa_quad_bits[i], 1, 1, mpa_quad_codes[i], 1, 1);
        }

        for(i=0;i<9;i++) {
            k = 0;
            for(j=0;j<22;j++) {
                band_index_long[i][j] = k;
                k += band_size_long[i][j];
            }
            band_index_long[i][22] = k;
        }

	/* compute n ^ (4/3) and store it in mantissa/exp format */
	if (!av_mallocz_static(&table_4_3_exp,
			       TABLE_4_3_SIZE * sizeof(table_4_3_exp[0])))
	    return -1;
	if (!av_mallocz_static(&table_4_3_value,
			       TABLE_4_3_SIZE * sizeof(table_4_3_value[0])))
            return -1;
        
        int_pow_init();
        for(i=1;i<TABLE_4_3_SIZE;i++) {
            int e, m;
            m = int_pow(i, &e);
#if 0
            /* test code */
            {
                double f, fm;
                int e1, m1;
                f = pow((double)i, 4.0 / 3.0);
                fm = frexp(f, &e1);
                m1 = FIXR(2 * fm);
#if FRAC_BITS <= 15
                if ((unsigned short)m1 != m1) {
                    m1 = m1 >> 1;
                    e1++;
                }
#endif
                e1--;
                if (m != m1 || e != e1) {
                    printf("%4d: m=%x m1=%x e=%d e1=%d\n",
                           i, m, m1, e, e1);
                }
            }
#endif
            /* normalized to FRAC_BITS */
            table_4_3_value[i] = m;
            table_4_3_exp[i] = e;
        }
        
        for(i=0;i<7;i++) {
            float f;
            int v;
            if (i != 6) {
                f = tan((double)i * M_PI / 12.0);
                v = FIXR(f / (1.0 + f));
            } else {
                v = FIXR(1.0);
            }
            is_table[0][i] = v;
            is_table[1][6 - i] = v;
        }
        /* invalid values */
        for(i=7;i<16;i++)
            is_table[0][i] = is_table[1][i] = 0.0;

        for(i=0;i<16;i++) {
            double f;
            int e, k;

            for(j=0;j<2;j++) {
                e = -(j + 1) * ((i + 1) >> 1);
                f = pow(2.0, e / 4.0);
                k = i & 1;
                is_table_lsf[j][k ^ 1][i] = FIXR(f);
                is_table_lsf[j][k][i] = FIXR(1.0);
                dprintf("is_table_lsf %d %d: %x %x\n", 
                        i, j, is_table_lsf[j][0][i], is_table_lsf[j][1][i]);
            }
        }

        for(i=0;i<8;i++) {
            float ci, cs, ca;
            ci = ci_table[i];
            cs = 1.0 / sqrt(1.0 + ci * ci);
            ca = cs * ci;
            csa_table[i][0] = FIX(cs);
            csa_table[i][1] = FIX(ca);
            csa_table[i][2] = FIX(ca) + FIX(cs);
            csa_table[i][3] = FIX(ca) - FIX(cs); 
            csa_table_float[i][0] = cs;
            csa_table_float[i][1] = ca;
            csa_table_float[i][2] = ca + cs;
            csa_table_float[i][3] = ca - cs; 
//            printf("%d %d %d %d\n", FIX(cs), FIX(cs-1), FIX(ca), FIX(cs)-FIX(ca));
        }

        /* compute mdct windows */
        for(i=0;i<36;i++) {
            int v;
            v = FIXR(sin(M_PI * (i + 0.5) / 36.0));
            mdct_win[0][i] = v;
            mdct_win[1][i] = v;
            mdct_win[3][i] = v;
        }
        for(i=0;i<6;i++) {
            mdct_win[1][18 + i] = FIXR(1.0);
            mdct_win[1][24 + i] = FIXR(sin(M_PI * ((i + 6) + 0.5) / 12.0));
            mdct_win[1][30 + i] = FIXR(0.0);

            mdct_win[3][i] = FIXR(0.0);
            mdct_win[3][6 + i] = FIXR(sin(M_PI * (i + 0.5) / 12.0));
            mdct_win[3][12 + i] = FIXR(1.0);
        }

        for(i=0;i<12;i++)
            mdct_win[2][i] = FIXR(sin(M_PI * (i + 0.5) / 12.0));
        
        /* NOTE: we do frequency inversion adter the MDCT by changing
           the sign of the right window coefs */
        for(j=0;j<4;j++) {
            for(i=0;i<36;i+=2) {
                mdct_win[j + 4][i] = mdct_win[j][i];
                mdct_win[j + 4][i + 1] = -mdct_win[j][i + 1];
            }
        }

#if defined(DEBUG)
        for(j=0;j<8;j++) {
            printf("win%d=\n", j);
            for(i=0;i<36;i++)
                printf("%f, ", (double)mdct_win[j][i] / FRAC_ONE);
            printf("\n");
        }
#endif
        init = 1;
    }

    s->inbuf_index = 0;
    s->inbuf = &s->inbuf1[s->inbuf_index][BACKSTEP_SIZE];
    s->inbuf_ptr = s->inbuf;
#ifdef DEBUG
    s->frame_count = 0;
#endif
    return 0;
}

/* tab[i][j] = 1.0 / (2.0 * cos(pi*(2*k+1) / 2^(6 - j))) */

/* cos(i*pi/64) */

#define COS0_0  FIXR(0.50060299823519630134)
#define COS0_1  FIXR(0.50547095989754365998)
#define COS0_2  FIXR(0.51544730992262454697)
#define COS0_3  FIXR(0.53104259108978417447)
#define COS0_4  FIXR(0.55310389603444452782)
#define COS0_5  FIXR(0.58293496820613387367)
#define COS0_6  FIXR(0.62250412303566481615)
#define COS0_7  FIXR(0.67480834145500574602)
#define COS0_8  FIXR(0.74453627100229844977)
#define COS0_9  FIXR(0.83934964541552703873)
#define COS0_10 FIXR(0.97256823786196069369)
#define COS0_11 FIXR(1.16943993343288495515)
#define COS0_12 FIXR(1.48416461631416627724)
#define COS0_13 FIXR(2.05778100995341155085)
#define COS0_14 FIXR(3.40760841846871878570)
#define COS0_15 FIXR(10.19000812354805681150)

#define COS1_0 FIXR(0.50241928618815570551)
#define COS1_1 FIXR(0.52249861493968888062)
#define COS1_2 FIXR(0.56694403481635770368)
#define COS1_3 FIXR(0.64682178335999012954)
#define COS1_4 FIXR(0.78815462345125022473)
#define COS1_5 FIXR(1.06067768599034747134)
#define COS1_6 FIXR(1.72244709823833392782)
#define COS1_7 FIXR(5.10114861868916385802)

#define COS2_0 FIXR(0.50979557910415916894)
#define COS2_1 FIXR(0.60134488693504528054)
#define COS2_2 FIXR(0.89997622313641570463)
#define COS2_3 FIXR(2.56291544774150617881)

#define COS3_0 FIXR(0.54119610014619698439)
#define COS3_1 FIXR(1.30656296487637652785)

#define COS4_0 FIXR(0.70710678118654752439)

/* butterfly operator */
#define BF(a, b, c)\
{\
    tmp0 = tab[a] + tab[b];\
    tmp1 = tab[a] - tab[b];\
    tab[a] = tmp0;\
    tab[b] = MULL(tmp1, c);\
}

#define BF1(a, b, c, d)\
{\
    BF(a, b, COS4_0);\
    BF(c, d, -COS4_0);\
    tab[c] += tab[d];\
}

#define BF2(a, b, c, d)\
{\
    BF(a, b, COS4_0);\
    BF(c, d, -COS4_0);\
    tab[c] += tab[d];\
    tab[a] += tab[c];\
    tab[c] += tab[b];\
    tab[b] += tab[d];\
}

#define ADD(a, b) tab[a] += tab[b]

/* DCT32 without 1/sqrt(2) coef zero scaling. */
static void dct32(int32_t *out, int32_t *tab)
{
    int tmp0, tmp1;

    /* pass 1 */
    BF(0, 31, COS0_0);
    BF(1, 30, COS0_1);
    BF(2, 29, COS0_2);
    BF(3, 28, COS0_3);
    BF(4, 27, COS0_4);
    BF(5, 26, COS0_5);
    BF(6, 25, COS0_6);
    BF(7, 24, COS0_7);
    BF(8, 23, COS0_8);
    BF(9, 22, COS0_9);
    BF(10, 21, COS0_10);
    BF(11, 20, COS0_11);
    BF(12, 19, COS0_12);
    BF(13, 18, COS0_13);
    BF(14, 17, COS0_14);
    BF(15, 16, COS0_15);

    /* pass 2 */
    BF(0, 15, COS1_0);
    BF(1, 14, COS1_1);
    BF(2, 13, COS1_2);
    BF(3, 12, COS1_3);
    BF(4, 11, COS1_4);
    BF(5, 10, COS1_5);
    BF(6,  9, COS1_6);
    BF(7,  8, COS1_7);
    
    BF(16, 31, -COS1_0);
    BF(17, 30, -COS1_1);
    BF(18, 29, -COS1_2);
    BF(19, 28, -COS1_3);
    BF(20, 27, -COS1_4);
    BF(21, 26, -COS1_5);
    BF(22, 25, -COS1_6);
    BF(23, 24, -COS1_7);
    
    /* pass 3 */
    BF(0, 7, COS2_0);
    BF(1, 6, COS2_1);
    BF(2, 5, COS2_2);
    BF(3, 4, COS2_3);
    
    BF(8, 15, -COS2_0);
    BF(9, 14, -COS2_1);
    BF(10, 13, -COS2_2);
    BF(11, 12, -COS2_3);
    
    BF(16, 23, COS2_0);
    BF(17, 22, COS2_1);
    BF(18, 21, COS2_2);
    BF(19, 20, COS2_3);
    
    BF(24, 31, -COS2_0);
    BF(25, 30, -COS2_1);
    BF(26, 29, -COS2_2);
    BF(27, 28, -COS2_3);

    /* pass 4 */
    BF(0, 3, COS3_0);
    BF(1, 2, COS3_1);
    
    BF(4, 7, -COS3_0);
    BF(5, 6, -COS3_1);
    
    BF(8, 11, COS3_0);
    BF(9, 10, COS3_1);
    
    BF(12, 15, -COS3_0);
    BF(13, 14, -COS3_1);
    
    BF(16, 19, COS3_0);
    BF(17, 18, COS3_1);
    
    BF(20, 23, -COS3_0);
    BF(21, 22, -COS3_1);
    
    BF(24, 27, COS3_0);
    BF(25, 26, COS3_1);
    
    BF(28, 31, -COS3_0);
    BF(29, 30, -COS3_1);
    
    /* pass 5 */
    BF1(0, 1, 2, 3);
    BF2(4, 5, 6, 7);
    BF1(8, 9, 10, 11);
    BF2(12, 13, 14, 15);
    BF1(16, 17, 18, 19);
    BF2(20, 21, 22, 23);
    BF1(24, 25, 26, 27);
    BF2(28, 29, 30, 31);
    
    /* pass 6 */
    
    ADD( 8, 12);
    ADD(12, 10);
    ADD(10, 14);
    ADD(14,  9);
    ADD( 9, 13);
    ADD(13, 11);
    ADD(11, 15);

    out[ 0] = tab[0];
    out[16] = tab[1];
    out[ 8] = tab[2];
    out[24] = tab[3];
    out[ 4] = tab[4];
    out[20] = tab[5];
    out[12] = tab[6];
    out[28] = tab[7];
    out[ 2] = tab[8];
    out[18] = tab[9];
    out[10] = tab[10];
    out[26] = tab[11];
    out[ 6] = tab[12];
    out[22] = tab[13];
    out[14] = tab[14];
    out[30] = tab[15];
    
    ADD(24, 28);
    ADD(28, 26);
    ADD(26, 30);
    ADD(30, 25);
    ADD(25, 29);
    ADD(29, 27);
    ADD(27, 31);

    out[ 1] = tab[16] + tab[24];
    out[17] = tab[17] + tab[25];
    out[ 9] = tab[18] + tab[26];
    out[25] = tab[19] + tab[27];
    out[ 5] = tab[20] + tab[28];
    out[21] = tab[21] + tab[29];
    out[13] = tab[22] + tab[30];
    out[29] = tab[23] + tab[31];
    out[ 3] = tab[24] + tab[20];
    out[19] = tab[25] + tab[21];
    out[11] = tab[26] + tab[22];
    out[27] = tab[27] + tab[23];
    out[ 7] = tab[28] + tab[18];
    out[23] = tab[29] + tab[19];
    out[15] = tab[30] + tab[17];
    out[31] = tab[31];
}

#define OUT_SHIFT (WFRAC_BITS + FRAC_BITS - 15)

#if FRAC_BITS <= 15

static inline int round_sample(int sum)
{
    int sum1;
    sum1 = (sum + (1 << (OUT_SHIFT - 1))) >> OUT_SHIFT;
    if (sum1 < -32768)
        sum1 = -32768;
    else if (sum1 > 32767)
        sum1 = 32767;
    return sum1;
}

#if defined(ARCH_POWERPC_405)

/* signed 16x16 -> 32 multiply add accumulate */
#define MACS(rt, ra, rb) \
    asm ("maclhw %0, %2, %3" : "=r" (rt) : "0" (rt), "r" (ra), "r" (rb));

/* signed 16x16 -> 32 multiply */
#define MULS(ra, rb) \
    ({ int __rt; asm ("mullhw %0, %1, %2" : "=r" (__rt) : "r" (ra), "r" (rb)); __rt; })

#else

/* signed 16x16 -> 32 multiply add accumulate */
#define MACS(rt, ra, rb) rt += (ra) * (rb)

/* signed 16x16 -> 32 multiply */
#define MULS(ra, rb) ((ra) * (rb))

#endif

#else

static inline int round_sample(int64_t sum) 
{
    int sum1;
    sum1 = (int)((sum + (int64_t_C(1) << (OUT_SHIFT - 1))) >> OUT_SHIFT);
    if (sum1 < -32768)
        sum1 = -32768;
    else if (sum1 > 32767)
        sum1 = 32767;
    return sum1;
}

#define MULS(ra, rb) MUL64(ra, rb)

#endif

#define SUM8(sum, op, w, p) \
{                                               \
    sum op MULS((w)[0 * 64], p[0 * 64]);\
    sum op MULS((w)[1 * 64], p[1 * 64]);\
    sum op MULS((w)[2 * 64], p[2 * 64]);\
    sum op MULS((w)[3 * 64], p[3 * 64]);\
    sum op MULS((w)[4 * 64], p[4 * 64]);\
    sum op MULS((w)[5 * 64], p[5 * 64]);\
    sum op MULS((w)[6 * 64], p[6 * 64]);\
    sum op MULS((w)[7 * 64], p[7 * 64]);\
}

#define SUM8P2(sum1, op1, sum2, op2, w1, w2, p) \
{                                               \
    int tmp;\
    tmp = p[0 * 64];\
    sum1 op1 MULS((w1)[0 * 64], tmp);\
    sum2 op2 MULS((w2)[0 * 64], tmp);\
    tmp = p[1 * 64];\
    sum1 op1 MULS((w1)[1 * 64], tmp);\
    sum2 op2 MULS((w2)[1 * 64], tmp);\
    tmp = p[2 * 64];\
    sum1 op1 MULS((w1)[2 * 64], tmp);\
    sum2 op2 MULS((w2)[2 * 64], tmp);\
    tmp = p[3 * 64];\
    sum1 op1 MULS((w1)[3 * 64], tmp);\
    sum2 op2 MULS((w2)[3 * 64], tmp);\
    tmp = p[4 * 64];\
    sum1 op1 MULS((w1)[4 * 64], tmp);\
    sum2 op2 MULS((w2)[4 * 64], tmp);\
    tmp = p[5 * 64];\
    sum1 op1 MULS((w1)[5 * 64], tmp);\
    sum2 op2 MULS((w2)[5 * 64], tmp);\
    tmp = p[6 * 64];\
    sum1 op1 MULS((w1)[6 * 64], tmp);\
    sum2 op2 MULS((w2)[6 * 64], tmp);\
    tmp = p[7 * 64];\
    sum1 op1 MULS((w1)[7 * 64], tmp);\
    sum2 op2 MULS((w2)[7 * 64], tmp);\
}


/* 32 sub band synthesis filter. Input: 32 sub band samples, Output:
   32 samples. */
/* XXX: optimize by avoiding ring buffer usage */
static void synth_filter(MPADecodeContext *s1,
                         int ch, int16_t *samples, int incr, 
                         int32_t sb_samples[SBLIMIT])
{
    int32_t tmp[32];
    register MPA_INT *synth_buf;
    const register MPA_INT *w, *w2, *p;
    int j, offset, v;
    int16_t *samples2;
#if FRAC_BITS <= 15
    int sum, sum2;
#else
    int64_t sum, sum2;
#endif
    
    dct32(tmp, sb_samples);
    
    offset = s1->synth_buf_offset[ch];
    synth_buf = s1->synth_buf[ch] + offset;

    for(j=0;j<32;j++) {
        v = tmp[j];
#if FRAC_BITS <= 15
        /* NOTE: can cause a loss in precision if very high amplitude
           sound */
        if (v > 32767)
            v = 32767;
        else if (v < -32768)
            v = -32768;
#endif
        synth_buf[j] = v;
    }
    /* copy to avoid wrap */
    memcpy(synth_buf + 512, synth_buf, 32 * sizeof(MPA_INT));

    samples2 = samples + 31 * incr;
    w = window;
    w2 = window + 31;

    sum = 0;
    p = synth_buf + 16;
    SUM8(sum, +=, w, p);
    p = synth_buf + 48;
    SUM8(sum, -=, w + 32, p);
    *samples = round_sample(sum);
    samples += incr;
    w++;

    /* we calculate two samples at the same time to avoid one memory
       access per two sample */
    for(j=1;j<16;j++) {
        sum = 0;
        sum2 = 0;
        p = synth_buf + 16 + j;
        SUM8P2(sum, +=, sum2, -=, w, w2, p);
        p = synth_buf + 48 - j;
        SUM8P2(sum, -=, sum2, -=, w + 32, w2 + 32, p);

        *samples = round_sample(sum);
        samples += incr;
        *samples2 = round_sample(sum2);
        samples2 -= incr;
        w++;
        w2--;
    }
    
    p = synth_buf + 32;
    sum = 0;
    SUM8(sum, -=, w + 32, p);
    *samples = round_sample(sum);

    offset = (offset - 32) & 511;
    s1->synth_buf_offset[ch] = offset;
}

/* cos(pi*i/24) */
#define C1  FIXR(0.99144486137381041114)
#define C3  FIXR(0.92387953251128675612)
#define C5  FIXR(0.79335334029123516458)
#define C7  FIXR(0.60876142900872063941)
#define C9  FIXR(0.38268343236508977173)
#define C11 FIXR(0.13052619222005159154)

/* 12 points IMDCT. We compute it "by hand" by factorizing obvious
   cases. */
static void imdct12(int *out, int *in)
{
    int tmp;
    int64_t in1_3, in1_9, in4_3, in4_9;

    in1_3 = MUL64(in[1], C3);
    in1_9 = MUL64(in[1], C9);
    in4_3 = MUL64(in[4], C3);
    in4_9 = MUL64(in[4], C9);
    
    tmp = FRAC_RND(MUL64(in[0], C7) - in1_3 - MUL64(in[2], C11) + 
                   MUL64(in[3], C1) - in4_9 - MUL64(in[5], C5));
    out[0] = tmp;
    out[5] = -tmp;
    tmp = FRAC_RND(MUL64(in[0] - in[3], C9) - in1_3 + 
                   MUL64(in[2] + in[5], C3) - in4_9);
    out[1] = tmp;
    out[4] = -tmp;
    tmp = FRAC_RND(MUL64(in[0], C11) - in1_9 + MUL64(in[2], C7) -
                   MUL64(in[3], C5) + in4_3 - MUL64(in[5], C1));
    out[2] = tmp;
    out[3] = -tmp;
    tmp = FRAC_RND(MUL64(-in[0], C5) + in1_9 + MUL64(in[2], C1) + 
                   MUL64(in[3], C11) - in4_3 - MUL64(in[5], C7));
    out[6] = tmp;
    out[11] = tmp;
    tmp = FRAC_RND(MUL64(-in[0] + in[3], C3) - in1_9 + 
                   MUL64(in[2] + in[5], C9) + in4_3);
    out[7] = tmp;
    out[10] = tmp;
    tmp = FRAC_RND(-MUL64(in[0], C1) - in1_3 - MUL64(in[2], C5) -
                   MUL64(in[3], C7) - in4_9 - MUL64(in[5], C11));
    out[8] = tmp;
    out[9] = tmp;
}

#undef C1
#undef C3
#undef C5
#undef C7
#undef C9
#undef C11

/* cos(pi*i/18) */
#define C1 FIXR(0.98480775301220805936)
#define C2 FIXR(0.93969262078590838405)
#define C3 FIXR(0.86602540378443864676)
#define C4 FIXR(0.76604444311897803520)
#define C5 FIXR(0.64278760968653932632)
#define C6 FIXR(0.5)
#define C7 FIXR(0.34202014332566873304)
#define C8 FIXR(0.17364817766693034885)

/* 0.5 / cos(pi*(2*i+1)/36) */
static const int icos36[9] = {
    FIXR(0.50190991877167369479),
    FIXR(0.51763809020504152469),
    FIXR(0.55168895948124587824),
    FIXR(0.61038729438072803416),
    FIXR(0.70710678118654752439),
    FIXR(0.87172339781054900991),
    FIXR(1.18310079157624925896),
    FIXR(1.93185165257813657349),