layer2.c

Go to the documentation of this file.

/*
    layer2.c: the layer 2 decoder, root of mpg123

    copyright 1994-2009 by the mpg123 project - free software under the terms of the LGPL 2.1
    see COPYING and AUTHORS files in distribution or http://mpg123.org
    initially written by Michael Hipp

    mpg123 started as mp2 decoder a long time ago...
    part of this file is required for layer 1, too.
*/


#include "mpg123lib_intern.h"
#ifndef NO_LAYER2
#include "l2tables.h"
#endif
#include "getbits.h"

#ifndef NO_LAYER12 /* Stuff  needed for layer I and II. */

static int grp_3tab[32 * 3] = { 0, };   /* used: 27 */
static int grp_5tab[128 * 3] = { 0, };  /* used: 125 */
static int grp_9tab[1024 * 3] = { 0, }; /* used: 729 */

#if defined(REAL_IS_FIXED) && defined(PRECALC_TABLES)
#include "l12_integer_tables.h"
#else
static const double mulmul[27] =
{
    0.0 , -2.0/3.0 , 2.0/3.0 ,
    2.0/7.0 , 2.0/15.0 , 2.0/31.0, 2.0/63.0 , 2.0/127.0 , 2.0/255.0 ,
    2.0/511.0 , 2.0/1023.0 , 2.0/2047.0 , 2.0/4095.0 , 2.0/8191.0 ,
    2.0/16383.0 , 2.0/32767.0 , 2.0/65535.0 ,
    -4.0/5.0 , -2.0/5.0 , 2.0/5.0, 4.0/5.0 ,
    -8.0/9.0 , -4.0/9.0 , -2.0/9.0 , 2.0/9.0 , 4.0/9.0 , 8.0/9.0
};
#endif

void init_layer12(void)
{
    const int base[3][9] =
    {
        { 1 , 0, 2 , } ,
        { 17, 18, 0 , 19, 20 , } ,
        { 21, 1, 22, 23, 0, 24, 25, 2, 26 }
    };
    int i,j,k,l,len;
    const int tablen[3] = { 3 , 5 , 9 };
    int *itable;
    int *tables[3] = { grp_3tab , grp_5tab , grp_9tab };

    for(i=0;i<3;i++)
    {
        itable = tables[i];
        len = tablen[i];
        for(j=0;j<len;j++)
        for(k=0;k<len;k++)
        for(l=0;l<len;l++)
        {
            *itable++ = base[i][l];
            *itable++ = base[i][k];
            *itable++ = base[i][j];
        }
    }
}

void init_layer12_stuff(mpg123_handle *fr, real* (*init_table)(mpg123_handle *fr, real *table, int m))
{
    int k;
    real *table;
    for(k=0;k<27;k++)
    {
        table = init_table(fr, fr->muls[k], k);
        *table++ = 0.0;
    }
}

real* init_layer12_table(mpg123_handle *fr, real *table, int m)
{
#if defined(REAL_IS_FIXED) && defined(PRECALC_TABLES)
    int i;
    for(i=0;i<63;i++)
    *table++ = layer12_table[m][i];
#else
    int i,j;
    for(j=3,i=0;i<63;i++,j--)
    *table++ = DOUBLE_TO_REAL_SCALE_LAYER12(mulmul[m] * pow(2.0,(double) j / 3.0));
#endif

    return table;
}

#ifdef OPT_MMXORSSE
real* init_layer12_table_mmx(mpg123_handle *fr, real *table, int m)
{
    int i,j;
    if(!fr->p.down_sample) 
    {
        for(j=3,i=0;i<63;i++,j--)
            *table++ = DOUBLE_TO_REAL(16384 * mulmul[m] * pow(2.0,(double) j / 3.0));
    }
    else
    {
        for(j=3,i=0;i<63;i++,j--)
        *table++ = DOUBLE_TO_REAL(mulmul[m] * pow(2.0,(double) j / 3.0));
    }
    return table;
}
#endif

#endif /* NO_LAYER12 */

/* The rest is the actual decoding of layer II data. */

#ifndef NO_LAYER2

void II_step_one(unsigned int *bit_alloc,int *scale,mpg123_handle *fr)
{
    int stereo = fr->stereo-1;
    int sblimit = fr->II_sblimit;
    int jsbound = fr->jsbound;
    int sblimit2 = fr->II_sblimit<<stereo;
    const struct al_table *alloc1 = fr->alloc;
    int i;
    unsigned int scfsi_buf[64];
    unsigned int *scfsi,*bita;
    int sc,step;

    bita = bit_alloc;
    if(stereo)
    {
        for(i=jsbound;i;i--,alloc1+=(1<<step))
        {
            step=alloc1->bits;
            *bita++ = (char) getbits(fr, step);
            *bita++ = (char) getbits(fr, step);
        }
        for(i=sblimit-jsbound;i;i--,alloc1+=(1<<step))
        {
            step=alloc1->bits;
            bita[0] = (char) getbits(fr, step);
            bita[1] = bita[0];
            bita+=2;
        }
        bita = bit_alloc;
        scfsi=scfsi_buf;

        for(i=sblimit2;i;i--)
        if(*bita++) *scfsi++ = (char) getbits_fast(fr, 2);
    }
    else /* mono */
    {
        for(i=sblimit;i;i--,alloc1+=(1<<step))
        {
            step=alloc1->bits;
            *bita++ = (char) getbits(fr, step);
        }
        bita = bit_alloc;
        scfsi=scfsi_buf;
        for(i=sblimit;i;i--)
        if(*bita++) *scfsi++ = (char) getbits_fast(fr, 2);
    }

    bita = bit_alloc;
    scfsi=scfsi_buf;
    for(i=sblimit2;i;i--)
    if(*bita++)
    switch(*scfsi++)
    {
        case 0: 
            *scale++ = getbits_fast(fr, 6);
            *scale++ = getbits_fast(fr, 6);
            *scale++ = getbits_fast(fr, 6);
        break;
        case 1 : 
            *scale++ = sc = getbits_fast(fr, 6);
            *scale++ = sc;
            *scale++ = getbits_fast(fr, 6);
        break;
        case 2: 
            *scale++ = sc = getbits_fast(fr, 6);
            *scale++ = sc;
            *scale++ = sc;
        break;
        default:              /* case 3 */
            *scale++ = getbits_fast(fr, 6);
            *scale++ = sc = getbits_fast(fr, 6);
            *scale++ = sc;
        break;
    }
}


void II_step_two(unsigned int *bit_alloc,real fraction[2][4][SBLIMIT],int *scale,mpg123_handle *fr,int x1)
{
    int i,j,k,ba;
    int stereo = fr->stereo;
    int sblimit = fr->II_sblimit;
    int jsbound = fr->jsbound;
    const struct al_table *alloc2,*alloc1 = fr->alloc;
    unsigned int *bita=bit_alloc;
    int d1,step;

    for(i=0;i<jsbound;i++,alloc1+=(1<<step))
    {
        step = alloc1->bits;
        for(j=0;j<stereo;j++)
        {
            if( (ba=*bita++) ) 
            {
                k=(alloc2 = alloc1+ba)->bits;
                if( (d1=alloc2->d) < 0) 
                {
                    real cm=fr->muls[k][scale[x1]];
                    fraction[j][0][i] = REAL_MUL_SCALE_LAYER12(DOUBLE_TO_REAL_15((int)getbits(fr, k) + d1), cm);
                    fraction[j][1][i] = REAL_MUL_SCALE_LAYER12(DOUBLE_TO_REAL_15((int)getbits(fr, k) + d1), cm);
                    fraction[j][2][i] = REAL_MUL_SCALE_LAYER12(DOUBLE_TO_REAL_15((int)getbits(fr, k) + d1), cm);
                }        
                else 
                {
                    const int *table[] = { 0,0,0,grp_3tab,0,grp_5tab,0,0,0,grp_9tab };
                    unsigned int idx,*tab,m=scale[x1];
                    idx = (unsigned int) getbits(fr, k);
                    tab = (unsigned int *) (table[d1] + idx + idx + idx);
                    fraction[j][0][i] = REAL_SCALE_LAYER12(fr->muls[*tab++][m]);
                    fraction[j][1][i] = REAL_SCALE_LAYER12(fr->muls[*tab++][m]);
                    fraction[j][2][i] = REAL_SCALE_LAYER12(fr->muls[*tab][m]);  
                }
                scale+=3;
            }
            else
            fraction[j][0][i] = fraction[j][1][i] = fraction[j][2][i] = DOUBLE_TO_REAL(0.0);
        }
    }

    for(i=jsbound;i<sblimit;i++,alloc1+=(1<<step))
    {
        step = alloc1->bits;
        bita++; /* channel 1 and channel 2 bitalloc are the same */
        if( (ba=*bita++) )
        {
            k=(alloc2 = alloc1+ba)->bits;
            if( (d1=alloc2->d) < 0)
            {
                real cm;
                cm=fr->muls[k][scale[x1+3]];
                fraction[0][0][i] = DOUBLE_TO_REAL_15((int)getbits(fr, k) + d1);
                fraction[0][1][i] = DOUBLE_TO_REAL_15((int)getbits(fr, k) + d1);
                fraction[0][2][i] = DOUBLE_TO_REAL_15((int)getbits(fr, k) + d1);
                fraction[1][0][i] = REAL_MUL_SCALE_LAYER12(fraction[0][0][i], cm);
                fraction[1][1][i] = REAL_MUL_SCALE_LAYER12(fraction[0][1][i], cm);
                fraction[1][2][i] = REAL_MUL_SCALE_LAYER12(fraction[0][2][i], cm);
                cm=fr->muls[k][scale[x1]];
                fraction[0][0][i] = REAL_MUL_SCALE_LAYER12(fraction[0][0][i], cm);
                fraction[0][1][i] = REAL_MUL_SCALE_LAYER12(fraction[0][1][i], cm);
                fraction[0][2][i] = REAL_MUL_SCALE_LAYER12(fraction[0][2][i], cm);
            }
            else
            {
                const int *table[] = { 0,0,0,grp_3tab,0,grp_5tab,0,0,0,grp_9tab };
                unsigned int idx,*tab,m1,m2;
                m1 = scale[x1]; m2 = scale[x1+3];
                idx = (unsigned int) getbits(fr, k);
                tab = (unsigned int *) (table[d1] + idx + idx + idx);
                fraction[0][0][i] = REAL_SCALE_LAYER12(fr->muls[*tab][m1]); fraction[1][0][i] = REAL_SCALE_LAYER12(fr->muls[*tab++][m2]);
                fraction[0][1][i] = REAL_SCALE_LAYER12(fr->muls[*tab][m1]); fraction[1][1][i] = REAL_SCALE_LAYER12(fr->muls[*tab++][m2]);
                fraction[0][2][i] = REAL_SCALE_LAYER12(fr->muls[*tab][m1]); fraction[1][2][i] = REAL_SCALE_LAYER12(fr->muls[*tab][m2]);
            }
            scale+=6;
        }
        else
        {
            fraction[0][0][i] = fraction[0][1][i] = fraction[0][2][i] =
            fraction[1][0][i] = fraction[1][1][i] = fraction[1][2][i] = DOUBLE_TO_REAL(0.0);
        }
/*
    Historic comment...
    should we use individual scalefac for channel 2 or
    is the current way the right one , where we just copy channel 1 to
    channel 2 ?? 
    The current 'strange' thing is, that we throw away the scalefac
    values for the second channel ...!!
    -> changed .. now we use the scalefac values of channel one !! 
*/
    }

    if(sblimit > (fr->down_sample_sblimit) )
    sblimit = fr->down_sample_sblimit;

    for(i=sblimit;i<SBLIMIT;i++)
    for (j=0;j<stereo;j++)
    fraction[j][0][i] = fraction[j][1][i] = fraction[j][2][i] = DOUBLE_TO_REAL(0.0);
}


static void II_select_table(mpg123_handle *fr)
{
    const int translate[3][2][16] =
    {
        {
            { 0,2,2,2,2,2,2,0,0,0,1,1,1,1,1,0 },
            { 0,2,2,0,0,0,1,1,1,1,1,1,1,1,1,0 }
        },
        {
            { 0,2,2,2,2,2,2,0,0,0,0,0,0,0,0,0 },
            { 0,2,2,0,0,0,0,0,0,0,0,0,0,0,0,0 }
        },
        {
            { 0,3,3,3,3,3,3,0,0,0,1,1,1,1,1,0 },
            { 0,3,3,0,0,0,1,1,1,1,1,1,1,1,1,0 }
        }
    };

    int table,sblim;
    const struct al_table *tables[5] = { alloc_0, alloc_1, alloc_2, alloc_3 , alloc_4 };
    const int sblims[5] = { 27 , 30 , 8, 12 , 30 };

    if(fr->sampling_frequency >= 3) /* Or equivalent: (fr->lsf == 1) */
    table = 4;
    else
    table = translate[fr->sampling_frequency][2-fr->stereo][fr->bitrate_index];

    sblim = sblims[table];
    fr->alloc      = tables[table];
    fr->II_sblimit = sblim;
}


int do_layer2(mpg123_handle *fr)
{
    int clip=0;
    int i,j;
    int stereo = fr->stereo;
    /* pick_table clears unused subbands */
    /* replacement for real fraction[2][4][SBLIMIT], needs alignment. */
    real (*fraction)[4][SBLIMIT] = fr->layer2.fraction;
    unsigned int bit_alloc[64];
    int scale[192];
    int single = fr->single;

    II_select_table(fr);
    fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ? (fr->mode_ext<<2)+4 : fr->II_sblimit;

    if(fr->jsbound > fr->II_sblimit)
    {
        fprintf(stderr, "Truncating stereo boundary to sideband limit.\n");
        fr->jsbound=fr->II_sblimit;
    }

    /* TODO: What happens with mono mixing, actually? */
    if(stereo == 1 || single == SINGLE_MIX) /* also, mix not really handled */
    single = SINGLE_LEFT;

    II_step_one(bit_alloc, scale, fr);

    for(i=0;i<SCALE_BLOCK;i++)
    {
        II_step_two(bit_alloc,fraction,scale,fr,i>>2);
        for(j=0;j<3;j++) 
        {
            if(single != SINGLE_STEREO)
            clip += (fr->synth_mono)(fraction[single][j], fr);
            else
            clip += (fr->synth_stereo)(fraction[0][j], fraction[1][j], fr);
        }
    }

    return clip;
}

#endif /* NO_LAYER2 */