g727.c

Reference Implementation of G.711 standard and other voice codecs

{
    Int16 ome = 15360;
    Int16 a1ul = (ome + 65536UL - a2p) & 65535;
    Int16 a1ll = (a2p + 65536UL - ome) & 65535;

    return (32768 <= a1t && a1t <= a1ll) ? a1ll :
           ((a1ul <= a1t && a1t <= 32767) ? a1ul : a1t);
}


Int16
g727_aprsc_trigb(Int8 tr, Int16 anp)
{
    Int16 anr;

    if (tr == 0)
        anr = anp;
    else if (tr == 1)
        anr = 0;
    else
        assert(0);

    return anr;
}


Int16
g727_upa1(g727_aprsc_state *st, Int8 pk0, Int8 sigpk)
{
    Int8 pks = pk0 ^ st->pk1;
    Int16 uga1;
    Int8 a1s;
    Int16 ula1;
    Int16 ua1;

    if (pks == 0 && sigpk == 0)
        uga1 = 192;
    else if (pks == 1 && sigpk == 0)
        uga1 = 65344;
    else if (sigpk == 1)
        uga1 = 0;
    else
        assert(0);

    a1s = st->a1 >> 15;

    if (a1s == 0)
        ula1 = (65536 - (st->a1 >> 8)) & 65535;
    else if (a1s == 1)
        ula1 = (65536 - ((st->a1 >> 8) + 65280UL)) & 65535;
    else
        assert(0);

    ua1 = (uga1 + ula1) & 65535;

    return (st->a1 + ua1) & 65535;
}


Int16
g727_upa2(g727_aprsc_state *st, Int8 pk0, Int8 sigpk)
{
    Int8 pks1 = pk0 ^ st->pk1;
    Int8 pks2 = pk0 ^ st->pk2;
    Int32 uga2a;
    Int8 a1s;
    Int32 fa1;
    Int32 fa;
    Int32 uga2b;
    Int8 uga2s;
    Int16 uga2;
    Int8 a2s;
    Int16 ula2;
    Int16 ua2;

    if (pks2 == 0)
        uga2a = 16384;
    else if (pks2 == 1)
        uga2a = 114688;
    else
        assert(0);

    a1s = st->a1 >> 15;

    if (a1s == 0)
        fa1 = (st->a1 <= 8191) ? ((Int32)st->a1 << 2) : (8191U << 2);
    else if (a1s == 1)
        fa1 = (st->a1 >= 57345) ? (((Int32)st->a1 << 2) & 131071) :
              (24577UL << 2);
    else
        assert(0);

    if (pks1 == 1)
        fa = fa1;
    else if (pks1 == 0)
        fa = (131072 - fa1) & 131071;
    else
        assert(0);

    uga2b = (uga2a + fa) & 131071;
    uga2s = uga2b >> 16;

    if (uga2s == 0 && sigpk == 0)
        uga2 = uga2b >> 7;
    else if (uga2s == 1 && sigpk == 0)
        uga2 = (uga2b >> 7) + 64512;
    else if (sigpk == 1)
        uga2 = 0;
    else
        assert(0);

    a2s = st->a2 >> 15;

    if (a2s == 0)
        ula2 = (65536 - (st->a2 >> 7)) & 65535;
    else if (a2s == 1)
        ula2 = (65536 - ((st->a2 >> 7) + 65024)) & 65535;
    else
        assert(0);

    ua2 = (uga2 + ula2) & 65535;

    return (st->a2 + ua2) & 65535;
}


Int16
g727_upb(Int8 un, Int16 bn, Int16 dq)
{
    Int16 dqmag = dq & 16383;
    Int16 ugbn;
    Int8 bns;
    Int16 ulbn;
    Int16 ubn;

    if (un == 0 && dqmag != 0)
        ugbn = 128;
    else if (un == 1 && dqmag != 0)
        ugbn = 65408;
    else if (dqmag == 0)
        ugbn = 0;
    else
        assert(0);

    bns = bn >> 15;

    if (bns == 0)
        ulbn = (65536 - (bn >> 8)) & 65535;
    else if (bns == 1)
        ulbn = (65536 - ((bn >> 8) + 65280)) & 65535;
    else
        assert(0);

    ubn = (ugbn + ulbn) & 65535;

    return (bn + ubn) & 65535;
}


Int8
g727_xor(Int16 dqn, Int16 dq)
{
    Int8 dqs = dq >> 14;
    Int8 dqns = dqn >> 10;

    return dqs ^ dqns;
}


/*---------- Reconstructed signal calculator ----------*/
/*---------- Feed-Forward Path (G.727 6.2.8) ----------*/

Int16
g727_get_srff(Int16 dqff, Int16 se)
{
    return g727_addb(dqff, se);
}


/*---------- Tone and Transition Detector (G.727 6.2.9) ----------*/

void
g727_ttd_reset(g727_ttd_state *st)
{
    st->td = 0;
}


Int8
g727_get_tr(g727_ttd_state *st, Int32 yl, Int16 dq)
{
    return g727_trans(st, yl, dq);
}


Int8
g727_get_tdp(Int16 a2p)
{
    return g727_tone(a2p);
}


void
g727_ttd_transit(g727_ttd_state *st, Int8 tr, Int8 tdp)
{
    st->td = g727_ttd_trigb(tr, tdp);
}


Int8
g727_tone(Int16 a2p)
{
    return (32768 <= a2p && a2p < 53760) ? 1 : 0;
}


Int8
g727_trans(g727_ttd_state *st, Int32 yl, Int16 dq)
{
    Int16 dqmag = dq & 16383;
    Int8 ylint = yl >> 15;
    Int8 ylfrac = (yl >> 10) & 31;

    Int32 thr1 = (32 + ylfrac) << ylint;
    Int32 thr2 = (ylint > 8) ? (31 << 9) : thr1;

    Int32 dqthr = (thr2 + (thr2 >> 1)) >> 1;

    return (dqmag > dqthr && st->td == 1) ? 1 : 0;
}


Int8
g727_ttd_trigb(Int8 tr, Int8 tdp)
{
    Int8 tdr;

    if (tr == 0)
        tdr = tdp;
    else if (tr == 1)
        tdr = 0;
    else
        assert(0);

    return tdr;
}


/*---------- Output PCM Format Conversion and Synchronous -----------*/
/*---------- Coding Adjustment (G.727 6.2.9) ------------------------*/

Int8
g727_get_sd(Int16 sr, Int16 se, Int8 in, Int16 y, short law, short rate)
{
    Int8 sp = g727_compress(sr, law);

    Int16 dl;
    Int8 ds;
    g727_log(&dl, &ds, g727_subta(g727_expand(sp, law), se));

    return g727_sync(in, sp, g727_subtb(dl, y), law, ds, rate);
}


Int8
g727_compress(Int16 sr, short law)
{
    Int8 is = sr >> 15;
    Int16 im;
    Int16 imag;
    Int16 sp;

    if (is == 0)
        im = sr;
    else if (is == 1)
        im = (65536 - sr) & 32767;
    else
        assert(0);

    if (law == 0)
        imag = im;
    else if (is == 0)
        imag = im >> 1;
    else if (is == 1)
        imag = (im + 1) >> 1;
    else
        assert(0);

    if (law == 1) {         /* A law */
        if (imag == 0)
            sp = 0;
        else {
            if (is == 1)
                imag -= 1;

            if (4095 < imag)
                sp = 0x7f;      /* Absolute maximum of PCM signal. */
            else if (2047 < imag)
                sp = 0x70 | ((imag >> 7) & 0xf);
            else if (1023 < imag)
                sp = 0x60 | ((imag >> 6) & 0xf);
            else if (511 < imag)
                sp = 0x50 | ((imag >> 5) & 0xf);
            else if (255 < imag)
                sp = 0x40 | ((imag >> 4) & 0xf);
            else if (127 < imag)
                sp = 0x30 | ((imag >> 3) & 0xf);
            else if (63 < imag)
                sp = 0x20 | ((imag >> 2) & 0xf);
            else if (31 < imag)
                sp = 0x10 | ((imag >> 1) & 0xf);
            else
                sp = (imag >> 1) & 0xf;
        }
    }
    else {                  /* U law */
        imag += 33;

        if (8191 < imag)
            sp = 0x7f;      /* Absolute maximum of PCM signal. */
        else if (4095 < imag)
            sp = 0x70 | ((imag >> 8) & 0xf);
        else if (2047 < imag)
            sp = 0x60 | ((imag >> 7) & 0xf);
        else if (1023 < imag)
            sp = 0x50 | ((imag >> 6) & 0xf);
        else if (511 < imag)
            sp = 0x40 | ((imag >> 5) & 0xf);
        else if (255 < imag)
            sp = 0x30 | ((imag >> 4) & 0xf);
        else if (127 < imag)
            sp = 0x20 | ((imag >> 3) & 0xf);
        else if (63 < imag)
            sp = 0x10 | ((imag >> 2) & 0xf);
        else
            sp = (imag >> 1) & 0xf;
    }

    sp |= is << 7;

    return sp;
}


Int8
g727_sync(Int8 in, Int8 sp, Int16 dlnx, short law, Int8 ds, short rate)
{
    Int8 is;
    Int8 im;
    Int8 id;
    Int8 sd;

    switch (rate) {
        case 5:
            is = in >> 4;

            if (is == 0)
                im = in + 16;
            else if (is == 1)
                im = in & 15;
            else
                assert(0);

            if (4096 <= dlnx)
                assert(0);
            else if (4089 <= dlnx)
                id = 18;
            else if (3961 <= dlnx)
                id = 17;
            else if (2048 <= dlnx)
                id = 16;
            else if (439 <= dlnx)
                id = 31;
            else if (405 <= dlnx)
                id = 30;
            else if (380 <= dlnx)
                id = 29;
            else if (356 <= dlnx)
                id = 28;
            else if (333 <= dlnx)
                id = 27;
            else if (310 <= dlnx)
                id = 26;
            else if (286 <= dlnx)
                id = 25;
            else if (261 <= dlnx)
                id = 24;
            else if (233 <= dlnx)
                id = 23;
            else if (202 <= dlnx)
                id = 22;
            else if (166 <= dlnx)
                id = 21;
            else if (123 <= dlnx)
                id = 20;
            else if (69 <= dlnx)
                id = 19;
            else
                id = 18;

            id = (ds == 1) ? ((~id) & 0x1f) : id;
            break;

        case 4:
            is = in >> 3;

            if (is == 0)
                im = in + 8;
            else if (is == 1)
                im = in & 7;
            else
                assert(0);

            if (4096 <= dlnx)
                assert(0);
            else if (4089 <= dlnx)
                id = 9;
            else if (2048 <= dlnx)
                id = 8;
            else if (405 <= dlnx)
                id = 15;
            else if (356 <= dlnx)
                id = 14;
            else if (310 <= dlnx)
                id = 13;
            else if (261 <= dlnx)
                id = 12;
            else if (202 <= dlnx)
                id = 11;
            else if (123 <= dlnx)
                id = 10;
            else
                id = 9;

            id = (ds == 1) ? ((~id) & 0xf) : id;
            break;

        case 3:
            is = in >> 2;

            if (is == 0)
                im = in + 4;
            else if (is == 1)
                im = in & 3;
            else
                assert(0);

            if (4096 <= dlnx)
                assert(0);
            else if (2048 <= dlnx)
                id = 4;
            else if (356 <= dlnx)
                id = 7;
            else if (261 <= dlnx)
                id = 6;
            else if (123 <= dlnx)
                id = 5;
            else
                id = 4;

            id = (ds == 1) ? ((~id) & 0x7) : id;
            break;

        case 2:
            is = in >> 1;

            if (is == 0)
                im = in + 2;
            else if (is == 1)
                im = in & 1;
            else
                assert(0);

            if (4096 <= dlnx)
                assert(0);
            else if (2048 <= dlnx)
                id = 2;
            else if (261 <= dlnx)
                id = 3;
            else
                id = 2;

            id = (ds == 1) ? ((~id) & 0x3) : id;
            break;

        default:
            assert(0);
    }

    if (id < im) {
        if (0xff < sp)
            assert(0);
        else if (0x80 < sp)
            sd = sp - 1;
        else if (sp == 0x80)
            sd = (law == 0) ? 1 : 0;
        else if (sp == 0x7f)
            sd = 0x7f;
        else
            sd = sp + 1;
    }
    else if (id > im) {
        if (0xff < sp)
            assert(0);
        else if (sp == 0xff)
            sd = sp;
        else if (0x7f < sp)
            sd = sp + 1;
        else if (0 < sp)
            sd = sp - 1;
        else
            sd = (law == 0) ? 0x81 : 0x80;
    }
    else
        sd = sp;

    return (law == 1) ? (0xd5 ^ sd) : (0xff ^ sd);
}