g72x.c

Vovida 社区开源的 SIP 协议源码

    dqthr = (thr2 + (thr2 >> 1)) >> 1; 	/* dqthr = 0.75 * thr2 */
    if (state_ptr->td == 0)		/* signal supposed voice */
        tr = 0;
    else if (mag <= dqthr)		/* supposed data, but small mag */
        tr = 0; 			/* treated as voice */
    else				/* signal is data (modem) */
        tr = 1;

    /*
     * Quantizer scale factor adaptation.
     */

    /* FUNCTW & FILTD & DELAY */
    /* update non-steady state step size multiplier */
    state_ptr->yu = y + ((wi - y) >> 5);

    /* LIMB */
    if (state_ptr->yu < 544)	/* 544 <= yu <= 5120 */
        state_ptr->yu = 544;
    else if (state_ptr->yu > 5120)
        state_ptr->yu = 5120;

    /* FILTE & DELAY */
    /* update steady state step size multiplier */
    state_ptr->yl += state_ptr->yu + (( -state_ptr->yl) >> 6);

    /*
     * Adaptive predictor coefficients.
     */
    if (tr == 1)
    {			/* reset a's and b's for modem signal */
        state_ptr->a[0] = 0;
        state_ptr->a[1] = 0;
        state_ptr->b[0] = 0;
        state_ptr->b[1] = 0;
        state_ptr->b[2] = 0;
        state_ptr->b[3] = 0;
        state_ptr->b[4] = 0;
        state_ptr->b[5] = 0;
    }
    else
    {			/* update a's and b's */
        pks1 = pk0 ^ state_ptr->pk[0]; 		/* UPA2 */

        /* update predictor pole a[1] */
        a2p = state_ptr->a[1] - (state_ptr->a[1] >> 7);
        if (dqsez != 0)
        {
            fa1 = (pks1) ? state_ptr->a[0] : -state_ptr->a[0];
            if (fa1 < -8191)	/* a2p = function of fa1 */
                a2p -= 0x100;
            else if (fa1 > 8191)
                a2p += 0xFF;
            else
                a2p += fa1 >> 5;

            if (pk0 ^ state_ptr->pk[1])
                /* LIMC */
                if (a2p <= -12160)
                    a2p = -12288;
                else if (a2p >= 12416)
                    a2p = 12288;
                else
                    a2p -= 0x80;
            else if (a2p <= -12416)
                a2p = -12288;
            else if (a2p >= 12160)
                a2p = 12288;
            else
                a2p += 0x80;
        }

        /* TRIGB & DELAY */
        state_ptr->a[1] = a2p;

        /* UPA1 */
        /* update predictor pole a[0] */
        state_ptr->a[0] -= state_ptr->a[0] >> 8;
        if (dqsez != 0)
        {
            if (pks1 == 0)
                state_ptr->a[0] += 192;
            else
                state_ptr->a[0] -= 192;
        }

        /* LIMD */
        a1ul = 15360 - a2p;
        if (state_ptr->a[0] < -a1ul)
            state_ptr->a[0] = -a1ul;
        else if (state_ptr->a[0] > a1ul)
            state_ptr->a[0] = a1ul;

        /* UPB : update predictor zeros b[6] */
        for (cnt = 0; cnt < 6; cnt++)
        {
            if (code_size == 5)		/* for 40Kbps G.723 */
                state_ptr->b[cnt] -= state_ptr->b[cnt] >> 9;
            else			/* for G.721 and 24Kbps G.723 */
                state_ptr->b[cnt] -= state_ptr->b[cnt] >> 8;
            if (dq & 0x7FFF)
            {			/* XOR */
                if ((dq ^ state_ptr->dq[cnt]) >= 0)
                    state_ptr->b[cnt] += 128;
                else
                    state_ptr->b[cnt] -= 128;
            }
        }
    }

    for (cnt = 5; cnt > 0; cnt--)
        state_ptr->dq[cnt] = state_ptr->dq[cnt - 1];
    /* FLOAT A : convert dq[0] to 4-bit exp, 6-bit mantissa f.p. */
    if (mag == 0)
    {
        state_ptr->dq[0] = (dq >= 0) ? 0x20 : 0xFC20;
    }
    else
    {
        exp = quan(mag, power2, 15);
        state_ptr->dq[0] = (dq >= 0) ?
                           (exp << 6) + ((mag << 6) >> exp) :
                           (exp << 6) + ((mag << 6) >> exp) - 0x400;
    }

    state_ptr->sr[1] = state_ptr->sr[0];
    /* FLOAT B : convert sr to 4-bit exp., 6-bit mantissa f.p. */
    if (sr == 0)
    {
        state_ptr->sr[0] = 0x20;
    }
    else if (sr > 0)
    {
        exp = quan(sr, power2, 15);
        state_ptr->sr[0] = (exp << 6) + ((sr << 6) >> exp);
    }
    else if (sr > -32768)
    {
        mag = -sr;
        exp = quan(mag, power2, 15);
        state_ptr->sr[0] = (exp << 6) + ((mag << 6) >> exp) - 0x400;
    }
    else
        state_ptr->sr[0] = 0xFC20;

    /* DELAY A */
    state_ptr->pk[1] = state_ptr->pk[0];
    state_ptr->pk[0] = pk0;

    /* TONE */
    if (tr == 1)		/* this sample has been treated as data */
        state_ptr->td = 0; 	/* next one will be treated as voice */
    else if (a2p < -11776)	/* small sample-to-sample correlation */
        state_ptr->td = 1; 	/* signal may be data */
    else				/* signal is voice */
        state_ptr->td = 0;

    /*
     * Adaptation speed control.
     */
    state_ptr->dms += (fi - state_ptr->dms) >> 5; 		/* FILTA */
    state_ptr->dml += (((fi << 2) - state_ptr->dml) >> 7); 	/* FILTB */

    if (tr == 1)
        state_ptr->ap = 256;
    else if (y < 1536)					/* SUBTC */
        state_ptr->ap += (0x200 - state_ptr->ap) >> 4;
    else if (state_ptr->td == 1)
        state_ptr->ap += (0x200 - state_ptr->ap) >> 4;
    else if (abs((state_ptr->dms << 2) - state_ptr->dml) >=
             (state_ptr->dml >> 3))
        state_ptr->ap += (0x200 - state_ptr->ap) >> 4;
    else
        state_ptr->ap += ( -state_ptr->ap) >> 4;
}

/*
 * tandem_adjust(sr, se, y, i, sign)
 *
 * At the end of ADPCM decoding, it simulates an encoder which may be receiving
 * the output of this decoder as a tandem process. If the output of the
 * simulated encoder differs from the input to this decoder, the decoder output
 * is adjusted by one level of A-law or u-law codes.
 *
 * Input:
 *	sr	decoder output linear PCM sample,
 *	se	predictor estimate sample,
 *	y	quantizer step size,
 *	i	decoder input code,
 *	sign	sign bit of code i
 *
 * Return:
 *	adjusted A-law or u-law compressed sample.
 */
int
tandem_adjust_alaw(
    int	sr, 	/* decoder output linear PCM sample */
    int	se, 	/* predictor estimate sample */
    int	y, 	/* quantizer step size */
    int	i, 	/* decoder input code */
    int	sign,
    short	*qtab)
{
    unsigned char	sp; 	/* A-law compressed 8-bit code */
    short	dx; 	/* prediction error */
    char	id; 	/* quantized prediction error */
    int	sd; 	/* adjusted A-law decoded sample value */
    int	im; 	/* biased magnitude of i */
    int	imx; 	/* biased magnitude of id */

    if (sr <= -32768)
        sr = -1;
    sp = linear2alaw((sr >> 1) << 3); 	/* short to A-law compression */
    dx = (alaw2linear(sp) >> 2) - se; 	/* 16-bit prediction error */
    id = quantize(dx, y, qtab, sign - 1);

    if (id == i)
    {			/* no adjustment on sp */
        return (sp);
    }
    else
    {			/* sp adjustment needed */
        /* ADPCM codes : 8, 9, ... F, 0, 1, ... , 6, 7 */
        im = i ^ sign; 		/* 2's complement to biased unsigned */
        imx = id ^ sign;

        if (imx > im)
        {		/* sp adjusted to next lower value */
            if (sp & 0x80)
            {
                sd = (sp == 0xD5) ? 0x55 :
                     ((sp ^ 0x55) - 1) ^ 0x55;
            }
            else
            {
                sd = (sp == 0x2A) ? 0x2A :
                     ((sp ^ 0x55) + 1) ^ 0x55;
            }
        }
        else
        {		/* sp adjusted to next higher value */
            if (sp & 0x80)
                sd = (sp == 0xAA) ? 0xAA :
                     ((sp ^ 0x55) + 1) ^ 0x55;
            else
                sd = (sp == 0x55) ? 0xD5 :
                     ((sp ^ 0x55) - 1) ^ 0x55;
        }
        return (sd);
    }
}

int
tandem_adjust_ulaw(
    int	sr, 	/* decoder output linear PCM sample */
    int	se, 	/* predictor estimate sample */
    int	y, 	/* quantizer step size */
    int	i, 	/* decoder input code */
    int	sign,
    short	*qtab)
{
    unsigned char	sp; 	/* u-law compressed 8-bit code */
    short	dx; 	/* prediction error */
    char	id; 	/* quantized prediction error */
    int	sd; 	/* adjusted u-law decoded sample value */
    int	im; 	/* biased magnitude of i */
    int	imx; 	/* biased magnitude of id */

    if (sr <= -32768)
        sr = 0;
    sp = linear2ulaw(sr << 2); 	/* short to u-law compression */
    dx = (ulaw2linear(sp) >> 2) - se; 	/* 16-bit prediction error */
    id = quantize(dx, y, qtab, sign - 1);
    if (id == i)
    {
        return (sp);
    }
    else
    {
        /* ADPCM codes : 8, 9, ... F, 0, 1, ... , 6, 7 */
        im = i ^ sign; 		/* 2's complement to biased unsigned */
        imx = id ^ sign;
        if (imx > im)
        {		/* sp adjusted to next lower value */
            if (sp & 0x80)
                sd = (sp == 0xFF) ? 0x7E : sp + 1;
            else
                sd = (sp == 0) ? 0 : sp - 1;

        }
        else
        {		/* sp adjusted to next higher value */
            if (sp & 0x80)
                sd = (sp == 0x80) ? 0x80 : sp - 1;
            else
                sd = (sp == 0x7F) ? 0xFE : sp + 1;
        }
        return (sd);
    }
}