/*      $OpenBSD: dsp.c,v 1.23 2026/03/15 14:05:25 ratchov Exp $        */
/*
 * Copyright (c) 2008-2012 Alexandre Ratchov <alex@caoua.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
#include <stdio.h>
#include <string.h>
#include "dsp.h"
#include "utils.h"

const int aparams_ctltovol[128] = {
                0,     65536,     68109,     70783,
            73562,     76450,     79451,     82570,
            85812,     89181,     92682,     96321,
           100102,    104032,    108116,    112361,
           116772,    121356,    126121,    131072,
           136218,    141566,    147123,    152899,
           158902,    165140,    171624,    178361,
           185364,    192641,    200204,    208064,
           216232,    224721,    233544,    242713,
           252241,    262144,    272436,    283131,
           294247,    305799,    317804,    330281,
           343247,    356723,    370728,    385282,
           400408,    416128,    432465,    449443,
           467088,    485425,    504482,    524288,
           544871,    566262,    588493,    611597,
           635608,    660561,    686495,    713446,
           741455,    770564,    800816,    832255,
           864929,    898885,    934175,    970850,
          1008965,   1048576,   1089742,   1132525,
          1176987,   1223194,   1271216,   1321123,
          1372989,   1426892,   1482910,   1541128,
          1601632,   1664511,   1729858,   1797771,
          1868350,   1941700,   2017930,   2097152,
          2179485,   2265049,   2353974,   2446389,
          2542432,   2642246,   2745978,   2853783,
          2965821,   3082257,   3203264,   3329021,
          3459716,   3595542,   3736700,   3883400,
          4035859,   4194304,   4358969,   4530099,
          4707947,   4892777,   5084864,   5284492,
          5491957,   5707567,   5931642,   6164513,
          6406527,   6658043,   6919432,   7191084,
          7473400,   7766800,   8071719,   8388608
};

const int resamp_filt[RESAMP_LENGTH / RESAMP_STEP + 1] = {
              0,       0,       3,       9,      22,      42,      73,     116,
            174,     248,     341,     454,     589,     749,     934,    1148,
           1392,    1666,    1974,    2316,    2693,    3107,    3560,    4051,
           4582,    5154,    5766,    6420,    7116,    7853,    8632,    9451,
          10311,   11210,   12148,   13123,   14133,   15178,   16253,   17359,
          18491,   19647,   20824,   22018,   23226,   24443,   25665,   26888,
          28106,   29315,   30509,   31681,   32826,   33938,   35009,   36033,
          37001,   37908,   38744,   39502,   40174,   40750,   41223,   41582,
          41819,   41925,   41890,   41704,   41358,   40842,   40147,   39261,
          38176,   36881,   35366,   33623,   31641,   29411,   26923,   24169,
          21140,   17827,   14222,   10317,    6105,    1580,   -3267,   -8440,
         -13944,  -19785,  -25967,  -32492,  -39364,  -46584,  -54153,  -62072,
         -70339,  -78953,  -87911,  -97209, -106843, -116806, -127092, -137692,
        -148596, -159795, -171276, -183025, -195029, -207271, -219735, -232401,
        -245249, -258259, -271407, -284670, -298021, -311434, -324880, -338329,
        -351750, -365111, -378378, -391515, -404485, -417252, -429775, -442015,
        -453930, -465477, -476613, -487294, -497472, -507102, -516137, -524527,
        -532225, -539181, -545344, -550664, -555090, -558571, -561055, -562490,
        -562826, -562010, -559990, -556717, -552139, -546205, -538866, -530074,
        -519779, -507936, -494496, -479416, -462652, -444160, -423901, -401835,
        -377923, -352132, -324425, -294772, -263143, -229509, -193847, -156134,
        -116348,  -74474,  -30494,   15601,   63822,  114174,  166661,  221283,
         278037,  336916,  397911,  461009,  526194,  593446,  662741,  734054,
         807354,  882608,  959779, 1038826, 1119706, 1202370, 1286768, 1372846,
        1460546, 1549808, 1640566, 1732753, 1826299, 1921130, 2017169, 2114336,
        2212550, 2311723, 2411770, 2512598, 2614116, 2716228, 2818836, 2921841,
        3025142, 3128636, 3232218, 3335782, 3439219, 3542423, 3645282, 3747687,
        3849526, 3950687, 4051059, 4150530, 4248987, 4346320, 4442415, 4537163,
        4630453, 4722177, 4812225, 4900493, 4986873, 5071263, 5153561, 5233668,
        5311485, 5386917, 5459872, 5530259, 5597992, 5662986, 5725160, 5784436,
        5840739, 5893999, 5944148, 5991122, 6034862, 6075313, 6112422, 6146142,
        6176430, 6203247, 6226559, 6246335, 6262551, 6275185, 6284220, 6289647,
        6291456, 6289647, 6284220, 6275185, 6262551, 6246335, 6226559, 6203247,
        6176430, 6146142, 6112422, 6075313, 6034862, 5991122, 5944148, 5893999,
        5840739, 5784436, 5725160, 5662986, 5597992, 5530259, 5459872, 5386917,
        5311485, 5233668, 5153561, 5071263, 4986873, 4900493, 4812225, 4722177,
        4630453, 4537163, 4442415, 4346320, 4248987, 4150530, 4051059, 3950687,
        3849526, 3747687, 3645282, 3542423, 3439219, 3335782, 3232218, 3128636,
        3025142, 2921841, 2818836, 2716228, 2614116, 2512598, 2411770, 2311723,
        2212550, 2114336, 2017169, 1921130, 1826299, 1732753, 1640566, 1549808,
        1460546, 1372846, 1286768, 1202370, 1119706, 1038826,  959779,  882608,
         807354,  734054,  662741,  593446,  526194,  461009,  397911,  336916,
         278037,  221283,  166661,  114174,   63822,   15601,  -30494,  -74474,
        -116348, -156134, -193847, -229509, -263143, -294772, -324425, -352132,
        -377923, -401835, -423901, -444160, -462652, -479416, -494496, -507936,
        -519779, -530074, -538866, -546205, -552139, -556717, -559990, -562010,
        -562826, -562490, -561055, -558571, -555090, -550664, -545344, -539181,
        -532225, -524527, -516137, -507102, -497472, -487294, -476613, -465477,
        -453930, -442015, -429775, -417252, -404485, -391515, -378378, -365111,
        -351750, -338329, -324880, -311434, -298021, -284670, -271407, -258259,
        -245249, -232401, -219735, -207271, -195029, -183025, -171276, -159795,
        -148596, -137692, -127092, -116806, -106843,  -97209,  -87911,  -78953,
         -70339,  -62072,  -54153,  -46584,  -39364,  -32492,  -25967,  -19785,
         -13944,   -8440,   -3267,    1580,    6105,   10317,   14222,   17827,
          21140,   24169,   26923,   29411,   31641,   33623,   35366,   36881,
          38176,   39261,   40147,   40842,   41358,   41704,   41890,   41925,
          41819,   41582,   41223,   40750,   40174,   39502,   38744,   37908,
          37001,   36033,   35009,   33938,   32826,   31681,   30509,   29315,
          28106,   26888,   25665,   24443,   23226,   22018,   20824,   19647,
          18491,   17359,   16253,   15178,   14133,   13123,   12148,   11210,
          10311,    9451,    8632,    7853,    7116,    6420,    5766,    5154,
           4582,    4051,    3560,    3107,    2693,    2316,    1974,    1666,
           1392,    1148,     934,     749,     589,     454,     341,     248,
            174,     116,      73,      42,      22,       9,       3,       0,
              0
};


/*
 * Generate a string corresponding to the encoding in par,
 * return the length of the resulting string.
 */
int
aparams_enctostr(struct aparams *par, char *ostr)
{
        char *p = ostr;

        *p++ = par->sig ? 's' : 'u';
        if (par->bits > 9)
                *p++ = '0' + par->bits / 10;
        *p++ = '0' + par->bits % 10;
        if (par->bps > 1) {
                *p++ = par->le ? 'l' : 'b';
                *p++ = 'e';
                if (par->bps != APARAMS_BPS(par->bits) ||
                    par->bits < par->bps * 8) {
                        *p++ = par->bps + '0';
                        if (par->bits < par->bps * 8) {
                                *p++ = par->msb ? 'm' : 'l';
                                *p++ = 's';
                                *p++ = 'b';
                        }
                }
        }
        *p++ = '\0';
        return p - ostr - 1;
}

/*
 * Parse an encoding string, examples: s8, u8, s16, s16le, s24be ...
 * set *istr to the char following the encoding. Return the number
 * of bytes consumed.
 */
int
aparams_strtoenc(struct aparams *par, char *istr)
{
        char *p = istr;
        int i, sig, bits, le, bps, msb;

#define IS_SEP(c)                       \
        (((c) < 'a' || (c) > 'z') &&    \
         ((c) < 'A' || (c) > 'Z') &&    \
         ((c) < '0' || (c) > '9'))

        /*
         * get signedness
         */
        if (*p == 's') {
                sig = 1;
        } else if (*p == 'u') {
                sig = 0;
        } else
                return 0;
        p++;

        /*
         * get number of bits per sample
         */
        bits = 0;
        for (i = 0; i < 2; i++) {
                if (*p < '0' || *p > '9')
                        break;
                bits = (bits * 10) + *p - '0';
                p++;
        }
        if (bits < BITS_MIN || bits > BITS_MAX)
                return 0;
        bps = APARAMS_BPS(bits);
        msb = 1;
        le = ADATA_LE;

        /*
         * get (optional) endianness
         */
        if (p[0] == 'l' && p[1] == 'e') {
                le = 1;
                p += 2;
        } else if (p[0] == 'b' && p[1] == 'e') {
                le = 0;
                p += 2;
        } else if (IS_SEP(*p)) {
                goto done;
        } else
                return 0;

        /*
         * get (optional) number of bytes
         */
        if (*p >= '0' && *p <= '9') {
                bps = *p - '0';
                if (bps < (bits + 7) / 8 ||
                    bps > (BITS_MAX + 7) / 8)
                        return 0;
                p++;

                /*
                 * get (optional) alignment
                 */
                if (p[0] == 'm' && p[1] == 's' && p[2] == 'b') {
                        msb = 1;
                        p += 3;
                } else if (p[0] == 'l' && p[1] == 's' && p[2] == 'b') {
                        msb = 0;
                        p += 3;
                } else if (IS_SEP(*p)) {
                        goto done;
                } else
                        return 0;
        } else if (!IS_SEP(*p))
                return 0;

done:
        par->msb = msb;
        par->sig = sig;
        par->bits = bits;
        par->bps = bps;
        par->le = le;
        return p - istr;
}

/*
 * Initialise parameters structure with the defaults natively supported
 * by the machine.
 */
void
aparams_init(struct aparams *par)
{
        par->bps = sizeof(adata_t);
        par->bits = ADATA_BITS;
        par->le = ADATA_LE;
        par->sig = 1;
        par->msb = 0;
}

/*
 * return true if encoding corresponds to what we store in adata_t
 */
int
aparams_native(struct aparams *par)
{
        return par->sig &&
            par->bps == sizeof(adata_t) &&
            par->bits == ADATA_BITS &&
            (par->bps == 1 || par->le == ADATA_LE) &&
            (par->bits == par->bps * 8 || !par->msb);
}

/*
 * Return the number of input and output frame that would be consumed
 * by resamp_do(p, *icnt, *ocnt).
 */
void
resamp_getcnt(struct resamp *p, int *icnt, int *ocnt)
{
        long long idiff, odiff;
        int cdiff;

        cdiff = p->oblksz - p->diff;
        idiff = (long long)*icnt * p->oblksz;
        odiff = (long long)*ocnt * p->iblksz;
        if (odiff - idiff >= cdiff)
                *ocnt = (idiff + cdiff + p->iblksz - 1) / p->iblksz;
        else
                *icnt = (odiff + p->diff) / p->oblksz;
}

/*
 * Resample the given number of frames. The number of output frames
 * must match the corresponding number of input frames. Either always
 * use icnt and ocnt such that:
 *
 *       icnt * oblksz = ocnt * iblksz
 *
 * or use resamp_getcnt() to calculate the proper numbers.
 */
void
resamp_do(struct resamp *p, adata_t *in, adata_t *out, int icnt, int ocnt)
{
        unsigned int nch;
        adata_t *idata;
        unsigned int oblksz;
        unsigned int ifr;
        int s, ds, diff;
        adata_t *odata;
        unsigned int iblksz;
        unsigned int ofr;
        unsigned int c;
        int64_t f[NCHAN_MAX];
        adata_t *ctxbuf, *ctx;
        unsigned int ctx_start;
        int q, qi, qf, n;

        /*
         * Partially copy structures into local variables, to avoid
         * unnecessary indirections; this also allows the compiler to
         * order local variables more "cache-friendly".
         */
        idata = in;
        odata = out;
        diff = p->diff;
        iblksz = p->iblksz;
        oblksz = p->oblksz;
        ctxbuf = p->ctx;
        ctx_start = p->ctx_start;
        nch = p->nch;
        ifr = icnt;
        ofr = ocnt;

        /*
         * Start conversion.
         */
#ifdef DEBUG
        logx(4, "resamp: copying %d -> %d frames, diff = %d", ifr, ofr, diff);
#endif
        for (;;) {
                if (diff >= oblksz) {
                        if (ifr == 0)
                                break;
                        ctx_start = (ctx_start - 1) & (RESAMP_NCTX - 1);
                        ctx = ctxbuf + ctx_start;
                        for (c = nch; c > 0; c--) {
                                *ctx = *idata++;
                                ctx += RESAMP_NCTX;
                        }
                        diff -= oblksz;
                        ifr--;
                } else {
                        if (ofr == 0)
                                break;

                        for (c = 0; c < nch; c++)
                                f[c] = 0;

                        q = diff * p->filt_step;
                        n = ctx_start;

                        while (q < RESAMP_LENGTH) {
                                qi = q >> RESAMP_STEP_BITS;
                                qf = q & (RESAMP_STEP - 1);
                                s = resamp_filt[qi];
                                ds = resamp_filt[qi + 1] - s;
                                s += (int64_t)qf * ds >> RESAMP_STEP_BITS;
                                ctx = ctxbuf;
                                for (c = 0; c < nch; c++) {
                                        f[c] += (int64_t)ctx[n] * s;
                                        ctx += RESAMP_NCTX;
                                }
                                q += p->filt_cutoff;
                                n = (n + 1) & (RESAMP_NCTX - 1);
                        }

                        for (c = 0; c < nch; c++) {
                                s = f[c] >> RESAMP_BITS;
                                s = (int64_t)s * p->filt_cutoff >> RESAMP_BITS;
#if ADATA_BITS == 16
                                /*
                                 * In 16-bit mode, we've no room for filter
                                 * overshoots, so we need to clip the signal
                                 * to avoid 16-bit integers to wrap around.
                                 * In 24-bit mode, samples may exceed the
                                 * [-1:1] range. Later, cmap_add() will clip
                                 * them, so no need to clip them here as well.
                                 */
                                if (s >= ADATA_UNIT)
                                        s = ADATA_UNIT - 1;
                                else if (s < -ADATA_UNIT)
                                        s = -ADATA_UNIT;
#endif
                                *odata++ = s;
                        }

                        diff += iblksz;
                        ofr--;
                }
        }
        p->diff = diff;
        p->ctx_start = ctx_start;
#ifdef DEBUG
        if (ifr != 0) {
                logx(0, "resamp_do: %d: too many input frames", ifr);
                panic();
        }
        if (ofr != 0) {
                logx(0, "resamp_do: %d: too many output frames", ofr);
                panic();
        }
#endif
}

static unsigned int
uint_gcd(unsigned int a, unsigned int b)
{
        unsigned int r;

        while (b > 0) {
                r = a % b;
                a = b;
                b = r;
        }
        return a;
}

/*
 * initialize resampler with ibufsz/obufsz factor and "nch" channels
 */
void
resamp_init(struct resamp *p, unsigned int iblksz,
    unsigned int oblksz, int nch)
{
        unsigned int g;

        /*
         * reduce iblksz/oblksz fraction
         */
        g = uint_gcd(iblksz, oblksz);
        iblksz /= g;
        oblksz /= g;

        /*
         * ensure weird rates don't cause integer overflow
         */
        while (iblksz > ADATA_UNIT || oblksz > ADATA_UNIT) {
                iblksz >>= 1;
                oblksz >>= 1;
        }

        p->iblksz = iblksz;
        p->oblksz = oblksz;
        p->diff = 0;
        p->nch = nch;
        p->ctx_start = 0;
        memset(p->ctx, 0, sizeof(p->ctx));
        if (p->iblksz < p->oblksz) {
                p->filt_cutoff = RESAMP_UNIT;
                p->filt_step = RESAMP_UNIT / p->oblksz;
        } else {
                p->filt_cutoff = (int64_t)RESAMP_UNIT * p->oblksz / p->iblksz;
                p->filt_step = RESAMP_UNIT / p->iblksz;
        }
#ifdef DEBUG
        logx(3, "resamp_init: %u/%u", iblksz, oblksz);
#endif
}

/*
 * encode "todo" frames from native to foreign encoding
 */
void
enc_do(struct conv *p, unsigned char *in, unsigned char *out, int todo)
{
        unsigned int f;
        adata_t *idata;
        unsigned int s;
        unsigned int oshift;
        unsigned int obias;
        unsigned int obps;
        unsigned int i;
        unsigned char *odata;
        int obnext;
        int osnext;

#ifdef DEBUG
        logx(4, "enc: copying %u frames", todo);
#endif
        /*
         * Partially copy structures into local variables, to avoid
         * unnecessary indirections; this also allows the compiler to
         * order local variables more "cache-friendly".
         */
        idata = (adata_t *)in;
        odata = out;
        oshift = p->shift;
        obias = p->bias;
        obps = p->bps;
        obnext = p->bnext;
        osnext = p->snext;

        /*
         * Start conversion.
         */
        odata += p->bfirst;
        for (f = todo * p->nch; f > 0; f--) {
                /* convert adata to u32 */
                s = (int)*idata++ + ADATA_UNIT;
                s <<= 32 - ADATA_BITS;
                /* convert u32 to uN */
                s >>= oshift;
                /* convert uN to sN */
                s -= obias;
                /* packetize sN */
                for (i = obps; i > 0; i--) {
                        *odata = (unsigned char)s;
                        s >>= 8;
                        odata += obnext;
                }
                odata += osnext;
        }
}

/*
 * store "todo" frames of silence in foreign encoding
 */
void
enc_sil_do(struct conv *p, unsigned char *out, int todo)
{
        unsigned int f;
        unsigned int s;
        unsigned int oshift;
        int obias;
        unsigned int obps;
        unsigned int i;
        unsigned char *odata;
        int obnext;
        int osnext;

#ifdef DEBUG
        logx(4, "enc: silence %u frames", todo);
#endif
        /*
         * Partially copy structures into local variables, to avoid
         * unnecessary indirections; this also allows the compiler to
         * order local variables more "cache-friendly".
         */
        odata = out;
        oshift = p->shift;
        obias = p->bias;
        obps = p->bps;
        obnext = p->bnext;
        osnext = p->snext;

        /*
         * Start conversion.
         */
        odata += p->bfirst;
        for (f = todo * p->nch; f > 0; f--) {
                s = ((1U << 31) >> oshift) - obias;
                for (i = obps; i > 0; i--) {
                        *odata = (unsigned char)s;
                        s >>= 8;
                        odata += obnext;
                }
                odata += osnext;
        }
}

/*
 * initialize encoder from native to foreign encoding
 */
void
enc_init(struct conv *p, struct aparams *par, int nch)
{
#ifdef DEBUG
        char enc_str[ENCMAX];
#endif

        p->nch = nch;
        p->bps = par->bps;
        if (par->msb) {
                p->shift = 32 - par->bps * 8;
        } else {
                p->shift = 32 - par->bits;
        }
        if (par->sig) {
                p->bias = (1U << 31) >> p->shift;
        } else {
                p->bias = 0;
        }
        if (!par->le) {
                p->bfirst = par->bps - 1;
                p->bnext = -1;
                p->snext = 2 * par->bps;
        } else {
                p->bfirst = 0;
                p->bnext = 1;
                p->snext = 0;
        }
#ifdef DEBUG
        logx(3, "enc: %s, %d channels",
            (aparams_enctostr(par, enc_str), enc_str), p->nch);
#endif
}

/*
 * decode "todo" frames from foreign to native encoding
 */
void
dec_do(struct conv *p, unsigned char *in, unsigned char *out, int todo)
{
        unsigned int f;
        unsigned int ibps;
        unsigned int i;
        unsigned int s = 0xdeadbeef;
        unsigned char *idata;
        int ibnext;
        int isnext;
        unsigned int ibias;
        unsigned int ishift;
        adata_t *odata;

#ifdef DEBUG
        logx(4, "dec: copying %u frames", todo);
#endif
        /*
         * Partially copy structures into local variables, to avoid
         * unnecessary indirections; this also allows the compiler to
         * order local variables more "cache-friendly".
         */
        idata = in;
        odata = (adata_t *)out;
        ibps = p->bps;
        ibnext = p->bnext;
        ibias = p->bias;
        ishift = p->shift;
        isnext = p->snext;

        /*
         * Start conversion.
         */
        idata += p->bfirst;
        for (f = todo * p->nch; f > 0; f--) {
                for (i = ibps; i > 0; i--) {
                        s <<= 8;
                        s |= *idata;
                        idata += ibnext;
                }
                idata += isnext;
                s += ibias;
                s <<= ishift;
                s >>= 32 - ADATA_BITS;
                *odata++ = s - ADATA_UNIT;
        }
}

/*
 * initialize decoder from foreign to native encoding
 */
void
dec_init(struct conv *p, struct aparams *par, int nch)
{
#ifdef DEBUG
        char enc_str[ENCMAX];
#endif

        p->bps = par->bps;
        p->nch = nch;
        if (par->msb) {
                p->shift = 32 - par->bps * 8;
        } else {
                p->shift = 32 - par->bits;
        }
        if (par->sig) {
                p->bias = (1U << 31) >> p->shift;
        } else {
                p->bias = 0;
        }
        if (par->le) {
                p->bfirst = par->bps - 1;
                p->bnext = -1;
                p->snext = 2 * par->bps;
        } else {
                p->bfirst = 0;
                p->bnext = 1;
                p->snext = 0;
        }
#ifdef DEBUG
        logx(3, "dec: %s, %d channels",
            (aparams_enctostr(par, enc_str), enc_str), p->nch);
#endif
}

/*
 * mix "todo" input frames on the output with the given volume
 */
static void
cmap_add(struct cmap *p, void *in, void *out, int vol, int todo)
{
        adata_t *idata, *odata;
        int i, j, nch, istart, inext, onext, ostart, y, v;

#ifdef DEBUG
        logx(4, "cmap: adding %d frames", todo);
#endif
        idata = in;
        odata = out;
        ostart = p->ostart;
        onext = p->onext;
        istart = p->istart;
        inext = p->inext;
        nch = p->nch;
        v = vol;

        /*
         * map/mix input on the output
         */
        for (i = todo; i > 0; i--) {
                odata += ostart;
                idata += istart;
                for (j = nch; j > 0; j--) {
                        y = *odata + ADATA_MUL(*idata, v);
                        if (y >= ADATA_UNIT)
                                y = ADATA_UNIT - 1;
                        else if (y < -ADATA_UNIT)
                                y = -ADATA_UNIT;
                        *odata = y;
                        idata++;
                        odata++;
                }
                odata += onext;
                idata += inext;
        }
}

/*
 * overwrite output with "todo" input frames with the given volume
 */
static void
cmap_copy(struct cmap *p, void *in, void *out, int vol, int todo)
{
        adata_t *idata, *odata;
        int i, j, nch, istart, inext, onext, ostart, v;

#ifdef DEBUG
        logx(4, "cmap: copying %d frames", todo);
#endif
        idata = in;
        odata = out;
        ostart = p->ostart;
        onext = p->onext;
        istart = p->istart;
        inext = p->inext;
        nch = p->nch;
        v = vol;

        /*
         * copy to the output buffer
         */
        for (i = todo; i > 0; i--) {
                idata += istart;
                odata += ostart;
                for (j = nch; j > 0; j--) {
                        *odata = ADATA_MUL(*idata, v);
                        odata++;
                        idata++;
                }
                odata += onext;
                idata += inext;
        }
}

/*
 * Mix or overwrite "todo" input frames on the output with the given volume
 */
void
cmap_do(struct cmap *p, adata_t *in, adata_t *out, int vol, int todo, int mix)
{
        void (*copy_func)(struct cmap *, void *, void *, int, int);
        int offs, i;

        vol /= p->join;
        copy_func = mix ? cmap_add : cmap_copy;

        copy_func(p, in, out, vol, todo);

        offs = 0;
        for (i = p->join - 1; i > 0; i--) {
                offs += p->nch;
                cmap_add(p, in + offs, out, vol, todo);
        }
        offs = 0;
        for (i = p->expand - 1; i > 0; i--) {
                offs += p->nch;
                copy_func(p, in, out + offs, vol, todo);
        }
}

/*
 * initialize channel mapper, to map a subset of input channel range
 * into a subset of the output channel range
 */
void
cmap_init(struct cmap *p,
    int imin, int imax, int isubmin, int isubmax,
    int omin, int omax, int osubmin, int osubmax, int dup)
{
        int inch, onch, nch;

        /*
         * Ignore channels outside of the available sets
         */
        if (isubmin < imin)
                isubmin = imin;
        if (isubmax > imax)
                isubmax = imax;
        if (osubmin < omin)
                osubmin = omin;
        if (osubmax > omax)
                osubmax = omax;

        /*
         * Shrink the input or the output subset to make both subsets of
         * the same size
         */
        inch = isubmax - isubmin + 1;
        onch = osubmax - osubmin + 1;
        nch = (inch < onch) ? inch : onch;
        isubmax = isubmin + nch - 1;
        osubmax = osubmin + nch - 1;

        p->ostart = osubmin - omin;
        p->onext = omax - osubmax;
        p->istart = isubmin - imin;
        p->inext = imax - isubmax;
        p->nch = nch;

        /*
         * how many times we can join or expand the channels?
         */
        p->join = 1;
        p->expand = 1;
        if (dup && nch > 0) {
                if (inch > nch)
                        p->join = inch / nch;
                else if (onch > nch)
                        p->expand = onch / nch;
        }

#ifdef DEBUG
        logx(3, "%s: nch = %d, join = %d, expand = %d, "
            "ostart = %d, onext = %d, istart = %d, inext = %d",  __func__,
            p->nch, p->join, p->nch, p->ostart, p->onext, p->istart, p->inext);
#endif
}