/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2005-2009 Ariff Abdullah <ariff@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * feeder_rate: (Codename: Z Resampler), which means any effort to create
 *              future replacement for this resampler are simply absurd unless
 *              the world decide to add new alphabet after Z.
 *
 * FreeBSD bandlimited sinc interpolator, technically based on
 * "Digital Audio Resampling" by Julius O. Smith III
 *  - http://ccrma.stanford.edu/~jos/resample/
 *
 * The Good:
 * + all out fixed point integer operations, no soft-float or anything like
 *   that.
 * + classic polyphase converters with high quality coefficient's polynomial
 *   interpolators.
 * + fast, faster, or the fastest of its kind.
 * + compile time configurable.
 * + etc etc..
 *
 * The Bad:
 * - The z, z_, and Z_ . Due to mental block (or maybe just 0x7a69), I
 *   couldn't think of anything simpler than that (feeder_rate_xxx is just
 *   too long). Expect possible clashes with other zitizens (any?).
 */

#ifdef _KERNEL
#ifdef HAVE_KERNEL_OPTION_HEADERS
#include "opt_snd.h"
#endif
#include <dev/sound/pcm/sound.h>
#include <dev/sound/pcm/pcm.h>
#include "feeder_if.h"

#define SND_USE_FXDIV
#include "snd_fxdiv_gen.h"
#endif

#include "feeder_rate_gen.h"

#if !defined(_KERNEL) && defined(SND_DIAGNOSTIC)
#undef Z_DIAGNOSTIC
#define Z_DIAGNOSTIC            1
#elif defined(_KERNEL)
#undef Z_DIAGNOSTIC
#endif

#ifndef Z_QUALITY_DEFAULT
#define Z_QUALITY_DEFAULT       Z_QUALITY_LINEAR
#endif

#define Z_RESERVOIR             2048
#define Z_RESERVOIR_MAX         131072

#define Z_SINC_MAX              0x3fffff
#define Z_SINC_DOWNMAX          48              /* 384000 / 8000 */

#ifdef _KERNEL
#define Z_POLYPHASE_MAX         183040          /* 286 taps, 640 phases */
#else
#define Z_POLYPHASE_MAX         1464320         /* 286 taps, 5120 phases */
#endif

#define Z_RATE_DEFAULT          48000

#ifdef _KERNEL
#undef Z_USE_ALPHADRIFT
#define Z_USE_ALPHADRIFT        1
#endif

#define Z_FACTOR_MIN            1
#define Z_FACTOR_MAX            Z_MASK
#define Z_FACTOR_SAFE(v)        (!((v) < Z_FACTOR_MIN || (v) > Z_FACTOR_MAX))

struct z_info;

typedef void (*z_resampler_t)(struct z_info *, uint8_t *);

struct z_info {
        int32_t rsrc, rdst;     /* original source / destination rates */
        int32_t src, dst;       /* rounded source / destination rates */
        int32_t channels;       /* total channels */
        int32_t bps;            /* bytes-per-sample */
        int32_t quality;        /* resampling quality */

        int32_t z_gx, z_gy;     /* interpolation / decimation ratio */
        int32_t z_alpha;        /* output sample time phase / drift */
        uint8_t *z_delay;       /* FIR delay line / linear buffer */
        int32_t *z_coeff;       /* FIR coefficients */
        int32_t *z_dcoeff;      /* FIR coefficients differences */
        int32_t *z_pcoeff;      /* FIR polyphase coefficients */
        int32_t z_scale;        /* output scaling */
        int32_t z_dx;           /* input sample drift increment */
        int32_t z_dy;           /* output sample drift increment */
#ifdef Z_USE_ALPHADRIFT
        int32_t z_alphadrift;   /* alpha drift rate */
        int32_t z_startdrift;   /* buffer start position drift rate */
#endif
        int32_t z_mask;         /* delay line full length mask */
        int32_t z_size;         /* half width of FIR taps */
        int32_t z_full;         /* full size of delay line */
        int32_t z_alloc;        /* largest allocated full size of delay line */
        int32_t z_start;        /* buffer processing start position */
        int32_t z_pos;          /* current position for the next feed */
#ifdef Z_DIAGNOSTIC
        uint32_t z_cycle;       /* output cycle, purely for statistical */
#endif
        int32_t z_maxfeed;      /* maximum feed to avoid 32bit overflow */

        z_resampler_t z_resample;
};

int feeder_rate_min = FEEDRATE_RATEMIN;
int feeder_rate_max = FEEDRATE_RATEMAX;
int feeder_rate_round = FEEDRATE_ROUNDHZ;
int feeder_rate_quality = Z_QUALITY_DEFAULT;

static int feeder_rate_polyphase_max = Z_POLYPHASE_MAX;

#ifdef _KERNEL
static char feeder_rate_presets[] = FEEDER_RATE_PRESETS;
SYSCTL_STRING(_hw_snd, OID_AUTO, feeder_rate_presets, CTLFLAG_RD,
    &feeder_rate_presets, 0, "compile-time rate presets");
SYSCTL_INT(_hw_snd, OID_AUTO, feeder_rate_polyphase_max, CTLFLAG_RWTUN,
    &feeder_rate_polyphase_max, 0, "maximum allowable polyphase entries");

static int
sysctl_hw_snd_feeder_rate_min(SYSCTL_HANDLER_ARGS)
{
        int err, val;

        val = feeder_rate_min;
        err = sysctl_handle_int(oidp, &val, 0, req);

        if (err != 0 || req->newptr == NULL || val == feeder_rate_min)
                return (err);

        if (!(Z_FACTOR_SAFE(val) && val < feeder_rate_max))
                return (EINVAL);

        feeder_rate_min = val;

        return (0);
}
SYSCTL_PROC(_hw_snd, OID_AUTO, feeder_rate_min,
    CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_MPSAFE, 0, sizeof(int),
    sysctl_hw_snd_feeder_rate_min, "I",
    "minimum allowable rate");

static int
sysctl_hw_snd_feeder_rate_max(SYSCTL_HANDLER_ARGS)
{
        int err, val;

        val = feeder_rate_max;
        err = sysctl_handle_int(oidp, &val, 0, req);

        if (err != 0 || req->newptr == NULL || val == feeder_rate_max)
                return (err);

        if (!(Z_FACTOR_SAFE(val) && val > feeder_rate_min))
                return (EINVAL);

        feeder_rate_max = val;

        return (0);
}
SYSCTL_PROC(_hw_snd, OID_AUTO, feeder_rate_max,
    CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_MPSAFE, 0, sizeof(int),
    sysctl_hw_snd_feeder_rate_max, "I",
    "maximum allowable rate");

static int
sysctl_hw_snd_feeder_rate_round(SYSCTL_HANDLER_ARGS)
{
        int err, val;

        val = feeder_rate_round;
        err = sysctl_handle_int(oidp, &val, 0, req);

        if (err != 0 || req->newptr == NULL || val == feeder_rate_round)
                return (err);

        if (val < FEEDRATE_ROUNDHZ_MIN || val > FEEDRATE_ROUNDHZ_MAX)
                return (EINVAL);

        feeder_rate_round = val - (val % FEEDRATE_ROUNDHZ);

        return (0);
}
SYSCTL_PROC(_hw_snd, OID_AUTO, feeder_rate_round,
    CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_MPSAFE, 0, sizeof(int),
    sysctl_hw_snd_feeder_rate_round, "I",
    "sample rate converter rounding threshold");

static int
sysctl_hw_snd_feeder_rate_quality(SYSCTL_HANDLER_ARGS)
{
        struct snddev_info *d;
        struct pcm_channel *c;
        struct pcm_feeder *f;
        int i, err, val;

        val = feeder_rate_quality;
        err = sysctl_handle_int(oidp, &val, 0, req);

        if (err != 0 || req->newptr == NULL || val == feeder_rate_quality)
                return (err);

        if (val < Z_QUALITY_MIN || val > Z_QUALITY_MAX)
                return (EINVAL);

        feeder_rate_quality = val;

        /*
         * Traverse all available channels on each device and try to
         * set resampler quality if and only if it is exist as
         * part of feeder chains and the channel is idle.
         */
        bus_topo_lock();
        for (i = 0; pcm_devclass != NULL &&
            i < devclass_get_maxunit(pcm_devclass); i++) {
                d = devclass_get_softc(pcm_devclass, i);
                if (!PCM_REGISTERED(d))
                        continue;
                PCM_LOCK(d);
                PCM_WAIT(d);
                PCM_ACQUIRE(d);
                CHN_FOREACH(c, d, channels.pcm) {
                        CHN_LOCK(c);
                        f = feeder_find(c, FEEDER_RATE);
                        if (f == NULL || f->data == NULL || CHN_STARTED(c)) {
                                CHN_UNLOCK(c);
                                continue;
                        }
                        (void)FEEDER_SET(f, FEEDRATE_QUALITY, val);
                        CHN_UNLOCK(c);
                }
                PCM_RELEASE(d);
                PCM_UNLOCK(d);
        }
        bus_topo_unlock();

        return (0);
}
SYSCTL_PROC(_hw_snd, OID_AUTO, feeder_rate_quality,
    CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_MPSAFE, 0, sizeof(int),
    sysctl_hw_snd_feeder_rate_quality, "I",
    "sample rate converter quality ("__XSTRING(Z_QUALITY_MIN)"=low .. "
    __XSTRING(Z_QUALITY_MAX)"=high)");
#endif  /* _KERNEL */

/*
 * Resampler type.
 */
#define Z_IS_ZOH(i)             ((i)->quality == Z_QUALITY_ZOH)
#define Z_IS_LINEAR(i)          ((i)->quality == Z_QUALITY_LINEAR)
#define Z_IS_SINC(i)            ((i)->quality > Z_QUALITY_LINEAR)

/*
 * Macroses for accurate sample time drift calculations.
 *
 * gy2gx : given the amount of output, return the _exact_ required amount of
 *         input.
 * gx2gy : given the amount of input, return the _maximum_ amount of output
 *         that will be generated.
 * drift : given the amount of input and output, return the elapsed
 *         sample-time.
 */
#define _Z_GCAST(x)             ((uint64_t)(x))

#if defined(__i386__)
/*
 * This is where i386 being beaten to a pulp. Fortunately this function is
 * rarely being called and if it is, it will decide the best (hopefully)
 * fastest way to do the division. If we can ensure that everything is dword
 * aligned, letting the compiler to call udivdi3 to do the division can be
 * faster compared to this.
 *
 * amd64 is the clear winner here, no question about it.
 */
static __inline uint32_t
Z_DIV(uint64_t v, uint32_t d)
{
        uint32_t hi, lo, quo, rem;

        hi = v >> 32;
        lo = v & 0xffffffff;

        /*
         * As much as we can, try to avoid long division like a plague.
         */
        if (hi == 0)
                quo = lo / d;
        else
                __asm("divl %2"
                    : "=a" (quo), "=d" (rem)
                    : "r" (d), "0" (lo), "1" (hi));

        return (quo);
}
#else
#define Z_DIV(x, y)             ((x) / (y))
#endif

#define _Z_GY2GX(i, a, v)                                               \
        Z_DIV(((_Z_GCAST((i)->z_gx) * (v)) + ((i)->z_gy - (a) - 1)),    \
        (i)->z_gy)

#define _Z_GX2GY(i, a, v)                                               \
        Z_DIV(((_Z_GCAST((i)->z_gy) * (v)) + (a)), (i)->z_gx)

#define _Z_DRIFT(i, x, y)                                               \
        ((_Z_GCAST((i)->z_gy) * (x)) - (_Z_GCAST((i)->z_gx) * (y)))

#define z_gy2gx(i, v)           _Z_GY2GX(i, (i)->z_alpha, v)
#define z_gx2gy(i, v)           _Z_GX2GY(i, (i)->z_alpha, v)
#define z_drift(i, x, y)        _Z_DRIFT(i, x, y)

/*
 * Macroses for SINC coefficients table manipulations.. whatever.
 */
#define Z_SINC_COEFF_IDX(i)     ((i)->quality - Z_QUALITY_LINEAR - 1)

#define Z_SINC_LEN(i)                                                   \
        ((int32_t)(((uint64_t)z_coeff_tab[Z_SINC_COEFF_IDX(i)].len <<   \
            Z_SHIFT) / (i)->z_dy))

#define Z_SINC_BASE_LEN(i)                                              \
        ((z_coeff_tab[Z_SINC_COEFF_IDX(i)].len - 1) >> (Z_DRIFT_SHIFT - 1))

/*
 * Macroses for linear delay buffer operations. Alignment is not
 * really necessary since we're not using true circular buffer, but it
 * will help us guard against possible trespasser. To be honest,
 * the linear block operations does not need guarding at all due to
 * accurate drifting!
 */
#define z_align(i, v)           ((v) & (i)->z_mask)
#define z_next(i, o, v)         z_align(i, (o) + (v))
#define z_prev(i, o, v)         z_align(i, (o) - (v))
#define z_fetched(i)            (z_align(i, (i)->z_pos - (i)->z_start) - 1)
#define z_free(i)               ((i)->z_full - (i)->z_pos)

/*
 * Macroses for Bla Bla .. :)
 */
#define z_copy(src, dst, sz)    (void)memcpy(dst, src, sz)
#define z_feed(...)             FEEDER_FEED(__VA_ARGS__)

static __inline uint32_t
z_min(uint32_t x, uint32_t y)
{

        return ((x < y) ? x : y);
}

static int32_t
z_gcd(int32_t x, int32_t y)
{
        int32_t w;

        while (y != 0) {
                w = x % y;
                x = y;
                y = w;
        }

        return (x);
}

static int32_t
z_roundpow2(int32_t v)
{
        int32_t i;

        i = 1;

        /*
         * Let it overflow at will..
         */
        while (i > 0 && i < v)
                i <<= 1;

        return (i);
}

/*
 * Zero Order Hold, the worst of the worst, an insult against quality,
 * but super fast.
 */
static void
z_feed_zoh(struct z_info *info, uint8_t *dst)
{
        uint32_t cnt;
        uint8_t *src;

        cnt = info->channels * info->bps;
        src = info->z_delay + (info->z_start * cnt);

        /*
         * This is a bit faster than doing bcopy() since we're dealing
         * with possible unaligned samples.
         */
        do {
                *dst++ = *src++;
        } while (--cnt != 0);
}

/*
 * Linear Interpolation. This at least sounds better (perceptually) and fast,
 * but without any proper filtering which means aliasing still exist and
 * could become worst with a right sample. Interpolation centered within
 * Z_LINEAR_ONE between the present and previous sample and everything is
 * done with simple 32bit scaling arithmetic.
 */
#define Z_DECLARE_LINEAR(SIGN, BIT, ENDIAN)                                     \
static void                                                                     \
z_feed_linear_##SIGN##BIT##ENDIAN(struct z_info *info, uint8_t *dst)            \
{                                                                               \
        int32_t z;                                                              \
        intpcm_t x, y;                                                          \
        uint32_t ch;                                                            \
        uint8_t *sx, *sy;                                                       \
                                                                                \
        z = ((uint32_t)info->z_alpha * info->z_dx) >> Z_LINEAR_UNSHIFT;         \
                                                                                \
        sx = info->z_delay + (info->z_start * info->channels *                  \
            PCM_##BIT##_BPS);                                                   \
        sy = sx - (info->channels * PCM_##BIT##_BPS);                           \
                                                                                \
        ch = info->channels;                                                    \
                                                                                \
        do {                                                                    \
                x = pcm_sample_read(sx, AFMT_##SIGN##BIT##_##ENDIAN);           \
                y = pcm_sample_read(sy, AFMT_##SIGN##BIT##_##ENDIAN);           \
                x = Z_LINEAR_INTERPOLATE_##BIT(z, x, y);                        \
                pcm_sample_write(dst, x, AFMT_##SIGN##BIT##_##ENDIAN);          \
                sx += PCM_##BIT##_BPS;                                          \
                sy += PCM_##BIT##_BPS;                                          \
                dst += PCM_##BIT##_BPS;                                         \
        } while (--ch != 0);                                                    \
}

/*
 * Userland clipping diagnostic check, not enabled in kernel compilation.
 * While doing sinc interpolation, unrealistic samples like full scale sine
 * wav will clip, but for other things this will not make any noise at all.
 * Everybody should learn how to normalized perceived loudness of their own
 * music/sounds/samples (hint: ReplayGain).
 */
#ifdef Z_DIAGNOSTIC
#define Z_CLIP_CHECK(v, BIT)    do {                                    \
        if ((v) > PCM_S##BIT##_MAX) {                                   \
                fprintf(stderr, "Overflow: v=%jd, max=%jd\n",           \
                    (intmax_t)(v), (intmax_t)PCM_S##BIT##_MAX);         \
        } else if ((v) < PCM_S##BIT##_MIN) {                            \
                fprintf(stderr, "Underflow: v=%jd, min=%jd\n",          \
                    (intmax_t)(v), (intmax_t)PCM_S##BIT##_MIN);         \
        }                                                               \
} while (0)
#else
#define Z_CLIP_CHECK(...)
#endif

/*
 * Sine Cardinal (SINC) Interpolation. Scaling is done in 64 bit, so
 * there's no point to hold the plate any longer. All samples will be
 * shifted to a full 32 bit, scaled and restored during write for
 * maximum dynamic range (only for downsampling).
 */
#define _Z_SINC_ACCUMULATE(SIGN, BIT, ENDIAN, adv)                      \
        c += z >> Z_SHIFT;                                              \
        z &= Z_MASK;                                                    \
        coeff = Z_COEFF_INTERPOLATE(z, z_coeff[c], z_dcoeff[c]);        \
        x = pcm_sample_read(p, AFMT_##SIGN##BIT##_##ENDIAN);            \
        v += Z_NORM_##BIT((intpcm64_t)x * coeff);                       \
        z += info->z_dy;                                                \
        p adv##= info->channels * PCM_##BIT##_BPS

/* 
 * XXX GCC4 optimization is such a !@#$%, need manual unrolling.
 */
#if defined(__GNUC__) && __GNUC__ >= 4
#define Z_SINC_ACCUMULATE(...)  do {                                    \
        _Z_SINC_ACCUMULATE(__VA_ARGS__);                                \
        _Z_SINC_ACCUMULATE(__VA_ARGS__);                                \
} while (0)
#define Z_SINC_ACCUMULATE_DECR          2
#else
#define Z_SINC_ACCUMULATE(...)  do {                                    \
        _Z_SINC_ACCUMULATE(__VA_ARGS__);                                \
} while (0)
#define Z_SINC_ACCUMULATE_DECR          1
#endif

#define Z_DECLARE_SINC(SIGN, BIT, ENDIAN)                                       \
static void                                                                     \
z_feed_sinc_##SIGN##BIT##ENDIAN(struct z_info *info, uint8_t *dst)              \
{                                                                               \
        intpcm64_t v;                                                           \
        intpcm_t x;                                                             \
        uint8_t *p;                                                             \
        int32_t coeff, z, *z_coeff, *z_dcoeff;                                  \
        uint32_t c, center, ch, i;                                              \
                                                                                \
        z_coeff = info->z_coeff;                                                \
        z_dcoeff = info->z_dcoeff;                                              \
        center = z_prev(info, info->z_start, info->z_size);                     \
        ch = info->channels * PCM_##BIT##_BPS;                                  \
        dst += ch;                                                              \
                                                                                \
        do {                                                                    \
                dst -= PCM_##BIT##_BPS;                                         \
                ch -= PCM_##BIT##_BPS;                                          \
                v = 0;                                                          \
                z = info->z_alpha * info->z_dx;                                 \
                c = 0;                                                          \
                p = info->z_delay + (z_next(info, center, 1) *                  \
                    info->channels * PCM_##BIT##_BPS) + ch;                     \
                for (i = info->z_size; i != 0; i -= Z_SINC_ACCUMULATE_DECR)     \
                        Z_SINC_ACCUMULATE(SIGN, BIT, ENDIAN, +);                \
                z = info->z_dy - (info->z_alpha * info->z_dx);                  \
                c = 0;                                                          \
                p = info->z_delay + (center * info->channels *                  \
                    PCM_##BIT##_BPS) + ch;                                      \
                for (i = info->z_size; i != 0; i -= Z_SINC_ACCUMULATE_DECR)     \
                        Z_SINC_ACCUMULATE(SIGN, BIT, ENDIAN, -);                \
                if (info->z_scale != Z_ONE)                                     \
                        v = Z_SCALE_##BIT(v, info->z_scale);                    \
                else                                                            \
                        v >>= Z_COEFF_SHIFT - Z_GUARD_BIT_##BIT;                \
                Z_CLIP_CHECK(v, BIT);                                           \
                pcm_sample_write(dst, pcm_clamp(v, AFMT_##SIGN##BIT##_##ENDIAN),\
                    AFMT_##SIGN##BIT##_##ENDIAN);                               \
        } while (ch != 0);                                                      \
}

#define Z_DECLARE_SINC_POLYPHASE(SIGN, BIT, ENDIAN)                             \
static void                                                                     \
z_feed_sinc_polyphase_##SIGN##BIT##ENDIAN(struct z_info *info, uint8_t *dst)    \
{                                                                               \
        intpcm64_t v;                                                           \
        intpcm_t x;                                                             \
        uint8_t *p;                                                             \
        int32_t ch, i, start, *z_pcoeff;                                        \
                                                                                \
        ch = info->channels * PCM_##BIT##_BPS;                                  \
        dst += ch;                                                              \
        start = z_prev(info, info->z_start, (info->z_size << 1) - 1) * ch;      \
                                                                                \
        do {                                                                    \
                dst -= PCM_##BIT##_BPS;                                         \
                ch -= PCM_##BIT##_BPS;                                          \
                v = 0;                                                          \
                p = info->z_delay + start + ch;                                 \
                z_pcoeff = info->z_pcoeff +                                     \
                    ((info->z_alpha * info->z_size) << 1);                      \
                for (i = info->z_size; i != 0; i--) {                           \
                        x = pcm_sample_read(p, AFMT_##SIGN##BIT##_##ENDIAN);    \
                        v += Z_NORM_##BIT((intpcm64_t)x * *z_pcoeff);           \
                        z_pcoeff++;                                             \
                        p += info->channels * PCM_##BIT##_BPS;                  \
                        x = pcm_sample_read(p, AFMT_##SIGN##BIT##_##ENDIAN);    \
                        v += Z_NORM_##BIT((intpcm64_t)x * *z_pcoeff);           \
                        z_pcoeff++;                                             \
                        p += info->channels * PCM_##BIT##_BPS;                  \
                }                                                               \
                if (info->z_scale != Z_ONE)                                     \
                        v = Z_SCALE_##BIT(v, info->z_scale);                    \
                else                                                            \
                        v >>= Z_COEFF_SHIFT - Z_GUARD_BIT_##BIT;                \
                Z_CLIP_CHECK(v, BIT);                                           \
                pcm_sample_write(dst, pcm_clamp(v, AFMT_##SIGN##BIT##_##ENDIAN),\
                    AFMT_##SIGN##BIT##_##ENDIAN);                               \
        } while (ch != 0);                                                      \
}

#define Z_DECLARE(SIGN, BIT, ENDIAN)                                    \
        Z_DECLARE_LINEAR(SIGN, BIT, ENDIAN)                             \
        Z_DECLARE_SINC(SIGN, BIT, ENDIAN)                               \
        Z_DECLARE_SINC_POLYPHASE(SIGN, BIT, ENDIAN)

Z_DECLARE(S, 16, LE)
Z_DECLARE(S, 32, LE)
Z_DECLARE(S, 16, BE)
Z_DECLARE(S, 32, BE)
Z_DECLARE(S,  8, NE)
Z_DECLARE(S, 24, LE)
Z_DECLARE(S, 24, BE)
Z_DECLARE(U,  8, NE)
Z_DECLARE(U, 16, LE)
Z_DECLARE(U, 24, LE)
Z_DECLARE(U, 32, LE)
Z_DECLARE(U, 16, BE)
Z_DECLARE(U, 24, BE)
Z_DECLARE(U, 32, BE)
Z_DECLARE(F, 32, LE)
Z_DECLARE(F, 32, BE)

enum {
        Z_RESAMPLER_ZOH,
        Z_RESAMPLER_LINEAR,
        Z_RESAMPLER_SINC,
        Z_RESAMPLER_SINC_POLYPHASE,
        Z_RESAMPLER_LAST
};

#define Z_RESAMPLER_IDX(i)                                              \
        (Z_IS_SINC(i) ? Z_RESAMPLER_SINC : (i)->quality)

#define Z_RESAMPLER_ENTRY(SIGN, BIT, ENDIAN)                                    \
        {                                                                       \
            AFMT_##SIGN##BIT##_##ENDIAN,                                        \
            {                                                                   \
                [Z_RESAMPLER_ZOH]    = z_feed_zoh,                              \
                [Z_RESAMPLER_LINEAR] = z_feed_linear_##SIGN##BIT##ENDIAN,       \
                [Z_RESAMPLER_SINC]   = z_feed_sinc_##SIGN##BIT##ENDIAN,         \
                [Z_RESAMPLER_SINC_POLYPHASE]   =                                \
                    z_feed_sinc_polyphase_##SIGN##BIT##ENDIAN                   \
            }                                                                   \
        }

static const struct {
        uint32_t format;
        z_resampler_t resampler[Z_RESAMPLER_LAST];
} z_resampler_tab[] = {
        Z_RESAMPLER_ENTRY(S, 16, LE),
        Z_RESAMPLER_ENTRY(S, 32, LE),
        Z_RESAMPLER_ENTRY(S, 16, BE),
        Z_RESAMPLER_ENTRY(S, 32, BE),
        Z_RESAMPLER_ENTRY(S,  8, NE),
        Z_RESAMPLER_ENTRY(S, 24, LE),
        Z_RESAMPLER_ENTRY(S, 24, BE),
        Z_RESAMPLER_ENTRY(U,  8, NE),
        Z_RESAMPLER_ENTRY(U, 16, LE),
        Z_RESAMPLER_ENTRY(U, 24, LE),
        Z_RESAMPLER_ENTRY(U, 32, LE),
        Z_RESAMPLER_ENTRY(U, 16, BE),
        Z_RESAMPLER_ENTRY(U, 24, BE),
        Z_RESAMPLER_ENTRY(U, 32, BE),
        Z_RESAMPLER_ENTRY(F, 32, LE),
        Z_RESAMPLER_ENTRY(F, 32, BE),
};

#define Z_RESAMPLER_TAB_SIZE                                            \
        ((int32_t)(sizeof(z_resampler_tab) / sizeof(z_resampler_tab[0])))

static void
z_resampler_reset(struct z_info *info)
{

        info->src = info->rsrc - (info->rsrc % ((feeder_rate_round > 0 &&
            info->rsrc > feeder_rate_round) ? feeder_rate_round : 1));
        info->dst = info->rdst - (info->rdst % ((feeder_rate_round > 0 &&
            info->rdst > feeder_rate_round) ? feeder_rate_round : 1));
        info->z_gx = 1;
        info->z_gy = 1;
        info->z_alpha = 0;
        info->z_resample = NULL;
        info->z_size = 1;
        info->z_coeff = NULL;
        info->z_dcoeff = NULL;
        free(info->z_pcoeff, M_DEVBUF);
        info->z_pcoeff = NULL;
        info->z_scale = Z_ONE;
        info->z_dx = Z_FULL_ONE;
        info->z_dy = Z_FULL_ONE;
#ifdef Z_DIAGNOSTIC
        info->z_cycle = 0;
#endif
        if (info->quality < Z_QUALITY_MIN)
                info->quality = Z_QUALITY_MIN;
        else if (info->quality > Z_QUALITY_MAX)
                info->quality = Z_QUALITY_MAX;
}

static int32_t
z_resampler_sinc_len(struct z_info *info)
{
        int32_t c, z, len, lmax;

        if (!Z_IS_SINC(info))
                return (1);

        /*
         * A rather careful (or useless) way to calculate filter length.
         * Z_SINC_LEN() itself is accurate enough to do its job. Extra
         * sanity checking is not going to hurt though..
         */
        c = 0;
        z = info->z_dy;
        len = 0;
        lmax = z_coeff_tab[Z_SINC_COEFF_IDX(info)].len;

        do {
                c += z >> Z_SHIFT;
                z &= Z_MASK;
                z += info->z_dy;
        } while (c < lmax && ++len > 0);

        if (len != Z_SINC_LEN(info)) {
#ifdef _KERNEL
                printf("%s(): sinc l=%d != Z_SINC_LEN=%d\n",
                    __func__, len, Z_SINC_LEN(info));
#else
                fprintf(stderr, "%s(): sinc l=%d != Z_SINC_LEN=%d\n",
                    __func__, len, Z_SINC_LEN(info));
                return (-1);
#endif
        }

        return (len);
}

#define Z_POLYPHASE_COEFF_SHIFT         0

/*
 * Pick suitable polynomial interpolators based on filter oversampled ratio
 * (2 ^ Z_DRIFT_SHIFT).
 */
#if !(defined(Z_COEFF_INTERP_ZOH) || defined(Z_COEFF_INTERP_LINEAR) ||          \
    defined(Z_COEFF_INTERP_QUADRATIC) || defined(Z_COEFF_INTERP_HERMITE) ||     \
    defined(Z_COEFF_INTER_BSPLINE) || defined(Z_COEFF_INTERP_OPT32X) ||         \
    defined(Z_COEFF_INTERP_OPT16X) || defined(Z_COEFF_INTERP_OPT8X) ||          \
    defined(Z_COEFF_INTERP_OPT4X) || defined(Z_COEFF_INTERP_OPT2X))
#if Z_DRIFT_SHIFT >= 6
#define Z_COEFF_INTERP_BSPLINE          1
#elif Z_DRIFT_SHIFT >= 5
#define Z_COEFF_INTERP_OPT32X           1
#elif Z_DRIFT_SHIFT == 4
#define Z_COEFF_INTERP_OPT16X           1
#elif Z_DRIFT_SHIFT == 3
#define Z_COEFF_INTERP_OPT8X            1
#elif Z_DRIFT_SHIFT == 2
#define Z_COEFF_INTERP_OPT4X            1
#elif Z_DRIFT_SHIFT == 1
#define Z_COEFF_INTERP_OPT2X            1
#else
#error "Z_DRIFT_SHIFT screwed!"
#endif
#endif

/*
 * In classic polyphase mode, the actual coefficients for each phases need to
 * be calculated based on default prototype filters. For highly oversampled
 * filter, linear or quadradatic interpolator should be enough. Anything less
 * than that require 'special' interpolators to reduce interpolation errors.
 *
 * "Polynomial Interpolators for High-Quality Resampling of Oversampled Audio"
 *    by Olli Niemitalo
 *    - http://www.student.oulu.fi/~oniemita/dsp/deip.pdf
 *
 */
static int32_t
z_coeff_interpolate(int32_t z, int32_t *z_coeff)
{
        int32_t coeff;
#if defined(Z_COEFF_INTERP_ZOH)

        /* 1-point, 0th-order (Zero Order Hold) */
        z = z;
        coeff = z_coeff[0];
#elif defined(Z_COEFF_INTERP_LINEAR)
        int32_t zl0, zl1;

        /* 2-point, 1st-order Linear */
        zl0 = z_coeff[0];
        zl1 = z_coeff[1] - z_coeff[0];

        coeff = Z_RSHIFT((int64_t)zl1 * z, Z_SHIFT) + zl0;
#elif defined(Z_COEFF_INTERP_QUADRATIC)
        int32_t zq0, zq1, zq2;

        /* 3-point, 2nd-order Quadratic */
        zq0 = z_coeff[0];
        zq1 = z_coeff[1] - z_coeff[-1];
        zq2 = z_coeff[1] + z_coeff[-1] - (z_coeff[0] << 1);

        coeff = Z_RSHIFT((Z_RSHIFT((int64_t)zq2 * z, Z_SHIFT) +
            zq1) * z, Z_SHIFT + 1) + zq0;
#elif defined(Z_COEFF_INTERP_HERMITE)
        int32_t zh0, zh1, zh2, zh3;

        /* 4-point, 3rd-order Hermite */
        zh0 = z_coeff[0];
        zh1 = z_coeff[1] - z_coeff[-1];
        zh2 = (z_coeff[-1] << 1) - (z_coeff[0] * 5) + (z_coeff[1] << 2) -
            z_coeff[2];
        zh3 = z_coeff[2] - z_coeff[-1] + ((z_coeff[0] - z_coeff[1]) * 3);

        coeff = Z_RSHIFT((Z_RSHIFT((Z_RSHIFT((int64_t)zh3 * z, Z_SHIFT) +
            zh2) * z, Z_SHIFT) + zh1) * z, Z_SHIFT + 1) + zh0;
#elif defined(Z_COEFF_INTERP_BSPLINE)
        int32_t zb0, zb1, zb2, zb3;

        /* 4-point, 3rd-order B-Spline */
        zb0 = Z_RSHIFT(0x15555555LL * (((int64_t)z_coeff[0] << 2) +
            z_coeff[-1] + z_coeff[1]), 30);
        zb1 = z_coeff[1] - z_coeff[-1];
        zb2 = z_coeff[-1] + z_coeff[1] - (z_coeff[0] << 1);
        zb3 = Z_RSHIFT(0x15555555LL * (((z_coeff[0] - z_coeff[1]) * 3) +
            z_coeff[2] - z_coeff[-1]), 30);

        coeff = (Z_RSHIFT((Z_RSHIFT((Z_RSHIFT((int64_t)zb3 * z, Z_SHIFT) +
            zb2) * z, Z_SHIFT) + zb1) * z, Z_SHIFT) + zb0 + 1) >> 1;
#elif defined(Z_COEFF_INTERP_OPT32X)
        int32_t zoz, zoe1, zoe2, zoe3, zoo1, zoo2, zoo3;
        int32_t zoc0, zoc1, zoc2, zoc3, zoc4, zoc5;

        /* 6-point, 5th-order Optimal 32x */
        zoz = z - (Z_ONE >> 1);
        zoe1 = z_coeff[1] + z_coeff[0];
        zoe2 = z_coeff[2] + z_coeff[-1];
        zoe3 = z_coeff[3] + z_coeff[-2];
        zoo1 = z_coeff[1] - z_coeff[0];
        zoo2 = z_coeff[2] - z_coeff[-1];
        zoo3 = z_coeff[3] - z_coeff[-2];

        zoc0 = Z_RSHIFT((0x1ac2260dLL * zoe1) + (0x0526cdcaLL * zoe2) +
            (0x00170c29LL * zoe3), 30);
        zoc1 = Z_RSHIFT((0x14f8a49aLL * zoo1) + (0x0d6d1109LL * zoo2) +
            (0x008cd4dcLL * zoo3), 30);
        zoc2 = Z_RSHIFT((-0x0d3e94a4LL * zoe1) + (0x0bddded4LL * zoe2) +
            (0x0160b5d0LL * zoe3), 30);
        zoc3 = Z_RSHIFT((-0x0de10cc4LL * zoo1) + (0x019b2a7dLL * zoo2) +
            (0x01cfe914LL * zoo3), 30);
        zoc4 = Z_RSHIFT((0x02aa12d7LL * zoe1) + (-0x03ff1bb3LL * zoe2) +
            (0x015508ddLL * zoe3), 30);
        zoc5 = Z_RSHIFT((0x051d29e5LL * zoo1) + (-0x028e7647LL * zoo2) +
            (0x0082d81aLL * zoo3), 30);

        coeff = Z_RSHIFT((Z_RSHIFT((Z_RSHIFT((Z_RSHIFT((Z_RSHIFT(
            (int64_t)zoc5 * zoz, Z_SHIFT) +
            zoc4) * zoz, Z_SHIFT) + zoc3) * zoz, Z_SHIFT) +
            zoc2) * zoz, Z_SHIFT) + zoc1) * zoz, Z_SHIFT) + zoc0;
#elif defined(Z_COEFF_INTERP_OPT16X)
        int32_t zoz, zoe1, zoe2, zoe3, zoo1, zoo2, zoo3;
        int32_t zoc0, zoc1, zoc2, zoc3, zoc4, zoc5;

        /* 6-point, 5th-order Optimal 16x */
        zoz = z - (Z_ONE >> 1);
        zoe1 = z_coeff[1] + z_coeff[0];
        zoe2 = z_coeff[2] + z_coeff[-1];
        zoe3 = z_coeff[3] + z_coeff[-2];
        zoo1 = z_coeff[1] - z_coeff[0];
        zoo2 = z_coeff[2] - z_coeff[-1];
        zoo3 = z_coeff[3] - z_coeff[-2];

        zoc0 = Z_RSHIFT((0x1ac2260dLL * zoe1) + (0x0526cdcaLL * zoe2) +
            (0x00170c29LL * zoe3), 30);
        zoc1 = Z_RSHIFT((0x14f8a49aLL * zoo1) + (0x0d6d1109LL * zoo2) +
            (0x008cd4dcLL * zoo3), 30);
        zoc2 = Z_RSHIFT((-0x0d3e94a4LL * zoe1) + (0x0bddded4LL * zoe2) +
            (0x0160b5d0LL * zoe3), 30);
        zoc3 = Z_RSHIFT((-0x0de10cc4LL * zoo1) + (0x019b2a7dLL * zoo2) +
            (0x01cfe914LL * zoo3), 30);
        zoc4 = Z_RSHIFT((0x02aa12d7LL * zoe1) + (-0x03ff1bb3LL * zoe2) +
            (0x015508ddLL * zoe3), 30);
        zoc5 = Z_RSHIFT((0x051d29e5LL * zoo1) + (-0x028e7647LL * zoo2) +
            (0x0082d81aLL * zoo3), 30);

        coeff = Z_RSHIFT((Z_RSHIFT((Z_RSHIFT((Z_RSHIFT((Z_RSHIFT(
            (int64_t)zoc5 * zoz, Z_SHIFT) +
            zoc4) * zoz, Z_SHIFT) + zoc3) * zoz, Z_SHIFT) +
            zoc2) * zoz, Z_SHIFT) + zoc1) * zoz, Z_SHIFT) + zoc0;
#elif defined(Z_COEFF_INTERP_OPT8X)
        int32_t zoz, zoe1, zoe2, zoe3, zoo1, zoo2, zoo3;
        int32_t zoc0, zoc1, zoc2, zoc3, zoc4, zoc5;

        /* 6-point, 5th-order Optimal 8x */
        zoz = z - (Z_ONE >> 1);
        zoe1 = z_coeff[1] + z_coeff[0];
        zoe2 = z_coeff[2] + z_coeff[-1];
        zoe3 = z_coeff[3] + z_coeff[-2];
        zoo1 = z_coeff[1] - z_coeff[0];
        zoo2 = z_coeff[2] - z_coeff[-1];
        zoo3 = z_coeff[3] - z_coeff[-2];

        zoc0 = Z_RSHIFT((0x1aa9b47dLL * zoe1) + (0x053d9944LL * zoe2) +
            (0x0018b23fLL * zoe3), 30);
        zoc1 = Z_RSHIFT((0x14a104d1LL * zoo1) + (0x0d7d2504LL * zoo2) +
            (0x0094b599LL * zoo3), 30);
        zoc2 = Z_RSHIFT((-0x0d22530bLL * zoe1) + (0x0bb37a2cLL * zoe2) +
            (0x016ed8e0LL * zoe3), 30);
        zoc3 = Z_RSHIFT((-0x0d744b1cLL * zoo1) + (0x01649591LL * zoo2) +
            (0x01dae93aLL * zoo3), 30);
        zoc4 = Z_RSHIFT((0x02a7ee1bLL * zoe1) + (-0x03fbdb24LL * zoe2) +
            (0x0153ed07LL * zoe3), 30);
        zoc5 = Z_RSHIFT((0x04cf9b6cLL * zoo1) + (-0x0266b378LL * zoo2) +
            (0x007a7c26LL * zoo3), 30);

        coeff = Z_RSHIFT((Z_RSHIFT((Z_RSHIFT((Z_RSHIFT((Z_RSHIFT(
            (int64_t)zoc5 * zoz, Z_SHIFT) +
            zoc4) * zoz, Z_SHIFT) + zoc3) * zoz, Z_SHIFT) +
            zoc2) * zoz, Z_SHIFT) + zoc1) * zoz, Z_SHIFT) + zoc0;
#elif defined(Z_COEFF_INTERP_OPT4X)
        int32_t zoz, zoe1, zoe2, zoe3, zoo1, zoo2, zoo3;
        int32_t zoc0, zoc1, zoc2, zoc3, zoc4, zoc5;

        /* 6-point, 5th-order Optimal 4x */
        zoz = z - (Z_ONE >> 1);
        zoe1 = z_coeff[1] + z_coeff[0];
        zoe2 = z_coeff[2] + z_coeff[-1];
        zoe3 = z_coeff[3] + z_coeff[-2];
        zoo1 = z_coeff[1] - z_coeff[0];
        zoo2 = z_coeff[2] - z_coeff[-1];
        zoo3 = z_coeff[3] - z_coeff[-2];

        zoc0 = Z_RSHIFT((0x1a8eda43LL * zoe1) + (0x0556ee38LL * zoe2) +
            (0x001a3784LL * zoe3), 30);
        zoc1 = Z_RSHIFT((0x143d863eLL * zoo1) + (0x0d910e36LL * zoo2) +
            (0x009ca889LL * zoo3), 30);
        zoc2 = Z_RSHIFT((-0x0d026821LL * zoe1) + (0x0b837773LL * zoe2) +
            (0x017ef0c6LL * zoe3), 30);
        zoc3 = Z_RSHIFT((-0x0cef1502LL * zoo1) + (0x01207a8eLL * zoo2) +
            (0x01e936dbLL * zoo3), 30);
        zoc4 = Z_RSHIFT((0x029fe643LL * zoe1) + (-0x03ef3fc8LL * zoe2) +
            (0x014f5923LL * zoe3), 30);
        zoc5 = Z_RSHIFT((0x043a9d08LL * zoo1) + (-0x02154febLL * zoo2) +
            (0x00670dbdLL * zoo3), 30);

        coeff = Z_RSHIFT((Z_RSHIFT((Z_RSHIFT((Z_RSHIFT((Z_RSHIFT(
            (int64_t)zoc5 * zoz, Z_SHIFT) +
            zoc4) * zoz, Z_SHIFT) + zoc3) * zoz, Z_SHIFT) +
            zoc2) * zoz, Z_SHIFT) + zoc1) * zoz, Z_SHIFT) + zoc0;
#elif defined(Z_COEFF_INTERP_OPT2X)
        int32_t zoz, zoe1, zoe2, zoe3, zoo1, zoo2, zoo3;
        int32_t zoc0, zoc1, zoc2, zoc3, zoc4, zoc5;

        /* 6-point, 5th-order Optimal 2x */
        zoz = z - (Z_ONE >> 1);
        zoe1 = z_coeff[1] + z_coeff[0];
        zoe2 = z_coeff[2] + z_coeff[-1];
        zoe3 = z_coeff[3] + z_coeff[-2];
        zoo1 = z_coeff[1] - z_coeff[0];
        zoo2 = z_coeff[2] - z_coeff[-1];
        zoo3 = z_coeff[3] - z_coeff[-2];

        zoc0 = Z_RSHIFT((0x19edb6fdLL * zoe1) + (0x05ebd062LL * zoe2) +
            (0x00267881LL * zoe3), 30);
        zoc1 = Z_RSHIFT((0x1223af76LL * zoo1) + (0x0de3dd6bLL * zoo2) +
            (0x00d683cdLL * zoo3), 30);
        zoc2 = Z_RSHIFT((-0x0c3ee068LL * zoe1) + (0x0a5c3769LL * zoe2) +
            (0x01e2aceaLL * zoe3), 30);
        zoc3 = Z_RSHIFT((-0x0a8ab614LL * zoo1) + (-0x0019522eLL * zoo2) +
            (0x022cefc7LL * zoo3), 30);
        zoc4 = Z_RSHIFT((0x0276187dLL * zoe1) + (-0x03a801e8LL * zoe2) +
            (0x0131d935LL * zoe3), 30);
        zoc5 = Z_RSHIFT((0x02c373f5LL * zoo1) + (-0x01275f83LL * zoo2) +
            (0x0018ee79LL * zoo3), 30);

        coeff = Z_RSHIFT((Z_RSHIFT((Z_RSHIFT((Z_RSHIFT((Z_RSHIFT(
            (int64_t)zoc5 * zoz, Z_SHIFT) +
            zoc4) * zoz, Z_SHIFT) + zoc3) * zoz, Z_SHIFT) +
            zoc2) * zoz, Z_SHIFT) + zoc1) * zoz, Z_SHIFT) + zoc0;
#else
#error "Interpolation type screwed!"
#endif

#if Z_POLYPHASE_COEFF_SHIFT > 0
        coeff = Z_RSHIFT(coeff, Z_POLYPHASE_COEFF_SHIFT);
#endif
        return (coeff);
}

static int
z_resampler_build_polyphase(struct z_info *info)
{
        int32_t alpha, c, i, z, idx;

        /* Let this be here first. */
        free(info->z_pcoeff, M_DEVBUF);
        info->z_pcoeff = NULL;

        if (feeder_rate_polyphase_max < 1)
                return (ENOTSUP);

        if (((int64_t)info->z_size * info->z_gy * 2) >
            feeder_rate_polyphase_max) {
#ifndef _KERNEL
                fprintf(stderr, "Polyphase entries exceed: [%d/%d] %jd > %d\n",
                    info->z_gx, info->z_gy,
                    (intmax_t)info->z_size * info->z_gy * 2,
                    feeder_rate_polyphase_max);
#endif
                return (E2BIG);
        }

        info->z_pcoeff = malloc(sizeof(int32_t) *
            info->z_size * info->z_gy * 2, M_DEVBUF, M_NOWAIT | M_ZERO);
        if (info->z_pcoeff == NULL)
                return (ENOMEM);

        for (alpha = 0; alpha < info->z_gy; alpha++) {
                z = alpha * info->z_dx;
                c = 0;
                for (i = info->z_size; i != 0; i--) {
                        c += z >> Z_SHIFT;
                        z &= Z_MASK;
                        idx = (alpha * info->z_size * 2) +
                            (info->z_size * 2) - i;
                        info->z_pcoeff[idx] =
                            z_coeff_interpolate(z, info->z_coeff + c);
                        z += info->z_dy;
                }
                z = info->z_dy - (alpha * info->z_dx);
                c = 0;
                for (i = info->z_size; i != 0; i--) {
                        c += z >> Z_SHIFT;
                        z &= Z_MASK;
                        idx = (alpha * info->z_size * 2) + i - 1;
                        info->z_pcoeff[idx] =
                            z_coeff_interpolate(z, info->z_coeff + c);
                        z += info->z_dy;
                }
        }

#ifndef _KERNEL
        fprintf(stderr, "Polyphase: [%d/%d] %d entries\n",
            info->z_gx, info->z_gy, info->z_size * info->z_gy * 2);
#endif

        return (0);
}

static int
z_resampler_setup(struct pcm_feeder *f)
{
        struct z_info *info;
        int64_t gy2gx_max, gx2gy_max;
        uint32_t format;
        int32_t align, i, z_scale;
        int adaptive;

        info = f->data;
        z_resampler_reset(info);

        if (info->src == info->dst)
                return (0);

        /* Shrink by greatest common divisor. */
        i = z_gcd(info->src, info->dst);
        info->z_gx = info->src / i;
        info->z_gy = info->dst / i;

        /* Too big, or too small. Bail out. */
        if (!(Z_FACTOR_SAFE(info->z_gx) && Z_FACTOR_SAFE(info->z_gy)))
                return (EINVAL);

        format = f->desc.in;
        adaptive = 0;
        z_scale = 0;

        /*
         * Setup everything: filter length, conversion factor, etc.
         */
        if (Z_IS_SINC(info)) {
                /*
                 * Downsampling, or upsampling scaling factor. As long as the
                 * factor can be represented by a fraction of 1 << Z_SHIFT,
                 * we're pretty much in business. Scaling is not needed for
                 * upsampling, so we just slap Z_ONE there.
                 */
                if (info->z_gx > info->z_gy)
                        /*
                         * If the downsampling ratio is beyond sanity,
                         * enable semi-adaptive mode. Although handling
                         * extreme ratio is possible, the result of the
                         * conversion is just pointless, unworthy,
                         * nonsensical noises, etc.
                         */
                        if ((info->z_gx / info->z_gy) > Z_SINC_DOWNMAX)
                                z_scale = Z_ONE / Z_SINC_DOWNMAX;
                        else
                                z_scale = ((uint64_t)info->z_gy << Z_SHIFT) /
                                    info->z_gx;
                else
                        z_scale = Z_ONE;

                /*
                 * This is actually impossible, unless anything above
                 * overflow.
                 */
                if (z_scale < 1)
                        return (E2BIG);

                /*
                 * Calculate sample time/coefficients index drift. It is
                 * a constant for upsampling, but downsampling require
                 * heavy duty filtering with possible too long filters.
                 * If anything goes wrong, revisit again and enable
                 * adaptive mode.
                 */
z_setup_adaptive_sinc:
                free(info->z_pcoeff, M_DEVBUF);
                info->z_pcoeff = NULL;

                if (adaptive == 0) {
                        info->z_dy = z_scale << Z_DRIFT_SHIFT;
                        if (info->z_dy < 1)
                                return (E2BIG);
                        info->z_scale = z_scale;
                } else {
                        info->z_dy = Z_FULL_ONE;
                        info->z_scale = Z_ONE;
                }

                /* Smallest drift increment. */
                info->z_dx = info->z_dy / info->z_gy;

                /*
                 * Overflow or underflow. Try adaptive, let it continue and
                 * retry.
                 */
                if (info->z_dx < 1) {
                        if (adaptive == 0) {
                                adaptive = 1;
                                goto z_setup_adaptive_sinc;
                        }
                        return (E2BIG);
                }

                /*
                 * Round back output drift.
                 */
                info->z_dy = info->z_dx * info->z_gy;

                for (i = 0; i < Z_COEFF_TAB_SIZE; i++) {
                        if (Z_SINC_COEFF_IDX(info) != i)
                                continue;
                        /*
                         * Calculate required filter length and guard
                         * against possible abusive result. Note that
                         * this represents only 1/2 of the entire filter
                         * length.
                         */
                        info->z_size = z_resampler_sinc_len(info);

                        /*
                         * Multiple of 2 rounding, for better accumulator
                         * performance.
                         */
                        info->z_size &= ~1;

                        if (info->z_size < 2 || info->z_size > Z_SINC_MAX) {
                                if (adaptive == 0) {
                                        adaptive = 1;
                                        goto z_setup_adaptive_sinc;
                                }
                                return (E2BIG);
                        }
                        info->z_coeff = z_coeff_tab[i].coeff + Z_COEFF_OFFSET;
                        info->z_dcoeff = z_coeff_tab[i].dcoeff;
                        break;
                }

                if (info->z_coeff == NULL || info->z_dcoeff == NULL)
                        return (EINVAL);
        } else if (Z_IS_LINEAR(info)) {
                /*
                 * Don't put much effort if we're doing linear interpolation.
                 * Just center the interpolation distance within Z_LINEAR_ONE,
                 * and be happy about it.
                 */
                info->z_dx = Z_LINEAR_FULL_ONE / info->z_gy;
        }

        /*
         * We're safe for now, lets continue.. Look for our resampler
         * depending on configured format and quality.
         */
        for (i = 0; i < Z_RESAMPLER_TAB_SIZE; i++) {
                int ridx;

                if (AFMT_ENCODING(format) != z_resampler_tab[i].format)
                        continue;
                if (Z_IS_SINC(info) && adaptive == 0 &&
                    z_resampler_build_polyphase(info) == 0)
                        ridx = Z_RESAMPLER_SINC_POLYPHASE;
                else
                        ridx = Z_RESAMPLER_IDX(info);
                info->z_resample = z_resampler_tab[i].resampler[ridx];
                break;
        }

        if (info->z_resample == NULL)
                return (EINVAL);

        info->bps = AFMT_BPS(format);
        align = info->channels * info->bps;

        /*
         * Calculate largest value that can be fed into z_gy2gx() and
         * z_gx2gy() without causing (signed) 32bit overflow. z_gy2gx() will
         * be called early during feeding process to determine how much input
         * samples that is required to generate requested output, while
         * z_gx2gy() will be called just before samples filtering /
         * accumulation process based on available samples that has been
         * calculated using z_gx2gy().
         *
         * Now that is damn confusing, I guess ;-) .
         */
        gy2gx_max = (((uint64_t)info->z_gy * INT32_MAX) - info->z_gy + 1) /
            info->z_gx;

        if ((gy2gx_max * align) > SND_FXDIV_MAX)
                gy2gx_max = SND_FXDIV_MAX / align;

        if (gy2gx_max < 1)
                return (E2BIG);

        gx2gy_max = (((uint64_t)info->z_gx * INT32_MAX) - info->z_gy) /
            info->z_gy;

        if (gx2gy_max > INT32_MAX)
                gx2gy_max = INT32_MAX;

        if (gx2gy_max < 1)
                return (E2BIG);

        /*
         * Ensure that z_gy2gx() at its largest possible calculated value
         * (alpha = 0) will not cause overflow further late during z_gx2gy()
         * stage.
         */
        if (z_gy2gx(info, gy2gx_max) > _Z_GCAST(gx2gy_max))
                return (E2BIG);

        info->z_maxfeed = gy2gx_max * align;

#ifdef Z_USE_ALPHADRIFT
        info->z_startdrift = z_gy2gx(info, 1);
        info->z_alphadrift = z_drift(info, info->z_startdrift, 1);
#endif

        i = z_gy2gx(info, 1);
        info->z_full = z_roundpow2((info->z_size << 1) + i);

        /*
         * Too big to be true, and overflowing left and right like mad ..
         */
        if ((info->z_full * align) < 1) {
                if (adaptive == 0 && Z_IS_SINC(info)) {
                        adaptive = 1;
                        goto z_setup_adaptive_sinc;
                }
                return (E2BIG);
        }

        /*
         * Increase full buffer size if its too small to reduce cyclic
         * buffer shifting in main conversion/feeder loop.
         */
        while (info->z_full < Z_RESERVOIR_MAX &&
            (info->z_full - (info->z_size << 1)) < Z_RESERVOIR)
                info->z_full <<= 1;

        /* Initialize buffer position. */
        info->z_mask = info->z_full - 1;
        info->z_start = z_prev(info, info->z_size << 1, 1);
        info->z_pos = z_next(info, info->z_start, 1);

        /*
         * Allocate or reuse delay line buffer, whichever makes sense.
         */
        i = info->z_full * align;
        if (i < 1)
                return (E2BIG);

        if (info->z_delay == NULL || info->z_alloc < i ||
            i <= (info->z_alloc >> 1)) {
                free(info->z_delay, M_DEVBUF);
                info->z_delay = malloc(i, M_DEVBUF, M_NOWAIT | M_ZERO);
                if (info->z_delay == NULL)
                        return (ENOMEM);
                info->z_alloc = i;
        }

        /*
         * Zero out head of buffer to avoid pops and clicks.
         */
        memset(info->z_delay, sndbuf_zerodata(f->desc.out),
            info->z_pos * align);

#ifdef Z_DIAGNOSTIC
        /*
         * XXX Debuging mess !@#$%^
         */
#define dumpz(x)        fprintf(stderr, "\t%12s = %10u : %-11d\n",      \
                            "z_"__STRING(x), (uint32_t)info->z_##x,     \
                            (int32_t)info->z_##x)
        fprintf(stderr, "\n%s():\n", __func__);
        fprintf(stderr, "\tchannels=%d, bps=%d, format=0x%08x, quality=%d\n",
            info->channels, info->bps, format, info->quality);
        fprintf(stderr, "\t%d (%d) -> %d (%d), ",
            info->src, info->rsrc, info->dst, info->rdst);
        fprintf(stderr, "[%d/%d]\n", info->z_gx, info->z_gy);
        fprintf(stderr, "\tminreq=%d, ", z_gy2gx(info, 1));
        if (adaptive != 0)
                z_scale = Z_ONE;
        fprintf(stderr, "factor=0x%08x/0x%08x (%f)\n",
            z_scale, Z_ONE, (double)z_scale / Z_ONE);
        fprintf(stderr, "\tbase_length=%d, ", Z_SINC_BASE_LEN(info));
        fprintf(stderr, "adaptive=%s\n", (adaptive != 0) ? "YES" : "NO");
        dumpz(size);
        dumpz(alloc);
        if (info->z_alloc < 1024)
                fprintf(stderr, "\t%15s%10d Bytes\n",
                    "", info->z_alloc);
        else if (info->z_alloc < (1024 << 10))
                fprintf(stderr, "\t%15s%10d KBytes\n",
                    "", info->z_alloc >> 10);
        else if (info->z_alloc < (1024 << 20))
                fprintf(stderr, "\t%15s%10d MBytes\n",
                    "", info->z_alloc >> 20);
        else
                fprintf(stderr, "\t%15s%10d GBytes\n",
                    "", info->z_alloc >> 30);
        fprintf(stderr, "\t%12s   %10d (min output samples)\n",
            "",
            (int32_t)z_gx2gy(info, info->z_full - (info->z_size << 1)));
        fprintf(stderr, "\t%12s   %10d (min allocated output samples)\n",
            "",
            (int32_t)z_gx2gy(info, (info->z_alloc / align) -
            (info->z_size << 1)));
        fprintf(stderr, "\t%12s = %10d\n",
            "z_gy2gx()", (int32_t)z_gy2gx(info, 1));
        fprintf(stderr, "\t%12s = %10d -> z_gy2gx() -> %d\n",
            "Max", (int32_t)gy2gx_max, (int32_t)z_gy2gx(info, gy2gx_max));
        fprintf(stderr, "\t%12s = %10d\n",
            "z_gx2gy()", (int32_t)z_gx2gy(info, 1));
        fprintf(stderr, "\t%12s = %10d -> z_gx2gy() -> %d\n",
            "Max", (int32_t)gx2gy_max, (int32_t)z_gx2gy(info, gx2gy_max));
        dumpz(maxfeed);
        dumpz(full);
        dumpz(start);
        dumpz(pos);
        dumpz(scale);
        fprintf(stderr, "\t%12s   %10f\n", "",
            (double)info->z_scale / Z_ONE);
        dumpz(dx);
        fprintf(stderr, "\t%12s   %10f\n", "",
            (double)info->z_dx / info->z_dy);
        dumpz(dy);
        fprintf(stderr, "\t%12s   %10d (drift step)\n", "",
            info->z_dy >> Z_SHIFT);
        fprintf(stderr, "\t%12s   %10d (scaling differences)\n", "",
            (z_scale << Z_DRIFT_SHIFT) - info->z_dy);
        fprintf(stderr, "\t%12s = %u bytes\n",
            "intpcm32_t", sizeof(intpcm32_t));
        fprintf(stderr, "\t%12s = 0x%08x, smallest=%.16lf\n",
            "Z_ONE", Z_ONE, (double)1.0 / (double)Z_ONE);
#endif

        return (0);
}

static int
z_resampler_set(struct pcm_feeder *f, int what, int32_t value)
{
        struct z_info *info;
        int32_t oquality;

        info = f->data;

        switch (what) {
        case FEEDRATE_SRC:
                if (value < feeder_rate_min || value > feeder_rate_max)
                        return (E2BIG);
                if (value == info->rsrc)
                        return (0);
                info->rsrc = value;
                break;
        case FEEDRATE_DST:
                if (value < feeder_rate_min || value > feeder_rate_max)
                        return (E2BIG);
                if (value == info->rdst)
                        return (0);
                info->rdst = value;
                break;
        case FEEDRATE_QUALITY:
                if (value < Z_QUALITY_MIN || value > Z_QUALITY_MAX)
                        return (EINVAL);
                if (value == info->quality)
                        return (0);
                /*
                 * If we failed to set the requested quality, restore
                 * the old one. We cannot afford leaving it broken since
                 * passive feeder chains like vchans never reinitialize
                 * itself.
                 */
                oquality = info->quality;
                info->quality = value;
                if (z_resampler_setup(f) == 0)
                        return (0);
                info->quality = oquality;
                break;
        case FEEDRATE_CHANNELS:
                if (value < SND_CHN_MIN || value > SND_CHN_MAX)
                        return (EINVAL);
                if (value == info->channels)
                        return (0);
                info->channels = value;
                break;
        default:
                return (EINVAL);
        }

        return (z_resampler_setup(f));
}

static int
z_resampler_get(struct pcm_feeder *f, int what)
{
        struct z_info *info;

        info = f->data;

        switch (what) {
        case FEEDRATE_SRC:
                return (info->rsrc);
        case FEEDRATE_DST:
                return (info->rdst);
        case FEEDRATE_QUALITY:
                return (info->quality);
        case FEEDRATE_CHANNELS:
                return (info->channels);
        }

        return (-1);
}

static int
z_resampler_init(struct pcm_feeder *f)
{
        struct z_info *info;
        int ret;

        if (f->desc.in != f->desc.out)
                return (EINVAL);

        info = malloc(sizeof(*info), M_DEVBUF, M_NOWAIT | M_ZERO);
        if (info == NULL)
                return (ENOMEM);

        info->rsrc = Z_RATE_DEFAULT;
        info->rdst = Z_RATE_DEFAULT;
        info->quality = feeder_rate_quality;
        info->channels = AFMT_CHANNEL(f->desc.in);

        f->data = info;

        ret = z_resampler_setup(f);
        if (ret != 0) {
                free(info->z_pcoeff, M_DEVBUF);
                free(info->z_delay, M_DEVBUF);
                free(info, M_DEVBUF);
                f->data = NULL;
        }

        return (ret);
}

static int
z_resampler_free(struct pcm_feeder *f)
{
        struct z_info *info;

        info = f->data;
        free(info->z_pcoeff, M_DEVBUF);
        free(info->z_delay, M_DEVBUF);
        free(info, M_DEVBUF);

        f->data = NULL;

        return (0);
}

static uint32_t
z_resampler_feed_internal(struct pcm_feeder *f, struct pcm_channel *c,
    uint8_t *b, uint32_t count, void *source)
{
        struct z_info *info;
        int32_t alphadrift, startdrift, reqout, ocount, reqin, align;
        int32_t fetch, fetched, start, cp;
        uint8_t *dst;

        info = f->data;
        if (info->z_resample == NULL)
                return (z_feed(f->source, c, b, count, source));

        /*
         * Calculate sample size alignment and amount of sample output.
         * We will do everything in sample domain, but at the end we
         * will jump back to byte domain.
         */
        align = info->channels * info->bps;
        ocount = SND_FXDIV(count, align);
        if (ocount == 0)
                return (0);

        /*
         * Calculate amount of input samples that is needed to generate
         * exact amount of output.
         */
        reqin = z_gy2gx(info, ocount) - z_fetched(info);

#ifdef Z_USE_ALPHADRIFT
        startdrift = info->z_startdrift;
        alphadrift = info->z_alphadrift;
#else
        startdrift = _Z_GY2GX(info, 0, 1);
        alphadrift = z_drift(info, startdrift, 1);
#endif

        dst = b;

        do {
                if (reqin != 0) {
                        fetch = z_min(z_free(info), reqin);
                        if (fetch == 0) {
                                /*
                                 * No more free spaces, so wind enough
                                 * samples back to the head of delay line
                                 * in byte domain.
                                 */
                                fetched = z_fetched(info);
                                start = z_prev(info, info->z_start,
                                    (info->z_size << 1) - 1);
                                cp = (info->z_size << 1) + fetched;
                                z_copy(info->z_delay + (start * align),
                                    info->z_delay, cp * align);
                                info->z_start =
                                    z_prev(info, info->z_size << 1, 1);
                                info->z_pos =
                                    z_next(info, info->z_start, fetched + 1);
                                fetch = z_min(z_free(info), reqin);
#ifdef Z_DIAGNOSTIC
                                if (1) {
                                        static uint32_t kk = 0;
                                        fprintf(stderr,
                                            "Buffer Move: "
                                            "start=%d fetched=%d cp=%d "
                                            "cycle=%u [%u]\r",
                                            start, fetched, cp, info->z_cycle,
                                            ++kk);
                                }
                                info->z_cycle = 0;
#endif
                        }
                        if (fetch != 0) {
                                /*
                                 * Fetch in byte domain and jump back
                                 * to sample domain.
                                 */
                                fetched = SND_FXDIV(z_feed(f->source, c,
                                    info->z_delay + (info->z_pos * align),
                                    fetch * align, source), align);
                                /*
                                 * Prepare to convert fetched buffer,
                                 * or mark us done if we cannot fulfill
                                 * the request.
                                 */
                                reqin -= fetched;
                                info->z_pos += fetched;
                                if (fetched != fetch)
                                        reqin = 0;
                        }
                }

                reqout = z_min(z_gx2gy(info, z_fetched(info)), ocount);
                if (reqout != 0) {
                        ocount -= reqout;

                        /*
                         * Drift.. drift.. drift..
                         *
                         * Notice that there are 2 methods of doing the drift
                         * operations: The former is much cleaner (in a sense
                         * of mathematical readings of my eyes), but slower
                         * due to integer division in z_gy2gx(). Nevertheless,
                         * both should give the same exact accurate drifting
                         * results, so the later is favourable.
                         */
                        do {
                                info->z_resample(info, dst);
                                info->z_alpha += alphadrift;
                                if (info->z_alpha < info->z_gy)
                                        info->z_start += startdrift;
                                else {
                                        info->z_start += startdrift - 1;
                                        info->z_alpha -= info->z_gy;
                                }
                                dst += align;
#ifdef Z_DIAGNOSTIC
                                info->z_cycle++;
#endif
                        } while (--reqout != 0);
                }
        } while (reqin != 0 && ocount != 0);

        /*
         * Back to byte domain..
         */
        return (dst - b);
}

static int
z_resampler_feed(struct pcm_feeder *f, struct pcm_channel *c, uint8_t *b,
    uint32_t count, void *source)
{
        uint32_t feed, maxfeed, left;

        /*
         * Split count to smaller chunks to avoid possible 32bit overflow.
         */
        maxfeed = ((struct z_info *)(f->data))->z_maxfeed;
        left = count;

        do {
                feed = z_resampler_feed_internal(f, c, b,
                    z_min(maxfeed, left), source);
                b += feed;
                left -= feed;
        } while (left != 0 && feed != 0);

        return (count - left);
}

static kobj_method_t feeder_rate_methods[] = {
        KOBJMETHOD(feeder_init,         z_resampler_init),
        KOBJMETHOD(feeder_free,         z_resampler_free),
        KOBJMETHOD(feeder_set,          z_resampler_set),
        KOBJMETHOD(feeder_get,          z_resampler_get),
        KOBJMETHOD(feeder_feed,         z_resampler_feed),
        KOBJMETHOD_END
};

FEEDER_DECLARE(feeder_rate, FEEDER_RATE);