ref: 2024869a595118d686682b38386c594c717ea5bd
dir: /src/effects.c/
/* SoX Effects chain (c) 2007 robs@users.sourceforge.net
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at
* your option) any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
* General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#define LSX_EFF_ALIAS
#include "sox_i.h"
#include <assert.h>
#include <string.h>
#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif
#define DEBUG_EFFECTS_CHAIN 0
/* Default effect handler functions for do-nothing situations: */
static int default_function(sox_effect_t * effp UNUSED)
{
USED(effp);
return SOX_SUCCESS;
}
/* Pass through samples verbatim */
int lsx_flow_copy(sox_effect_t * effp UNUSED, const sox_sample_t * ibuf,
sox_sample_t * obuf, size_t * isamp, size_t * osamp)
{
USED(effp);
*isamp = *osamp = min(*isamp, *osamp);
memcpy(obuf, ibuf, *isamp * sizeof(*obuf));
return SOX_SUCCESS;
}
/* Inform no more samples to drain */
static int default_drain(sox_effect_t * effp UNUSED, sox_sample_t *obuf UNUSED, size_t *osamp)
{
USED(effp); USED(obuf);
*osamp = 0;
return SOX_EOF;
}
/* Check that no parameters have been given */
static int default_getopts(sox_effect_t * effp, int argc, char **argv UNUSED)
{
USED(argv);
return --argc? lsx_usage(effp) : SOX_SUCCESS;
}
/* Partially initialise the effect structure; signal info will come later */
sox_effect_t * sox_create_effect(sox_effect_handler_t const * eh)
{
sox_effect_t * effp = lsx_calloc(1, sizeof(*effp));
effp->obuf = NULL;
effp->global_info = sox_get_effects_globals();
effp->handler = *eh;
if (!effp->handler.getopts) effp->handler.getopts = default_getopts;
if (!effp->handler.start ) effp->handler.start = default_function;
if (!effp->handler.flow ) effp->handler.flow = lsx_flow_copy;
if (!effp->handler.drain ) effp->handler.drain = default_drain;
if (!effp->handler.stop ) effp->handler.stop = default_function;
if (!effp->handler.kill ) effp->handler.kill = default_function;
effp->priv = lsx_calloc(1, effp->handler.priv_size);
return effp;
} /* sox_create_effect */
int sox_effect_options(sox_effect_t *effp, int argc, char * const argv[])
{
int result;
char * * argv2 = lsx_malloc((argc + 1) * sizeof(*argv2));
argv2[0] = (char *)effp->handler.name;
if(argv != NULL)
memcpy(argv2 + 1, argv, argc * sizeof(*argv2));
result = effp->handler.getopts(effp, argc + 1, argv2);
free(argv2);
return result;
} /* sox_effect_options */
/* Effects chain: */
sox_effects_chain_t * sox_create_effects_chain(
sox_encodinginfo_t const * in_enc, sox_encodinginfo_t const * out_enc)
{
sox_effects_chain_t * result = lsx_calloc(1, sizeof(sox_effects_chain_t));
result->global_info = *sox_get_effects_globals();
result->in_enc = in_enc;
result->out_enc = out_enc;
return result;
} /* sox_create_effects_chain */
void sox_delete_effects_chain(sox_effects_chain_t *ecp)
{
if (ecp && ecp->length)
sox_delete_effects(ecp);
free(ecp->effects);
free(ecp);
} /* sox_delete_effects_chain */
/* Effect can call in start() or flow() to set minimum input size to flow() */
int lsx_effect_set_imin(sox_effect_t * effp, size_t imin)
{
if (imin > sox_globals.bufsiz / effp->flows) {
lsx_fail("sox_bufsiz not big enough");
return SOX_EOF;
}
effp->imin = imin;
return SOX_SUCCESS;
}
/* Effects table to be extended in steps of EFF_TABLE_STEP */
#define EFF_TABLE_STEP 8
/* Add an effect to the chain. *in is the input signal for this effect. *out is
* a suggestion as to what the output signal should be, but depending on its
* given options and *in, the effect can choose to do differently. Whatever
* output rate and channels the effect does produce are written back to *in,
* ready for the next effect in the chain.
*/
int sox_add_effect(sox_effects_chain_t * chain, sox_effect_t * effp, sox_signalinfo_t * in, sox_signalinfo_t const * out)
{
int ret, (*start)(sox_effect_t * effp) = effp->handler.start;
size_t f;
sox_effect_t eff0; /* Copy of effect for flow 0 before calling start */
effp->global_info = &chain->global_info;
effp->in_signal = *in;
effp->out_signal = *out;
effp->in_encoding = chain->in_enc;
effp->out_encoding = chain->out_enc;
if (!(effp->handler.flags & SOX_EFF_CHAN))
effp->out_signal.channels = in->channels;
if (!(effp->handler.flags & SOX_EFF_RATE))
effp->out_signal.rate = in->rate;
if (!(effp->handler.flags & SOX_EFF_PREC))
effp->out_signal.precision = (effp->handler.flags & SOX_EFF_MODIFY)?
in->precision : SOX_SAMPLE_PRECISION;
if (!(effp->handler.flags & SOX_EFF_GAIN))
effp->out_signal.mult = in->mult;
effp->flows =
(effp->handler.flags & SOX_EFF_MCHAN)? 1 : effp->in_signal.channels;
effp->clips = 0;
effp->imin = 0;
eff0 = *effp, eff0.priv = lsx_memdup(eff0.priv, eff0.handler.priv_size);
eff0.in_signal.mult = NULL; /* Only used in channel 0 */
ret = start(effp);
if (ret == SOX_EFF_NULL) {
lsx_report("has no effect in this configuration");
free(eff0.priv);
effp->handler.kill(effp);
free(effp->priv);
effp->priv = NULL;
return SOX_SUCCESS;
}
if (ret != SOX_SUCCESS) {
free(eff0.priv);
return SOX_EOF;
}
if (in->mult)
lsx_debug("mult=%g", *in->mult);
if (!(effp->handler.flags & SOX_EFF_LENGTH)) {
effp->out_signal.length = in->length;
if (effp->out_signal.length != SOX_UNKNOWN_LEN) {
if (effp->handler.flags & SOX_EFF_CHAN)
effp->out_signal.length =
effp->out_signal.length / in->channels * effp->out_signal.channels;
if (effp->handler.flags & SOX_EFF_RATE)
effp->out_signal.length =
effp->out_signal.length / in->rate * effp->out_signal.rate + .5;
}
}
*in = effp->out_signal;
if (chain->length == chain->table_size) {
chain->table_size += EFF_TABLE_STEP;
lsx_debug_more("sox_add_effect: extending effects table, "
"new size = %" PRIuPTR, chain->table_size);
lsx_revalloc(chain->effects, chain->table_size);
}
chain->effects[chain->length] =
lsx_calloc(effp->flows, sizeof(chain->effects[chain->length][0]));
chain->effects[chain->length][0] = *effp;
for (f = 1; f < effp->flows; ++f) {
chain->effects[chain->length][f] = eff0;
chain->effects[chain->length][f].flow = f;
chain->effects[chain->length][f].priv = lsx_memdup(eff0.priv, eff0.handler.priv_size);
if (start(&chain->effects[chain->length][f]) != SOX_SUCCESS) {
free(eff0.priv);
return SOX_EOF;
}
}
++chain->length;
free(eff0.priv);
return SOX_SUCCESS;
}
/* An effect's output buffer (effp->obuf) generally has this layout:
* |. . . A1A2A3B1B2B3C1C2C3. . . . . . . . . . . . . . . . . . |
* ^0 ^obeg ^oend ^bufsiz
* (where A1 is the first sample of channel 1, A2 the first sample of
* channel 2, etc.), i.e. the channels are interleaved.
* However, while sox_flow_effects() is running, output buffers are
* adapted to how the following effect expects its input, to avoid
* back-and-forth conversions. If the following effect operates on
* each of several channels separately (flows > 1), the layout is
* changed to this uninterleaved form:
* |. A1B1C1. . . . . . . A2B2C2. . . . . . . A3B3C3. . . . . . |
* ^0 ^obeg ^oend ^bufsiz
* <--- channel 1 ----><--- channel 2 ----><--- channel 3 ---->
* The buffer is logically subdivided into channel buffers of size
* bufsiz/flows each, starting at offsets 0, bufsiz/flows,
* 2*(bufsiz/flows) etc. Within the channel buffers, the data starts
* at position obeg/flows and ends before oend/flows. In case bufsiz
* is not evenly divisible by flows, there will be an unused area at
* the very end of the output buffer.
* The interleave() and deinterleave() functions convert between these
* two representations.
*/
static void interleave(size_t flows, size_t length, sox_sample_t *from,
size_t bufsiz, size_t offset, sox_sample_t *to);
static void deinterleave(size_t flows, size_t length, sox_sample_t *from,
sox_sample_t *to, size_t bufsiz, size_t offset);
static int flow_effect(sox_effects_chain_t * chain, size_t n)
{
sox_effect_t *effp1 = chain->effects[n - 1];
sox_effect_t *effp = chain->effects[n];
int effstatus = SOX_SUCCESS;
size_t f;
size_t idone = effp1->oend - effp1->obeg;
size_t obeg = sox_globals.bufsiz - effp->oend;
sox_bool il_change = (effp->flows == 1) !=
(chain->length == n + 1 || chain->effects[n+1]->flows == 1);
#if DEBUG_EFFECTS_CHAIN
size_t pre_idone = idone;
size_t pre_odone = obeg;
#endif
if (effp->flows == 1) { /* Run effect on all channels at once */
idone -= idone % effp->in_signal.channels;
effstatus = effp->handler.flow(effp, effp1->obuf + effp1->obeg,
il_change ? chain->il_buf : effp->obuf + effp->oend,
&idone, &obeg);
if (obeg % effp->out_signal.channels != 0) {
lsx_fail("multi-channel effect flowed asymmetrically!");
effstatus = SOX_EOF;
}
if (il_change)
deinterleave(chain->effects[n+1]->flows, obeg, chain->il_buf,
effp->obuf, sox_globals.bufsiz, effp->oend);
} else { /* Run effect on each channel individually */
sox_sample_t *obuf = il_change ? chain->il_buf : effp->obuf;
size_t flow_offs = sox_globals.bufsiz/effp->flows;
size_t idone_min = SOX_SIZE_MAX, idone_max = 0;
size_t odone_min = SOX_SIZE_MAX, odone_max = 0;
#ifdef HAVE_OPENMP_3_1
#pragma omp parallel for \
if(sox_globals.use_threads) \
schedule(static) default(none) \
shared(effp,effp1,idone,obeg,obuf,flow_offs,chain,n,effstatus) \
reduction(min:idone_min,odone_min) reduction(max:idone_max,odone_max)
#elif defined HAVE_OPENMP
#pragma omp parallel for \
if(sox_globals.use_threads) \
schedule(static) default(none) \
shared(effp,effp1,idone,obeg,obuf,flow_offs,chain,n,effstatus) \
firstprivate(idone_min,odone_min,idone_max,odone_max) \
lastprivate(idone_min,odone_min,idone_max,odone_max)
#endif
for (f = 0; f < effp->flows; ++f) {
size_t idonec = idone / effp->flows;
size_t odonec = obeg / effp->flows;
int eff_status_c = effp->handler.flow(&chain->effects[n][f],
effp1->obuf + f*flow_offs + effp1->obeg/effp->flows,
obuf + f*flow_offs + effp->oend/effp->flows,
&idonec, &odonec);
idone_min = min(idonec, idone_min); idone_max = max(idonec, idone_max);
odone_min = min(odonec, odone_min); odone_max = max(odonec, odone_max);
if (eff_status_c != SOX_SUCCESS)
effstatus = SOX_EOF;
}
if (idone_min != idone_max || odone_min != odone_max) {
lsx_fail("flowed asymmetrically!");
effstatus = SOX_EOF;
}
idone = effp->flows * idone_max;
obeg = effp->flows * odone_max;
if (il_change)
interleave(effp->flows, obeg, chain->il_buf, sox_globals.bufsiz,
effp->oend, effp->obuf + effp->oend);
}
effp1->obeg += idone;
if (effp1->obeg == effp1->oend)
effp1->obeg = effp1->oend = 0;
else if (effp1->oend - effp1->obeg < effp->imin) { /* Need to refill? */
size_t flow_offs = sox_globals.bufsiz/effp->flows;
for (f = 0; f < effp->flows; ++f)
memcpy(effp1->obuf + f * flow_offs,
effp1->obuf + f * flow_offs + effp1->obeg/effp->flows,
(effp1->oend - effp1->obeg)/effp->flows * sizeof(*effp1->obuf));
effp1->oend -= effp1->obeg;
effp1->obeg = 0;
}
effp->oend += obeg;
#if DEBUG_EFFECTS_CHAIN
lsx_report("\t" "flow: %2" PRIuPTR " (%1" PRIuPTR ") "
"%5" PRIuPTR " %5" PRIuPTR " %5" PRIuPTR " %5" PRIuPTR " "
"%5" PRIuPTR " [%" PRIuPTR "-%" PRIuPTR "]",
n, effp->flows, pre_idone, pre_odone, idone, obeg,
effp1->oend - effp1->obeg, effp1->obeg, effp1->oend);
#endif
return effstatus == SOX_SUCCESS? SOX_SUCCESS : SOX_EOF;
}
/* The same as flow_effect but with no input */
static int drain_effect(sox_effects_chain_t * chain, size_t n)
{
sox_effect_t *effp = chain->effects[n];
int effstatus = SOX_SUCCESS;
size_t f;
size_t obeg = sox_globals.bufsiz - effp->oend;
sox_bool il_change = (effp->flows == 1) !=
(chain->length == n + 1 || chain->effects[n+1]->flows == 1);
#if DEBUG_EFFECTS_CHAIN
size_t pre_odone = obeg;
#endif
if (effp->flows == 1) { /* Run effect on all channels at once */
effstatus = effp->handler.drain(effp,
il_change ? chain->il_buf : effp->obuf + effp->oend,
&obeg);
if (obeg % effp->out_signal.channels != 0) {
lsx_fail("multi-channel effect drained asymmetrically!");
effstatus = SOX_EOF;
}
if (il_change)
deinterleave(chain->effects[n+1]->flows, obeg, chain->il_buf,
effp->obuf, sox_globals.bufsiz, effp->oend);
} else { /* Run effect on each channel individually */
sox_sample_t *obuf = il_change ? chain->il_buf : effp->obuf;
size_t flow_offs = sox_globals.bufsiz/effp->flows;
size_t odone_last = 0; /* Initialised to prevent warning */
for (f = 0; f < effp->flows; ++f) {
size_t odonec = obeg / effp->flows;
int eff_status_c = effp->handler.drain(&chain->effects[n][f],
obuf + f*flow_offs + effp->oend/effp->flows,
&odonec);
if (f && (odonec != odone_last)) {
lsx_fail("drained asymmetrically!");
effstatus = SOX_EOF;
}
odone_last = odonec;
if (eff_status_c != SOX_SUCCESS)
effstatus = SOX_EOF;
}
obeg = effp->flows * odone_last;
if (il_change)
interleave(effp->flows, obeg, chain->il_buf, sox_globals.bufsiz,
effp->oend, effp->obuf + effp->oend);
}
if (!obeg) /* This is the only thing that drain has and flow hasn't */
effstatus = SOX_EOF;
effp->oend += obeg;
#if DEBUG_EFFECTS_CHAIN
lsx_report("\t" "drain: %2" PRIuPTR " (%1" PRIuPTR ") "
"%5" PRIuPTR " %5" PRIuPTR " %5" PRIuPTR " %5" PRIuPTR,
n, effp->flows, (size_t)0, pre_odone, (size_t)0, obeg);
#endif
return effstatus == SOX_SUCCESS? SOX_SUCCESS : SOX_EOF;
}
/* Flow data through the effects chain until an effect or callback gives EOF */
int sox_flow_effects(sox_effects_chain_t * chain, int (* callback)(sox_bool all_done, void * client_data), void * client_data)
{
int flow_status = SOX_SUCCESS;
size_t e, source_e = 0; /* effect indices */
size_t max_flows = 0;
sox_bool draining = sox_true;
for (e = 0; e < chain->length; ++e) {
sox_effect_t *effp = chain->effects[e];
effp->obuf =
lsx_realloc(effp->obuf, sox_globals.bufsiz * sizeof(*effp->obuf));
/* Memory will be freed by sox_delete_effect() later. */
/* Possibly there was already a buffer, if this is a used effect;
it may still contain samples in that case. */
if (effp->oend > sox_globals.bufsiz) {
lsx_warn("buffer size insufficient; buffered samples were dropped");
/* can only happen if bufsize has been reduced since the last run */
effp->obeg = effp->oend = 0;
}
max_flows = max(max_flows, effp->flows);
}
if (max_flows > 1) /* might need interleave buffer */
chain->il_buf = lsx_malloc(sox_globals.bufsiz * sizeof(sox_sample_t));
else
chain->il_buf = NULL;
/* Go through the effects, and if there are samples in one of the
buffers, deinterleave it (if necessary). */
for (e = 0; e + 1 < chain->length; e++) {
sox_effect_t *effp = chain->effects[e];
if (effp->oend > effp->obeg && chain->effects[e+1]->flows > 1) {
sox_sample_t *sw = chain->il_buf; chain->il_buf = effp->obuf; effp->obuf = sw;
deinterleave(chain->effects[e+1]->flows, effp->oend - effp->obeg,
chain->il_buf, effp->obuf, sox_globals.bufsiz, effp->obeg);
}
}
e = chain->length - 1;
while (source_e < chain->length) {
#define have_imin (e > 0 && e < chain->length && chain->effects[e - 1]->oend - chain->effects[e - 1]->obeg >= chain->effects[e]->imin)
size_t osize = chain->effects[e]->oend - chain->effects[e]->obeg;
if (e == source_e && (draining || !have_imin)) {
if (drain_effect(chain, e) == SOX_EOF) {
++source_e;
draining = sox_false;
}
} else if (have_imin && flow_effect(chain, e) == SOX_EOF) {
flow_status = SOX_EOF;
if (e == chain->length - 1)
break;
source_e = e;
draining = sox_true;
}
if (e < chain->length && chain->effects[e]->oend - chain->effects[e]->obeg > osize) /* False for output */
++e;
else if (e == source_e)
draining = sox_true;
else if (e < source_e)
e = source_e;
else
--e;
if (callback && callback(source_e == chain->length, client_data) != SOX_SUCCESS) {
flow_status = SOX_EOF; /* Client has requested to stop the flow. */
break;
}
}
/* If an effect's output buffer still has samples, and if it is
uninterleaved, then re-interleave it. Necessary since it might
be reused, and at that time possibly followed by an MCHAN effect. */
for (e = 0; e + 1 < chain->length; e++) {
sox_effect_t *effp = chain->effects[e];
if (effp->oend > effp->obeg && chain->effects[e+1]->flows > 1) {
sox_sample_t *sw = chain->il_buf; chain->il_buf = effp->obuf; effp->obuf = sw;
interleave(chain->effects[e+1]->flows, effp->oend - effp->obeg,
chain->il_buf, sox_globals.bufsiz, effp->obeg, effp->obuf);
}
}
free(chain->il_buf);
return flow_status;
}
sox_uint64_t sox_effects_clips(sox_effects_chain_t * chain)
{
size_t i, f;
uint64_t clips = 0;
for (i = 1; i < chain->length - 1; ++i)
for (f = 0; f < chain->effects[i][0].flows; ++f)
clips += chain->effects[i][f].clips;
return clips;
}
sox_uint64_t sox_stop_effect(sox_effect_t *effp)
{
size_t f;
uint64_t clips = 0;
for (f = 0; f < effp->flows; ++f) {
effp[f].handler.stop(&effp[f]);
clips += effp[f].clips;
}
return clips;
}
void sox_push_effect_last(sox_effects_chain_t *chain, sox_effect_t *effp)
{
if (chain->length == chain->table_size) {
chain->table_size += EFF_TABLE_STEP;
lsx_debug_more("sox_push_effect_last: extending effects table, "
"new size = %" PRIuPTR, chain->table_size);
lsx_revalloc(chain->effects, chain->table_size);
}
chain->effects[chain->length++] = effp;
} /* sox_push_effect_last */
sox_effect_t *sox_pop_effect_last(sox_effects_chain_t *chain)
{
if (chain->length > 0)
{
sox_effect_t *effp;
chain->length--;
effp = chain->effects[chain->length];
chain->effects[chain->length] = NULL;
return effp;
}
else
return NULL;
} /* sox_pop_effect_last */
/* Free resources related to effect.
* Note: This currently closes down the effect which might
* not be obvious from name.
*/
void sox_delete_effect(sox_effect_t *effp)
{
uint64_t clips;
size_t f;
if ((clips = sox_stop_effect(effp)) != 0)
lsx_warn("%s clipped %" PRIu64 " samples; decrease volume?",
effp->handler.name, clips);
if (effp->obeg != effp->oend)
lsx_debug("output buffer still held %" PRIuPTR " samples; dropped.",
(effp->oend - effp->obeg)/effp->out_signal.channels);
/* May or may not indicate a problem; it is normal if the user aborted
processing, or if an effect like "trim" stopped early. */
effp->handler.kill(effp); /* N.B. only one kill; not one per flow */
for (f = 0; f < effp->flows; ++f)
free(effp[f].priv);
free(effp->obuf);
free(effp);
}
void sox_delete_effect_last(sox_effects_chain_t *chain)
{
if (chain->length > 0)
{
chain->length--;
sox_delete_effect(chain->effects[chain->length]);
chain->effects[chain->length] = NULL;
}
} /* sox_delete_effect_last */
/* Remove all effects from the chain.
* Note: This currently closes down the effect which might
* not be obvious from name.
*/
void sox_delete_effects(sox_effects_chain_t * chain)
{
size_t e;
for (e = 0; e < chain->length; ++e) {
sox_delete_effect(chain->effects[e]);
chain->effects[e] = NULL;
}
chain->length = 0;
}
/*----------------------------- Effects library ------------------------------*/
static sox_effect_fn_t s_sox_effect_fns[] = {
#define EFFECT(f) lsx_##f##_effect_fn,
#include "effects.h"
#undef EFFECT
NULL
};
const sox_effect_fn_t*
sox_get_effect_fns(void)
{
return s_sox_effect_fns;
}
/* Find a named effect in the effects library */
sox_effect_handler_t const * sox_find_effect(char const * name)
{
int e;
sox_effect_fn_t const * fns = sox_get_effect_fns();
for (e = 0; fns[e]; ++e) {
const sox_effect_handler_t *eh = fns[e] ();
if (eh && eh->name && strcasecmp(eh->name, name) == 0)
return eh; /* Found it. */
}
return NULL;
}
/*----------------------------- Helper functions -----------------------------*/
/* interleave() parameters:
* flows: number of samples per wide sample
* length: number of samples to copy
* [pertaining to the (non-interleaved) source buffer:]
* from: start address
* bufsiz: total size
* offset: position at which to start reading
* [pertaining to the (interleaved) destination buffer:]
* to: start address
*/
static void interleave(size_t flows, size_t length, sox_sample_t *from,
size_t bufsiz, size_t offset, sox_sample_t *to)
{
size_t i;
const size_t wide_samples = length/flows;
const size_t flow_offs = bufsiz/flows;
from += offset/flows;
for (i = 0; i < wide_samples; i++) {
sox_sample_t *inner_from = from + i;
sox_sample_t *inner_to = to + i * flows;
size_t f;
for (f = 0; f < flows; f++) {
*inner_to++ = *inner_from;
inner_from += flow_offs;
}
}
}
/* deinterleave() parameters:
* flows: number of samples per wide sample
* length: number of samples to copy
* [pertaining to the (interleaved) source buffer:]
* from: start address
* [pertaining to the (non-interleaved) destination buffer:]
* to: start address
* bufsiz: total size
* offset: position at which to start writing
*/
static void deinterleave(size_t flows, size_t length, sox_sample_t *from,
sox_sample_t *to, size_t bufsiz, size_t offset)
{
const size_t wide_samples = length/flows;
const size_t flow_offs = bufsiz/flows;
size_t f;
to += offset/flows;
for (f = 0; f < flows; f++) {
sox_sample_t *inner_to = to + f*flow_offs;
sox_sample_t *inner_from = from + f;
size_t i = wide_samples;
while (i--) {
*inner_to++ = *inner_from;
inner_from += flows;
}
}
}