ref: 8e0b24e434340582d01a78f26c8fdc68c8f9862e
dir: /src/rate.c/
/* Effect: change sample rate Copyright (c) 2008,12 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
*/
/* Inspired by, and builds upon some of the ideas presented in:
* `The Quest For The Perfect Resampler' by Laurent De Soras;
* http://ldesoras.free.fr/doc/articles/resampler-en.pdf */
#ifdef NDEBUG /* Enable assert always. */
#undef NDEBUG /* Must undef above assert.h or other that might include it. */
#endif
#include "sox_i.h"
#include "fft4g.h"
#include "dft_filter.h"
#include <assert.h>
#include <string.h>
#define calloc lsx_calloc
#define malloc lsx_malloc
#define raw_coef_t double
#define sample_t double
#define TO_SOX SOX_FLOAT_64BIT_TO_SAMPLE
#define FROM_SOX SOX_SAMPLE_TO_FLOAT_64BIT
#define coef(coef_p, interp_order, fir_len, phase_num, coef_interp_num, fir_coef_num) coef_p[(fir_len) * ((interp_order) + 1) * (phase_num) + ((interp_order) + 1) * (fir_coef_num) + (interp_order - coef_interp_num)]
static sample_t * prepare_coefs(raw_coef_t const * coefs, int num_coefs,
int num_phases, int interp_order, int multiplier)
{
int i, j, length = num_coefs * num_phases;
sample_t * result = malloc(length * (interp_order + 1) * sizeof(*result));
double fm1 = coefs[0], f1 = 0, f2 = 0;
for (i = num_coefs - 1; i >= 0; --i)
for (j = num_phases - 1; j >= 0; --j) {
double f0 = fm1, b = 0, c = 0, d = 0; /* = 0 to kill compiler warning */
int pos = i * num_phases + j - 1;
fm1 = (pos > 0 ? coefs[pos - 1] : 0) * multiplier;
switch (interp_order) {
case 1: b = f1 - f0; break;
case 2: b = f1 - (.5 * (f2+f0) - f1) - f0; c = .5 * (f2+f0) - f1; break;
case 3: c=.5*(f1+fm1)-f0;d=(1/6.)*(f2-f1+fm1-f0-4*c);b=f1-f0-d-c; break;
default: if (interp_order) assert(0);
}
#define coef_coef(x) \
coef(result, interp_order, num_coefs, j, x, num_coefs - 1 - i)
coef_coef(0) = f0;
if (interp_order > 0) coef_coef(1) = b;
if (interp_order > 1) coef_coef(2) = c;
if (interp_order > 2) coef_coef(3) = d;
#undef coef_coef
f2 = f1, f1 = f0;
}
return result;
}
typedef struct { /* Data that are shared between channels and stages */
sample_t * poly_fir_coefs;
dft_filter_t dft_filter[2];
} rate_shared_t;
struct stage;
typedef void (* stage_fn_t)(struct stage * input, fifo_t * output);
typedef struct stage {
rate_shared_t * shared;
fifo_t fifo;
int pre; /* Number of past samples to store */
int pre_post; /* pre + number of future samples to store */
int preload; /* Number of zero samples to pre-load the fifo */
int which; /* Which, if any, of the 2 dft filters to use */
stage_fn_t fn;
/* For poly_fir & spline: */
union { /* 32bit.32bit fixed point arithmetic */
#if defined(WORDS_BIGENDIAN)
struct {int32_t integer; uint32_t fraction;} parts;
#else
struct {uint32_t fraction; int32_t integer;} parts;
#endif
int64_t all;
#define MULT32 (65536. * 65536.)
} at, step;
int L, remL, remM;
double out_in_ratio;
} stage_t;
#define stage_occupancy(s) max(0, fifo_occupancy(&(s)->fifo) - (s)->pre_post)
#define stage_read_p(s) ((sample_t *)fifo_read_ptr(&(s)->fifo) + (s)->pre)
static void cubic_spline_fn(stage_t * p, fifo_t * output_fifo)
{
int i, num_in = stage_occupancy(p), max_num_out = 1 + num_in*p->out_in_ratio;
sample_t const * input = stage_read_p(p);
sample_t * output = fifo_reserve(output_fifo, max_num_out);
for (i = 0; p->at.parts.integer < num_in; ++i, p->at.all += p->step.all) {
sample_t const * s = input + p->at.parts.integer;
sample_t x = p->at.parts.fraction * (1 / MULT32);
sample_t b = .5*(s[1]+s[-1])-*s, a = (1/6.)*(s[2]-s[1]+s[-1]-*s-4*b);
sample_t c = s[1]-*s-a-b;
output[i] = ((a*x + b)*x + c)*x + *s;
}
assert(max_num_out - i >= 0);
fifo_trim_by(output_fifo, max_num_out - i);
fifo_read(&p->fifo, p->at.parts.integer, NULL);
p->at.parts.integer = 0;
}
static void dft_stage_fn(stage_t * p, fifo_t * output_fifo)
{
sample_t * output, tmp;
int i, j, num_in = max(0, fifo_occupancy(&p->fifo));
rate_shared_t const * s = p->shared;
dft_filter_t const * f = &s->dft_filter[p->which];
int const overlap = f->num_taps - 1;
while (p->remL + p->L * num_in >= f->dft_length) {
div_t divd = div(f->dft_length - overlap - p->remL + p->L - 1, p->L);
sample_t const * input = fifo_read_ptr(&p->fifo);
fifo_read(&p->fifo, divd.quot, NULL);
num_in -= divd.quot;
output = fifo_reserve(output_fifo, f->dft_length);
if (p->L == 2 || p->L == 4) { /* F-domain */
int portion = f->dft_length / p->L;
memcpy(output, input, (unsigned)portion * sizeof(*output));
lsx_safe_rdft(portion, 1, output);
for (i = portion + 2; i < (portion << 1); i += 2)
output[i] = output[(portion << 1) - i],
output[i+1] = -output[(portion << 1) - i + 1];
output[portion] = output[1];
output[portion + 1] = 0;
output[1] = output[0];
for (portion <<= 1; i < f->dft_length; i += portion, portion <<= 1) {
memcpy(output + i, output, portion * sizeof(*output));
output[i + 1] = 0;
}
} else {
if (p->L == 1)
memcpy(output, input, f->dft_length * sizeof(*output));
else {
memset(output, 0, f->dft_length * sizeof(*output));
for (j = 0, i = p->remL; i < f->dft_length; ++j, i += p->L)
output[i] = input[j];
p->remL = p->L - 1 - divd.rem;
}
lsx_safe_rdft(f->dft_length, 1, output);
}
output[0] *= f->coefs[0];
if (p->step.parts.integer > 0) {
output[1] *= f->coefs[1];
for (i = 2; i < f->dft_length; i += 2) {
tmp = output[i];
output[i ] = f->coefs[i ] * tmp - f->coefs[i+1] * output[i+1];
output[i+1] = f->coefs[i+1] * tmp + f->coefs[i ] * output[i+1];
}
lsx_safe_rdft(f->dft_length, -1, output);
if (p->step.parts.integer != 1) {
for (j = 0, i = p->remM; i < f->dft_length - overlap; ++j, i += p->step.parts.integer)
output[j] = output[i];
p->remM = i - (f->dft_length - overlap);
fifo_trim_by(output_fifo, f->dft_length - j);
}
else fifo_trim_by(output_fifo, overlap);
}
else { /* F-domain */
int m = -p->step.parts.integer;
for (i = 2; i < (f->dft_length >> m); i += 2) {
tmp = output[i];
output[i ] = f->coefs[i ] * tmp - f->coefs[i+1] * output[i+1];
output[i+1] = f->coefs[i+1] * tmp + f->coefs[i ] * output[i+1];
}
output[1] = f->coefs[i] * output[i] - f->coefs[i+1] * output[i+1];
lsx_safe_rdft(f->dft_length >> m, -1, output);
fifo_trim_by(output_fifo, (((1 << m) - 1) * f->dft_length + overlap) >> m);
}
}
}
static void setup_dft_stage(rate_shared_t * shared, int which, stage_t * stage, int L, int M, sox_bool allow_aliasing)
{
stage->fn = dft_stage_fn;
stage->preload = shared->dft_filter[which].post_peak / L;
stage->remL = shared->dft_filter[which].post_peak % L;
stage->L = L;
stage->step.parts.integer = abs(3-M) == 1 && !allow_aliasing? -M/2 : M;
stage->which = which;
}
static void init_dft_filter(rate_shared_t * p, unsigned which, int num_taps,
sample_t const h[], double Fp, double Fc, double Fn, double att,
int multiplier, double phase, sox_bool allow_aliasing)
{
dft_filter_t * f = &p->dft_filter[which];
int dft_length, i;
if (f->num_taps)
return;
if (h) {
dft_length = lsx_set_dft_length(num_taps);
f->coefs = calloc(dft_length, sizeof(*f->coefs));
for (i = 0; i < num_taps; ++i)
f->coefs[(i + dft_length - num_taps + 1) & (dft_length - 1)]
= h[abs(num_taps / 2 - i)] / dft_length * 2 * multiplier;
f->post_peak = num_taps / 2;
}
else {
int k = 4 << (phase == 50 && multiplier == 4 && Fn == 4);
double * h2 = lsx_design_lpf(Fp, Fc, Fn, allow_aliasing, att, &num_taps, -k, -1.);
if (phase != 50)
lsx_fir_to_phase(&h2, &num_taps, &f->post_peak, phase);
else f->post_peak = num_taps / 2;
dft_length = lsx_set_dft_length(num_taps);
f->coefs = calloc(dft_length, sizeof(*f->coefs));
for (i = 0; i < num_taps; ++i)
f->coefs[(i + dft_length - num_taps + 1) & (dft_length - 1)]
= h2[i] / dft_length * 2 * multiplier;
free(h2);
}
assert(num_taps & 1);
f->num_taps = num_taps;
f->dft_length = dft_length;
lsx_debug("fir_len=%i dft_length=%i Fp=%g Fc=%g Fn=%g att=%g mult=%i",
num_taps, dft_length, Fp, Fc, Fn, att, multiplier);
lsx_safe_rdft(dft_length, 1, f->coefs);
}
#include "rate_filters.h"
typedef struct {
double factor;
uint64_t samples_in, samples_out;
int input_stage_num, output_stage_num;
stage_t * stages;
} rate_t;
#define pre_stage p->stages[-1]
#define frac_stage p->stages[level]
#define post_stage p->stages[level + have_frac_stage]
#define have_frac_stage (realM * fracL != 1)
typedef enum {Default = -1, Quick, Low, Medium, High, Very} quality_t;
static void rate_init(rate_t * p, rate_shared_t * shared, double factor,
quality_t quality, int interp_order, double phase, double bandwidth,
sox_bool allow_aliasing)
{
int i, preL = 1, preM = 1, level = 0, fracL = 1, postL = 1, postM = 1;
sox_bool upsample = sox_false;
double realM = factor;
assert(factor > 0);
p->factor = factor;
if (quality < Quick || quality > Very)
quality = High;
if (quality != Quick) while (sox_true) {
const int max_divisor = 2048; /* Keep coef table size ~< 500kb */
double epsilon;
upsample = realM < 1;
for (i = realM, level = 0; i >>= 1; ++level); /* log base 2 */
realM /= 1 << (level + !upsample);
epsilon = fabs((uint32_t)(realM * MULT32 + .5) / (realM * MULT32) - 1);
for (i = 2; i <= max_divisor && fracL == 1; ++i) {
double try_d = realM * i;
int try = try_d + .5;
if (fabs(try / try_d - 1) <= epsilon) { /* N.B. beware of long doubles */
if (try == i)
realM = 1, fracL = 2, level += !upsample, upsample = sox_false;
else realM = try, fracL = i;
}
}
if (upsample) {
if (postL == 1 && (realM != 1 || fracL > 5) && fracL / realM > 4) {
realM = realM * (postL = min((fracL / realM), 4)) / fracL, fracL = 1;
continue;
}
else if ((realM == 2 && fracL == 3) || (realM == 3 && fracL == 4))
preL = fracL, preM = realM, fracL = realM = 1;
else if (fracL < 6 && realM == 1)
preL = fracL, fracL = 1;
else if (quality > Low) {
preL = 2;
if (fracL % preL)
realM *= preL;
else fracL /= preL;
}
}
else {
if (fracL > 2) {
int L = fracL, M = realM;
for (i = level + 1; i && !(L & 1); L >>= 1, --i);
if (((M <<= i) < 7 && L < 3) || M == 4) {
preL = L, preM = M, realM = fracL = 1, level = 0, upsample = sox_true;
break;
}
}
postM = 2;
if (fracL == 2)
--fracL, postM -= !level, level -= !!level;
}
break;
}
p->stages = (stage_t *)calloc((size_t)level + 4, sizeof(*p->stages)) + 1;
for (i = -1; i <= level + 1; ++i)
p->stages[i].shared = shared;
p->output_stage_num = level;
frac_stage.step.all = realM * MULT32 + .5;
frac_stage.out_in_ratio = MULT32 * fracL / frac_stage.step.all;
if (quality == Quick) {
frac_stage.fn = cubic_spline_fn;
frac_stage.pre_post = max(3, frac_stage.step.parts.integer);
frac_stage.preload = frac_stage.pre = 1;
++p->output_stage_num;
}
else if (have_frac_stage) {
int n = (4 - (quality == Low)) * upsample + range_limit(quality, Medium, Very) - Medium;
poly_fir_t const * f = &poly_firs[n];
poly_fir1_t const * f1;
if (f->num_coefs & 1) {
if (fracL != 1 && (fracL & 1))
fracL <<= 1, realM *= 2, frac_stage.step.all <<= 1;
frac_stage.at.all = fracL * .5 * MULT32 + .5;
}
frac_stage.L = fracL;
if (interp_order < 0)
interp_order = quality > High;
interp_order = fracL == 1? 1 + interp_order : 0;
f1 = &f->interp[interp_order];
if (!frac_stage.shared->poly_fir_coefs) {
int phases = fracL == 1? (1 << f1->phase_bits) : fracL;
int num_taps = f->num_coefs * phases - 1;
raw_coef_t * coefs = lsx_design_lpf(
f->pass, f->stop, 1., sox_false, f->att, &num_taps, phases, -1.);
assert(num_taps == f->num_coefs * phases - 1);
frac_stage.shared->poly_fir_coefs =
prepare_coefs(coefs, f->num_coefs, phases, interp_order, 1);
lsx_debug("fir_len=%i phases=%i coef_interp=%i size=%s",
f->num_coefs, phases, interp_order,
lsx_sigfigs3((num_taps +1.) * (interp_order + 1) * sizeof(sample_t)));
free(coefs);
}
frac_stage.fn = f1->fn;
frac_stage.pre_post = f->num_coefs - 1;
frac_stage.pre = 0;
frac_stage.preload = frac_stage.pre_post >> 1;
++p->output_stage_num;
}
if (quality == Low && !upsample) { /* dft is slower here, so */
post_stage.fn = half_sample_low; /* use normal convolution */
post_stage.pre_post = 2 * (array_length(half_fir_coefs_low) - 1);
post_stage.preload = post_stage.pre = post_stage.pre_post >> 1;
++p->output_stage_num;
}
else if (quality != Quick) {
typedef struct {double bw, a;} filter_t;
static filter_t const filters[] = {
{.724, 100}, {.931, 110}, {.931, 125}, {.931, 170}};
filter_t const * f = &filters[quality - Low];
double att = allow_aliasing? (34./33)* f->a : f->a; /* negate att degrade */
double bw = bandwidth? 1 - (1 - bandwidth / 100) / LSX_TO_3dB : f->bw;
double min = 1 - (allow_aliasing? LSX_MAX_TBW0A : LSX_MAX_TBW0) / 100;
double pass = bw * fracL / realM / 2;
assert((size_t)(quality - Low) < array_length(filters));
if (preL * preM != 1) {
init_dft_filter(shared, 0, 0, 0, bw, 1., (double)max(preL, preM), att, preL, phase, allow_aliasing);
setup_dft_stage(shared, 0, &pre_stage, preL, preM, allow_aliasing);
--p->input_stage_num;
}
else if (level && have_frac_stage && (1 - pass) / (1 - bw) > 2)
init_dft_filter(shared, 0, 0, NULL, max(pass, min), 1., 2., att, 1, phase, allow_aliasing);
if (postL * postM != 1) {
init_dft_filter(shared, 1, 0, 0,
bw * (upsample? factor * postL / postM : 1),
1., (double)(upsample? postL : postM), att, postL, phase, allow_aliasing);
setup_dft_stage(shared, 1, &post_stage, postL, postM, allow_aliasing);
++p->output_stage_num;
}
}
for (i = p->input_stage_num; i <= p->output_stage_num; ++i) {
stage_t * s = &p->stages[i];
if (i >= 0 && i < level - have_frac_stage) {
s->fn = half_sample_25;
s->pre_post = 4 * array_length(half_fir_coefs_25);
s->preload = s->pre = s->pre_post >> 1;
}
else if (level && i == level - 1) {
if (shared->dft_filter[0].num_taps)
setup_dft_stage(shared, 0, s, 1, 2, allow_aliasing);
else *s = post_stage;
}
fifo_create(&s->fifo, (int)sizeof(sample_t));
memset(fifo_reserve(&s->fifo, s->preload), 0, sizeof(sample_t)*s->preload);
if (i < p->output_stage_num)
lsx_debug("stage=%-3ipre_post=%-3ipre=%-3ipreload=%i",
i, s->pre_post, s->pre, s->preload);
}
}
static void rate_process(rate_t * p)
{
stage_t * stage = p->stages + p->input_stage_num;
int i;
for (i = p->input_stage_num; i < p->output_stage_num; ++i, ++stage)
stage->fn(stage, &(stage+1)->fifo);
}
static sample_t * rate_input(rate_t * p, sample_t const * samples, size_t n)
{
p->samples_in += n;
return fifo_write(&p->stages[p->input_stage_num].fifo, (int)n, samples);
}
static sample_t const * rate_output(rate_t * p, sample_t * samples, size_t * n)
{
fifo_t * fifo = &p->stages[p->output_stage_num].fifo;
p->samples_out += *n = min(*n, (size_t)fifo_occupancy(fifo));
return fifo_read(fifo, (int)*n, samples);
}
static void rate_flush(rate_t * p)
{
fifo_t * fifo = &p->stages[p->output_stage_num].fifo;
uint64_t samples_out = p->samples_in / p->factor + .5;
size_t remaining = samples_out - p->samples_out;
sample_t * buff = calloc(1024, sizeof(*buff));
if ((int)remaining > 0) {
while ((size_t)fifo_occupancy(fifo) < remaining) {
rate_input(p, buff, (size_t) 1024);
rate_process(p);
}
fifo_trim_to(fifo, (int)remaining);
p->samples_in = 0;
}
free(buff);
}
static void rate_close(rate_t * p)
{
rate_shared_t * shared = p->stages[0].shared;
int i;
for (i = p->input_stage_num; i <= p->output_stage_num; ++i)
fifo_delete(&p->stages[i].fifo);
free(shared->dft_filter[0].coefs);
if (shared->dft_filter[1].coefs != shared->dft_filter[0].coefs)
free(shared->dft_filter[1].coefs);
free(shared->poly_fir_coefs);
memset(shared, 0, sizeof(*shared));
free(p->stages - 1);
}
/*------------------------------- SoX Wrapper --------------------------------*/
typedef struct {
sox_rate_t out_rate;
int quality;
double coef_interp, phase, bandwidth;
sox_bool allow_aliasing;
rate_t rate;
rate_shared_t shared, * shared_ptr;
} priv_t;
static int create(sox_effect_t * effp, int argc, char **argv)
{
priv_t * p = (priv_t *) effp->priv;
int c;
char * dummy_p, * found_at, * opts = "+i:b:p:MILaosqlmhv", * qopts = opts +13;
lsx_getopt_t optstate;
lsx_getopt_init(argc, argv, opts, NULL, lsx_getopt_flag_none, 1, &optstate);
p->quality = -1;
p->phase = 50;
p->shared_ptr = &p->shared;
while ((c = lsx_getopt(&optstate)) != -1) switch (c) {
GETOPT_NUMERIC(optstate, 'i', coef_interp, 1 , 3)
GETOPT_NUMERIC(optstate, 'p', phase, 0 , 100)
GETOPT_NUMERIC(optstate, 'b', bandwidth, 100 - LSX_MAX_TBW3, 99.7)
case 'M': p->phase = 0; break;
case 'I': p->phase = 25; break;
case 'L': p->phase = 50; break;
case 'a': p->allow_aliasing = sox_true; break;
case 's': p->bandwidth = 99; break;
default: if ((found_at = strchr(qopts, c))) p->quality = found_at - qopts;
else {lsx_fail("unknown option `-%c'", optstate.opt); return lsx_usage(effp);}
}
argc -= optstate.ind, argv += optstate.ind;
if ((unsigned)p->quality < 2 && (p->bandwidth || p->phase != 50 || p->allow_aliasing)) {
lsx_fail("override options not allowed with this quality level");
return SOX_EOF;
}
if (p->bandwidth && p->bandwidth < 100 - LSX_MAX_TBW3A && p->allow_aliasing) {
lsx_fail("minimum allowed bandwidth with aliasing is %g%%", 100 - LSX_MAX_TBW3A);
return SOX_EOF;
}
if (argc) {
if ((p->out_rate = lsx_parse_frequency(*argv, &dummy_p)) <= 0 || *dummy_p)
return lsx_usage(effp);
argc--; argv++;
effp->out_signal.rate = p->out_rate;
}
return argc? lsx_usage(effp) : SOX_SUCCESS;
}
static int start(sox_effect_t * effp)
{
priv_t * p = (priv_t *) effp->priv;
double out_rate = p->out_rate != 0 ? p->out_rate : effp->out_signal.rate;
if (effp->in_signal.rate == out_rate)
return SOX_EFF_NULL;
if (effp->in_signal.mult)
*effp->in_signal.mult *= .705; /* 1/(2/sinc(pi/3)-1); see De Soras 4.1.2 */
effp->out_signal.channels = effp->in_signal.channels;
effp->out_signal.rate = out_rate;
rate_init(&p->rate, p->shared_ptr, effp->in_signal.rate / out_rate,
p->quality, (int)p->coef_interp - 1, p->phase, p->bandwidth,
p->allow_aliasing);
return SOX_SUCCESS;
}
static int flow(sox_effect_t * effp, const sox_sample_t * ibuf,
sox_sample_t * obuf, size_t * isamp, size_t * osamp)
{
priv_t * p = (priv_t *)effp->priv;
size_t i, odone = *osamp;
SOX_SAMPLE_LOCALS;
sample_t const * s = rate_output(&p->rate, NULL, &odone);
for (i = 0; i < odone; ++i) *obuf++ = TO_SOX(*s++, effp->clips);
if (*isamp && odone < *osamp) {
sample_t * t = rate_input(&p->rate, NULL, *isamp);
for (i = *isamp; i; --i) *t++ = FROM_SOX(*ibuf++,);
rate_process(&p->rate);
}
else *isamp = 0;
*osamp = odone;
return SOX_SUCCESS;
}
static int drain(sox_effect_t * effp, sox_sample_t * obuf, size_t * osamp)
{
priv_t * p = (priv_t *)effp->priv;
static size_t isamp = 0;
rate_flush(&p->rate);
return flow(effp, 0, obuf, &isamp, osamp);
}
static int stop(sox_effect_t * effp)
{
priv_t * p = (priv_t *) effp->priv;
rate_close(&p->rate);
return SOX_SUCCESS;
}
sox_effect_handler_t const * lsx_rate_effect_fn(void)
{
static sox_effect_handler_t handler = {
"rate", 0, SOX_EFF_RATE, create, start, flow, drain, stop, 0, sizeof(priv_t)
};
static char const * lines[] = {
"[-q|-l|-m|-h|-v] [override-options] RATE[k]",
" BAND-",
" QUALITY WIDTH REJ dB TYPICAL USE",
" -q quick n/a ~30 @ Fs/4 playback on ancient hardware",
" -l low 80% 100 playback on old hardware",
" -m medium 95% 100 audio playback",
" -h high (default) 95% 125 16-bit mastering (use with dither)",
" -v very high 95% 175 24-bit mastering",
" OVERRIDE OPTIONS (only with -m, -h, -v)",
" -M/-I/-L Phase response = minimum/intermediate/linear(default)",
" -s Steep filter (band-width = 99%)",
" -a Allow aliasing above the pass-band",
" -b 74-99.7 Any band-width %",
" -p 0-100 Any phase response (0 = minimum, 25 = intermediate,",
" 50 = linear, 100 = maximum)",
};
static char * usage;
handler.usage = lsx_usage_lines(&usage, lines, array_length(lines));
return &handler;
}