gstreamer/gst-libs/gst/resample/resample.c

/* Resampling library
 * Copyright (C) <2001> David A. Schleef <ds@schleef.org>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <string.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>

#include "private.h"
#include <gst/gstplugin.h>
#include <gst/gstversion.h>

inline double
sinc (double x)
{
  if (x == 0)
    return 1;
  return sin (x) / x;
}

inline double
window_func (double x)
{
  x = 1 - x * x;
  return x * x;
}

signed short
double_to_s16 (double x)
{
  if (x < -32768) {
    printf ("clipped\n");
    return -32768;
  }
  if (x > 32767) {
    printf ("clipped\n");
    return -32767;
  }
  return rint (x);
}

signed short
double_to_s16_ppcasm (double x)
{
  if (x < -32768) {
    return -32768;
  }
  if (x > 32767) {
    return -32767;
  }
  return rint (x);
}

void
gst_resample_init (gst_resample_t * r)
{
  r->i_start = 0;
  if (r->filter_length & 1) {
    r->o_start = 0;
  } else {
    r->o_start = r->o_inc * 0.5;
  }

  memset (r->acc, 0, sizeof (r->acc));

  gst_resample_reinit (r);
}

void
gst_resample_reinit (gst_resample_t * r)
{
  /* i_inc is the number of samples that the output increments for
   * each input sample.  o_inc is the opposite. */
  r->i_inc = (double) r->o_rate / r->i_rate;
  r->o_inc = (double) r->i_rate / r->o_rate;

  r->halftaps = (r->filter_length - 1.0) * 0.5;

  if (r->format == GST_RESAMPLE_S16) {
    switch (r->method) {
      default:
      case GST_RESAMPLE_NEAREST:
	r->scale = gst_resample_nearest_s16;
	break;
      case GST_RESAMPLE_BILINEAR:
	r->scale = gst_resample_bilinear_s16;
	break;
      case GST_RESAMPLE_SINC_SLOW:
	r->scale = gst_resample_sinc_s16;
	break;
      case GST_RESAMPLE_SINC:
	r->scale = gst_resample_sinc_ft_s16;
	break;
    }
  } else if (r->format == GST_RESAMPLE_FLOAT) {
    switch (r->method) {
      default:
      case GST_RESAMPLE_NEAREST:
	r->scale = gst_resample_nearest_float;
	break;
      case GST_RESAMPLE_BILINEAR:
	r->scale = gst_resample_bilinear_float;
	break;
      case GST_RESAMPLE_SINC_SLOW:
	r->scale = gst_resample_sinc_float;
	break;
      case GST_RESAMPLE_SINC:
	r->scale = gst_resample_sinc_ft_float;
	break;
    }
  } else {
    fprintf (stderr, "gst_resample: Unexpected format \"%d\"\n", r->format);
  }
}

/*
 * Prepare to be confused.
 *
 * We keep a "timebase" that is based on output samples.  The zero
 * of the timebase cooresponds to the next output sample that will
 * be written.
 *
 * i_start is the "time" that corresponds to the first input sample
 * in an incoming buffer.  Since the output depends on input samples
 * ahead in time, i_start will tend to be around halftaps.
 *
 * i_start_buf is the time of the first sample in the temporary
 * buffer.
 */
void
gst_resample_scale (gst_resample_t * r, void *i_buf, unsigned int i_size)
{
  int o_size;

  r->i_buf = i_buf;

  r->i_samples = i_size / 2 / r->channels;

  r->i_start_buf = r->i_start - r->filter_length * r->i_inc;

  /* i_start is the offset (in a given output sample) that is the
   * beginning of the current input buffer */
  r->i_end = r->i_start + r->i_inc * r->i_samples;

  r->o_samples = floor (r->i_end - r->halftaps * r->i_inc);

  o_size = r->o_samples * r->channels * 2;
  r->o_buf = r->get_buffer (r->priv, o_size);

  if (r->verbose) {
    printf ("gst_resample_scale: i_buf=%p i_size=%d\n", i_buf, i_size);
    printf ("gst_resample_scale: i_samples=%d o_samples=%d i_inc=%g o_buf=%p\n",
	r->i_samples, r->o_samples, r->i_inc, r->o_buf);
    printf ("gst_resample_scale: i_start=%g i_end=%g o_start=%g\n",
	r->i_start, r->i_end, r->o_start);
  }

  if ((r->filter_length + r->i_samples) * sizeof (double) * 2 > r->buffer_len) {
    int size = (r->filter_length + r->i_samples) * sizeof (double) * 2;

    if (r->verbose) {
      printf ("gst_resample temp buffer size=%d\n", size);
    }
    if (r->buffer)
      free (r->buffer);
    r->buffer_len = size;
    r->buffer = malloc (size);
    memset (r->buffer, 0, size);
  }

  if (r->format == GST_RESAMPLE_S16) {
    if (r->channels == 2) {
      conv_double_short (r->buffer + r->filter_length * sizeof (double) * 2,
	  r->i_buf, r->i_samples * 2);
    } else {
      conv_double_short_dstr (r->buffer +
	  r->filter_length * sizeof (double) * 2, r->i_buf, r->i_samples,
	  sizeof (double) * 2);
    }
  } else if (r->format == GST_RESAMPLE_FLOAT) {
    if (r->channels == 2) {
      conv_double_float (r->buffer + r->filter_length * sizeof (double) * 2,
	  r->i_buf, r->i_samples * 2);
    } else {
      conv_double_float_dstr (r->buffer +
	  r->filter_length * sizeof (double) * 2, r->i_buf, r->i_samples,
	  sizeof (double) * 2);
    }
  }

  r->scale (r);

  memcpy (r->buffer,
      r->buffer + r->i_samples * sizeof (double) * 2,
      r->filter_length * sizeof (double) * 2);

  /* updating times */
  r->i_start += r->i_samples * r->i_inc;
  r->o_start += r->o_samples * r->o_inc - r->i_samples;

  /* adjusting timebase zero */
  r->i_start -= r->o_samples;
}

void
gst_resample_nearest_s16 (gst_resample_t * r)
{
  signed short *i_ptr, *o_ptr;
  int i_count = 0;
  double a;
  int i;

  i_ptr = (signed short *) r->i_buf;
  o_ptr = (signed short *) r->o_buf;

  a = r->o_start;
  i_count = 0;
#define SCALE_LOOP(COPY,INC) \
	for (i = 0; i < r->o_samples; i++) {	\
		COPY;							\
		a += r->o_inc;						\
		while (a >= 1) {				\
			a -= 1;						\
			i_ptr+=INC;					\
			i_count++;					\
		}								\
		o_ptr+=INC;						\
   	}

  switch (r->channels) {
    case 1:
      SCALE_LOOP (o_ptr[0] = i_ptr[0], 1);
      break;
    case 2:
      SCALE_LOOP (o_ptr[0] = i_ptr[0]; o_ptr[1] = i_ptr[1], 2);
      break;
    default:
    {
      int n, n_chan = r->channels;

      SCALE_LOOP (for (n = 0; n < n_chan; n++) o_ptr[n] = i_ptr[n], n_chan);
    }
  }
  if (i_count != r->i_samples) {
    printf ("handled %d in samples (expected %d)\n", i_count, r->i_samples);
  }
}

void
gst_resample_bilinear_s16 (gst_resample_t * r)
{
  signed short *i_ptr, *o_ptr;
  int o_count = 0;
  double b;
  int i;
  double acc0, acc1;

  i_ptr = (signed short *) r->i_buf;
  o_ptr = (signed short *) r->o_buf;

  acc0 = r->acc[0];
  acc1 = r->acc[1];
  b = r->i_start;
  for (i = 0; i < r->i_samples; i++) {
    b += r->i_inc;
    /*printf("in %d\n",i_ptr[0]); */
    if (b >= 2) {
      printf ("not expecting b>=2\n");
    }
    if (b >= 1) {
      acc0 += (1.0 - (b - r->i_inc)) * i_ptr[0];
      acc1 += (1.0 - (b - r->i_inc)) * i_ptr[1];

      o_ptr[0] = rint (acc0);
      /*printf("out %d\n",o_ptr[0]); */
      o_ptr[1] = rint (acc1);
      o_ptr += 2;
      o_count++;

      b -= 1.0;

      acc0 = b * i_ptr[0];
      acc1 = b * i_ptr[1];
    } else {
      acc0 += i_ptr[0] * r->i_inc;
      acc1 += i_ptr[1] * r->i_inc;
    }
    i_ptr += 2;
  }
  r->acc[0] = acc0;
  r->acc[1] = acc1;

  if (o_count != r->o_samples) {
    printf ("handled %d out samples (expected %d)\n", o_count, r->o_samples);
  }
}

void
gst_resample_sinc_slow_s16 (gst_resample_t * r)
{
  signed short *i_ptr, *o_ptr;
  int i, j;
  double c0, c1;
  double a;
  int start;
  double center;
  double weight;

  if (!r->buffer) {
    int size = r->filter_length * 2 * r->channels;

    printf ("gst_resample temp buffer\n");
    r->buffer = malloc (size);
    memset (r->buffer, 0, size);
  }

  i_ptr = (signed short *) r->i_buf;
  o_ptr = (signed short *) r->o_buf;

  a = r->i_start;
#define GETBUF(index,chan) (((index)<0) \
			? ((short *)(r->buffer))[((index)+r->filter_length)*2+(chan)] \
			: i_ptr[(index)*2+(chan)])
  {
    double sinx, cosx, sind, cosd;
    double x, d;
    double t;

    for (i = 0; i < r->o_samples; i++) {
      start = floor (a) - r->filter_length;
      center = a - r->halftaps;
      x = M_PI * (start - center) * r->o_inc;
      sinx = sin (M_PI * (start - center) * r->o_inc);
      cosx = cos (M_PI * (start - center) * r->o_inc);
      d = M_PI * r->o_inc;
      sind = sin (M_PI * r->o_inc);
      cosd = cos (M_PI * r->o_inc);
      c0 = 0;
      c1 = 0;
      for (j = 0; j < r->filter_length; j++) {
	weight = (x == 0) ? 1 : (sinx / x);
/*printf("j %d sin %g cos %g\n",j,sinx,cosx); */
/*printf("j %d sin %g x %g sinc %g\n",j,sinx,x,weight); */
	c0 += weight * GETBUF ((start + j), 0);
	c1 += weight * GETBUF ((start + j), 1);
	t = cosx * cosd - sinx * sind;
	sinx = cosx * sind + sinx * cosd;
	cosx = t;
	x += d;
      }
      o_ptr[0] = rint (c0);
      o_ptr[1] = rint (c1);
      o_ptr += 2;
      a += r->o_inc;
    }
  }
#undef GETBUF

  memcpy (r->buffer,
      i_ptr + (r->i_samples - r->filter_length) * r->channels,
      r->filter_length * 2 * r->channels);
}

/* only works for channels == 2 ???? */
void
gst_resample_sinc_s16 (gst_resample_t * r)
{
  double *ptr;
  signed short *o_ptr;
  int i, j;
  double c0, c1;
  double a;
  int start;
  double center;
  double weight;
  double x0, x, d;
  double scale;

  ptr = (double *) r->buffer;
  o_ptr = (signed short *) r->o_buf;

  /* scale provides a cutoff frequency for the low
   * pass filter aspects of sinc().  scale=M_PI
   * will cut off at the input frequency, which is
   * good for up-sampling, but will cause aliasing
   * for downsampling.  Downsampling needs to be
   * cut off at o_rate, thus scale=M_PI*r->i_inc. */
  /* actually, it needs to be M_PI*r->i_inc*r->i_inc.
   * Need to research why. */
  scale = M_PI * r->i_inc;
  for (i = 0; i < r->o_samples; i++) {
    a = r->o_start + i * r->o_inc;
    start = floor (a - r->halftaps);
/*printf("%d: a=%g start=%d end=%d\n",i,a,start,start+r->filter_length-1); */
    center = a;
    /*x = M_PI * (start - center) * r->o_inc; */
    /*d = M_PI * r->o_inc; */
    /*x = (start - center) * r->o_inc; */
    x0 = (start - center) * r->o_inc;
    d = r->o_inc;
    c0 = 0;
    c1 = 0;
    for (j = 0; j < r->filter_length; j++) {
      x = x0 + d * j;
      weight = sinc (x * scale * r->i_inc) * scale / M_PI;
      weight *= window_func (x / r->halftaps * r->i_inc);
      c0 += weight * ptr[(start + j + r->filter_length) * 2 + 0];
      c1 += weight * ptr[(start + j + r->filter_length) * 2 + 1];
    }
    o_ptr[0] = double_to_s16 (c0);
    o_ptr[1] = double_to_s16 (c1);
    o_ptr += 2;
  }
}

/*
 * Resampling audio is best done using a sinc() filter.
 *
 *
 *  out[t] = Sum( in[t'] * sinc((t-t')/delta_t), all t')
 *
 * The immediate problem with this algorithm is that it involves a
 * sum over an infinite number of input samples, both in the past
 * and future.  Note that even though sinc(x) is bounded by 1/x,
 * and thus decays to 0 for large x, since sum(x,{x=0,1..,n}) diverges
 * as log(n), we need to be careful about convergence.  This is
 * typically done by using a windowing function, which also makes
 * the sum over a finite number of input samples.
 *
 * The next problem is computational:  sinc(), and especially
 * sinc() multiplied by a non-trivial windowing function is expensive
 * to calculate, and also difficult to find SIMD optimizations.  Since
 * the time increment on input and output is different, it is not
 * possible to use a FIR filter, because the taps would have to be
 * recalculated for every t.
 *
 * To get around the expense of calculating sinc() for every point,
 * we pre-calculate sinc() at a number of points, and then interpolate
 * for the values we want in calculations.  The interpolation method
 * chosen is bi-cubic, which requires both the evalated function and
 * its derivative at every pre-sampled point.  Also, if the sampled
 * points are spaced commensurate with the input delta_t, we notice
 * that the interpolating weights are the same for every input point.
 * This decreases the number of operations to 4 multiplies and 4 adds
 * for each tap, regardless of the complexity of the filtering function.
 * 
 * At this point, it is possible to rearrange the problem as the sum
 * of 4 properly weghted FIR filters.  Typical SIMD computation units
 * are highly optimized for FIR filters, making long filter lengths
 * reasonable.
 */

static functable_t *ft;

double out_tmp[10000];

void
gst_resample_sinc_ft_s16 (gst_resample_t * r)
{
  double *ptr;
  signed short *o_ptr;
  int i;

  /*int j; */
  double c0, c1;

  /*double a; */
  double start_f, start_x;
  int start;
  double center;

  /*double weight; */
  double x, d;
  double scale;
  int n = 4;

  scale = r->i_inc;		/* cutoff at 22050 */
  /*scale = 1.0;          // cutoff at 24000 */
  /*scale = r->i_inc * 0.5;       // cutoff at 11025 */

  if (!ft) {
    ft = malloc (sizeof (*ft));
    memset (ft, 0, sizeof (*ft));

    ft->len = (r->filter_length + 2) * n;
    ft->offset = 1.0 / n;
    ft->start = -ft->len * 0.5 * ft->offset;

    ft->func_x = functable_sinc;
    ft->func_dx = functable_dsinc;
    ft->scale = M_PI * scale;

    ft->func2_x = functable_window_std;
    ft->func2_dx = functable_window_dstd;
    ft->scale2 = 1.0 / r->halftaps;

    functable_init (ft);

    /*printf("len=%d offset=%g start=%g\n",ft->len,ft->offset,ft->start); */
  }

  ptr = r->buffer;
  o_ptr = (signed short *) r->o_buf;

  center = r->o_start;
  start_x = center - r->halftaps;
  start_f = floor (start_x);
  start_x -= start_f;
  start = start_f;
  for (i = 0; i < r->o_samples; i++) {
    /*start_f = floor(center - r->halftaps); */
/*printf("%d: a=%g start=%d end=%d\n",i,a,start,start+r->filter_length-1); */
    x = start_f - center;
    d = 1;
    c0 = 0;
    c1 = 0;
/*#define slow */
#ifdef slow
    for (j = 0; j < r->filter_length; j++) {
      weight = functable_eval (ft, x) * scale;
      /*weight = sinc(M_PI * scale * x)*scale*r->i_inc; */
      /*weight *= window_func(x / r->halftaps); */
      c0 += weight * ptr[(start + j + r->filter_length) * 2 + 0];
      c1 += weight * ptr[(start + j + r->filter_length) * 2 + 1];
      x += d;
    }
#else
    functable_fir2 (ft,
	&c0, &c1, x, n, ptr + (start + r->filter_length) * 2, r->filter_length);
    c0 *= scale;
    c1 *= scale;
#endif

    out_tmp[2 * i + 0] = c0;
    out_tmp[2 * i + 1] = c1;
    center += r->o_inc;
    start_x += r->o_inc;
    while (start_x >= 1.0) {
      start_f++;
      start_x -= 1.0;
      start++;
    }
  }

  if (r->channels == 2) {
    conv_short_double (r->o_buf, out_tmp, 2 * r->o_samples);
  } else {
    conv_short_double_sstr (r->o_buf, out_tmp, r->o_samples,
	2 * sizeof (double));
  }
}

/********
 ** float code below
 ********/


void
gst_resample_nearest_float (gst_resample_t * r)
{
  float *i_ptr, *o_ptr;
  int i_count = 0;
  double a;
  int i;

  i_ptr = (float *) r->i_buf;
  o_ptr = (float *) r->o_buf;

  a = r->o_start;
  i_count = 0;
#define SCALE_LOOP(COPY,INC) \
	for (i = 0; i < r->o_samples; i++) {	\
		COPY;							\
		a += r->o_inc;						\
		while (a >= 1) {				\
			a -= 1;						\
			i_ptr+=INC;					\
			i_count++;					\
		}								\
		o_ptr+=INC;						\
   	}

  switch (r->channels) {
    case 1:
      SCALE_LOOP (o_ptr[0] = i_ptr[0], 1);
      break;
    case 2:
      SCALE_LOOP (o_ptr[0] = i_ptr[0]; o_ptr[1] = i_ptr[1], 2);
      break;
    default:
    {
      int n, n_chan = r->channels;

      SCALE_LOOP (for (n = 0; n < n_chan; n++) o_ptr[n] = i_ptr[n], n_chan);
    }
  }
  if (i_count != r->i_samples) {
    printf ("handled %d in samples (expected %d)\n", i_count, r->i_samples);
  }
}

void
gst_resample_bilinear_float (gst_resample_t * r)
{
  float *i_ptr, *o_ptr;
  int o_count = 0;
  double b;
  int i;
  double acc0, acc1;

  i_ptr = (float *) r->i_buf;
  o_ptr = (float *) r->o_buf;

  acc0 = r->acc[0];
  acc1 = r->acc[1];
  b = r->i_start;
  for (i = 0; i < r->i_samples; i++) {
    b += r->i_inc;
    /*printf("in %d\n",i_ptr[0]); */
    if (b >= 2) {
      printf ("not expecting b>=2\n");
    }
    if (b >= 1) {
      acc0 += (1.0 - (b - r->i_inc)) * i_ptr[0];
      acc1 += (1.0 - (b - r->i_inc)) * i_ptr[1];

      o_ptr[0] = acc0;
      /*printf("out %d\n",o_ptr[0]); */
      o_ptr[1] = acc1;
      o_ptr += 2;
      o_count++;

      b -= 1.0;

      acc0 = b * i_ptr[0];
      acc1 = b * i_ptr[1];
    } else {
      acc0 += i_ptr[0] * r->i_inc;
      acc1 += i_ptr[1] * r->i_inc;
    }
    i_ptr += 2;
  }
  r->acc[0] = acc0;
  r->acc[1] = acc1;

  if (o_count != r->o_samples) {
    printf ("handled %d out samples (expected %d)\n", o_count, r->o_samples);
  }
}

void
gst_resample_sinc_slow_float (gst_resample_t * r)
{
  float *i_ptr, *o_ptr;
  int i, j;
  double c0, c1;
  double a;
  int start;
  double center;
  double weight;

  if (!r->buffer) {
    int size = r->filter_length * sizeof (float) * r->channels;

    printf ("gst_resample temp buffer\n");
    r->buffer = malloc (size);
    memset (r->buffer, 0, size);
  }

  i_ptr = (float *) r->i_buf;
  o_ptr = (float *) r->o_buf;

  a = r->i_start;
#define GETBUF(index,chan) (((index)<0) \
			? ((float *)(r->buffer))[((index)+r->filter_length)*2+(chan)] \
			: i_ptr[(index)*2+(chan)])
  {
    double sinx, cosx, sind, cosd;
    double x, d;
    double t;

    for (i = 0; i < r->o_samples; i++) {
      start = floor (a) - r->filter_length;
      center = a - r->halftaps;
      x = M_PI * (start - center) * r->o_inc;
      sinx = sin (M_PI * (start - center) * r->o_inc);
      cosx = cos (M_PI * (start - center) * r->o_inc);
      d = M_PI * r->o_inc;
      sind = sin (M_PI * r->o_inc);
      cosd = cos (M_PI * r->o_inc);
      c0 = 0;
      c1 = 0;
      for (j = 0; j < r->filter_length; j++) {
	weight = (x == 0) ? 1 : (sinx / x);
/*printf("j %d sin %g cos %g\n",j,sinx,cosx); */
/*printf("j %d sin %g x %g sinc %g\n",j,sinx,x,weight); */
	c0 += weight * GETBUF ((start + j), 0);
	c1 += weight * GETBUF ((start + j), 1);
	t = cosx * cosd - sinx * sind;
	sinx = cosx * sind + sinx * cosd;
	cosx = t;
	x += d;
      }
      o_ptr[0] = c0;
      o_ptr[1] = c1;
      o_ptr += 2;
      a += r->o_inc;
    }
  }
#undef GETBUF

  memcpy (r->buffer,
      i_ptr + (r->i_samples - r->filter_length) * r->channels,
      r->filter_length * sizeof (float) * r->channels);
}

/* only works for channels == 2 ???? */
void
gst_resample_sinc_float (gst_resample_t * r)
{
  double *ptr;
  float *o_ptr;
  int i, j;
  double c0, c1;
  double a;
  int start;
  double center;
  double weight;
  double x0, x, d;
  double scale;

  ptr = (double *) r->buffer;
  o_ptr = (float *) r->o_buf;

  /* scale provides a cutoff frequency for the low
   * pass filter aspects of sinc().  scale=M_PI
   * will cut off at the input frequency, which is
   * good for up-sampling, but will cause aliasing
   * for downsampling.  Downsampling needs to be
   * cut off at o_rate, thus scale=M_PI*r->i_inc. */
  /* actually, it needs to be M_PI*r->i_inc*r->i_inc.
   * Need to research why. */
  scale = M_PI * r->i_inc;
  for (i = 0; i < r->o_samples; i++) {
    a = r->o_start + i * r->o_inc;
    start = floor (a - r->halftaps);
/*printf("%d: a=%g start=%d end=%d\n",i,a,start,start+r->filter_length-1); */
    center = a;
    /*x = M_PI * (start - center) * r->o_inc; */
    /*d = M_PI * r->o_inc; */
    /*x = (start - center) * r->o_inc; */
    x0 = (start - center) * r->o_inc;
    d = r->o_inc;
    c0 = 0;
    c1 = 0;
    for (j = 0; j < r->filter_length; j++) {
      x = x0 + d * j;
      weight = sinc (x * scale * r->i_inc) * scale / M_PI;
      weight *= window_func (x / r->halftaps * r->i_inc);
      c0 += weight * ptr[(start + j + r->filter_length) * 2 + 0];
      c1 += weight * ptr[(start + j + r->filter_length) * 2 + 1];
    }
    o_ptr[0] = c0;
    o_ptr[1] = c1;
    o_ptr += 2;
  }
}

void
gst_resample_sinc_ft_float (gst_resample_t * r)
{
  double *ptr;
  float *o_ptr;
  int i;

  /*int j; */
  double c0, c1;

  /*double a; */
  double start_f, start_x;
  int start;
  double center;

  /*double weight; */
  double x, d;
  double scale;
  int n = 4;

  scale = r->i_inc;		/* cutoff at 22050 */
  /*scale = 1.0;          // cutoff at 24000 */
  /*scale = r->i_inc * 0.5;       // cutoff at 11025 */

  if (!ft) {
    ft = malloc (sizeof (*ft));
    memset (ft, 0, sizeof (*ft));

    ft->len = (r->filter_length + 2) * n;
    ft->offset = 1.0 / n;
    ft->start = -ft->len * 0.5 * ft->offset;

    ft->func_x = functable_sinc;
    ft->func_dx = functable_dsinc;
    ft->scale = M_PI * scale;

    ft->func2_x = functable_window_std;
    ft->func2_dx = functable_window_dstd;
    ft->scale2 = 1.0 / r->halftaps;

    functable_init (ft);

    /*printf("len=%d offset=%g start=%g\n",ft->len,ft->offset,ft->start); */
  }

  ptr = r->buffer;
  o_ptr = (float *) r->o_buf;

  center = r->o_start;
  start_x = center - r->halftaps;
  start_f = floor (start_x);
  start_x -= start_f;
  start = start_f;
  for (i = 0; i < r->o_samples; i++) {
    /*start_f = floor(center - r->halftaps); */
/*printf("%d: a=%g start=%d end=%d\n",i,a,start,start+r->filter_length-1); */
    x = start_f - center;
    d = 1;
    c0 = 0;
    c1 = 0;
/*#define slow */
#ifdef slow
    for (j = 0; j < r->filter_length; j++) {
      weight = functable_eval (ft, x) * scale;
      /*weight = sinc(M_PI * scale * x)*scale*r->i_inc; */
      /*weight *= window_func(x / r->halftaps); */
      c0 += weight * ptr[(start + j + r->filter_length) * 2 + 0];
      c1 += weight * ptr[(start + j + r->filter_length) * 2 + 1];
      x += d;
    }
#else
    functable_fir2 (ft,
	&c0, &c1, x, n, ptr + (start + r->filter_length) * 2, r->filter_length);
    c0 *= scale;
    c1 *= scale;
#endif

    out_tmp[2 * i + 0] = c0;
    out_tmp[2 * i + 1] = c1;
    center += r->o_inc;
    start_x += r->o_inc;
    while (start_x >= 1.0) {
      start_f++;
      start_x -= 1.0;
      start++;
    }
  }

  if (r->channels == 2) {
    conv_float_double (r->o_buf, out_tmp, 2 * r->o_samples);
  } else {
    conv_float_double_sstr (r->o_buf, out_tmp, r->o_samples,
	2 * sizeof (double));
  }
}

static gboolean
plugin_init (GstPlugin * plugin)
{
  return TRUE;
}

GST_PLUGIN_DEFINE (GST_VERSION_MAJOR,
    GST_VERSION_MINOR,
    "gstresample",
    "Resampling routines for use in audio plugins",
    plugin_init, VERSION, GST_LICENSE, GST_PACKAGE, GST_ORIGIN);