common_audio/signal_processing/resample_fractional.c

/*
 *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

/*
 * This file contains the resampling functions between 48, 44, 32 and 24 kHz.
 * The description headers can be found in signal_processing_library.h
 *
 */

#include "common_audio/signal_processing/include/signal_processing_library.h"

// interpolation coefficients
static const int16_t kCoefficients48To32[2][8] = {
    {778, -2050, 1087, 23285, 12903, -3783, 441, 222},
    {222, 441, -3783, 12903, 23285, 1087, -2050, 778}};

static const int16_t kCoefficients32To24[3][8] = {
    {767, -2362, 2434, 24406, 10620, -3838, 721, 90},
    {386, -381, -2646, 19062, 19062, -2646, -381, 386},
    {90, 721, -3838, 10620, 24406, 2434, -2362, 767}};

static const int16_t kCoefficients44To32[4][9] = {
    {117, -669, 2245, -6183, 26267, 13529, -3245, 845, -138},
    {-101, 612, -2283, 8532, 29790, -5138, 1789, -524, 91},
    {50, -292, 1016, -3064, 32010, 3933, -1147, 315, -53},
    {-156, 974, -3863, 18603, 21691, -6246, 2353, -712, 126}};

//   Resampling ratio: 2/3
// input:  int32_t (normalized, not saturated) :: size 3 * K
// output: int32_t (shifted 15 positions to the left, + offset 16384) :: size 2
// * K
//      K: number of blocks

void WebRtcSpl_Resample48khzTo32khz(const int32_t* In, int32_t* Out, size_t K) {
  /////////////////////////////////////////////////////////////
  // Filter operation:
  //
  // Perform resampling (3 input samples -> 2 output samples);
  // process in sub blocks of size 3 samples.
  int32_t tmp;
  size_t m;

  for (m = 0; m < K; m++) {
    tmp = 1 << 14;
    tmp += kCoefficients48To32[0][0] * In[0];
    tmp += kCoefficients48To32[0][1] * In[1];
    tmp += kCoefficients48To32[0][2] * In[2];
    tmp += kCoefficients48To32[0][3] * In[3];
    tmp += kCoefficients48To32[0][4] * In[4];
    tmp += kCoefficients48To32[0][5] * In[5];
    tmp += kCoefficients48To32[0][6] * In[6];
    tmp += kCoefficients48To32[0][7] * In[7];
    Out[0] = tmp;

    tmp = 1 << 14;
    tmp += kCoefficients48To32[1][0] * In[1];
    tmp += kCoefficients48To32[1][1] * In[2];
    tmp += kCoefficients48To32[1][2] * In[3];
    tmp += kCoefficients48To32[1][3] * In[4];
    tmp += kCoefficients48To32[1][4] * In[5];
    tmp += kCoefficients48To32[1][5] * In[6];
    tmp += kCoefficients48To32[1][6] * In[7];
    tmp += kCoefficients48To32[1][7] * In[8];
    Out[1] = tmp;

    // update pointers
    In += 3;
    Out += 2;
  }
}

//   Resampling ratio: 3/4
// input:  int32_t (normalized, not saturated) :: size 4 * K
// output: int32_t (shifted 15 positions to the left, + offset 16384) :: size 3
// * K
//      K: number of blocks

void WebRtcSpl_Resample32khzTo24khz(const int32_t* In, int32_t* Out, size_t K) {
  /////////////////////////////////////////////////////////////
  // Filter operation:
  //
  // Perform resampling (4 input samples -> 3 output samples);
  // process in sub blocks of size 4 samples.
  size_t m;
  int32_t tmp;

  for (m = 0; m < K; m++) {
    tmp = 1 << 14;
    tmp += kCoefficients32To24[0][0] * In[0];
    tmp += kCoefficients32To24[0][1] * In[1];
    tmp += kCoefficients32To24[0][2] * In[2];
    tmp += kCoefficients32To24[0][3] * In[3];
    tmp += kCoefficients32To24[0][4] * In[4];
    tmp += kCoefficients32To24[0][5] * In[5];
    tmp += kCoefficients32To24[0][6] * In[6];
    tmp += kCoefficients32To24[0][7] * In[7];
    Out[0] = tmp;

    tmp = 1 << 14;
    tmp += kCoefficients32To24[1][0] * In[1];
    tmp += kCoefficients32To24[1][1] * In[2];
    tmp += kCoefficients32To24[1][2] * In[3];
    tmp += kCoefficients32To24[1][3] * In[4];
    tmp += kCoefficients32To24[1][4] * In[5];
    tmp += kCoefficients32To24[1][5] * In[6];
    tmp += kCoefficients32To24[1][6] * In[7];
    tmp += kCoefficients32To24[1][7] * In[8];
    Out[1] = tmp;

    tmp = 1 << 14;
    tmp += kCoefficients32To24[2][0] * In[2];
    tmp += kCoefficients32To24[2][1] * In[3];
    tmp += kCoefficients32To24[2][2] * In[4];
    tmp += kCoefficients32To24[2][3] * In[5];
    tmp += kCoefficients32To24[2][4] * In[6];
    tmp += kCoefficients32To24[2][5] * In[7];
    tmp += kCoefficients32To24[2][6] * In[8];
    tmp += kCoefficients32To24[2][7] * In[9];
    Out[2] = tmp;

    // update pointers
    In += 4;
    Out += 3;
  }
}

//
// fractional resampling filters
//   Fout = 11/16 * Fin
//   Fout =  8/11 * Fin
//

// compute two inner-products and store them to output array
static void WebRtcSpl_ResampDotProduct(const int32_t* in1,
                                       const int32_t* in2,
                                       const int16_t* coef_ptr,
                                       int32_t* out1,
                                       int32_t* out2) {
  int32_t tmp1 = 16384;
  int32_t tmp2 = 16384;
  int16_t coef;

  coef = coef_ptr[0];
  tmp1 += coef * in1[0];
  tmp2 += coef * in2[-0];

  coef = coef_ptr[1];
  tmp1 += coef * in1[1];
  tmp2 += coef * in2[-1];

  coef = coef_ptr[2];
  tmp1 += coef * in1[2];
  tmp2 += coef * in2[-2];

  coef = coef_ptr[3];
  tmp1 += coef * in1[3];
  tmp2 += coef * in2[-3];

  coef = coef_ptr[4];
  tmp1 += coef * in1[4];
  tmp2 += coef * in2[-4];

  coef = coef_ptr[5];
  tmp1 += coef * in1[5];
  tmp2 += coef * in2[-5];

  coef = coef_ptr[6];
  tmp1 += coef * in1[6];
  tmp2 += coef * in2[-6];

  coef = coef_ptr[7];
  tmp1 += coef * in1[7];
  tmp2 += coef * in2[-7];

  coef = coef_ptr[8];
  *out1 = tmp1 + coef * in1[8];
  *out2 = tmp2 + coef * in2[-8];
}

//   Resampling ratio: 8/11
// input:  int32_t (normalized, not saturated) :: size 11 * K
// output: int32_t (shifted 15 positions to the left, + offset 16384) :: size  8
// * K
//      K: number of blocks

void WebRtcSpl_Resample44khzTo32khz(const int32_t* In, int32_t* Out, size_t K) {
  /////////////////////////////////////////////////////////////
  // Filter operation:
  //
  // Perform resampling (11 input samples -> 8 output samples);
  // process in sub blocks of size 11 samples.
  int32_t tmp;
  size_t m;

  for (m = 0; m < K; m++) {
    tmp = 1 << 14;

    // first output sample
    Out[0] = ((int32_t)In[3] << 15) + tmp;

    // sum and accumulate filter coefficients and input samples
    tmp += kCoefficients44To32[3][0] * In[5];
    tmp += kCoefficients44To32[3][1] * In[6];
    tmp += kCoefficients44To32[3][2] * In[7];
    tmp += kCoefficients44To32[3][3] * In[8];
    tmp += kCoefficients44To32[3][4] * In[9];
    tmp += kCoefficients44To32[3][5] * In[10];
    tmp += kCoefficients44To32[3][6] * In[11];
    tmp += kCoefficients44To32[3][7] * In[12];
    tmp += kCoefficients44To32[3][8] * In[13];
    Out[4] = tmp;

    // sum and accumulate filter coefficients and input samples
    WebRtcSpl_ResampDotProduct(&In[0], &In[17], kCoefficients44To32[0], &Out[1],
                               &Out[7]);

    // sum and accumulate filter coefficients and input samples
    WebRtcSpl_ResampDotProduct(&In[2], &In[15], kCoefficients44To32[1], &Out[2],
                               &Out[6]);

    // sum and accumulate filter coefficients and input samples
    WebRtcSpl_ResampDotProduct(&In[3], &In[14], kCoefficients44To32[2], &Out[3],
                               &Out[5]);

    // update pointers
    In += 11;
    Out += 8;
  }
}