src/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;
    }
}