1/*
2 *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
3 *
4 *  Use of this source code is governed by a BSD-style license
5 *  that can be found in the LICENSE file in the root of the source
6 *  tree. An additional intellectual property rights grant can be found
7 *  in the file PATENTS.  All contributing project authors may
8 *  be found in the AUTHORS file in the root of the source tree.
9 */
10
11#include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
12
13// TODO(Bjornv): Change the function parameter order to WebRTC code style.
14// C version of WebRtcSpl_DownsampleFast() for generic platforms.
15int WebRtcSpl_DownsampleFastC(const int16_t* data_in,
16                              size_t data_in_length,
17                              int16_t* data_out,
18                              size_t data_out_length,
19                              const int16_t* __restrict coefficients,
20                              size_t coefficients_length,
21                              int factor,
22                              size_t delay) {
23  size_t i = 0;
24  size_t j = 0;
25  int32_t out_s32 = 0;
26  size_t endpos = delay + factor * (data_out_length - 1) + 1;
27
28  // Return error if any of the running conditions doesn't meet.
29  if (data_out_length == 0 || coefficients_length == 0
30                           || data_in_length < endpos) {
31    return -1;
32  }
33
34  for (i = delay; i < endpos; i += factor) {
35    out_s32 = 2048;  // Round value, 0.5 in Q12.
36
37    for (j = 0; j < coefficients_length; j++) {
38      out_s32 += coefficients[j] * data_in[i - j];  // Q12.
39    }
40
41    out_s32 >>= 12;  // Q0.
42
43    // Saturate and store the output.
44    *data_out++ = WebRtcSpl_SatW32ToW16(out_s32);
45  }
46
47  return 0;
48}
49