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 "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.
WebRtcSpl_DownsampleFastC(const int16_t * data_in,int data_in_length,int16_t * data_out,int data_out_length,const int16_t * __restrict coefficients,int coefficients_length,int factor,int delay)15 int WebRtcSpl_DownsampleFastC(const int16_t* data_in,
16 int data_in_length,
17 int16_t* data_out,
18 int data_out_length,
19 const int16_t* __restrict coefficients,
20 int coefficients_length,
21 int factor,
22 int delay) {
23 int i = 0;
24 int j = 0;
25 int32_t out_s32 = 0;
26 int 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