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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.
WebRtcSpl_DownsampleFastC(const int16_t * data_in,size_t data_in_length,int16_t * data_out,size_t data_out_length,const int16_t * __restrict coefficients,size_t coefficients_length,int factor,size_t delay)15 int 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