1 /*
2 * Copyright (c) 2011 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
12 /*
13 * This file contains the function WebRtcSpl_DownsampleFast().
14 * The description header can be found in signal_processing_library.h
15 *
16 */
17
18 #include "signal_processing_library.h"
19
WebRtcSpl_DownsampleFast(WebRtc_Word16 * in_ptr,WebRtc_Word16 in_length,WebRtc_Word16 * out_ptr,WebRtc_Word16 out_length,WebRtc_Word16 * B,WebRtc_Word16 B_length,WebRtc_Word16 factor,WebRtc_Word16 delay)20 int WebRtcSpl_DownsampleFast(WebRtc_Word16 *in_ptr, WebRtc_Word16 in_length,
21 WebRtc_Word16 *out_ptr, WebRtc_Word16 out_length,
22 WebRtc_Word16 *B, WebRtc_Word16 B_length, WebRtc_Word16 factor,
23 WebRtc_Word16 delay)
24 {
25 WebRtc_Word32 o;
26 int i, j;
27
28 WebRtc_Word16 *downsampled_ptr = out_ptr;
29 WebRtc_Word16 *b_ptr;
30 WebRtc_Word16 *x_ptr;
31 WebRtc_Word16 endpos = delay
32 + (WebRtc_Word16)WEBRTC_SPL_MUL_16_16(factor, (out_length - 1)) + 1;
33
34 if (in_length < endpos)
35 {
36 return -1;
37 }
38
39 for (i = delay; i < endpos; i += factor)
40 {
41 b_ptr = &B[0];
42 x_ptr = &in_ptr[i];
43
44 o = (WebRtc_Word32)2048; // Round val
45
46 for (j = 0; j < B_length; j++)
47 {
48 o += WEBRTC_SPL_MUL_16_16(*b_ptr++, *x_ptr--);
49 }
50
51 o = WEBRTC_SPL_RSHIFT_W32(o, 12);
52
53 // If output is higher than 32768, saturate it. Same with negative side
54
55 *downsampled_ptr++ = WebRtcSpl_SatW32ToW16(o);
56 }
57
58 return 0;
59 }
60