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_FilterAR().
14 * The description header can be found in signal_processing_library.h
15 *
16 */
17
18 #include "signal_processing_library.h"
19
WebRtcSpl_FilterAR(G_CONST WebRtc_Word16 * a,int a_length,G_CONST WebRtc_Word16 * x,int x_length,WebRtc_Word16 * state,int state_length,WebRtc_Word16 * state_low,int state_low_length,WebRtc_Word16 * filtered,WebRtc_Word16 * filtered_low,int filtered_low_length)20 int WebRtcSpl_FilterAR(G_CONST WebRtc_Word16* a,
21 int a_length,
22 G_CONST WebRtc_Word16* x,
23 int x_length,
24 WebRtc_Word16* state,
25 int state_length,
26 WebRtc_Word16* state_low,
27 int state_low_length,
28 WebRtc_Word16* filtered,
29 WebRtc_Word16* filtered_low,
30 int filtered_low_length)
31 {
32 WebRtc_Word32 o;
33 WebRtc_Word32 oLOW;
34 int i, j, stop;
35 G_CONST WebRtc_Word16* x_ptr = &x[0];
36 WebRtc_Word16* filteredFINAL_ptr = filtered;
37 WebRtc_Word16* filteredFINAL_LOW_ptr = filtered_low;
38
39 for (i = 0; i < x_length; i++)
40 {
41 // Calculate filtered[i] and filtered_low[i]
42 G_CONST WebRtc_Word16* a_ptr = &a[1];
43 WebRtc_Word16* filtered_ptr = &filtered[i - 1];
44 WebRtc_Word16* filtered_low_ptr = &filtered_low[i - 1];
45 WebRtc_Word16* state_ptr = &state[state_length - 1];
46 WebRtc_Word16* state_low_ptr = &state_low[state_length - 1];
47
48 o = (WebRtc_Word32)(*x_ptr++) << 12;
49 oLOW = (WebRtc_Word32)0;
50
51 stop = (i < a_length) ? i + 1 : a_length;
52 for (j = 1; j < stop; j++)
53 {
54 o -= WEBRTC_SPL_MUL_16_16(*a_ptr, *filtered_ptr--);
55 oLOW -= WEBRTC_SPL_MUL_16_16(*a_ptr++, *filtered_low_ptr--);
56 }
57 for (j = i + 1; j < a_length; j++)
58 {
59 o -= WEBRTC_SPL_MUL_16_16(*a_ptr, *state_ptr--);
60 oLOW -= WEBRTC_SPL_MUL_16_16(*a_ptr++, *state_low_ptr--);
61 }
62
63 o += (oLOW >> 12);
64 *filteredFINAL_ptr = (WebRtc_Word16)((o + (WebRtc_Word32)2048) >> 12);
65 *filteredFINAL_LOW_ptr++ = (WebRtc_Word16)(o - ((WebRtc_Word32)(*filteredFINAL_ptr++)
66 << 12));
67 }
68
69 // Save the filter state
70 if (x_length >= state_length)
71 {
72 WebRtcSpl_CopyFromEndW16(filtered, x_length, a_length - 1, state);
73 WebRtcSpl_CopyFromEndW16(filtered_low, x_length, a_length - 1, state_low);
74 } else
75 {
76 for (i = 0; i < state_length - x_length; i++)
77 {
78 state[i] = state[i + x_length];
79 state_low[i] = state_low[i + x_length];
80 }
81 for (i = 0; i < x_length; i++)
82 {
83 state[state_length - x_length + i] = filtered[i];
84 state[state_length - x_length + i] = filtered_low[i];
85 }
86 }
87
88 return x_length;
89 }
90