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 "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
19
WebRtcSpl_FilterAR(const int16_t * a,size_t a_length,const int16_t * x,size_t x_length,int16_t * state,size_t state_length,int16_t * state_low,size_t state_low_length,int16_t * filtered,int16_t * filtered_low,size_t filtered_low_length)20 size_t WebRtcSpl_FilterAR(const int16_t* a,
21 size_t a_length,
22 const int16_t* x,
23 size_t x_length,
24 int16_t* state,
25 size_t state_length,
26 int16_t* state_low,
27 size_t state_low_length,
28 int16_t* filtered,
29 int16_t* filtered_low,
30 size_t filtered_low_length)
31 {
32 int32_t o;
33 int32_t oLOW;
34 size_t i, j, stop;
35 const int16_t* x_ptr = &x[0];
36 int16_t* filteredFINAL_ptr = filtered;
37 int16_t* filteredFINAL_LOW_ptr = filtered_low;
38
39 for (i = 0; i < x_length; i++)
40 {
41 // Calculate filtered[i] and filtered_low[i]
42 const int16_t* a_ptr = &a[1];
43 int16_t* filtered_ptr = &filtered[i - 1];
44 int16_t* filtered_low_ptr = &filtered_low[i - 1];
45 int16_t* state_ptr = &state[state_length - 1];
46 int16_t* state_low_ptr = &state_low[state_length - 1];
47
48 o = (int32_t)(*x_ptr++) << 12;
49 oLOW = (int32_t)0;
50
51 stop = (i < a_length) ? i + 1 : a_length;
52 for (j = 1; j < stop; j++)
53 {
54 o -= *a_ptr * *filtered_ptr--;
55 oLOW -= *a_ptr++ * *filtered_low_ptr--;
56 }
57 for (j = i + 1; j < a_length; j++)
58 {
59 o -= *a_ptr * *state_ptr--;
60 oLOW -= *a_ptr++ * *state_low_ptr--;
61 }
62
63 o += (oLOW >> 12);
64 *filteredFINAL_ptr = (int16_t)((o + (int32_t)2048) >> 12);
65 *filteredFINAL_LOW_ptr++ = (int16_t)(o - ((int32_t)(*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