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 "common_audio/signal_processing/include/signal_processing_library.h"
19
20 #include "rtc_base/checks.h"
21
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)22 size_t WebRtcSpl_FilterAR(const int16_t* a,
23 size_t a_length,
24 const int16_t* x,
25 size_t x_length,
26 int16_t* state,
27 size_t state_length,
28 int16_t* state_low,
29 size_t state_low_length,
30 int16_t* filtered,
31 int16_t* filtered_low,
32 size_t filtered_low_length)
33 {
34 int64_t o;
35 int32_t oLOW;
36 size_t i, j, stop;
37 const int16_t* x_ptr = &x[0];
38 int16_t* filteredFINAL_ptr = filtered;
39 int16_t* filteredFINAL_LOW_ptr = filtered_low;
40
41 for (i = 0; i < x_length; i++)
42 {
43 // Calculate filtered[i] and filtered_low[i]
44 const int16_t* a_ptr = &a[1];
45 // The index can become negative, but the arrays will never be indexed
46 // with it when negative. Nevertheless, the index cannot be a size_t
47 // because of this.
48 int filtered_ix = (int)i - 1;
49 int16_t* state_ptr = &state[state_length - 1];
50 int16_t* state_low_ptr = &state_low[state_length - 1];
51
52 o = (int32_t)(*x_ptr++) * (1 << 12);
53 oLOW = (int32_t)0;
54
55 stop = (i < a_length) ? i + 1 : a_length;
56 for (j = 1; j < stop; j++)
57 {
58 RTC_DCHECK_GE(filtered_ix, 0);
59 o -= *a_ptr * filtered[filtered_ix];
60 oLOW -= *a_ptr++ * filtered_low[filtered_ix];
61 --filtered_ix;
62 }
63 for (j = i + 1; j < a_length; j++)
64 {
65 o -= *a_ptr * *state_ptr--;
66 oLOW -= *a_ptr++ * *state_low_ptr--;
67 }
68
69 o += (oLOW >> 12);
70 *filteredFINAL_ptr = (int16_t)((o + (int32_t)2048) >> 12);
71 *filteredFINAL_LOW_ptr++ =
72 (int16_t)(o - ((int32_t)(*filteredFINAL_ptr++) * (1 << 12)));
73 }
74
75 // Save the filter state
76 if (x_length >= state_length)
77 {
78 WebRtcSpl_CopyFromEndW16(filtered, x_length, a_length - 1, state);
79 WebRtcSpl_CopyFromEndW16(filtered_low, x_length, a_length - 1, state_low);
80 } else
81 {
82 for (i = 0; i < state_length - x_length; i++)
83 {
84 state[i] = state[i + x_length];
85 state_low[i] = state_low[i + x_length];
86 }
87 for (i = 0; i < x_length; i++)
88 {
89 state[state_length - x_length + i] = filtered[i];
90 state_low[state_length - x_length + i] = filtered_low[i];
91 }
92 }
93
94 return x_length;
95 }
96