acelp_filters.c
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1 /*
2  * various filters for ACELP-based codecs
3  *
4  * Copyright (c) 2008 Vladimir Voroshilov
5  *
6  * This file is part of Libav.
7  *
8  * Libav is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2.1 of the License, or (at your option) any later version.
12  *
13  * Libav is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with Libav; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
23 #include <inttypes.h>
24 
25 #include "avcodec.h"
26 #include "acelp_filters.h"
27 
28 const int16_t ff_acelp_interp_filter[61] = { /* (0.15) */
29  29443, 28346, 25207, 20449, 14701, 8693,
30  3143, -1352, -4402, -5865, -5850, -4673,
31  -2783, -672, 1211, 2536, 3130, 2991,
32  2259, 1170, 0, -1001, -1652, -1868,
33  -1666, -1147, -464, 218, 756, 1060,
34  1099, 904, 550, 135, -245, -514,
35  -634, -602, -451, -231, 0, 191,
36  308, 340, 296, 198, 78, -36,
37  -120, -163, -165, -132, -79, -19,
38  34, 73, 91, 89, 70, 38,
39  0,
40 };
41 
42 void ff_acelp_interpolate(int16_t* out, const int16_t* in,
43  const int16_t* filter_coeffs, int precision,
44  int frac_pos, int filter_length, int length)
45 {
46  int n, i;
47 
48  assert(frac_pos >= 0 && frac_pos < precision);
49 
50  for (n = 0; n < length; n++) {
51  int idx = 0;
52  int v = 0x4000;
53 
54  for (i = 0; i < filter_length;) {
55 
56  /* The reference G.729 and AMR fixed point code performs clipping after
57  each of the two following accumulations.
58  Since clipping affects only the synthetic OVERFLOW test without
59  causing an int type overflow, it was moved outside the loop. */
60 
61  /* R(x):=ac_v[-k+x]
62  v += R(n-i)*ff_acelp_interp_filter(t+6i)
63  v += R(n+i+1)*ff_acelp_interp_filter(6-t+6i) */
64 
65  v += in[n + i] * filter_coeffs[idx + frac_pos];
66  idx += precision;
67  i++;
68  v += in[n - i] * filter_coeffs[idx - frac_pos];
69  }
70  if (av_clip_int16(v >> 15) != (v >> 15))
71  av_log(NULL, AV_LOG_WARNING, "overflow that would need cliping in ff_acelp_interpolate()\n");
72  out[n] = v >> 15;
73  }
74 }
75 
76 void ff_acelp_interpolatef(float *out, const float *in,
77  const float *filter_coeffs, int precision,
78  int frac_pos, int filter_length, int length)
79 {
80  int n, i;
81 
82  for (n = 0; n < length; n++) {
83  int idx = 0;
84  float v = 0;
85 
86  for (i = 0; i < filter_length;) {
87  v += in[n + i] * filter_coeffs[idx + frac_pos];
88  idx += precision;
89  i++;
90  v += in[n - i] * filter_coeffs[idx - frac_pos];
91  }
92  out[n] = v;
93  }
94 }
95 
96 
97 void ff_acelp_high_pass_filter(int16_t* out, int hpf_f[2],
98  const int16_t* in, int length)
99 {
100  int i;
101  int tmp;
102 
103  for (i = 0; i < length; i++) {
104  tmp = (hpf_f[0]* 15836LL) >> 13;
105  tmp += (hpf_f[1]* -7667LL) >> 13;
106  tmp += 7699 * (in[i] - 2*in[i-1] + in[i-2]);
107 
108  /* With "+0x800" rounding, clipping is needed
109  for ALGTHM and SPEECH tests. */
110  out[i] = av_clip_int16((tmp + 0x800) >> 12);
111 
112  hpf_f[1] = hpf_f[0];
113  hpf_f[0] = tmp;
114  }
115 }
116 
117 void ff_acelp_apply_order_2_transfer_function(float *out, const float *in,
118  const float zero_coeffs[2],
119  const float pole_coeffs[2],
120  float gain, float mem[2], int n)
121 {
122  int i;
123  float tmp;
124 
125  for (i = 0; i < n; i++) {
126  tmp = gain * in[i] - pole_coeffs[0] * mem[0] - pole_coeffs[1] * mem[1];
127  out[i] = tmp + zero_coeffs[0] * mem[0] + zero_coeffs[1] * mem[1];
128 
129  mem[1] = mem[0];
130  mem[0] = tmp;
131  }
132 }
133 
134 void ff_tilt_compensation(float *mem, float tilt, float *samples, int size)
135 {
136  float new_tilt_mem = samples[size - 1];
137  int i;
138 
139  for (i = size - 1; i > 0; i--)
140  samples[i] -= tilt * samples[i - 1];
141 
142  samples[0] -= tilt * *mem;
143  *mem = new_tilt_mem;
144 }
145