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 "libavutil/common.h"
26 #include "avcodec.h"
27 #include "acelp_filters.h"
28 
29 const int16_t ff_acelp_interp_filter[61] = { /* (0.15) */
30  29443, 28346, 25207, 20449, 14701, 8693,
31  3143, -1352, -4402, -5865, -5850, -4673,
32  -2783, -672, 1211, 2536, 3130, 2991,
33  2259, 1170, 0, -1001, -1652, -1868,
34  -1666, -1147, -464, 218, 756, 1060,
35  1099, 904, 550, 135, -245, -514,
36  -634, -602, -451, -231, 0, 191,
37  308, 340, 296, 198, 78, -36,
38  -120, -163, -165, -132, -79, -19,
39  34, 73, 91, 89, 70, 38,
40  0,
41 };
42 
43 void ff_acelp_interpolate(int16_t* out, const int16_t* in,
44  const int16_t* filter_coeffs, int precision,
45  int frac_pos, int filter_length, int length)
46 {
47  int n, i;
48 
49  assert(frac_pos >= 0 && frac_pos < precision);
50 
51  for (n = 0; n < length; n++) {
52  int idx = 0;
53  int v = 0x4000;
54 
55  for (i = 0; i < filter_length;) {
56 
57  /* The reference G.729 and AMR fixed point code performs clipping after
58  each of the two following accumulations.
59  Since clipping affects only the synthetic OVERFLOW test without
60  causing an int type overflow, it was moved outside the loop. */
61 
62  /* R(x):=ac_v[-k+x]
63  v += R(n-i)*ff_acelp_interp_filter(t+6i)
64  v += R(n+i+1)*ff_acelp_interp_filter(6-t+6i) */
65 
66  v += in[n + i] * filter_coeffs[idx + frac_pos];
67  idx += precision;
68  i++;
69  v += in[n - i] * filter_coeffs[idx - frac_pos];
70  }
71  if (av_clip_int16(v >> 15) != (v >> 15))
72  av_log(NULL, AV_LOG_WARNING, "overflow that would need cliping in ff_acelp_interpolate()\n");
73  out[n] = v >> 15;
74  }
75 }
76 
77 void ff_acelp_interpolatef(float *out, const float *in,
78  const float *filter_coeffs, int precision,
79  int frac_pos, int filter_length, int length)
80 {
81  int n, i;
82 
83  for (n = 0; n < length; n++) {
84  int idx = 0;
85  float v = 0;
86 
87  for (i = 0; i < filter_length;) {
88  v += in[n + i] * filter_coeffs[idx + frac_pos];
89  idx += precision;
90  i++;
91  v += in[n - i] * filter_coeffs[idx - frac_pos];
92  }
93  out[n] = v;
94  }
95 }
96 
97 
98 void ff_acelp_high_pass_filter(int16_t* out, int hpf_f[2],
99  const int16_t* in, int length)
100 {
101  int i;
102  int tmp;
103 
104  for (i = 0; i < length; i++) {
105  tmp = (hpf_f[0]* 15836LL) >> 13;
106  tmp += (hpf_f[1]* -7667LL) >> 13;
107  tmp += 7699 * (in[i] - 2*in[i-1] + in[i-2]);
108 
109  /* With "+0x800" rounding, clipping is needed
110  for ALGTHM and SPEECH tests. */
111  out[i] = av_clip_int16((tmp + 0x800) >> 12);
112 
113  hpf_f[1] = hpf_f[0];
114  hpf_f[0] = tmp;
115  }
116 }
117 
118 void ff_acelp_apply_order_2_transfer_function(float *out, const float *in,
119  const float zero_coeffs[2],
120  const float pole_coeffs[2],
121  float gain, float mem[2], int n)
122 {
123  int i;
124  float tmp;
125 
126  for (i = 0; i < n; i++) {
127  tmp = gain * in[i] - pole_coeffs[0] * mem[0] - pole_coeffs[1] * mem[1];
128  out[i] = tmp + zero_coeffs[0] * mem[0] + zero_coeffs[1] * mem[1];
129 
130  mem[1] = mem[0];
131  mem[0] = tmp;
132  }
133 }
134 
135 void ff_tilt_compensation(float *mem, float tilt, float *samples, int size)
136 {
137  float new_tilt_mem = samples[size - 1];
138  int i;
139 
140  for (i = size - 1; i > 0; i--)
141  samples[i] -= tilt * samples[i - 1];
142 
143  samples[0] -= tilt * *mem;
144  *mem = new_tilt_mem;
145 }
void ff_acelp_high_pass_filter(int16_t *out, int hpf_f[2], const int16_t *in, int length)
high-pass filtering and upscaling (4.2.5 of G.729).
Definition: acelp_filters.c:98
static int16_t * samples
int size
void ff_acelp_apply_order_2_transfer_function(float *out, const float *in, const float zero_coeffs[2], const float pole_coeffs[2], float gain, float mem[2], int n)
Apply an order 2 rational transfer function in-place.
const int16_t ff_acelp_interp_filter[61]
low-pass Finite Impulse Response filter coefficients.
Definition: acelp_filters.c:29
void av_log(void *avcl, int level, const char *fmt,...)
Definition: log.c:146
void ff_tilt_compensation(float *mem, float tilt, float *samples, int size)
Apply tilt compensation filter, 1 - tilt * z-1.
NULL
Definition: eval.c:52
external API header
void ff_acelp_interpolate(int16_t *out, const int16_t *in, const int16_t *filter_coeffs, int precision, int frac_pos, int filter_length, int length)
Generic FIR interpolation routine.
Definition: acelp_filters.c:43
common internal and external API header
void ff_acelp_interpolatef(float *out, const float *in, const float *filter_coeffs, int precision, int frac_pos, int filter_length, int length)
Floating point version of ff_acelp_interpolate()
Definition: acelp_filters.c:77