ffmpeg / libavcodec / acelp_filters.c @ 2912e87a
History  View  Annotate  Download (4.47 KB)
1 
/*


2 
* various filters for ACELPbased 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 021101301 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(ni)*ff_acelp_interp_filter(t+6i)

63 
v += R(n+i+1)*ff_acelp_interp_filter(6t+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[i1] + in[i2]); 
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 