This repository has been archived by the owner on Aug 1, 2020. It is now read-only.
-
Notifications
You must be signed in to change notification settings - Fork 33
/
convert.c
282 lines (234 loc) · 7.51 KB
/
convert.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
// Part of dump1090, a Mode S message decoder for RTLSDR devices.
//
// convert.c: support for various IQ -> magnitude conversions
//
// Copyright (c) 2015 Oliver Jowett <[email protected]>
//
// This file is free software: you may copy, redistribute and/or modify it
// under the terms of the GNU General Public License as published by the
// Free Software Foundation, either version 2 of the License, or (at your
// option) any later version.
//
// This file is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http:https://www.gnu.org/licenses/>.
#include "dump1090.h"
struct converter_state {
float dc_a;
float dc_b;
float z1_I;
float z1_Q;
};
static void convert_uc8_nodc(void *iq_data,
uint16_t *mag_data,
unsigned nsamples,
struct converter_state *state,
double *out_power)
{
uint16_t *in = iq_data;
unsigned i;
uint64_t power = 0;
uint16_t mag;
MODES_NOTUSED(state);
// unroll this a bit
for (i = 0; i < (nsamples>>3); ++i) {
mag = Modes.maglut[*in++];
*mag_data++ = mag;
power += (uint32_t)mag * (uint32_t)mag;
mag = Modes.maglut[*in++];
*mag_data++ = mag;
power += (uint32_t)mag * (uint32_t)mag;
mag = Modes.maglut[*in++];
*mag_data++ = mag;
power += (uint32_t)mag * (uint32_t)mag;
mag = Modes.maglut[*in++];
*mag_data++ = mag;
power += (uint32_t)mag * (uint32_t)mag;
mag = Modes.maglut[*in++];
*mag_data++ = mag;
power += (uint32_t)mag * (uint32_t)mag;
mag = Modes.maglut[*in++];
*mag_data++ = mag;
power += (uint32_t)mag * (uint32_t)mag;
mag = Modes.maglut[*in++];
*mag_data++ = mag;
power += (uint32_t)mag * (uint32_t)mag;
mag = Modes.maglut[*in++];
*mag_data++ = mag;
power += (uint32_t)mag * (uint32_t)mag;
}
for (i = 0; i < (nsamples&7); ++i) {
mag = Modes.maglut[*in++];
*mag_data++ = mag;
power += (uint32_t)mag * (uint32_t)mag;
}
if (out_power) {
*out_power = power / 65535.0 / 65535.0;
}
}
static void convert_uc8_generic(void *iq_data,
uint16_t *mag_data,
unsigned nsamples,
struct converter_state *state,
double *out_power)
{
uint8_t *in = iq_data;
float power = 0.0;
float z1_I = state->z1_I;
float z1_Q = state->z1_Q;
const float dc_a = state->dc_a;
const float dc_b = state->dc_b;
unsigned i;
uint8_t I, Q;
float fI, fQ, magsq;
for (i = 0; i < nsamples; ++i) {
I = *in++;
Q = *in++;
fI = (I - 127.5) / 127.5;
fQ = (Q - 127.5) / 127.5;
// DC block
z1_I = fI * dc_a + z1_I * dc_b;
z1_Q = fQ * dc_a + z1_Q * dc_b;
fI -= z1_I;
fQ -= z1_Q;
magsq = fI * fI + fQ * fQ;
if (magsq > 1)
magsq = 1;
power += magsq;
*mag_data++ = (uint16_t)(sqrtf(magsq) * 65535.0 + 0.5);
}
state->z1_I = z1_I;
state->z1_Q = z1_Q;
if (out_power)
*out_power = power;
}
static void convert_sc16_generic(void *iq_data,
uint16_t *mag_data,
unsigned nsamples,
struct converter_state *state,
double *out_power)
{
uint16_t *in = iq_data;
float power = 0.0;
float z1_I = state->z1_I;
float z1_Q = state->z1_Q;
const float dc_a = state->dc_a;
const float dc_b = state->dc_b;
unsigned i;
int16_t I, Q;
float fI, fQ, magsq;
for (i = 0; i < nsamples; ++i) {
I = (int16_t)le16toh(*in++);
Q = (int16_t)le16toh(*in++);
fI = I / 32768.0;
fQ = Q / 32768.0;
// DC block
z1_I = fI * dc_a + z1_I * dc_b;
z1_Q = fQ * dc_a + z1_Q * dc_b;
fI -= z1_I;
fQ -= z1_Q;
magsq = fI * fI + fQ * fQ;
if (magsq > 1)
magsq = 1;
power += magsq;
*mag_data++ = (uint16_t)(sqrtf(magsq) * 65535.0 + 0.5);
}
state->z1_I = z1_I;
state->z1_Q = z1_Q;
if (out_power)
*out_power = power;
}
static void convert_sc16q11_generic(void *iq_data,
uint16_t *mag_data,
unsigned nsamples,
struct converter_state *state,
double *out_power)
{
uint16_t *in = iq_data;
float power = 0.0;
float z1_I = state->z1_I;
float z1_Q = state->z1_Q;
const float dc_a = state->dc_a;
const float dc_b = state->dc_b;
unsigned i;
int16_t I, Q;
float fI, fQ, magsq;
for (i = 0; i < nsamples; ++i) {
I = (int16_t)le16toh(*in++);
Q = (int16_t)le16toh(*in++);
fI = I / 2048.0;
fQ = Q / 2048.0;
// DC block
z1_I = fI * dc_a + z1_I * dc_b;
z1_Q = fQ * dc_a + z1_Q * dc_b;
fI -= z1_I;
fQ -= z1_Q;
magsq = fI * fI + fQ * fQ;
if (magsq > 1)
magsq = 1;
power += magsq;
*mag_data++ = (uint16_t)(sqrtf(magsq) * 65535.0 + 0.5);
}
state->z1_I = z1_I;
state->z1_Q = z1_Q;
if (out_power)
*out_power = power;
}
static struct {
input_format_t format;
int can_filter_dc;
iq_convert_fn fn;
const char *description;
} converters_table[] = {
// In order of preference
{ INPUT_UC8, 0, convert_uc8_nodc, "UC8, integer/table path" },
{ INPUT_UC8, 1, convert_uc8_generic, "UC8, float path" },
{ INPUT_SC16, 1, convert_sc16_generic, "SC16, float path" },
{ INPUT_SC16Q11, 1, convert_sc16q11_generic, "SC16Q11, float path" },
{ 0, 0, NULL, NULL }
};
iq_convert_fn init_converter(input_format_t format,
double sample_rate,
int filter_dc,
struct converter_state **out_state)
{
int i;
for (i = 0; converters_table[i].fn; ++i) {
if (converters_table[i].format != format)
continue;
if (filter_dc && !converters_table[i].can_filter_dc)
continue;
break;
}
if (!converters_table[i].fn) {
fprintf(stderr, "no suitable converter for format=%d dc=%d\n",
format, filter_dc);
return NULL;
}
fprintf(stderr, "Using sample converter: %s\n", converters_table[i].description);
*out_state = malloc(sizeof(struct converter_state));
if (! *out_state) {
fprintf(stderr, "can't allocate converter state\n");
return NULL;
}
(*out_state)->z1_I = 0;
(*out_state)->z1_Q = 0;
if (filter_dc) {
// init DC block @ 1Hz
(*out_state)->dc_b = exp(-2.0 * M_PI * 1.0 / sample_rate);
(*out_state)->dc_a = 1.0 - (*out_state)->dc_b;
} else {
// if the converter does filtering, make sure it has no effect
(*out_state)->dc_b = 1.0;
(*out_state)->dc_a = 0.0;
}
return converters_table[i].fn;
}
void cleanup_converter(struct converter_state *state)
{
free(state);
}