forked from captainjack64/hacktv
-
Notifications
You must be signed in to change notification settings - Fork 0
/
videocrypts.c
313 lines (259 loc) · 7.22 KB
/
videocrypts.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
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
/* hacktv - Analogue video transmitter for the HackRF */
/*=======================================================================*/
/* Copyright 2019 Philip Heron <[email protected]> */
/* */
/* This program is free software: you can redistribute it and/or modify */
/* it under the terms of the GNU General Public License as published by */
/* the Free Software Foundation, either version 3 of the License, or */
/* (at your option) any later version. */
/* */
/* This program 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://www.gnu.org/licenses/>. */
/* -=== Videocrypt S encoder ===-
*
* This is untested on real hardware and should be considered just a
* simulation. The VBI data *may* be valid but the shuffling sequence
* is definitly not. There may also be colour distortion due to hacktv
* not operating at the specified sample rate of FPAL * 4.
*/
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "video.h"
/* The first line of each block */
static const int _block_start[12] = {
28, 75, 122, 169, 216, 263,
340, 387, 434, 481, 528, 575,
};
/* Header synchronisation sequence */
static const uint8_t _sequence[8] = {
0x81,0x92,0xA3,0xB4,0xC5,0xD6,0xE7,0xF0,
};
/* Hamming codes */
static const uint8_t _hamming[16] = {
0x15,0x02,0x49,0x5E,0x64,0x73,0x38,0x2F,
0xD0,0xC7,0x8C,0x9B,0xA1,0xB6,0xFD,0xEA,
};
/* Reverse bits in an 8-bit value */
static uint8_t _reverse(uint8_t b)
{
b = (b & 0xF0) >> 4 | (b & 0x0F) << 4;
b = (b & 0xCC) >> 2 | (b & 0x33) << 2;
b = (b & 0xAA) >> 1 | (b & 0x55) << 1;
return(b);
}
/* Reverse nibbles in a byte */
static inline uint8_t _rnibble(uint8_t a)
{
return((a >> 4) | (a << 4));
}
/* Apply VBI frame interleaving */
static void _interleave(uint8_t *frame)
{
int b, i, j;
int offset[6] = { 0, 6, 12, 20, 26, 32 };
uint8_t r[8];
uint8_t m;
for(b = 0; b < 6; b++)
{
uint8_t *s = frame + offset[b];
s[0] = _reverse(s[0]);
s[7] = _reverse(s[7]);
for(i = 0, m = 0x80; i < 8; i++, m >>= 1)
{
r[i] = 0x00;
for(j = 0; j < 8; j++)
{
r[i] |= ((m & s[j]) ? 1 : 0) << j;
}
}
memcpy(s, r, 8);
}
}
/* Encode VBI data */
static void _encode_vbi(uint8_t vbi[40], const uint8_t data[16], uint8_t a, uint8_t b)
{
int x;
/* Set the information (a, b) and initial check bytes for each field */
vbi[ 9] = vbi[ 0] = a;
vbi[19] = vbi[10] = b;
/* Copy the eight security bytes for each field,
* while updating the check byte */
for(x = 0; x < 8; x++)
{
vbi[ 9] += vbi[ 1 + x] = data[0 + x];
vbi[19] += vbi[11 + x] = data[8 + x];
}
/* Hamming code the VBI data */
for(x = 19; x >= 0; x--)
{
vbi[x * 2 + 1] = _hamming[vbi[x] & 0x0F];
vbi[x * 2 + 0] = _hamming[vbi[x] >> 4];
}
/* Interleave the VBI data */
_interleave(vbi);
}
static void _block_shuffle(vcs_t *s)
{
int i, t, r;
for(i = 0; i < 47; i++)
{
s->block[i] = i;
}
for(i = 0; i < 47; i++)
{
r = rand() % 47;
t = s->block[i];
s->block[i] = s->block[r];
s->block[r] = t;
}
}
int vcs_init(vcs_t *s, vid_t *vid, const char *mode)
{
double f;
int x;
memset(s, 0, sizeof(vcs_t));
s->vid = vid;
s->mode = 0x00;
s->counter = 0;
if(strcmp(mode, "free") == 0)
{
/* Nothing yet */
}
else
{
fprintf(stderr, "Unrecognised Videocrypt S mode '%s'.\n", mode);
return(VID_ERROR);
}
/* Sample rate ratio */
f = (double) s->vid->width / VCS_WIDTH;
/* Quick and dirty sample rate conversion array */
for(x = 0; x < VCS_WIDTH; x++)
{
s->video_scale[x] = round(x * f);
}
/* Allocate memory for the delay */
s->vid->olines += VCS_DELAY_LINES;
return(VID_OK);
}
void vcs_free(vcs_t *s)
{
/* Nothing */
}
void vcs_render_line(vcs_t *s)
{
int x, j;
uint8_t *bline = NULL;
int line;
/* Calculate which line is about to be transmitted due to the delay */
line = s->vid->line - VCS_DELAY_LINES;
if(line < 1) line += s->vid->conf.lines;
/* Swap the active line with the oldest line in the delay buffer,
* with active video offset in j if necessary. */
j = 0;
if((line >= 28 && line <= 309) ||
(line >= 340 && line <= 621))
{
int block;
int bline;
/* Calculate the line number,
* 0 - 281 top field,
* 282 - 563 bottom field
*/
x = line - (line < 340 ? 28 : 340 - 282);
/* Calculate block number and block line */
block = x / 47;
bline = x % 47;
if(bline == 0)
{
_block_shuffle(s);
}
/* Calculate target block/line */
block = (block + 1) % 12;
bline = s->block[bline];
/* Calculate position in delay buffer */
j = (_block_start[block] + bline) - line;
if(j < 0) j += s->vid->conf.lines - 1;
}
vid_adj_delay(s->vid, VCS_DELAY_LINES);
if(j > 0)
{
int16_t *dline = s->vid->oline[s->vid->odelay + j];
for(x = s->vid->active_left * 2; x < s->vid->width * 2; x += 2)
{
s->vid->output[x] = dline[x];
}
}
/* On the first line of each frame, generate the VBI data */
if(line == 1)
{
uint8_t crc;
if((s->counter & 1) == 0)
{
/* The active message is updated every 2nd frame */
for(crc = x = 0; x < 31; x++)
{
crc += s->message[x] = 0x00;
}
s->message[x] = ~crc + 1;
}
if((s->counter & 1) == 0)
{
/* The first half of the message */
_encode_vbi(
s->vbi, s->message,
_sequence[(s->counter >> 1) & 7],
s->counter & 0xFF
);
}
else
{
/* The second half of the message */
_encode_vbi(
s->vbi, s->message + 16,
_rnibble(_sequence[(s->counter >> 1) & 7]),
(s->counter & 0x08 ? 0x00 : s->mode)
);
}
/* After 64 frames, advance to the next block and codeword */
s->counter++;
}
/* Set a pointer to the VBI data to render on this line, or NULL if none */
if(line >= VCS_VBI_FIELD_1_START &&
line < VCS_VBI_FIELD_1_START + VCS_VBI_LINES_PER_FIELD)
{
/* Top field VBI */
bline = &s->vbi[(line - VCS_VBI_FIELD_1_START) * VCS_VBI_BYTES_PER_LINE];
}
else if(line >= VCS_VBI_FIELD_2_START &&
line < VCS_VBI_FIELD_2_START + VCS_VBI_LINES_PER_FIELD)
{
/* Bottom field VBI */
bline = &s->vbi[(line - VCS_VBI_FIELD_2_START + VCS_VBI_LINES_PER_FIELD) * VCS_VBI_BYTES_PER_LINE];
}
if(bline)
{
int b, c;
/* Videocrypt S's VBI data sits in the active video area. Clear it first */
for(x = s->vid->active_left; x < s->vid->active_left + s->vid->active_width; x++)
{
s->vid->output[x * 2] = s->vid->black_level;
}
x = s->video_scale[VCS_VBI_LEFT];
for(b = 0; b < VCS_VBI_BITS_PER_LINE; b++)
{
c = (bline[b / 8] >> (b % 8)) & 1;
c = c ? s->vid->white_level : s->vid->black_level;
for(; x < s->video_scale[VCS_VBI_LEFT + VCS_VBI_SAMPLES_PER_BIT * (b + 1)]; x++)
{
s->vid->output[x * 2] = c;
}
}
}
}