| blob | 44eac9b3be6c75b5a2f51c5d5e8de8f857cae622 |
1 .. SPDX-License-Identifier: GPL-2.0
3 ==============================
4 Using the Digital TV Framework
5 ==============================
7 Introduction
8 ~~~~~~~~~~~~
10 One significant difference between Digital TV and Analogue TV that the
11 unwary (like myself) should consider is that, although the component
12 structure of DVB-T cards are substantially similar to Analogue TV cards,
13 they function in substantially different ways.
15 The purpose of an Analogue TV is to receive and display an Analogue
16 Television signal. An Analogue TV signal (otherwise known as composite
17 video) is an analogue encoding of a sequence of image frames (25 frames
18 per second in Europe) rasterised using an interlacing technique.
19 Interlacing takes two fields to represent one frame. Therefore, an
20 Analogue TV card for a PC has the following purpose:
22 * Tune the receiver to receive a broadcast signal
23 * demodulate the broadcast signal
24 * demultiplex the analogue video signal and analogue audio
25 signal.
27 .. note::
29 some countries employ a digital audio signal
30 embedded within the modulated composite analogue signal -
31 using NICAM signaling.)
33 * digitize the analogue video signal and make the resulting datastream
34 available to the data bus.
36 The digital datastream from an Analogue TV card is generated by
37 circuitry on the card and is often presented uncompressed. For a PAL TV
38 signal encoded at a resolution of 768x576 24-bit color pixels over 25
39 frames per second - a fair amount of data is generated and must be
40 processed by the PC before it can be displayed on the video monitor
41 screen. Some Analogue TV cards for PCs have onboard MPEG2 encoders which
42 permit the raw digital data stream to be presented to the PC in an
43 encoded and compressed form - similar to the form that is used in
44 Digital TV.
46 The purpose of a simple budget digital TV card (DVB-T,C or S) is to
47 simply:
49 * Tune the received to receive a broadcast signal. * Extract the encoded
50 digital datastream from the broadcast signal.
51 * Make the encoded digital datastream (MPEG2) available to the data bus.
53 The significant difference between the two is that the tuner on the
54 analogue TV card spits out an Analogue signal, whereas the tuner on the
55 digital TV card spits out a compressed encoded digital datastream. As
56 the signal is already digitised, it is trivial to pass this datastream
57 to the PC databus with minimal additional processing and then extract
58 the digital video and audio datastreams passing them to the appropriate
59 software or hardware for decoding and viewing.
61 Getting the card going
62 ~~~~~~~~~~~~~~~~~~~~~~
64 The Device Driver API for DVB under Linux will the following
65 device nodes via the devfs filesystem:
67 * /dev/dvb/adapter0/demux0
68 * /dev/dvb/adapter0/dvr0
69 * /dev/dvb/adapter0/frontend0
71 The ``/dev/dvb/adapter0/dvr0`` device node is used to read the MPEG2
72 Data Stream and the ``/dev/dvb/adapter0/frontend0`` device node is used
73 to tune the frontend tuner module. The ``/dev/dvb/adapter0/demux0`` is
74 used to control what programs will be received.
76 Depending on the card's feature set, the Device Driver API could also
77 expose other device nodes:
79 * /dev/dvb/adapter0/ca0
80 * /dev/dvb/adapter0/audio0
81 * /dev/dvb/adapter0/net0
82 * /dev/dvb/adapter0/osd0
83 * /dev/dvb/adapter0/video0
85 The ``/dev/dvb/adapter0/ca0`` is used to decode encrypted channels. The
86 other device nodes are found only on devices that use the av7110
87 driver, with is now obsoleted, together with the extra API whose such
88 devices use.
90 Receiving a digital TV channel
91 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
93 This section attempts to explain how it works and how this affects the
94 configuration of a Digital TV card.
96 On this example, we're considering tuning into DVB-T channels in
97 Australia, at the Melbourne region.
99 The frequencies broadcast by Mount Dandenong transmitters are,
100 currently:
102 Table 1. Transponder Frequencies Mount Dandenong, Vic, Aus.
104 =========== ===========
105 Broadcaster Frequency
106 =========== ===========
107 Seven 177.500 Mhz
108 SBS 184.500 Mhz
109 Nine 191.625 Mhz
110 Ten 219.500 Mhz
111 ABC 226.500 Mhz
112 Channel 31 557.625 Mhz
113 =========== ===========
115 The digital TV Scan utilities (like dvbv5-scan) have use a set of
116 compiled-in defaults for various countries and regions. Those are
117 currently provided as a separate package, called dtv-scan-tables. It's
118 git tree is located at LinuxTV.org:
120 https://git.linuxtv.org/dtv-scan-tables.git/
122 If none of the tables there suit, you can specify a data file on the
123 command line which contains the transponder frequencies. Here is a
124 sample file for the above channel transponders, in the old "channel"
125 format::
127 # Data file for DVB scan program
128 #
129 # C Frequency SymbolRate FEC QAM
130 # S Frequency Polarisation SymbolRate FEC
131 # T Frequency Bandwidth FEC FEC2 QAM Mode Guard Hier
133 T 177500000 7MHz AUTO AUTO QAM64 8k 1/16 NONE
134 T 184500000 7MHz AUTO AUTO QAM64 8k 1/8 NONE
135 T 191625000 7MHz AUTO AUTO QAM64 8k 1/16 NONE
136 T 219500000 7MHz AUTO AUTO QAM64 8k 1/16 NONE
137 T 226500000 7MHz AUTO AUTO QAM64 8k 1/16 NONE
138 T 557625000 7MHz AUTO AUTO QPSK 8k 1/16 NONE
140 Nowadays, we prefer to use a newer format, with is more verbose and easier
141 to understand. With the new format, the "Seven" channel transponder's
142 data is represented by::
144 [Seven]
145 DELIVERY_SYSTEM = DVBT
146 FREQUENCY = 177500000
147 BANDWIDTH_HZ = 7000000
148 CODE_RATE_HP = AUTO
149 CODE_RATE_LP = AUTO
150 MODULATION = QAM/64
151 TRANSMISSION_MODE = 8K
152 GUARD_INTERVAL = 1/16
153 HIERARCHY = NONE
154 INVERSION = AUTO
156 For an updated version of the complete table, please see:
158 https://git.linuxtv.org/dtv-scan-tables.git/tree/dvb-t/au-Melbourne
160 When the Digital TV scanning utility runs, it will output a file
161 containing the information for all the audio and video programs that
162 exists into each channel's transponders which the card's frontend can
163 lock onto. (i.e. any whose signal is strong enough at your antenna).
165 Here's the output of the dvbv5 tools from a channel scan took from
166 Melburne::
168 [ABC HDTV]
169 SERVICE_ID = 560
170 VIDEO_PID = 2307
171 AUDIO_PID = 0
172 DELIVERY_SYSTEM = DVBT
173 FREQUENCY = 226500000
174 INVERSION = OFF
175 BANDWIDTH_HZ = 7000000
176 CODE_RATE_HP = 3/4
177 CODE_RATE_LP = 3/4
178 MODULATION = QAM/64
179 TRANSMISSION_MODE = 8K
180 GUARD_INTERVAL = 1/16
181 HIERARCHY = NONE
183 [ABC TV Melbourne]
184 SERVICE_ID = 561
185 VIDEO_PID = 512
186 AUDIO_PID = 650
187 DELIVERY_SYSTEM = DVBT
188 FREQUENCY = 226500000
189 INVERSION = OFF
190 BANDWIDTH_HZ = 7000000
191 CODE_RATE_HP = 3/4
192 CODE_RATE_LP = 3/4
193 MODULATION = QAM/64
194 TRANSMISSION_MODE = 8K
195 GUARD_INTERVAL = 1/16
196 HIERARCHY = NONE
198 [ABC TV 2]
199 SERVICE_ID = 562
200 VIDEO_PID = 512
201 AUDIO_PID = 650
202 DELIVERY_SYSTEM = DVBT
203 FREQUENCY = 226500000
204 INVERSION = OFF
205 BANDWIDTH_HZ = 7000000
206 CODE_RATE_HP = 3/4
207 CODE_RATE_LP = 3/4
208 MODULATION = QAM/64
209 TRANSMISSION_MODE = 8K
210 GUARD_INTERVAL = 1/16
211 HIERARCHY = NONE
213 [ABC TV 3]
214 SERVICE_ID = 563
215 VIDEO_PID = 512
216 AUDIO_PID = 650
217 DELIVERY_SYSTEM = DVBT
218 FREQUENCY = 226500000
219 INVERSION = OFF
220 BANDWIDTH_HZ = 7000000
221 CODE_RATE_HP = 3/4
222 CODE_RATE_LP = 3/4
223 MODULATION = QAM/64
224 TRANSMISSION_MODE = 8K
225 GUARD_INTERVAL = 1/16
226 HIERARCHY = NONE
228 [ABC TV 4]
229 SERVICE_ID = 564
230 VIDEO_PID = 512
231 AUDIO_PID = 650
232 DELIVERY_SYSTEM = DVBT
233 FREQUENCY = 226500000
234 INVERSION = OFF
235 BANDWIDTH_HZ = 7000000
236 CODE_RATE_HP = 3/4
237 CODE_RATE_LP = 3/4
238 MODULATION = QAM/64
239 TRANSMISSION_MODE = 8K
240 GUARD_INTERVAL = 1/16
241 HIERARCHY = NONE
243 [ABC DiG Radio]
244 SERVICE_ID = 566
245 VIDEO_PID = 0
246 AUDIO_PID = 2311
247 DELIVERY_SYSTEM = DVBT
248 FREQUENCY = 226500000
249 INVERSION = OFF
250 BANDWIDTH_HZ = 7000000
251 CODE_RATE_HP = 3/4
252 CODE_RATE_LP = 3/4
253 MODULATION = QAM/64
254 TRANSMISSION_MODE = 8K
255 GUARD_INTERVAL = 1/16
256 HIERARCHY = NONE
258 [TEN Digital]
259 SERVICE_ID = 1585
260 VIDEO_PID = 512
261 AUDIO_PID = 650
262 DELIVERY_SYSTEM = DVBT
263 FREQUENCY = 219500000
264 INVERSION = OFF
265 BANDWIDTH_HZ = 7000000
266 CODE_RATE_HP = 3/4
267 CODE_RATE_LP = 1/2
268 MODULATION = QAM/64
269 TRANSMISSION_MODE = 8K
270 GUARD_INTERVAL = 1/16
271 HIERARCHY = NONE
273 [TEN Digital 1]
274 SERVICE_ID = 1586
275 VIDEO_PID = 512
276 AUDIO_PID = 650
277 DELIVERY_SYSTEM = DVBT
278 FREQUENCY = 219500000
279 INVERSION = OFF
280 BANDWIDTH_HZ = 7000000
281 CODE_RATE_HP = 3/4
282 CODE_RATE_LP = 1/2
283 MODULATION = QAM/64
284 TRANSMISSION_MODE = 8K
285 GUARD_INTERVAL = 1/16
286 HIERARCHY = NONE
288 [TEN Digital 2]
289 SERVICE_ID = 1587
290 VIDEO_PID = 512
291 AUDIO_PID = 650
292 DELIVERY_SYSTEM = DVBT
293 FREQUENCY = 219500000
294 INVERSION = OFF
295 BANDWIDTH_HZ = 7000000
296 CODE_RATE_HP = 3/4
297 CODE_RATE_LP = 1/2
298 MODULATION = QAM/64
299 TRANSMISSION_MODE = 8K
300 GUARD_INTERVAL = 1/16
301 HIERARCHY = NONE
303 [TEN Digital 3]
304 SERVICE_ID = 1588
305 VIDEO_PID = 512
306 AUDIO_PID = 650
307 DELIVERY_SYSTEM = DVBT
308 FREQUENCY = 219500000
309 INVERSION = OFF
310 BANDWIDTH_HZ = 7000000
311 CODE_RATE_HP = 3/4
312 CODE_RATE_LP = 1/2
313 MODULATION = QAM/64
314 TRANSMISSION_MODE = 8K
315 GUARD_INTERVAL = 1/16
316 HIERARCHY = NONE
318 [TEN Digital]
319 SERVICE_ID = 1589
320 VIDEO_PID = 512
321 AUDIO_PID = 650
322 DELIVERY_SYSTEM = DVBT
323 FREQUENCY = 219500000
324 INVERSION = OFF
325 BANDWIDTH_HZ = 7000000
326 CODE_RATE_HP = 3/4
327 CODE_RATE_LP = 1/2
328 MODULATION = QAM/64
329 TRANSMISSION_MODE = 8K
330 GUARD_INTERVAL = 1/16
331 HIERARCHY = NONE
333 [TEN Digital 4]
334 SERVICE_ID = 1590
335 VIDEO_PID = 512
336 AUDIO_PID = 650
337 DELIVERY_SYSTEM = DVBT
338 FREQUENCY = 219500000
339 INVERSION = OFF
340 BANDWIDTH_HZ = 7000000
341 CODE_RATE_HP = 3/4
342 CODE_RATE_LP = 1/2
343 MODULATION = QAM/64
344 TRANSMISSION_MODE = 8K
345 GUARD_INTERVAL = 1/16
346 HIERARCHY = NONE
348 [TEN Digital]
349 SERVICE_ID = 1591
350 VIDEO_PID = 512
351 AUDIO_PID = 650
352 DELIVERY_SYSTEM = DVBT
353 FREQUENCY = 219500000
354 INVERSION = OFF
355 BANDWIDTH_HZ = 7000000
356 CODE_RATE_HP = 3/4
357 CODE_RATE_LP = 1/2
358 MODULATION = QAM/64
359 TRANSMISSION_MODE = 8K
360 GUARD_INTERVAL = 1/16
361 HIERARCHY = NONE
363 [TEN HD]
364 SERVICE_ID = 1592
365 VIDEO_PID = 514
366 AUDIO_PID = 0
367 DELIVERY_SYSTEM = DVBT
368 FREQUENCY = 219500000
369 INVERSION = OFF
370 BANDWIDTH_HZ = 7000000
371 CODE_RATE_HP = 3/4
372 CODE_RATE_LP = 1/2
373 MODULATION = QAM/64
374 TRANSMISSION_MODE = 8K
375 GUARD_INTERVAL = 1/16
376 HIERARCHY = NONE
378 [TEN Digital]
379 SERVICE_ID = 1593
380 VIDEO_PID = 512
381 AUDIO_PID = 650
382 DELIVERY_SYSTEM = DVBT
383 FREQUENCY = 219500000
384 INVERSION = OFF
385 BANDWIDTH_HZ = 7000000
386 CODE_RATE_HP = 3/4
387 CODE_RATE_LP = 1/2
388 MODULATION = QAM/64
389 TRANSMISSION_MODE = 8K
390 GUARD_INTERVAL = 1/16
391 HIERARCHY = NONE
393 [Nine Digital]
394 SERVICE_ID = 1072
395 VIDEO_PID = 513
396 AUDIO_PID = 660
397 DELIVERY_SYSTEM = DVBT
398 FREQUENCY = 191625000
399 INVERSION = OFF
400 BANDWIDTH_HZ = 7000000
401 CODE_RATE_HP = 3/4
402 CODE_RATE_LP = 1/2
403 MODULATION = QAM/64
404 TRANSMISSION_MODE = 8K
405 GUARD_INTERVAL = 1/16
406 HIERARCHY = NONE
408 [Nine Digital HD]
409 SERVICE_ID = 1073
410 VIDEO_PID = 512
411 AUDIO_PID = 0
412 DELIVERY_SYSTEM = DVBT
413 FREQUENCY = 191625000
414 INVERSION = OFF
415 BANDWIDTH_HZ = 7000000
416 CODE_RATE_HP = 3/4
417 CODE_RATE_LP = 1/2
418 MODULATION = QAM/64
419 TRANSMISSION_MODE = 8K
420 GUARD_INTERVAL = 1/16
421 HIERARCHY = NONE
423 [Nine Guide]
424 SERVICE_ID = 1074
425 VIDEO_PID = 514
426 AUDIO_PID = 670
427 DELIVERY_SYSTEM = DVBT
428 FREQUENCY = 191625000
429 INVERSION = OFF
430 BANDWIDTH_HZ = 7000000
431 CODE_RATE_HP = 3/4
432 CODE_RATE_LP = 1/2
433 MODULATION = QAM/64
434 TRANSMISSION_MODE = 8K
435 GUARD_INTERVAL = 1/16
436 HIERARCHY = NONE
438 [7 Digital]
439 SERVICE_ID = 1328
440 VIDEO_PID = 769
441 AUDIO_PID = 770
442 DELIVERY_SYSTEM = DVBT
443 FREQUENCY = 177500000
444 INVERSION = OFF
445 BANDWIDTH_HZ = 7000000
446 CODE_RATE_HP = 2/3
447 CODE_RATE_LP = 2/3
448 MODULATION = QAM/64
449 TRANSMISSION_MODE = 8K
450 GUARD_INTERVAL = 1/8
451 HIERARCHY = NONE
453 [7 Digital 1]
454 SERVICE_ID = 1329
455 VIDEO_PID = 769
456 AUDIO_PID = 770
457 DELIVERY_SYSTEM = DVBT
458 FREQUENCY = 177500000
459 INVERSION = OFF
460 BANDWIDTH_HZ = 7000000
461 CODE_RATE_HP = 2/3
462 CODE_RATE_LP = 2/3
463 MODULATION = QAM/64
464 TRANSMISSION_MODE = 8K
465 GUARD_INTERVAL = 1/8
466 HIERARCHY = NONE
468 [7 Digital 2]
469 SERVICE_ID = 1330
470 VIDEO_PID = 769
471 AUDIO_PID = 770
472 DELIVERY_SYSTEM = DVBT
473 FREQUENCY = 177500000
474 INVERSION = OFF
475 BANDWIDTH_HZ = 7000000
476 CODE_RATE_HP = 2/3
477 CODE_RATE_LP = 2/3
478 MODULATION = QAM/64
479 TRANSMISSION_MODE = 8K
480 GUARD_INTERVAL = 1/8
481 HIERARCHY = NONE
483 [7 Digital 3]
484 SERVICE_ID = 1331
485 VIDEO_PID = 769
486 AUDIO_PID = 770
487 DELIVERY_SYSTEM = DVBT
488 FREQUENCY = 177500000
489 INVERSION = OFF
490 BANDWIDTH_HZ = 7000000
491 CODE_RATE_HP = 2/3
492 CODE_RATE_LP = 2/3
493 MODULATION = QAM/64
494 TRANSMISSION_MODE = 8K
495 GUARD_INTERVAL = 1/8
496 HIERARCHY = NONE
498 [7 HD Digital]
499 SERVICE_ID = 1332
500 VIDEO_PID = 833
501 AUDIO_PID = 834
502 DELIVERY_SYSTEM = DVBT
503 FREQUENCY = 177500000
504 INVERSION = OFF
505 BANDWIDTH_HZ = 7000000
506 CODE_RATE_HP = 2/3
507 CODE_RATE_LP = 2/3
508 MODULATION = QAM/64
509 TRANSMISSION_MODE = 8K
510 GUARD_INTERVAL = 1/8
511 HIERARCHY = NONE
513 [7 Program Guide]
514 SERVICE_ID = 1334
515 VIDEO_PID = 865
516 AUDIO_PID = 866
517 DELIVERY_SYSTEM = DVBT
518 FREQUENCY = 177500000
519 INVERSION = OFF
520 BANDWIDTH_HZ = 7000000
521 CODE_RATE_HP = 2/3
522 CODE_RATE_LP = 2/3
523 MODULATION = QAM/64
524 TRANSMISSION_MODE = 8K
525 GUARD_INTERVAL = 1/8
526 HIERARCHY = NONE
528 [SBS HD]
529 SERVICE_ID = 784
530 VIDEO_PID = 102
531 AUDIO_PID = 103
532 DELIVERY_SYSTEM = DVBT
533 FREQUENCY = 536500000
534 INVERSION = OFF
535 BANDWIDTH_HZ = 7000000
536 CODE_RATE_HP = 2/3
537 CODE_RATE_LP = 2/3
538 MODULATION = QAM/64
539 TRANSMISSION_MODE = 8K
540 GUARD_INTERVAL = 1/8
541 HIERARCHY = NONE
543 [SBS DIGITAL 1]
544 SERVICE_ID = 785
545 VIDEO_PID = 161
546 AUDIO_PID = 81
547 DELIVERY_SYSTEM = DVBT
548 FREQUENCY = 536500000
549 INVERSION = OFF
550 BANDWIDTH_HZ = 7000000
551 CODE_RATE_HP = 2/3
552 CODE_RATE_LP = 2/3
553 MODULATION = QAM/64
554 TRANSMISSION_MODE = 8K
555 GUARD_INTERVAL = 1/8
556 HIERARCHY = NONE
558 [SBS DIGITAL 2]
559 SERVICE_ID = 786
560 VIDEO_PID = 162
561 AUDIO_PID = 83
562 DELIVERY_SYSTEM = DVBT
563 FREQUENCY = 536500000
564 INVERSION = OFF
565 BANDWIDTH_HZ = 7000000
566 CODE_RATE_HP = 2/3
567 CODE_RATE_LP = 2/3
568 MODULATION = QAM/64
569 TRANSMISSION_MODE = 8K
570 GUARD_INTERVAL = 1/8
571 HIERARCHY = NONE
573 [SBS EPG]
574 SERVICE_ID = 787
575 VIDEO_PID = 163
576 AUDIO_PID = 85
577 DELIVERY_SYSTEM = DVBT
578 FREQUENCY = 536500000
579 INVERSION = OFF
580 BANDWIDTH_HZ = 7000000
581 CODE_RATE_HP = 2/3
582 CODE_RATE_LP = 2/3
583 MODULATION = QAM/64
584 TRANSMISSION_MODE = 8K
585 GUARD_INTERVAL = 1/8
586 HIERARCHY = NONE
588 [SBS RADIO 1]
589 SERVICE_ID = 798
590 VIDEO_PID = 0
591 AUDIO_PID = 201
592 DELIVERY_SYSTEM = DVBT
593 FREQUENCY = 536500000
594 INVERSION = OFF
595 BANDWIDTH_HZ = 7000000
596 CODE_RATE_HP = 2/3
597 CODE_RATE_LP = 2/3
598 MODULATION = QAM/64
599 TRANSMISSION_MODE = 8K
600 GUARD_INTERVAL = 1/8
601 HIERARCHY = NONE
603 [SBS RADIO 2]
604 SERVICE_ID = 799
605 VIDEO_PID = 0
606 AUDIO_PID = 202
607 DELIVERY_SYSTEM = DVBT
608 FREQUENCY = 536500000
609 INVERSION = OFF
610 BANDWIDTH_HZ = 7000000
611 CODE_RATE_HP = 2/3
612 CODE_RATE_LP = 2/3
613 MODULATION = QAM/64
614 TRANSMISSION_MODE = 8K
615 GUARD_INTERVAL = 1/8
616 HIERARCHY = NONE