요약·해설과 원문, 전문 번역을 서로 분리했습니다. API 이름, symbol, source path는 원문 표기를 사용합니다.
1. 요약·해설
원문의 핵심 논리와 kernel programming 관점의 보충 설명입니다. 아래의 전문 번역과는 별도로 작성했습니다.
DVB device node 역할
dvb_intro.rst:61-89`frontend0`, `demux0`, `dvr0`, `ca0` 등 device node가 tuning, program 선택, stream 읽기와 conditional access를 어떻게 나누는지 정리합니다.
주파수 table과 channel scan
dvb_intro.rst:90-616Melbourne DVB-T 예제로 `dtv-scan-tables`, 예전 channel format, 현재 format, `dvbv5` scan 결과의 SERVICE_ID·PID·변조 parameter 관계를 보여 줍니다.
이 문서는 `devfs`와 obsolete된 `av7110`을 언급하는 역사적 설명을 포함합니다. 실제 시스템에서는 사용 중인 kernel과 DVB userspace 도구의 현재 문서를 함께 확인해야 합니다.
2. 영어 원문 전체
번역 기준이 된 Linux v6.18.37 원문입니다. 줄 번호는 이 버전의 파일 좌표입니다.
원문 전체 펼치기
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
3. 한국어 전문 번역
영어 원문의 문단 순서와 의미를 유지한 전체 번역입니다. 코드, 함수명, symbol과 URL은 원문 표기를 유지합니다.
디지털 TV와 아날로그 TV의 차이
1-60Digital TV와 Analogue TV 사이에는 주의하지 않으면 놓치기 쉬운 중요한 차이가 있습니다. DVB-T card와 Analogue TV card의 부품 구성은 상당히 비슷하지만, 실제 동작 방식은 크게 다릅니다.
Analogue TV의 목적은 아날로그 텔레비전 신호를 수신해 표시하는 것입니다. Composite video라고도 부르는 Analogue TV 신호는 image frame의 연속을 analogue 방식으로 부호화한 것입니다. 유럽에서는 초당 25 frame이며 interlacing 기법으로 rasterise합니다. Interlacing은 두 field로 한 frame을 나타냅니다. 따라서 PC용 Analogue TV card는 다음 작업을 수행합니다.
- 수신기를 방송 신호의 주파수에 맞춥니다.
- 방송 신호를 demodulate합니다.
- Analogue video signal과 analogue audio signal을 demultiplex합니다.
일부 국가는 변조된 composite analogue signal 안에 NICAM signaling을 사용하는 digital audio signal을 삽입합니다.
- Analogue video signal을 digitize하고, 그 결과 datastream을 data bus에서 사용할 수 있게 합니다.
Analogue TV card의 digital datastream은 card의 회로가 생성하며, 압축되지 않은 상태로 제공되는 경우가 많습니다. PAL TV 신호를 768x576 해상도, 24-bit color pixel, 초당 25 frame으로 부호화하면 상당한 양의 데이터가 생깁니다. 이 데이터는 video monitor에 표시되기 전에 PC에서 처리되어야 합니다. 일부 PC용 Analogue TV card에는 onboard MPEG2 encoder가 있어 raw digital datastream을 Digital TV와 비슷한 encoded·compressed 형태로 PC에 전달할 수 있습니다.
단순한 보급형 digital TV card(DVB-T, DVB-C 또는 DVB-S)의 목적은 다음과 같습니다.
- 수신기를 방송 신호의 주파수에 맞춥니다.
- 방송 신호에서 encoded digital datastream을 추출합니다.
- Encoded digital datastream(MPEG2)을 data bus에서 사용할 수 있게 합니다.
두 방식의 핵심 차이는 Analogue TV card의 tuner가 analogue signal을 내보내는 반면, digital TV card의 tuner는 압축·부호화된 digital datastream을 내보낸다는 점입니다. 신호가 이미 digitize되어 있으므로 추가 처리를 거의 하지 않고 이 datastream을 PC data bus로 전달할 수 있습니다. 이후 digital video와 audio datastream을 추출해 적절한 software 또는 hardware로 보내 decoding하고 시청합니다.
DVB device node
61-89Linux의 DVB Device Driver API는 devfs filesystem을 통해 다음 device node를 제공합니다.
- `/dev/dvb/adapter0/demux0`
- `/dev/dvb/adapter0/dvr0`
- `/dev/dvb/adapter0/frontend0`
`/dev/dvb/adapter0/dvr0` device node는 MPEG2 Data Stream을 읽는 데 사용하고, `/dev/dvb/adapter0/frontend0`은 frontend tuner module을 조정하는 데 사용합니다. `/dev/dvb/adapter0/demux0`은 어떤 program을 수신할지 제어합니다.
Card의 기능 구성에 따라 Device Driver API는 다음 device node도 노출할 수 있습니다.
- `/dev/dvb/adapter0/ca0`
- `/dev/dvb/adapter0/audio0`
- `/dev/dvb/adapter0/net0`
- `/dev/dvb/adapter0/osd0`
- `/dev/dvb/adapter0/video0`
`/dev/dvb/adapter0/ca0`은 암호화된 channel을 decode하는 데 사용합니다. 나머지 device node는 이제 obsolete된 `av7110` driver를 사용하는 장치에서만 찾을 수 있으며, 이 장치들이 쓰던 추가 API 역시 obsolete 상태입니다.
Melbourne DVB-T transponder 주파수
90-125이 절은 digital TV 수신이 어떻게 동작하고 그 과정이 Digital TV card 설정에 어떤 영향을 미치는지 설명합니다. 예제에서는 Australia Melbourne 지역의 DVB-T channel을 수신합니다.
Mount Dandenong 송신소가 당시 방송하던 주파수는 다음과 같습니다.
| Broadcaster | Frequency |
|---|---|
| Seven | 177.500 Mhz |
| SBS | 184.500 Mhz |
| Nine | 191.625 Mhz |
| Ten | 219.500 Mhz |
| ABC | 226.500 Mhz |
| Channel 31 | 557.625 Mhz |
`dvbv5-scan` 같은 Digital TV scan utility는 여러 국가와 지역에 대해 compile 시 포함된 기본값을 사용합니다. 이 데이터는 현재 `dtv-scan-tables`라는 별도 package로 제공되며, git tree는 LinuxTV.org에 있습니다.
제공된 table 중 적합한 것이 없으면 transponder frequency를 담은 data file을 command line에서 지정할 수 있습니다. 다음 구간은 위 channel transponder를 예전 `channel` format으로 표현한 예제입니다.
예전 channel format
126-139# Data file for DVB scan program
#
# C Frequency SymbolRate FEC QAM
# S Frequency Polarisation SymbolRate FEC
# T Frequency Bandwidth FEC FEC2 QAM Mode Guard Hier
T 177500000 7MHz AUTO AUTO QAM64 8k 1/16 NONE
T 184500000 7MHz AUTO AUTO QAM64 8k 1/8 NONE
T 191625000 7MHz AUTO AUTO QAM64 8k 1/16 NONE
T 219500000 7MHz AUTO AUTO QAM64 8k 1/16 NONE
T 226500000 7MHz AUTO AUTO QAM64 8k 1/16 NONE
T 557625000 7MHz AUTO AUTO QPSK 8k 1/16 NONE새로운 channel format
140-159현재는 더 자세하고 이해하기 쉬운 새로운 format을 권장합니다. 새 format에서 `Seven` channel transponder의 data는 다음과 같이 표현합니다.
[Seven]
DELIVERY_SYSTEM = DVBT
FREQUENCY = 177500000
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = AUTO
CODE_RATE_LP = AUTO
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
INVERSION = AUTO전체 table의 최신판은 다음 위치에서 확인할 수 있습니다.
dvbv5 channel scan 출력
160-616Digital TV scanning utility를 실행하면 card의 frontend가 lock할 수 있는 각 channel transponder 안의 모든 audio·video program 정보를 담은 file이 출력됩니다. 즉 antenna에서 신호가 충분히 강한 transponder가 대상입니다.
다음은 Melbourne에서 수행한 channel scan의 `dvbv5` 도구 출력입니다. `SERVICE_ID`, `VIDEO_PID`, `AUDIO_PID`, delivery system, frequency, coding rate, modulation, transmission mode, guard interval 등의 값은 원문 그대로 보존합니다.
[ABC HDTV]
SERVICE_ID = 560
VIDEO_PID = 2307
AUDIO_PID = 0
DELIVERY_SYSTEM = DVBT
FREQUENCY = 226500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 3/4
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[ABC TV Melbourne]
SERVICE_ID = 561
VIDEO_PID = 512
AUDIO_PID = 650
DELIVERY_SYSTEM = DVBT
FREQUENCY = 226500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 3/4
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[ABC TV 2]
SERVICE_ID = 562
VIDEO_PID = 512
AUDIO_PID = 650
DELIVERY_SYSTEM = DVBT
FREQUENCY = 226500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 3/4
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[ABC TV 3]
SERVICE_ID = 563
VIDEO_PID = 512
AUDIO_PID = 650
DELIVERY_SYSTEM = DVBT
FREQUENCY = 226500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 3/4
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[ABC TV 4]
SERVICE_ID = 564
VIDEO_PID = 512
AUDIO_PID = 650
DELIVERY_SYSTEM = DVBT
FREQUENCY = 226500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 3/4
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[ABC DiG Radio]
SERVICE_ID = 566
VIDEO_PID = 0
AUDIO_PID = 2311
DELIVERY_SYSTEM = DVBT
FREQUENCY = 226500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 3/4
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[TEN Digital]
SERVICE_ID = 1585
VIDEO_PID = 512
AUDIO_PID = 650
DELIVERY_SYSTEM = DVBT
FREQUENCY = 219500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 1/2
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[TEN Digital 1]
SERVICE_ID = 1586
VIDEO_PID = 512
AUDIO_PID = 650
DELIVERY_SYSTEM = DVBT
FREQUENCY = 219500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 1/2
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[TEN Digital 2]
SERVICE_ID = 1587
VIDEO_PID = 512
AUDIO_PID = 650
DELIVERY_SYSTEM = DVBT
FREQUENCY = 219500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 1/2
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[TEN Digital 3]
SERVICE_ID = 1588
VIDEO_PID = 512
AUDIO_PID = 650
DELIVERY_SYSTEM = DVBT
FREQUENCY = 219500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 1/2
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[TEN Digital]
SERVICE_ID = 1589
VIDEO_PID = 512
AUDIO_PID = 650
DELIVERY_SYSTEM = DVBT
FREQUENCY = 219500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 1/2
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[TEN Digital 4]
SERVICE_ID = 1590
VIDEO_PID = 512
AUDIO_PID = 650
DELIVERY_SYSTEM = DVBT
FREQUENCY = 219500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 1/2
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[TEN Digital]
SERVICE_ID = 1591
VIDEO_PID = 512
AUDIO_PID = 650
DELIVERY_SYSTEM = DVBT
FREQUENCY = 219500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 1/2
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[TEN HD]
SERVICE_ID = 1592
VIDEO_PID = 514
AUDIO_PID = 0
DELIVERY_SYSTEM = DVBT
FREQUENCY = 219500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 1/2
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[TEN Digital]
SERVICE_ID = 1593
VIDEO_PID = 512
AUDIO_PID = 650
DELIVERY_SYSTEM = DVBT
FREQUENCY = 219500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 1/2
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[Nine Digital]
SERVICE_ID = 1072
VIDEO_PID = 513
AUDIO_PID = 660
DELIVERY_SYSTEM = DVBT
FREQUENCY = 191625000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 1/2
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[Nine Digital HD]
SERVICE_ID = 1073
VIDEO_PID = 512
AUDIO_PID = 0
DELIVERY_SYSTEM = DVBT
FREQUENCY = 191625000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 1/2
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[Nine Guide]
SERVICE_ID = 1074
VIDEO_PID = 514
AUDIO_PID = 670
DELIVERY_SYSTEM = DVBT
FREQUENCY = 191625000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 3/4
CODE_RATE_LP = 1/2
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/16
HIERARCHY = NONE
[7 Digital]
SERVICE_ID = 1328
VIDEO_PID = 769
AUDIO_PID = 770
DELIVERY_SYSTEM = DVBT
FREQUENCY = 177500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 2/3
CODE_RATE_LP = 2/3
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/8
HIERARCHY = NONE
[7 Digital 1]
SERVICE_ID = 1329
VIDEO_PID = 769
AUDIO_PID = 770
DELIVERY_SYSTEM = DVBT
FREQUENCY = 177500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 2/3
CODE_RATE_LP = 2/3
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/8
HIERARCHY = NONE
[7 Digital 2]
SERVICE_ID = 1330
VIDEO_PID = 769
AUDIO_PID = 770
DELIVERY_SYSTEM = DVBT
FREQUENCY = 177500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 2/3
CODE_RATE_LP = 2/3
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/8
HIERARCHY = NONE
[7 Digital 3]
SERVICE_ID = 1331
VIDEO_PID = 769
AUDIO_PID = 770
DELIVERY_SYSTEM = DVBT
FREQUENCY = 177500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 2/3
CODE_RATE_LP = 2/3
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/8
HIERARCHY = NONE
[7 HD Digital]
SERVICE_ID = 1332
VIDEO_PID = 833
AUDIO_PID = 834
DELIVERY_SYSTEM = DVBT
FREQUENCY = 177500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 2/3
CODE_RATE_LP = 2/3
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/8
HIERARCHY = NONE
[7 Program Guide]
SERVICE_ID = 1334
VIDEO_PID = 865
AUDIO_PID = 866
DELIVERY_SYSTEM = DVBT
FREQUENCY = 177500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 2/3
CODE_RATE_LP = 2/3
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/8
HIERARCHY = NONE
[SBS HD]
SERVICE_ID = 784
VIDEO_PID = 102
AUDIO_PID = 103
DELIVERY_SYSTEM = DVBT
FREQUENCY = 536500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 2/3
CODE_RATE_LP = 2/3
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/8
HIERARCHY = NONE
[SBS DIGITAL 1]
SERVICE_ID = 785
VIDEO_PID = 161
AUDIO_PID = 81
DELIVERY_SYSTEM = DVBT
FREQUENCY = 536500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 2/3
CODE_RATE_LP = 2/3
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/8
HIERARCHY = NONE
[SBS DIGITAL 2]
SERVICE_ID = 786
VIDEO_PID = 162
AUDIO_PID = 83
DELIVERY_SYSTEM = DVBT
FREQUENCY = 536500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 2/3
CODE_RATE_LP = 2/3
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/8
HIERARCHY = NONE
[SBS EPG]
SERVICE_ID = 787
VIDEO_PID = 163
AUDIO_PID = 85
DELIVERY_SYSTEM = DVBT
FREQUENCY = 536500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 2/3
CODE_RATE_LP = 2/3
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/8
HIERARCHY = NONE
[SBS RADIO 1]
SERVICE_ID = 798
VIDEO_PID = 0
AUDIO_PID = 201
DELIVERY_SYSTEM = DVBT
FREQUENCY = 536500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 2/3
CODE_RATE_LP = 2/3
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/8
HIERARCHY = NONE
[SBS RADIO 2]
SERVICE_ID = 799
VIDEO_PID = 0
AUDIO_PID = 202
DELIVERY_SYSTEM = DVBT
FREQUENCY = 536500000
INVERSION = OFF
BANDWIDTH_HZ = 7000000
CODE_RATE_HP = 2/3
CODE_RATE_LP = 2/3
MODULATION = QAM/64
TRANSMISSION_MODE = 8K
GUARD_INTERVAL = 1/8
HIERARCHY = NONE
Analogue TV와 DVB datastream
dvb_intro.rst:1-60Analogue card는 신호를 digitize해야 하지만 DVB card는 이미 부호화된 MPEG2 datastream을 data bus로 전달한다는 차이를 중심으로 설명합니다.