1 .. SPDX-License-Identifier: GPL-2.0 2 3 ============================== 4 Using the Digital TV Framework 5 ============================== 6 7 Introduction 8 ~~~~~~~~~~~~ 9 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. 14 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: 21 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. 26 27 .. note:: 28 29 some countries employ a digital audio signal 30 embedded within the modulated composite analogue signal - 31 using NICAM signaling.) 32 33 * digitize the analogue video signal and make the resulting datastream 34 available to the data bus. 35 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. 45 46 The purpose of a simple budget digital TV card (DVB-T,C or S) is to 47 simply: 48 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. 52 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. 60 61 Getting the card going 62 ~~~~~~~~~~~~~~~~~~~~~~ 63 64 The Device Driver API for DVB under Linux will the following 65 device nodes via the devfs filesystem: 66 67 * /dev/dvb/adapter0/demux0 68 * /dev/dvb/adapter0/dvr0 69 * /dev/dvb/adapter0/frontend0 70 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. 75 76 Depending on the card's feature set, the Device Driver API could also 77 expose other device nodes: 78 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 84 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. 89 90 Receiving a digital TV channel 91 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 92 93 This section attempts to explain how it works and how this affects the 94 configuration of a Digital TV card. 95 96 On this example, we're considering tuning into DVB-T channels in 97 Australia, at the Melbourne region. 98 99 The frequencies broadcast by Mount Dandenong transmitters are, 100 currently: 101 102 Table 1. Transponder Frequencies Mount Dandenong, Vic, Aus. 103 104 =========== =========== 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 =========== =========== 114 115 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: 119 120 https://git.linuxtv.org/dtv-scan-tables.git/ 121 122 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:: 126 127 # 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 132 133 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 139 140 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:: 143 144 [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 155 156 For an updated version of the complete table, please see: 157 158 https://git.linuxtv.org/dtv-scan-tables.git/tree/dvb-t/au-Melbourne 159 160 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). 164 165 Here's the output of the dvbv5 tools from a channel scan took from 166 Melburne:: 167 168 [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 182 183 [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 197 198 [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 212 213 [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 227 228 [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 242 243 [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 257 258 [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 272 273 [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 287 288 [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 302 303 [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 317 318 [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 332 333 [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 347 348 [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 362 363 [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 377 378 [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 392 393 [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 407 408 [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 422 423 [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 437 438 [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 452 453 [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 467 468 [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 482 483 [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 497 498 [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 512 513 [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 527 528 [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 542 543 [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 557 558 [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 572 573 [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 587 588 [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 602 603 [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
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