| .. SPDX-License-Identifier: GPL-2.0 |
| |
| ============================== |
| Using the Digital TV Framework |
| ============================== |
| |
| Introduction |
| ~~~~~~~~~~~~ |
| |
| One significant difference between Digital TV and Analogue TV that the |
| unwary (like myself) should consider is that, although the component |
| structure of DVB-T cards are substantially similar to Analogue TV cards, |
| they function in substantially different ways. |
| |
| The purpose of an Analogue TV is to receive and display an Analogue |
| Television signal. An Analogue TV signal (otherwise known as composite |
| video) is an analogue encoding of a sequence of image frames (25 frames |
| per second in Europe) rasterised using an interlacing technique. |
| Interlacing takes two fields to represent one frame. Therefore, an |
| Analogue TV card for a PC has the following purpose: |
| |
| * Tune the receiver to receive a broadcast signal |
| * demodulate the broadcast signal |
| * demultiplex the analogue video signal and analogue audio |
| signal. |
| |
| .. note:: |
| |
| some countries employ a digital audio signal |
| embedded within the modulated composite analogue signal - |
| using NICAM signaling.) |
| |
| * digitize the analogue video signal and make the resulting datastream |
| available to the data bus. |
| |
| The digital datastream from an Analogue TV card is generated by |
| circuitry on the card and is often presented uncompressed. For a PAL TV |
| signal encoded at a resolution of 768x576 24-bit color pixels over 25 |
| frames per second - a fair amount of data is generated and must be |
| processed by the PC before it can be displayed on the video monitor |
| screen. Some Analogue TV cards for PCs have onboard MPEG2 encoders which |
| permit the raw digital data stream to be presented to the PC in an |
| encoded and compressed form - similar to the form that is used in |
| Digital TV. |
| |
| The purpose of a simple budget digital TV card (DVB-T,C or S) is to |
| simply: |
| |
| * Tune the received to receive a broadcast signal. * Extract the encoded |
| digital datastream from the broadcast signal. |
| * Make the encoded digital datastream (MPEG2) available to the data bus. |
| |
| The significant difference between the two is that the tuner on the |
| analogue TV card spits out an Analogue signal, whereas the tuner on the |
| digital TV card spits out a compressed encoded digital datastream. As |
| the signal is already digitised, it is trivial to pass this datastream |
| to the PC databus with minimal additional processing and then extract |
| the digital video and audio datastreams passing them to the appropriate |
| software or hardware for decoding and viewing. |
| |
| Getting the card going |
| ~~~~~~~~~~~~~~~~~~~~~~ |
| |
| The Device Driver API for DVB under Linux will the following |
| device nodes via the devfs filesystem: |
| |
| * /dev/dvb/adapter0/demux0 |
| * /dev/dvb/adapter0/dvr0 |
| * /dev/dvb/adapter0/frontend0 |
| |
| The ``/dev/dvb/adapter0/dvr0`` device node is used to read the MPEG2 |
| Data Stream and the ``/dev/dvb/adapter0/frontend0`` device node is used |
| to tune the frontend tuner module. The ``/dev/dvb/adapter0/demux0`` is |
| used to control what programs will be received. |
| |
| Depending on the card's feature set, the Device Driver API could also |
| expose other device nodes: |
| |
| * /dev/dvb/adapter0/ca0 |
| * /dev/dvb/adapter0/audio0 |
| * /dev/dvb/adapter0/net0 |
| * /dev/dvb/adapter0/osd0 |
| * /dev/dvb/adapter0/video0 |
| |
| The ``/dev/dvb/adapter0/ca0`` is used to decode encrypted channels. The |
| other device nodes are found only on devices that use the av7110 |
| driver, with is now obsoleted, together with the extra API whose such |
| devices use. |
| |
| Receiving a digital TV channel |
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
| |
| This section attempts to explain how it works and how this affects the |
| configuration of a Digital TV card. |
| |
| On this example, we're considering tuning into DVB-T channels in |
| Australia, at the Melbourne region. |
| |
| The frequencies broadcast by Mount Dandenong transmitters are, |
| currently: |
| |
| Table 1. Transponder Frequencies Mount Dandenong, Vic, Aus. |
| |
| =========== =========== |
| 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 |
| =========== =========== |
| |
| The digital TV Scan utilities (like dvbv5-scan) have use a set of |
| compiled-in defaults for various countries and regions. Those are |
| currently provided as a separate package, called dtv-scan-tables. It's |
| git tree is located at LinuxTV.org: |
| |
| https://git.linuxtv.org/dtv-scan-tables.git/ |
| |
| If none of the tables there suit, you can specify a data file on the |
| command line which contains the transponder frequencies. Here is a |
| sample file for the above channel transponders, in the old "channel" |
| format:: |
| |
| # 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 NONE |
| |
| Nowadays, we prefer to use a newer format, with is more verbose and easier |
| to understand. With the new format, the "Seven" channel transponder's |
| data is represented by:: |
| |
| [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 = AUTO |
| |
| For an updated version of the complete table, please see: |
| |
| https://git.linuxtv.org/dtv-scan-tables.git/tree/dvb-t/au-Melbourne |
| |
| When the Digital TV scanning utility runs, it will output a file |
| containing the information for all the audio and video programs that |
| exists into each channel's transponders which the card's frontend can |
| lock onto. (i.e. any whose signal is strong enough at your antenna). |
| |
| Here's the output of the dvbv5 tools from a channel scan took from |
| Melburne:: |
| |
| [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 |
