| HOWTO: Get An Avermedia DVB-T working under Linux |
| ______________________________________________ |
| |
| Table of Contents |
| Assumptions and Introduction |
| The Avermedia DVB-T |
| Getting the card going |
| Receiving DVB-T in Australia |
| Known Limitations |
| Further Update |
| |
| Assumptions and Introduction |
| |
| It is assumed that the reader understands the basic structure |
| of the Linux Kernel DVB drivers and the general principles of |
| Digital TV. |
| |
| One significant difference between Digital TV and Analogue TV |
| that the unwary (like myself) should consider is that, |
| although the component structure of budget 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 per second) rasterised using an |
| interlacing technique. Interlacing takes two fields to |
| represent one frame. Computers today are at their best when |
| dealing with digital signals, not analogue signals and a |
| composite video signal is about as far removed from a digital |
| data stream as you can get. 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 - |
| NICAM.) |
| * 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. |
| _________________________________________________________ |
| |
| The Avermedia DVB-T |
| |
| The Avermedia DVB-T is a budget PCI DVB card. It has 3 inputs: |
| |
| * RF Tuner Input |
| * Composite Video Input (RCA Jack) |
| * SVIDEO Input (Mini-DIN) |
| |
| The RF Tuner Input is the input to the tuner module of the |
| card. The Tuner is otherwise known as the "Frontend" . The |
| Frontend of the Avermedia DVB-T is a Microtune 7202D. A timely |
| post to the linux-dvb mailing list ascertained that the |
| Microtune 7202D is supported by the sp887x driver which is |
| found in the dvb-hw CVS module. |
| |
| The DVB-T card is based around the BT878 chip which is a very |
| common multimedia bridge and often found on Analogue TV cards. |
| There is no on-board MPEG2 decoder, which means that all MPEG2 |
| decoding must be done in software, or if you have one, on an |
| MPEG2 hardware decoding card or chipset. |
| _________________________________________________________ |
| |
| Getting the card going |
| |
| In order to fire up the card, it is necessary to load a number |
| of modules from the DVB driver set. Prior to this it will have |
| been necessary to download these drivers from the linuxtv CVS |
| server and compile them successfully. |
| |
| Depending on the card's feature set, the Device Driver API for |
| DVB under Linux will expose some of the following device files |
| in the /dev tree: |
| |
| * /dev/dvb/adapter0/audio0 |
| * /dev/dvb/adapter0/ca0 |
| * /dev/dvb/adapter0/demux0 |
| * /dev/dvb/adapter0/dvr0 |
| * /dev/dvb/adapter0/frontend0 |
| * /dev/dvb/adapter0/net0 |
| * /dev/dvb/adapter0/osd0 |
| * /dev/dvb/adapter0/video0 |
| |
| The primary device nodes that we are interested in (at this |
| stage) for the Avermedia DVB-T are: |
| |
| * /dev/dvb/adapter0/dvr0 |
| * /dev/dvb/adapter0/frontend0 |
| |
| The dvr0 device node is used to read the MPEG2 Data Stream and |
| the frontend0 node is used to tune the frontend tuner module. |
| |
| At this stage, it has not been able to ascertain the |
| functionality of the remaining device nodes in respect of the |
| Avermedia DVBT. However, full functionality in respect of |
| tuning, receiving and supplying the MPEG2 data stream is |
| possible with the currently available versions of the driver. |
| It may be possible that additional functionality is available |
| from the card (i.e. viewing the additional analogue inputs |
| that the card presents), but this has not been tested yet. If |
| I get around to this, I'll update the document with whatever I |
| find. |
| |
| To power up the card, load the following modules in the |
| following order: |
| |
| * modprobe bttv (normally loaded automatically) |
| * modprobe dvb-bt8xx (or place dvb-bt8xx in /etc/modules) |
| |
| Insertion of these modules into the running kernel will |
| activate the appropriate DVB device nodes. It is then possible |
| to start accessing the card with utilities such as scan, tzap, |
| dvbstream etc. |
| |
| The frontend module sp887x.o, requires an external firmware. |
| Please use the command "get_dvb_firmware sp887x" to download |
| it. Then copy it to /usr/lib/hotplug/firmware or /lib/firmware/ |
| (depending on configuration of firmware hotplug). |
| |
| Receiving DVB-T in Australia |
| |
| I have no experience of DVB-T in other countries other than |
| Australia, so I will attempt to explain how it works here in |
| Melbourne and how this affects the configuration of the DVB-T |
| card. |
| |
| The Digital Broadcasting Australia website has a Reception |
| locatortool which provides information on transponder channels |
| and frequencies. My local transmitter happens to be Mount |
| Dandenong. |
| |
| The frequencies broadcast by Mount Dandenong are: |
| |
| Table 1. Transponder Frequencies Mount Dandenong, Vic, Aus. |
| Broadcaster Channel Frequency |
| ABC VHF 12 226.5 MHz |
| TEN VHF 11 219.5 MHz |
| NINE VHF 8 191.625 MHz |
| SEVEN VHF 6 177.5 MHz |
| SBS UHF 29 536.5 MHz |
| |
| The Scan utility has a set of compiled-in defaults for various |
| countries and regions, but if they do not suit, or if you have |
| a pre-compiled scan binary, 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: |
| # 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 226500000 7MHz 2/3 NONE QAM64 8k 1/8 NONE |
| T 191625000 7MHz 2/3 NONE QAM64 8k 1/8 NONE |
| T 219500000 7MHz 2/3 NONE QAM64 8k 1/8 NONE |
| T 177500000 7MHz 2/3 NONE QAM64 8k 1/8 NONE |
| T 536500000 7MHz 2/3 NONE QAM64 8k 1/8 NONE |
| |
| The defaults for the transponder frequency and other |
| modulation parameters were obtained from www.dba.org.au. |
| |
| When Scan runs, it will output channels.conf information for |
| any channel's transponders which the card's frontend can lock |
| onto. (i.e. any whose signal is strong enough at your |
| antenna). |
| |
| Here's my channels.conf file for anyone who's interested: |
| ABC HDTV:226500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64 |
| :TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:2307:0:560 |
| ABC TV Melbourne:226500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_ |
| 4:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:65 |
| 0:561 |
| ABC TV 2:226500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64 |
| :TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:562 |
| ABC TV 3:226500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64 |
| :TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:563 |
| ABC TV 4:226500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64 |
| :TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:564 |
| ABC DiG Radio:226500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:Q |
| AM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:0:2311:56 |
| 6 |
| TEN Digital:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM |
| _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:158 |
| 5 |
| TEN Digital 1:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:Q |
| AM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:1 |
| 586 |
| TEN Digital 2:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:Q |
| AM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:1 |
| 587 |
| TEN Digital 3:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:Q |
| AM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:1 |
| 588 |
| TEN Digital:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM |
| _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:158 |
| 9 |
| TEN Digital 4:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:Q |
| AM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:1 |
| 590 |
| TEN Digital:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM |
| _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:159 |
| 1 |
| TEN HD:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_64:T |
| RANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:514:0:1592 |
| TEN Digital:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM |
| _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:159 |
| 3 |
| Nine Digital:191625000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QA |
| M_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:513:660:10 |
| 72 |
| Nine Digital HD:191625000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2 |
| :QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:0:1 |
| 073 |
| Nine Guide:191625000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_ |
| 64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:514:670:1074 |
| 7 Digital:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM_6 |
| 4:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:769:770:1328 |
| 7 Digital 1:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM |
| _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:769:770:1329 |
| 7 Digital 2:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM |
| _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:769:770:1330 |
| 7 Digital 3:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM |
| _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:769:770:1331 |
| 7 HD Digital:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QA |
| M_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:833:834:133 |
| 2 |
| 7 Program Guide:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3 |
| :QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:865:866: |
| 1334 |
| SBS HD:536500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM_64:T |
| RANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:102:103:784 |
| SBS DIGITAL 1:536500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:Q |
| AM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:161:81:785 |
| SBS DIGITAL 2:536500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:Q |
| AM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:162:83:786 |
| SBS EPG:536500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM_64: |
| TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:163:85:787 |
| SBS RADIO 1:536500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM |
| _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:0:201:798 |
| SBS RADIO 2:536500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM |
| _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:0:202:799 |
| _________________________________________________________ |
| |
| Known Limitations |
| |
| At present I can say with confidence that the frontend tunes |
| via /dev/dvb/adapter{x}/frontend0 and supplies an MPEG2 stream |
| via /dev/dvb/adapter{x}/dvr0. I have not tested the |
| functionality of any other part of the card yet. I will do so |
| over time and update this document. |
| |
| There are some limitations in the i2c layer due to a returned |
| error message inconsistency. Although this generates errors in |
| dmesg and the system logs, it does not appear to affect the |
| ability of the frontend to function correctly. |
| _________________________________________________________ |
| |
| Further Update |
| |
| dvbstream and VideoLAN Client on windows works a treat with |
| DVB, in fact this is currently serving as my main way of |
| viewing DVB-T at the moment. Additionally, VLC is happily |
| decoding HDTV signals, although the PC is dropping the odd |
| frame here and there - I assume due to processing capability - |
| as all the decoding is being done under windows in software. |
| |
| Many thanks to Nigel Pearson for the updates to this document |
| since the recent revision of the driver. |
| |
| February 14th 2006 |
