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1 | HOWTO: Get An Avermedia DVB-T working under Linux | |
2 | ______________________________________________ | |
3 | ||
4 | Table of Contents | |
5 | Assumptions and Introduction | |
6 | The Avermedia DVB-T | |
7 | Getting the card going | |
8 | Receiving DVB-T in Australia | |
9 | Known Limitations | |
10 | Further Update | |
11 | ||
12 | Assumptions and Introduction | |
13 | ||
14 | It is assumed that the reader understands the basic structure | |
15 | of the Linux Kernel DVB drivers and the general principles of | |
16 | Digital TV. | |
17 | ||
18 | One significant difference between Digital TV and Analogue TV | |
19 | that the unwary (like myself) should consider is that, | |
20 | although the component structure of budget DVB-T cards are | |
21 | substantially similar to Analogue TV cards, they function in | |
22 | substantially different ways. | |
23 | ||
24 | The purpose of an Analogue TV is to receive and display an | |
25 | Analogue Television signal. An Analogue TV signal (otherwise | |
26 | known as composite video) is an analogue encoding of a | |
27 | sequence of image frames (25 per second) rasterised using an | |
28 | interlacing technique. Interlacing takes two fields to | |
29 | represent one frame. Computers today are at their best when | |
30 | dealing with digital signals, not analogue signals and a | |
31 | composite video signal is about as far removed from a digital | |
32 | data stream as you can get. Therefore, an Analogue TV card for | |
33 | a PC has the following purpose: | |
34 | ||
35 | * Tune the receiver to receive a broadcast signal | |
36 | * demodulate the broadcast signal | |
37 | * demultiplex the analogue video signal and analogue audio | |
38 | signal (note some countries employ a digital audio signal | |
39 | embedded within the modulated composite analogue signal - | |
40 | NICAM.) | |
41 | * digitize the analogue video signal and make the resulting | |
42 | datastream available to the data bus. | |
43 | ||
44 | The digital datastream from an Analogue TV card is generated | |
45 | by circuitry on the card and is often presented uncompressed. | |
46 | For a PAL TV signal encoded at a resolution of 768x576 24-bit | |
47 | color pixels over 25 frames per second - a fair amount of data | |
48 | is generated and must be processed by the PC before it can be | |
49 | displayed on the video monitor screen. Some Analogue TV cards | |
50 | for PCs have onboard MPEG2 encoders which permit the raw | |
51 | digital data stream to be presented to the PC in an encoded | |
52 | and compressed form - similar to the form that is used in | |
53 | Digital TV. | |
54 | ||
55 | The purpose of a simple budget digital TV card (DVB-T,C or S) | |
56 | is to simply: | |
57 | ||
58 | * Tune the received to receive a broadcast signal. | |
59 | * Extract the encoded digital datastream from the broadcast | |
60 | signal. | |
61 | * Make the encoded digital datastream (MPEG2) available to | |
62 | the data bus. | |
63 | ||
64 | The significant difference between the two is that the tuner | |
65 | on the analogue TV card spits out an Analogue signal, whereas | |
66 | the tuner on the digital TV card spits out a compressed | |
67 | encoded digital datastream. As the signal is already | |
68 | digitised, it is trivial to pass this datastream to the PC | |
69 | databus with minimal additional processing and then extract | |
70 | the digital video and audio datastreams passing them to the | |
71 | appropriate software or hardware for decoding and viewing. | |
72 | _________________________________________________________ | |
73 | ||
74 | The Avermedia DVB-T | |
75 | ||
76 | The Avermedia DVB-T is a budget PCI DVB card. It has 3 inputs: | |
77 | ||
78 | * RF Tuner Input | |
79 | * Composite Video Input (RCA Jack) | |
80 | * SVIDEO Input (Mini-DIN) | |
81 | ||
82 | The RF Tuner Input is the input to the tuner module of the | |
83 | card. The Tuner is otherwise known as the "Frontend" . The | |
84 | Frontend of the Avermedia DVB-T is a Microtune 7202D. A timely | |
85 | post to the linux-dvb mailing list ascertained that the | |
86 | Microtune 7202D is supported by the sp887x driver which is | |
87 | found in the dvb-hw CVS module. | |
88 | ||
89 | The DVB-T card is based around the BT878 chip which is a very | |
90 | common multimedia bridge and often found on Analogue TV cards. | |
91 | There is no on-board MPEG2 decoder, which means that all MPEG2 | |
92 | decoding must be done in software, or if you have one, on an | |
93 | MPEG2 hardware decoding card or chipset. | |
94 | _________________________________________________________ | |
95 | ||
96 | Getting the card going | |
97 | ||
98 | In order to fire up the card, it is necessary to load a number | |
99 | of modules from the DVB driver set. Prior to this it will have | |
100 | been necessary to download these drivers from the linuxtv CVS | |
101 | server and compile them successfully. | |
102 | ||
103 | Depending on the card's feature set, the Device Driver API for | |
104 | DVB under Linux will expose some of the following device files | |
105 | in the /dev tree: | |
106 | ||
107 | * /dev/dvb/adapter0/audio0 | |
108 | * /dev/dvb/adapter0/ca0 | |
109 | * /dev/dvb/adapter0/demux0 | |
110 | * /dev/dvb/adapter0/dvr0 | |
111 | * /dev/dvb/adapter0/frontend0 | |
112 | * /dev/dvb/adapter0/net0 | |
113 | * /dev/dvb/adapter0/osd0 | |
114 | * /dev/dvb/adapter0/video0 | |
115 | ||
116 | The primary device nodes that we are interested in (at this | |
117 | stage) for the Avermedia DVB-T are: | |
118 | ||
119 | * /dev/dvb/adapter0/dvr0 | |
120 | * /dev/dvb/adapter0/frontend0 | |
121 | ||
122 | The dvr0 device node is used to read the MPEG2 Data Stream and | |
123 | the frontend0 node is used to tune the frontend tuner module. | |
124 | ||
125 | At this stage, it has not been able to ascertain the | |
126 | functionality of the remaining device nodes in respect of the | |
127 | Avermedia DVBT. However, full functionality in respect of | |
128 | tuning, receiving and supplying the MPEG2 data stream is | |
129 | possible with the currently available versions of the driver. | |
130 | It may be possible that additional functionality is available | |
131 | from the card (i.e. viewing the additional analogue inputs | |
132 | that the card presents), but this has not been tested yet. If | |
133 | I get around to this, I'll update the document with whatever I | |
134 | find. | |
135 | ||
136 | To power up the card, load the following modules in the | |
137 | following order: | |
138 | ||
139 | * modprobe bttv (normally loaded automatically) | |
140 | * modprobe dvb-bt8xx (or place dvb-bt8xx in /etc/modules) | |
141 | ||
142 | Insertion of these modules into the running kernel will | |
143 | activate the appropriate DVB device nodes. It is then possible | |
144 | to start accessing the card with utilities such as scan, tzap, | |
145 | dvbstream etc. | |
146 | ||
147 | The frontend module sp887x.o, requires an external firmware. | |
148 | Please use the command "get_dvb_firmware sp887x" to download | |
149 | it. Then copy it to /usr/lib/hotplug/firmware or /lib/firmware/ | |
150 | (depending on configuration of firmware hotplug). | |
151 | ||
152 | Receiving DVB-T in Australia | |
153 | ||
154 | I have no experience of DVB-T in other countries other than | |
155 | Australia, so I will attempt to explain how it works here in | |
156 | Melbourne and how this affects the configuration of the DVB-T | |
157 | card. | |
158 | ||
159 | The Digital Broadcasting Australia website has a Reception | |
160 | locatortool which provides information on transponder channels | |
161 | and frequencies. My local transmitter happens to be Mount | |
162 | Dandenong. | |
163 | ||
164 | The frequencies broadcast by Mount Dandenong are: | |
165 | ||
166 | Table 1. Transponder Frequencies Mount Dandenong, Vic, Aus. | |
167 | Broadcaster Channel Frequency | |
168 | ABC VHF 12 226.5 MHz | |
169 | TEN VHF 11 219.5 MHz | |
170 | NINE VHF 8 191.625 MHz | |
171 | SEVEN VHF 6 177.5 MHz | |
172 | SBS UHF 29 536.5 MHz | |
173 | ||
174 | The Scan utility has a set of compiled-in defaults for various | |
175 | countries and regions, but if they do not suit, or if you have | |
176 | a pre-compiled scan binary, you can specify a data file on the | |
177 | command line which contains the transponder frequencies. Here | |
178 | is a sample file for the above channel transponders: | |
179 | # Data file for DVB scan program | |
180 | # | |
181 | # C Frequency SymbolRate FEC QAM | |
182 | # S Frequency Polarisation SymbolRate FEC | |
183 | # T Frequency Bandwidth FEC FEC2 QAM Mode Guard Hier | |
184 | T 226500000 7MHz 2/3 NONE QAM64 8k 1/8 NONE | |
185 | T 191625000 7MHz 2/3 NONE QAM64 8k 1/8 NONE | |
186 | T 219500000 7MHz 2/3 NONE QAM64 8k 1/8 NONE | |
187 | T 177500000 7MHz 2/3 NONE QAM64 8k 1/8 NONE | |
188 | T 536500000 7MHz 2/3 NONE QAM64 8k 1/8 NONE | |
189 | ||
190 | The defaults for the transponder frequency and other | |
191 | modulation parameters were obtained from www.dba.org.au. | |
192 | ||
193 | When Scan runs, it will output channels.conf information for | |
194 | any channel's transponders which the card's frontend can lock | |
195 | onto. (i.e. any whose signal is strong enough at your | |
196 | antenna). | |
197 | ||
198 | Here's my channels.conf file for anyone who's interested: | |
199 | ABC HDTV:226500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64 | |
200 | :TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:2307:0:560 | |
201 | ABC TV Melbourne:226500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_ | |
202 | 4:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:65 | |
203 | 0:561 | |
204 | ABC TV 2:226500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64 | |
205 | :TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:562 | |
206 | ABC TV 3:226500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64 | |
207 | :TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:563 | |
208 | ABC TV 4:226500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64 | |
209 | :TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:564 | |
210 | ABC DiG Radio:226500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:Q | |
211 | AM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:0:2311:56 | |
212 | 6 | |
213 | TEN Digital:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM | |
214 | _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:158 | |
215 | 5 | |
216 | TEN Digital 1:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:Q | |
217 | AM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:1 | |
218 | 586 | |
219 | TEN Digital 2:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:Q | |
220 | AM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:1 | |
221 | 587 | |
222 | TEN Digital 3:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:Q | |
223 | AM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:1 | |
224 | 588 | |
225 | TEN Digital:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM | |
226 | _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:158 | |
227 | 9 | |
228 | TEN Digital 4:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:Q | |
229 | AM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:1 | |
230 | 590 | |
231 | TEN Digital:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM | |
232 | _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:159 | |
233 | 1 | |
234 | TEN HD:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_64:T | |
235 | RANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:514:0:1592 | |
236 | TEN Digital:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM | |
237 | _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:159 | |
238 | 3 | |
239 | Nine Digital:191625000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QA | |
240 | M_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:513:660:10 | |
241 | 72 | |
242 | Nine Digital HD:191625000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2 | |
243 | :QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:0:1 | |
244 | 073 | |
245 | Nine Guide:191625000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_ | |
246 | 64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:514:670:1074 | |
247 | 7 Digital:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM_6 | |
248 | 4:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:769:770:1328 | |
249 | 7 Digital 1:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM | |
250 | _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:769:770:1329 | |
251 | 7 Digital 2:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM | |
252 | _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:769:770:1330 | |
253 | 7 Digital 3:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM | |
254 | _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:769:770:1331 | |
255 | 7 HD Digital:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QA | |
256 | M_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:833:834:133 | |
257 | 2 | |
258 | 7 Program Guide:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3 | |
259 | :QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:865:866: | |
260 | 1334 | |
261 | SBS HD:536500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM_64:T | |
262 | RANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:102:103:784 | |
263 | SBS DIGITAL 1:536500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:Q | |
264 | AM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:161:81:785 | |
265 | SBS DIGITAL 2:536500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:Q | |
266 | AM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:162:83:786 | |
267 | SBS EPG:536500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM_64: | |
268 | TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:163:85:787 | |
269 | SBS RADIO 1:536500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM | |
270 | _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:0:201:798 | |
271 | SBS RADIO 2:536500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM | |
272 | _64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:0:202:799 | |
273 | _________________________________________________________ | |
274 | ||
275 | Known Limitations | |
276 | ||
277 | At present I can say with confidence that the frontend tunes | |
278 | via /dev/dvb/adapter{x}/frontend0 and supplies an MPEG2 stream | |
279 | via /dev/dvb/adapter{x}/dvr0. I have not tested the | |
280 | functionality of any other part of the card yet. I will do so | |
281 | over time and update this document. | |
282 | ||
283 | There are some limitations in the i2c layer due to a returned | |
284 | error message inconsistency. Although this generates errors in | |
285 | dmesg and the system logs, it does not appear to affect the | |
286 | ability of the frontend to function correctly. | |
287 | _________________________________________________________ | |
288 | ||
289 | Further Update | |
290 | ||
291 | dvbstream and VideoLAN Client on windows works a treat with | |
292 | DVB, in fact this is currently serving as my main way of | |
293 | viewing DVB-T at the moment. Additionally, VLC is happily | |
294 | decoding HDTV signals, although the PC is dropping the odd | |
295 | frame here and there - I assume due to processing capability - | |
296 | as all the decoding is being done under windows in software. | |
297 | ||
298 | Many thanks to Nigel Pearson for the updates to this document | |
299 | since the recent revision of the driver. | |
300 | ||
301 | February 14th 2006 |