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 proceesed by the PC before it can be
49 displayed on the video monitor screen. Some Analogue TV cards
50 for PC's 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
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