1 .. SPDX-License-Identifier: GPL-2.0 2 3 FAQ 4 === 5 6 .. note:: 7 8 1. With Digital TV, a single physical channel may have different 9 contents inside it. The specs call each one as a *service*. 10 This is what a TV user would call "channel". So, in order to 11 avoid confusion, we're calling *transponders* as the physical 12 channel on this FAQ, and *services* for the logical channel. 13 2. The LinuxTV community maintains some Wiki pages with contain 14 a lot of information related to the media subsystem. If you 15 don't find an answer for your needs here, it is likely that 16 you'll be able to get something useful there. It is hosted 17 at: 18 19 https://www.linuxtv.org/wiki/ 20 21 Some very frequently asked questions about Linux Digital TV support 22 23 1. The signal seems to die a few seconds after tuning. 24 25 It's not a bug, it's a feature. Because the frontends have 26 significant power requirements (and hence get very hot), they 27 are powered down if they are unused (i.e. if the frontend device 28 is closed). The ``dvb-core`` module parameter ``dvb_shutdown_timeout`` 29 allow you to change the timeout (default 5 seconds). Setting the 30 timeout to 0 disables the timeout feature. 31 32 2. How can I watch TV? 33 34 Together with the Linux Kernel, the Digital TV developers support 35 some simple utilities which are mainly intended for testing 36 and to demonstrate how the DVB API works. This is called DVB v5 37 tools and are grouped together with the ``v4l-utils`` git repository: 38 39 https://git.linuxtv.org/v4l-utils.git/ 40 41 You can find more information at the LinuxTV wiki: 42 43 https://www.linuxtv.org/wiki/index.php/DVBv5_Tools 44 45 The first step is to get a list of services that are transmitted. 46 47 This is done by using several existing tools. You can use 48 for example the ``dvbv5-scan`` tool. You can find more information 49 about it at: 50 51 https://www.linuxtv.org/wiki/index.php/Dvbv5-scan 52 53 There are some other applications like ``w_scan`` [#]_ that do a 54 blind scan, trying hard to find all possible channels, but 55 those consumes a large amount of time to run. 56 57 .. [#] https://www.linuxtv.org/wiki/index.php/W_scan 58 59 Also, some applications like ``kaffeine`` have their own code 60 to scan for services. So, you don't need to use an external 61 application to obtain such list. 62 63 Most of such tools need a file containing a list of channel 64 transponders available on your area. So, LinuxTV developers 65 maintain tables of Digital TV channel transponders, receiving 66 patches from the community to keep them updated. 67 68 This list is hosted at: 69 70 https://git.linuxtv.org/dtv-scan-tables.git 71 72 And packaged on several distributions. 73 74 Kaffeine has some blind scan support for some terrestrial standards. 75 It also relies on DTV scan tables, although it contains a copy 76 of it internally (and, if requested by the user, it will download 77 newer versions of it). 78 79 If you are lucky you can just use one of the supplied channel 80 transponders. If not, you may need to seek for such info at 81 the Internet and create a new file. There are several sites with 82 contains physical channel lists. For cable and satellite, usually 83 knowing how to tune into a single channel is enough for the 84 scanning tool to identify the other channels. On some places, 85 this could also work for terrestrial transmissions. 86 87 Once you have a transponders list, you need to generate a services 88 list with a tool like ``dvbv5-scan``. 89 90 Almost all modern Digital TV cards don't have built-in hardware 91 MPEG-decoders. So, it is up to the application to get a MPEG-TS 92 stream provided by the board, split it into audio, video and other 93 data and decode. 94 95 3. Which Digital TV applications exist? 96 97 Several media player applications are capable of tuning into 98 digital TV channels, including Kaffeine, Vlc, mplayer and MythTV. 99 100 Kaffeine aims to be very user-friendly, and it is maintained 101 by one of the Kernel driver developers. 102 103 A comprehensive list of those and other apps can be found at: 104 105 https://www.linuxtv.org/wiki/index.php/TV_Related_Software 106 107 Some of the most popular ones are linked below: 108 109 https://kde.org/applications/multimedia/org.kde.kaffeine 110 KDE media player, focused on Digital TV support 111 112 https://www.linuxtv.org/vdrwiki/index.php/Main_Page 113 Klaus Schmidinger's Video Disk Recorder 114 115 https://linuxtv.org/downloads and https://git.linuxtv.org/ 116 Digital TV and other media-related applications and 117 Kernel drivers. The ``v4l-utils`` package there contains 118 several swiss knife tools for using with Digital TV. 119 120 http://sourceforge.net/projects/dvbtools/ 121 Dave Chapman's dvbtools package, including 122 dvbstream and dvbtune 123 124 http://www.dbox2.info/ 125 LinuxDVB on the dBox2 126 127 http://www.tuxbox.org/ 128 the TuxBox CVS many interesting DVB applications and the dBox2 129 DVB source 130 131 http://www.nenie.org/misc/mpsys/ 132 MPSYS: a MPEG2 system library and tools 133 134 https://www.videolan.org/vlc/index.pt.html 135 Vlc 136 137 http://mplayerhq.hu/ 138 MPlayer 139 140 http://xine.sourceforge.net/ and http://xinehq.de/ 141 Xine 142 143 http://www.mythtv.org/ 144 MythTV - analog TV and digital TV PVR 145 146 http://dvbsnoop.sourceforge.net/ 147 DVB sniffer program to monitor, analyze, debug, dump 148 or view dvb/mpeg/dsm-cc/mhp stream information (TS, 149 PES, SECTION) 150 151 4. Can't get a signal tuned correctly 152 153 That could be due to a lot of problems. On my personal experience, 154 usually TV cards need stronger signals than TV sets, and are more 155 sensitive to noise. So, perhaps you just need a better antenna or 156 cabling. Yet, it could also be some hardware or driver issue. 157 158 For example, if you are using a Technotrend/Hauppauge DVB-C card 159 *without* analog module, you might have to use module parameter 160 adac=-1 (dvb-ttpci.o). 161 162 Please see the FAQ page at linuxtv.org, as it could contain some 163 valuable information: 164 165 https://www.linuxtv.org/wiki/index.php/FAQ_%26_Troubleshooting 166 167 If that doesn't work, check at the linux-media ML archives, to 168 see if someone else had a similar problem with your hardware 169 and/or digital TV service provider: 170 171 https://lore.kernel.org/linux-media/ 172 173 If none of this works, you can try sending an e-mail to the 174 linux-media ML and see if someone else could shed some light. 175 The e-mail is linux-media AT vger.kernel.org. 176 177 5. The dvb_net device doesn't give me any packets at all 178 179 Run ``tcpdump`` on the ``dvb0_0`` interface. This sets the interface 180 into promiscuous mode so it accepts any packets from the PID 181 you have configured with the ``dvbnet`` utility. Check if there 182 are any packets with the IP addr and MAC addr you have 183 configured with ``ifconfig`` or with ``ip addr``. 184 185 If ``tcpdump`` doesn't give you any output, check the statistics 186 which ``ifconfig`` or ``netstat -ni`` outputs. (Note: If the MAC 187 address is wrong, ``dvb_net`` won't get any input; thus you have to 188 run ``tcpdump`` before checking the statistics.) If there are no 189 packets at all then maybe the PID is wrong. If there are error packets, 190 then either the PID is wrong or the stream does not conform to 191 the MPE standard (EN 301 192, http://www.etsi.org/). You can 192 use e.g. ``dvbsnoop`` for debugging. 193 194 6. The ``dvb_net`` device doesn't give me any multicast packets 195 196 Check your routes if they include the multicast address range. 197 Additionally make sure that "source validation by reversed path 198 lookup" is disabled:: 199 200 $ "echo 0 > /proc/sys/net/ipv4/conf/dvb0/rp_filter" 201 202 7. What are all those modules that need to be loaded? 203 204 In order to make it more flexible and support different hardware 205 combinations, the media subsystem is written on a modular way. 206 207 So, besides the Digital TV hardware module for the main chipset, 208 it also needs to load a frontend driver, plus the Digital TV 209 core. If the board also has remote controller, it will also 210 need the remote controller core and the remote controller tables. 211 The same happens if the board has support for analog TV: the 212 core support for video4linux need to be loaded. 213 214 The actual module names are Linux-kernel version specific, as, 215 from time to time, things change, in order to make the media 216 support more flexible.
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