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+.. SPDX-License-Identifier: GPL-2.0
+
+FAQ
+===
+
+.. note::
+
+ 1. With Digital TV, a single physical channel may have different
+ contents inside it. The specs call each one as a *service*.
+ This is what a TV user would call "channel". So, in order to
+ avoid confusion, we're calling *transponders* as the physical
+ channel on this FAQ, and *services* for the logical channel.
+ 2. The LinuxTV community maintains some Wiki pages with contain
+ a lot of information related to the media subsystem. If you
+ don't find an answer for your needs here, it is likely that
+ you'll be able to get something useful there. It is hosted
+ at:
+
+ https://www.linuxtv.org/wiki/
+
+Some very frequently asked questions about Linux Digital TV support
+
+1. The signal seems to die a few seconds after tuning.
+
+ It's not a bug, it's a feature. Because the frontends have
+ significant power requirements (and hence get very hot), they
+ are powered down if they are unused (i.e. if the frontend device
+ is closed). The ``dvb-core`` module parameter ``dvb_shutdown_timeout``
+ allow you to change the timeout (default 5 seconds). Setting the
+ timeout to 0 disables the timeout feature.
+
+2. How can I watch TV?
+
+ Together with the Linux Kernel, the Digital TV developers support
+ some simple utilities which are mainly intended for testing
+ and to demonstrate how the DVB API works. This is called DVB v5
+ tools and are grouped together with the ``v4l-utils`` git repository:
+
+ https://git.linuxtv.org/v4l-utils.git/
+
+ You can find more information at the LinuxTV wiki:
+
+ https://www.linuxtv.org/wiki/index.php/DVBv5_Tools
+
+ The first step is to get a list of services that are transmitted.
+
+ This is done by using several existing tools. You can use
+ for example the ``dvbv5-scan`` tool. You can find more information
+ about it at:
+
+ https://www.linuxtv.org/wiki/index.php/Dvbv5-scan
+
+ There are some other applications like ``w_scan`` [#]_ that do a
+ blind scan, trying hard to find all possible channels, but
+ those consumes a large amount of time to run.
+
+ .. [#] https://www.linuxtv.org/wiki/index.php/W_scan
+
+ Also, some applications like ``kaffeine`` have their own code
+ to scan for services. So, you don't need to use an external
+ application to obtain such list.
+
+ Most of such tools need a file containing a list of channel
+ transponders available on your area. So, LinuxTV developers
+ maintain tables of Digital TV channel transponders, receiving
+ patches from the community to keep them updated.
+
+ This list is hosted at:
+
+ https://git.linuxtv.org/dtv-scan-tables.git
+
+ And packaged on several distributions.
+
+ Kaffeine has some blind scan support for some terrestrial standards.
+ It also relies on DTV scan tables, although it contains a copy
+ of it internally (and, if requested by the user, it will download
+ newer versions of it).
+
+ If you are lucky you can just use one of the supplied channel
+ transponders. If not, you may need to seek for such info at
+ the Internet and create a new file. There are several sites with
+ contains physical channel lists. For cable and satellite, usually
+ knowing how to tune into a single channel is enough for the
+ scanning tool to identify the other channels. On some places,
+ this could also work for terrestrial transmissions.
+
+ Once you have a transponders list, you need to generate a services
+ list with a tool like ``dvbv5-scan``.
+
+ Almost all modern Digital TV cards don't have built-in hardware
+ MPEG-decoders. So, it is up to the application to get a MPEG-TS
+ stream provided by the board, split it into audio, video and other
+ data and decode.
+
+3. Which Digital TV applications exist?
+
+ Several media player applications are capable of tuning into
+ digital TV channels, including Kaffeine, Vlc, mplayer and MythTV.
+
+ Kaffeine aims to be very user-friendly, and it is maintained
+ by one of the Kernel driver developers.
+
+ A comprehensive list of those and other apps can be found at:
+
+ https://www.linuxtv.org/wiki/index.php/TV_Related_Software
+
+ Some of the most popular ones are linked below:
+
+ https://kde.org/applications/multimedia/org.kde.kaffeine
+ KDE media player, focused on Digital TV support
+
+ https://www.linuxtv.org/vdrwiki/index.php/Main_Page
+ Klaus Schmidinger's Video Disk Recorder
+
+ https://linuxtv.org/downloads and https://git.linuxtv.org/
+ Digital TV and other media-related applications and
+ Kernel drivers. The ``v4l-utils`` package there contains
+ several swiss knife tools for using with Digital TV.
+
+ http://sourceforge.net/projects/dvbtools/
+ Dave Chapman's dvbtools package, including
+ dvbstream and dvbtune
+
+ http://www.dbox2.info/
+ LinuxDVB on the dBox2
+
+ http://www.tuxbox.org/
+ the TuxBox CVS many interesting DVB applications and the dBox2
+ DVB source
+
+ http://www.nenie.org/misc/mpsys/
+ MPSYS: a MPEG2 system library and tools
+
+ https://www.videolan.org/vlc/index.pt.html
+ Vlc
+
+ http://mplayerhq.hu/
+ MPlayer
+
+ http://xine.sourceforge.net/ and http://xinehq.de/
+ Xine
+
+ http://www.mythtv.org/
+ MythTV - analog TV and digital TV PVR
+
+ http://dvbsnoop.sourceforge.net/
+ DVB sniffer program to monitor, analyze, debug, dump
+ or view dvb/mpeg/dsm-cc/mhp stream information (TS,
+ PES, SECTION)
+
+4. Can't get a signal tuned correctly
+
+ That could be due to a lot of problems. On my personal experience,
+ usually TV cards need stronger signals than TV sets, and are more
+ sensitive to noise. So, perhaps you just need a better antenna or
+ cabling. Yet, it could also be some hardware or driver issue.
+
+ For example, if you are using a Technotrend/Hauppauge DVB-C card
+ *without* analog module, you might have to use module parameter
+ adac=-1 (dvb-ttpci.o).
+
+ Please see the FAQ page at linuxtv.org, as it could contain some
+ valuable information:
+
+ https://www.linuxtv.org/wiki/index.php/FAQ_%26_Troubleshooting
+
+ If that doesn't work, check at the linux-media ML archives, to
+ see if someone else had a similar problem with your hardware
+ and/or digital TV service provider:
+
+ https://lore.kernel.org/linux-media/
+
+ If none of this works, you can try sending an e-mail to the
+ linux-media ML and see if someone else could shed some light.
+ The e-mail is linux-media AT vger.kernel.org.
+
+5. The dvb_net device doesn't give me any packets at all
+
+ Run ``tcpdump`` on the ``dvb0_0`` interface. This sets the interface
+ into promiscuous mode so it accepts any packets from the PID
+ you have configured with the ``dvbnet`` utility. Check if there
+ are any packets with the IP addr and MAC addr you have
+ configured with ``ifconfig`` or with ``ip addr``.
+
+ If ``tcpdump`` doesn't give you any output, check the statistics
+ which ``ifconfig`` or ``netstat -ni`` outputs. (Note: If the MAC
+ address is wrong, ``dvb_net`` won't get any input; thus you have to
+ run ``tcpdump`` before checking the statistics.) If there are no
+ packets at all then maybe the PID is wrong. If there are error packets,
+ then either the PID is wrong or the stream does not conform to
+ the MPE standard (EN 301 192, http://www.etsi.org/). You can
+ use e.g. ``dvbsnoop`` for debugging.
+
+6. The ``dvb_net`` device doesn't give me any multicast packets
+
+ Check your routes if they include the multicast address range.
+ Additionally make sure that "source validation by reversed path
+ lookup" is disabled::
+
+ $ "echo 0 > /proc/sys/net/ipv4/conf/dvb0/rp_filter"
+
+7. What are all those modules that need to be loaded?
+
+ In order to make it more flexible and support different hardware
+ combinations, the media subsystem is written on a modular way.
+
+ So, besides the Digital TV hardware module for the main chipset,
+ it also needs to load a frontend driver, plus the Digital TV
+ core. If the board also has remote controller, it will also
+ need the remote controller core and the remote controller tables.
+ The same happens if the board has support for analog TV: the
+ core support for video4linux need to be loaded.
+
+ The actual module names are Linux-kernel version specific, as,
+ from time to time, things change, in order to make the media
+ support more flexible.