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diff --git a/Documentation/admin-guide/media/faq.rst b/Documentation/admin-guide/media/faq.rst new file mode 100644 index 000000000..b63548b6f --- /dev/null +++ b/Documentation/admin-guide/media/faq.rst @@ -0,0 +1,216 @@ +.. 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. |