FAQ
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===
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.. note::
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This documentation is outdated. Please check at the DVB wiki
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at https://linuxtv.org/wiki for more updated info.
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Some very frequently asked questions about linuxtv-dvb
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1. The signal seems to die a few seconds after tuning.
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It's not a bug, it's a feature. Because the frontends have
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significant power requirements (and hence get very hot), they
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are powered down if they are unused (i.e. if the frontend device
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is closed). The dvb-core.o module parameter "dvb_shutdown_timeout"
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allow you to change the timeout (default 5 seconds). Setting the
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timeout to 0 disables the timeout feature.
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2. How can I watch TV?
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The driver distribution includes some simple utilities which
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are mainly intended for testing and to demonstrate how the
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DVB API works.
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Depending on whether you have a DVB-S, DVB-C or DVB-T card, use
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apps/szap/szap, czap or tzap. You must supply a channel list
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in ~/.[sct]zap/channels.conf. If you are lucky you can just copy
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one of the supplied channel lists, or you can create a new one
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by running apps/scan/scan. If you run scan on an unknown network
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you might have to supply some start data in apps/scan/initial.h.
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If you have a card with a built-in hardware MPEG-decoder the
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drivers create a video4linux device (/dev/v4l/video0) which
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you can use to watch TV with any v4l application. xawtv is known
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to work. Note that you cannot change channels with xawtv, you
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have to zap using [sct]zap. If you want a nice application for
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TV watching and record/playback, have a look at VDR.
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If your card does not have a hardware MPEG decoder you need
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a software MPEG decoder. Mplayer or xine are known to work.
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Newsflash: MythTV also has DVB support now.
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Note: Only very recent versions of Mplayer and xine can decode.
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MPEG2 transport streams (TS) directly. Then, run
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'[sct]zap channelname -r' in one xterm, and keep it running,
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and start 'mplayer - < /dev/dvb/adapter0/dvr0' or
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'xine stdin://mpeg2 < /dev/dvb/adapter0/dvr0' in a second xterm.
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That's all far from perfect, but it seems no one has written
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a nice DVB application which includes a builtin software MPEG
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decoder yet.
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Newsflash: Newest xine directly supports DVB. Just copy your
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channels.conf to ~/.xine and start 'xine dvb://', or select
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the DVB button in the xine GUI. Channel switching works using the
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numpad pgup/pgdown (NP9 / NP3) keys to scroll through the channel osd
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menu and pressing numpad-enter to switch to the selected channel.
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Note: Older versions of xine and mplayer understand MPEG program
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streams (PS) only, and can be used in conjunction with the
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ts2ps tool from the Metzler Brother's dvb-mpegtools package.
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3. Which other DVB applications exist?
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http://www.cadsoft.de/people/kls/vdr/
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Klaus Schmidinger's Video Disk Recorder
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http://www.metzlerbros.org/dvb/
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Metzler Bros. DVB development; alternate drivers and
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DVB utilities, include dvb-mpegtools and tuxzap.
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http://sourceforge.net/projects/dvbtools/
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Dave Chapman's dvbtools package, including
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dvbstream and dvbtune
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http://www.linuxdvb.tv/
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Henning Holtschneider's site with many interesting
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links and docs
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http://www.dbox2.info/
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LinuxDVB on the dBox2
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http://www.tuxbox.org/ and http://cvs.tuxbox.org/
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the TuxBox CVS many interesting DVB applications and the dBox2
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DVB source
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https://linuxtv.org/downloads
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DVB Swiss Army Knife library and utilities
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http://www.nenie.org/misc/mpsys/
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MPSYS: a MPEG2 system library and tools
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http://mplayerhq.hu/
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mplayer
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http://xine.sourceforge.net/ and http://xinehq.de/
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xine
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http://www.mythtv.org/
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MythTV - analog TV PVR, but now with DVB support, too
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(with software MPEG decode)
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http://dvbsnoop.sourceforge.net/
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DVB sniffer program to monitor, analyze, debug, dump
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or view dvb/mpeg/dsm-cc/mhp stream information (TS,
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PES, SECTION)
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4. Can't get a signal tuned correctly
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If you are using a Technotrend/Hauppauge DVB-C card *without* analog
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module, you might have to use module parameter adac=-1 (dvb-ttpci.o).
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5. The dvb_net device doesn't give me any packets at all
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Run tcpdump on the dvb0_0 interface. This sets the interface
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into promiscuous mode so it accepts any packets from the PID
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you have configured with the dvbnet utility. Check if there
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are any packets with the IP addr and MAC addr you have
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configured with ifconfig.
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If tcpdump doesn't give you any output, check the statistics
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which ifconfig outputs. (Note: If the MAC address is wrong,
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dvb_net won't get any input; thus you have to run tcpdump
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before checking the statistics.) If there are no packets at
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all then maybe the PID is wrong. If there are error packets,
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then either the PID is wrong or the stream does not conform to
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the MPE standard (EN 301 192, http://www.etsi.org/). You can
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use e.g. dvbsnoop for debugging.
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6. The dvb_net device doesn't give me any multicast packets
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Check your routes if they include the multicast address range.
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Additionally make sure that "source validation by reversed path
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lookup" is disabled:
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.. code-block:: none
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$ "echo 0 > /proc/sys/net/ipv4/conf/dvb0/rp_filter"
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7. What the hell are all those modules that need to be loaded?
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For a dvb-ttpci av7110 based full-featured card the following
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modules are loaded:
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- videodev: Video4Linux core module. This is the base module that
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gives you access to the "analog" tv picture of the av7110 mpeg2
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decoder.
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- v4l2-common: common functions for Video4Linux-2 drivers
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- v4l1-compat: backward compatibility layer for Video4Linux-1 legacy
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applications
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- dvb-core: DVB core module. This provides you with the
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/dev/dvb/adapter entries
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- saa7146: SAA7146 core driver. This is need to access any SAA7146
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based card in your system.
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- saa7146_vv: SAA7146 video and vbi functions. These are only needed
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for full-featured cards.
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- videobuf-dma-sg: capture helper module for the saa7146_vv driver. This
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one is responsible to handle capture buffers.
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- dvb-ttpci: The main driver for AV7110 based, full-featured
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DVB-S/C/T cards
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