Difference between revisions of "Testing your DVB device"

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This page provides a few suggestions on how to test that a properly installed DVB device<sup>'''1'''</sup> is functioning correctly. The command line steps described are also indispensable for quick setup and no frills viewing with DVB hardware under Linux.
''' First steps with a budget DVB card in Linux - Getting Started Howto '''
 
   
  +
{{Note|<sup>'''1'''</sup> In other words, this article assumes that you have already both:
This page gives you some suggestions how to test your DVB card installed on your system. It won't tell you greatly featured software to ''watch'' TV, neither how to install your specific hardware that you have (see the other pages of this wiki for that). But it will tell you software that will run in command-line mode (shell only, actually) and even on very modest software. And '''it won't take long''' to do these tests here.
 
  +
:* physically installed the device into, or attached it to, your system (refer to the manufacturer's instructions for such details) and
  +
:* installed the drivers for your hardware and have the proper modules loaded (see "[[How to Obtain, Build and Install V4L-DVB Device Drivers]]" for such details)<br>
  +
:Having completed such tasks, you should at least now have a ''/dev/dvb/adapter0/'' directory. (If you have additional DVB devices installed in your system, they will be assigned an increased ''adapter'' number accordingly).}}<br>
   
  +
== Comparison of DTV testing applications ==
Run all stuff on this page as root, for the beginning. Here, we assume you already installed the driver for your hardware and loaded the modules, i.e. you should have a non empty directory
 
/dev/dvb/adapter0/
 
   
  +
The following table lists the main features of the different command line DTV testing utilities. For specific information on usage, have a look at its specific wiki article.
  +
<br>
  +
  +
{| border=1 cellpadding=10 cellspacing=0 valign="top"
  +
|- bgcolor=#efefef valign="top"
  +
|'''feature \ utility'''
  +
|'''dvb-apps [[zap]]'''
  +
|'''[[Szap-s2]]'''
  +
|'''[[dvbtune]]''' and '''[[dvbstream]]''' from dvbtools
  +
|'''[[dvbsnoop]]'''
  +
|-
  +
|'''download'''
  +
|[http://linuxtv.org/hg/dvb-apps linuxtv.org/hg/dvb-apps]
  +
|[http://mercurial.intuxication.org/hg/szap-s2 http://mercurial.intuxication.org/hg/szap-s2]
  +
|[http://sourceforge.net/projects/dvbtools http://sourceforge.net/projects/dvbtools]
  +
|[http://dvbsnoop.sourceforge.net http://dvbsnoop.sourceforge.net]
  +
|-
  +
|'''supported delivery systems'''
  +
|DVB-S, DVB-C, DVB-T, ATSC
  +
|DVB-S, DVB-S2
  +
|DVB-S, DVB-C, DVB-T
  +
|DVB-S, DVB-C, DVB-T
  +
|-
  +
|'''comments'''
  +
|useful for debugging, but inappropriate for newer delivery systems.
  +
|satellite only.
  +
|outdated.
  +
|outdated, but still the most powerful tool for reading and parsing DVB tables. Hint: use another tool to tune and dvbsnoop in parallel to read data. Unfortunally, dvbsnoop misses support for newer descriptors.
  +
|-
  +
|'''supported features'''
  +
|
  +
* channel scan for legacy systems
  +
* tuning
  +
* streaming
  +
* show signal strength/lock
  +
|
  +
* tuning
  +
|
  +
* tuning (dvbtune)
  +
* streaming (dvbstream)
  +
|
  +
* analyse DVB tables and MPEG streams
  +
* show signal strength/lock
  +
|}
  +
  +
  +
  +
== Using dvb-apps ==
  +
  +
'''1. Obtain the dvb-apps package'''<BR>
  +
See the [[LinuxTV dvb-apps]] article for details on how to obtain the package. The dvb-apps package contains several useful tools.
  +
  +
'''2. Scan for the channels you can receive''' <BR>
  +
Refer to the [[Scan|(dvb)scan]] article for details of how to perform this step. Once familiar with the content of that article, you will recognize that this step can be summarized (in general form) by:
  +
mkdir ~/.''{a,c,s,t}''zap
  +
(dvb)scan /''path_to_the_initial_scan_file'' > ~/.''{a,c,s,t}''zap/channels.conf
  +
  +
Note that you may have both a program <code>scan</code> and <code>dvbscan</code> installed on your system, and only one of them may work.
  +
  +
'''3. Tune a frequency and program'''<BR>
  +
Refer to the [[Zap|zap]] article for details of how to perform this step. Once familiar with the content of that article, you will recognize that this step can be summarized (in general form) by:
  +
$ /usr/bin/''{a,c,s,t}''zap -r -c ~/.''{a,c,s,t}''zap/channels.conf "''channel name''"
  +
where, respective to the type of transmission, [[azap]] is used for [[ATSC]], [[czap]] for [[DVB-C]], [[szap]] for [[DVB-S]] and [[tzap]] for [[DVB-T]].
  +
Make sure you do not overlook the -r option for setting up the /dev/dvb/adapterX/dvr0 interface. Otherwise, you cannot record data from dvr0.
  +
  +
{{Note|If (dvb)scan was unable to correctly resolve the audio or video [[PID]] values for a channel in the previous step, a manual adjustment to the channels.conf file will be necessary to correct any inaccurately written PID(s) information. Such occurrences tend to be rare, but nonetheless, they do happen -- often, one only becomes aware of a problem with the PID values after unsuccessful attempts to tune a particular channel. The correct values may be determined using using [[dvbtraffic]] (see step '''4.c)''' below). Another method for finding correct PID values for a channel is also outlined in the section entitled "[[Scan#A_word_about_dvbscan_and_audio_streams|A word about dvbscan and audio streams]]".}}
  +
  +
  +
'''4. After you've tuned a frequency and program'''<BR>
  +
  +
'''a)''' You could now start up your simple TV watching application and decode the stream you have tuned.
  +
  +
For example, while keeping ''{a,c,s,t}''zap running in the first console shell, open up another console and run
  +
mplayer /dev/dvb/adapter0/dvr0 <options>
  +
If you have more than one dvb device installed in your system, then you will have to pass the correct ''adaptor'' number. See the [[MPlayer#Usage_with_more_complex_DVB_device_configurations|MPlayer article]] for some further information, as well as the MPlayer man page (i.e. in a console run "man mplayer") for a lengthy list of options.
  +
  +
  +
'''b)''' Or, you could now start up a datastreamer
  +
  +
  +
'''c)''' Or, alternatively, you may want to see some statistics of what's coming in for each channel and PID.
  +
Example:
  +
$ /usr/bin/dvbtraffic
  +
  +
dvbtraffic which will access the [[Device nodes and character devices#DVB character devices|/dev/dvb/adapter0/dvr0 logical device]].
  +
An example of output from dvbtraffic is:
  +
  +
0000 24 p/s 4 kb/s 37 kbit
  +
0010 20 p/s 3 kb/s 31 kbit
  +
0011 20 p/s 3 kb/s 31 kbit
  +
0012 70 p/s 12 kb/s 106 kbit
  +
0015 1 p/s 0 kb/s 2 kbit
  +
0080 26 p/s 4 kb/s 40 kbit
  +
0082 26 p/s 4 kb/s 40 kbit
  +
0087 25 p/s 4 kb/s 38 kbit
  +
0100 25 p/s 4 kb/s 38 kbit
  +
0101 25 p/s 4 kb/s 38 kbit
  +
0102 24 p/s 4 kb/s 37 kbit
  +
<span style="color:#ff0000">0200</span> 8567 p/s 1572 kb/s 12885 kbit <span style="color:#ff0000"> <--- </span>
  +
0201 4708 p/s 864 kb/s 7081 kbit
  +
0205 926 p/s 170 kb/s 1392 kbit
  +
0240 49 p/s 8 kb/s 75 kbit
  +
0241 49 p/s 8 kb/s 75 kbit
  +
<span style="color:#ff0000">028b</span> 261 p/s 47 kb/s 393 kbit <span style="color:#ff0000"> <--- </span>
  +
0294 174 p/s 31 kb/s 262 kbit
  +
0295 130 p/s 23 kb/s 196 kbit
  +
02bc 75 p/s 13 kb/s 113 kbit
  +
1fff 87 p/s 15 kb/s 131 kbit
  +
2000 15329 p/s 2814 kb/s 23055 kbit
  +
-PID--FREQ-----BANDWIDTH-BANDWIDTH-
  +
  +
In this case, for the frequency that has been tuned, PID 0x0200 is for the video stream of an HDTV channel and PID 0x028b is for the associated audio stream (both of these have been highlighted in red in the above output for easier visual identification). These PID values presented by dvbtraffuc are in hexadecimal form and need to be converted to their decimal representation (respectively, 512 and 651) for use in a channel.conf file.<BR>
  +
  +
This is the line you would create in the file "channel.conf" given the PID values from the dvbtraffic output shown above:
  +
  +
Nine High Def Gold Coast:746625000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:<span style="color:#ff0000">512</span>:<span style="color:#ff0000">651</span>:1138
   
== First steps using DVBtools ==
 
The [[dvb-utils]] have many useful tools with great functionality. Install it, e.g. with debian:
 
# apt-get install dvb-utils
 
For the beginning, do something like this: Adopt this line for your place
 
scan /usr/share/doc/dvb-utils/examples/scan/dvb-t/uk-Oxford
 
and you'll see what's coming in to the card. If that makes sense, repeat it like this:
 
mkdir /root/.tzap
 
scan /usr/share/doc/dvb-utils/examples/scan/dvb-t/uk-Oxford >/root/.tzap/channel.conf
 
This trys to find the programs it takes from the initial uk-Oxford configuration (or whatever your place is). Note that the screen output you get into your shell doesn't really say if you can recieve something or not. The file it creates is more important; it has lines like:
 
BBC ONE:578000000:INVERSION_AUTO:BANDWIDTH_8_MHZ:FEC_3_4:FEC_3_4:QAM_16:TRANSMISSION_MODE_2K:GUARD_INTERVAL_1_32:HIERARCHY_NONE:600:601:4171
 
which says that the stream on frequency 578000000 Hz has the two PIDs 600 and 601 for the video and audio stream of BBC ONE. This file with the data for your TV-programs, if stored into the place as above, can be used by the zapper tzap, e.g.:
 
tzap Bloomberg -- Bloomberg
 
That tunes automatically both channel and PIDs for video and audio to the channel called "Bloomberg -- Bloomberg". You could now start up your TV watching application or datastreamer. But we want to see some nice statistics of what's coming in for each channel and PID:
 
dvbtraffic
 
 
And finally
 
And finally
dvbdata
+
dvbdate
Note: if your signal is too weak and you recieve '''only some''' channels, the way to find out which is to look in the channel.conf file that you just created. If for a program the two PIDs (third and second last number in line) are 0, you can't recieve it. If the first PID is 0 and the second is not 0, then it's probably a radio channel.
 
   
  +
== Using dvbsnoop ==
  +
If the testing steps in the dvb-apps section above work fine, you can jump over this section here. On the other hand, [[dvbsnoop]] is a small, down-to-earth utility that is very handy for debugging and also seeing what is occuring with a dvb device (i.e. tuning works? data coming in? signal strong enough?).
   
== First steps using dvbsnoop ==
+
'''1. Obtain the dvbsnoop package'''<BR>
  +
See the [[dvbsnoop]] article for details on how to obtain the package.
As an alternative, [[dvbsnoop]] is a small, down-to-earth util. As it's very hardware-near, it's very handy for debugging and seeing what's going on with the card (tuning works? data coming in? signal strong enough?). (On the other side, if all in the section above works fine, you can jump over this section here.)
 
  +
Install it, e.g. with debian:
 
# apt-get install dvbsnoop
+
'''2. Testing with dvbsnoop'''<BR>
Then try things like
+
Try things like
 
dvbsnoop -help
 
dvbsnoop -help
 
dvbsnoop -s pidscan
 
dvbsnoop -s pidscan
Line 36: Line 141:
 
dvbsnoop -s bandwidth <PID>
 
dvbsnoop -s bandwidth <PID>
 
dvbsnoop <PID>
 
dvbsnoop <PID>
The latter will spit out a lot of hexdumps - at least you recieve '''something''' ;-)
+
The latter will spit out a lot of hexdumps - at least you receive '''something''' ;-)
  +
  +
== Save a TV program to your hard drive ==
  +
The handy thing about digital TV is, it comes in as a digital stream that you can save right away to your harddisk without any changes necessary to it. Therefore, hardly any CPU resources are needed -- just a lot of HD space (few GB per hour as the stream is MPEG-2 which is not as compressed as, for example, DivX/MPEG-4; it's even more as mostly one [[transport stream]] contains multiple [[PID]]s). There are several ways to do this. For example:
  +
  +
'''a) Using the combination of {a,c,s,t}zap and cat'ing the logical dvr device to save a program stream to disk''' <BR>
  +
If you have a channel tuned with {a,c,s,t}zap (and note that you MUST also be using the -r parameter to set up the logical dvr device in order for the following to work; see [[Zap]] for detail), open up another shell console and run (as root user):
  +
cat /dev/dvb/adapter0/dvr0 > <filename>
  +
The result is that particular program stream will be written to disk, and you should be able to play it back at any later time with your favourite media player.
   
  +
'''b) Using the combination of {a,c,s,t}zap and test_dvr to save an entire transport stream to disk'''
   
== Save a TV program to harddisk with dvbstream ==
 
The handy thing about digital TV is, it comes in as a digital stream that you can save right away to your harddisk without any changes necessary to it. Therefore, hardly any CPU resources are needed -- just a lot of HD space (few GB per hour as the stream is MPEG-2 which is not as compressed as for example DivX/MPEG-4). A good program that can do that (and more) is [[dvbstream]].
 
   
  +
'''c) Saving to disk with dvbstream''' <BR>
Install it, e.g. with debian:
 
  +
[[dvbstream]] is a useful program that, amongst other things, can save a DVB stream to disk.
# apt-get install dvbstream
 
  +
'''Method 1''': First tune into a channel, as described above in the zapping step, and then next have dvbstream save a particular stream to file. For example:
  +
tzap 'BBC ONE'
  +
dvbstream 600 601 -o > bbc1.mpeg
  +
The values "600 and 601" are, respectively, the video and audio [[PID]]s for the channel BBC ONE, as derived from the channels.conf file. So this is why it's important that you have your personal channels.conf file with all the PIDs so you can look them up.
   
  +
'''Method 2''': Alternatively, instead of using a combination of *zap and dvbstream, you can use dvbstream alone provided you pass which frequency to tune and list the correct PIDs. For example:
Let's tune into a channel with tzap as described above, and then you can just save the stream into a file like this:
 
tzap BBC ONE
 
dvbstream 600 601 -o >BBC1.mpeg
 
So this is why it's important that you have your personal channels.conf file with all the PIDs so you can look them up. Instead of using tzap you can do it all in one - tune the frequency and select the right PIDs:
 
 
dvbstream -f 578000 600 601 -o >bbc1.mpeg
 
dvbstream -f 578000 600 601 -o >bbc1.mpeg
   
Wait a few seconds and then press Ctrl+C to stop. You can open the MPEG file with players that play movie files (decode MPEG2), like mplayer, (g)xine or noatune.
+
Wait a few seconds and then press Ctrl+C to stop. You should then be able to open/playback the recorded file with any of your favourite media players (like Mplayer, (g)xine, noatune, etc. etc ) provided you have the correct decoders installed on your system (which, in general regards to DVB transmissions, are usually going to be MPEG-2, but can now also be MPEG-4).
   
If the file is rather small, e.g. smaller than 1 MB after a minute of recording, then you can't recieve this TV channel - maybe the reception is bad (too weak antenna signal) - or maybe your card's frequency is not tuned for the right sender? Watch out, some PIDs come up a few times (but for different frequencies).
+
If the file is rather small, e.g. smaller than 1 MB after a minute of recording, then you can't receive this TV channel - maybe the reception is bad (too weak antenna signal) - or maybe your card's frequency is not tuned for the right sender? Watch out, some PIDs come up a few times (but for different frequencies).
   
This might not be what you wanna do every day (unless you only watch BBC1 or you can easily memorise all your channels with their two PIDs) - but it's very fast and easy to do these steps, e.g. for a test.
+
This might not be what you wanna do every day (unless you only watch BBC1 or you can easily memorise all your channels with their two PIDs) - but it's very fast and easy to do these steps for testing purposes.
   
  +
==Next steps - More feature rich viewing software ==
  +
It is not the intention of this page to provide a detailed description of the use of DVB hardware with more complex Linux viewing software applications. Suffice it to say that you will have some choice. For example:
  +
* for light TV watching with a DVB device under Linux, [[MPlayer]], [[Xine]], [[Kaffeine]], [[Klear]] and a few others are often selected.
  +
* alternatively, for "Media Center" type applications, the usual first suspects are [[Freevo]], [[MythTV]], and [[VDR]], but there are others as well
  +
* you could use the streaming facilities of [[dvbstream]], [[Mumudvb]], dvblast, etc... and then watch the MPEG-2 stream (even possible on a different computer) with programs like Xine, MPlayer etc.
   
  +
For some further inspiration on what's possible with more advanced software usage see:
==More Software - next steps ==
 
  +
* the [[TV Related Software]] page, a commented software list, and
You have a lot of choice. Obviously, don't use analog-TV or full-featured-cards software but use budget-DVB-software. Don't get yourself confused that bttv was analog-TV first - it's come a long way and now the form you use is DVB. So xawtv for example will '''not''' work -- you just don't have /dev/video0 (instead you have /dev/dvb/adapter0).
 
  +
* [[Example setups]]
   
[[Xine]] and [[VDR]] probably are the first choice for a DVB card. Keep in mind, the TwinhanDTV Ter is is a budget card, not a [[Full-featured Card]] so you have to install the [[VDR Software Decoder Plugin]] if you wanna use VDR for watching (good luck). Xine will work right away.
 
   
  +
---------
Alternatively, you could use [[dvbstream]] and then watch the MPEG-2 stream (even possible on a different computer) with programs like xine, mplayer etc.
 
   
  +
(note: you'll need to install the [[VDR Software Decoder Plugin]] if you want to use VDR for watching with a software decoding card).
   
  +
* Digital Video Broadcasting – A practical guide by Hugo Mills [http://www.carfax.org.uk/docs/DVB/]
== See also ==
 
  +
[[Category:Drivers]]
* [[Example setup]]s (for more complex, more advanced, more powerful and more comfortable systems)
 
  +
[[Category:Software]]
* [[Commented software list]]
 

Latest revision as of 14:30, 19 December 2015

This page provides a few suggestions on how to test that a properly installed DVB device1 is functioning correctly. The command line steps described are also indispensable for quick setup and no frills viewing with DVB hardware under Linux.

Note: 1 In other words, this article assumes that you have already both:
  • physically installed the device into, or attached it to, your system (refer to the manufacturer's instructions for such details) and
  • installed the drivers for your hardware and have the proper modules loaded (see "How to Obtain, Build and Install V4L-DVB Device Drivers" for such details)
Having completed such tasks, you should at least now have a /dev/dvb/adapter0/ directory. (If you have additional DVB devices installed in your system, they will be assigned an increased adapter number accordingly).


Comparison of DTV testing applications

The following table lists the main features of the different command line DTV testing utilities. For specific information on usage, have a look at its specific wiki article.

feature \ utility dvb-apps zap Szap-s2 dvbtune and dvbstream from dvbtools dvbsnoop
download linuxtv.org/hg/dvb-apps http://mercurial.intuxication.org/hg/szap-s2 http://sourceforge.net/projects/dvbtools http://dvbsnoop.sourceforge.net
supported delivery systems DVB-S, DVB-C, DVB-T, ATSC DVB-S, DVB-S2 DVB-S, DVB-C, DVB-T DVB-S, DVB-C, DVB-T
comments useful for debugging, but inappropriate for newer delivery systems. satellite only. outdated. outdated, but still the most powerful tool for reading and parsing DVB tables. Hint: use another tool to tune and dvbsnoop in parallel to read data. Unfortunally, dvbsnoop misses support for newer descriptors.
supported features
  • channel scan for legacy systems
  • tuning
  • streaming
  • show signal strength/lock
  • tuning
  • tuning (dvbtune)
  • streaming (dvbstream)
  • analyse DVB tables and MPEG streams
  • show signal strength/lock


Using dvb-apps

1. Obtain the dvb-apps package
See the LinuxTV dvb-apps article for details on how to obtain the package. The dvb-apps package contains several useful tools.

2. Scan for the channels you can receive
Refer to the (dvb)scan article for details of how to perform this step. Once familiar with the content of that article, you will recognize that this step can be summarized (in general form) by:

mkdir ~/.{a,c,s,t}zap
(dvb)scan /path_to_the_initial_scan_file > ~/.{a,c,s,t}zap/channels.conf

Note that you may have both a program scan and dvbscan installed on your system, and only one of them may work.

3. Tune a frequency and program
Refer to the zap article for details of how to perform this step. Once familiar with the content of that article, you will recognize that this step can be summarized (in general form) by:

$ /usr/bin/{a,c,s,t}zap  -r -c ~/.{a,c,s,t}zap/channels.conf "channel name"

where, respective to the type of transmission, azap is used for ATSC, czap for DVB-C, szap for DVB-S and tzap for DVB-T. Make sure you do not overlook the -r option for setting up the /dev/dvb/adapterX/dvr0 interface. Otherwise, you cannot record data from dvr0.

Note: If (dvb)scan was unable to correctly resolve the audio or video PID values for a channel in the previous step, a manual adjustment to the channels.conf file will be necessary to correct any inaccurately written PID(s) information. Such occurrences tend to be rare, but nonetheless, they do happen -- often, one only becomes aware of a problem with the PID values after unsuccessful attempts to tune a particular channel. The correct values may be determined using using dvbtraffic (see step 4.c) below). Another method for finding correct PID values for a channel is also outlined in the section entitled "A word about dvbscan and audio streams".


4. After you've tuned a frequency and program

a) You could now start up your simple TV watching application and decode the stream you have tuned.

For example, while keeping {a,c,s,t}zap running in the first console shell, open up another console and run

mplayer /dev/dvb/adapter0/dvr0 <options>

If you have more than one dvb device installed in your system, then you will have to pass the correct adaptor number. See the MPlayer article for some further information, as well as the MPlayer man page (i.e. in a console run "man mplayer") for a lengthy list of options.


b) Or, you could now start up a datastreamer


c) Or, alternatively, you may want to see some statistics of what's coming in for each channel and PID. Example:

 $ /usr/bin/dvbtraffic 

dvbtraffic which will access the /dev/dvb/adapter0/dvr0 logical device. An example of output from dvbtraffic is:

0000    24 p/s     4 kb/s    37 kbit
0010    20 p/s     3 kb/s    31 kbit
0011    20 p/s     3 kb/s    31 kbit
0012    70 p/s    12 kb/s   106 kbit
0015     1 p/s     0 kb/s     2 kbit
0080    26 p/s     4 kb/s    40 kbit
0082    26 p/s     4 kb/s    40 kbit
0087    25 p/s     4 kb/s    38 kbit
0100    25 p/s     4 kb/s    38 kbit
0101    25 p/s     4 kb/s    38 kbit
0102    24 p/s     4 kb/s    37 kbit
0200  8567 p/s  1572 kb/s 12885 kbit    <--- 
0201  4708 p/s   864 kb/s  7081 kbit
0205   926 p/s   170 kb/s  1392 kbit
0240    49 p/s     8 kb/s    75 kbit
0241    49 p/s     8 kb/s    75 kbit
028b   261 p/s    47 kb/s   393 kbit    <--- 
0294   174 p/s    31 kb/s   262 kbit
0295   130 p/s    23 kb/s   196 kbit
02bc    75 p/s    13 kb/s   113 kbit
1fff    87 p/s    15 kb/s   131 kbit
2000 15329 p/s  2814 kb/s 23055 kbit
-PID--FREQ-----BANDWIDTH-BANDWIDTH-

In this case, for the frequency that has been tuned, PID 0x0200 is for the video stream of an HDTV channel and PID 0x028b is for the associated audio stream (both of these have been highlighted in red in the above output for easier visual identification). These PID values presented by dvbtraffuc are in hexadecimal form and need to be converted to their decimal representation (respectively, 512 and 651) for use in a channel.conf file.

This is the line you would create in the file "channel.conf" given the PID values from the dvbtraffic output shown above:

Nine High Def Gold Coast:746625000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:651:1138

And finally

 dvbdate

Using dvbsnoop

If the testing steps in the dvb-apps section above work fine, you can jump over this section here. On the other hand, dvbsnoop is a small, down-to-earth utility that is very handy for debugging and also seeing what is occuring with a dvb device (i.e. tuning works? data coming in? signal strong enough?).

1. Obtain the dvbsnoop package
See the dvbsnoop article for details on how to obtain the package.

2. Testing with dvbsnoop
Try things like

 dvbsnoop -help
 dvbsnoop -s pidscan

This will give out a lot of numbers, but if you understand the system of DVB you should see if they make sense. Go for one of the PIDs (choose a right one which is a bit difficult as you don't know what they stand for unless you used the scan line above) and try:

 dvbsnoop -s bandwidth <PID>
 dvbsnoop <PID>

The latter will spit out a lot of hexdumps - at least you receive something ;-)

Save a TV program to your hard drive

The handy thing about digital TV is, it comes in as a digital stream that you can save right away to your harddisk without any changes necessary to it. Therefore, hardly any CPU resources are needed -- just a lot of HD space (few GB per hour as the stream is MPEG-2 which is not as compressed as, for example, DivX/MPEG-4; it's even more as mostly one transport stream contains multiple PIDs). There are several ways to do this. For example:

a) Using the combination of {a,c,s,t}zap and cat'ing the logical dvr device to save a program stream to disk
If you have a channel tuned with {a,c,s,t}zap (and note that you MUST also be using the -r parameter to set up the logical dvr device in order for the following to work; see Zap for detail), open up another shell console and run (as root user):

cat /dev/dvb/adapter0/dvr0 > <filename> 

The result is that particular program stream will be written to disk, and you should be able to play it back at any later time with your favourite media player.

b) Using the combination of {a,c,s,t}zap and test_dvr to save an entire transport stream to disk


c) Saving to disk with dvbstream
dvbstream is a useful program that, amongst other things, can save a DVB stream to disk. Method 1: First tune into a channel, as described above in the zapping step, and then next have dvbstream save a particular stream to file. For example:

 tzap 'BBC ONE'
 dvbstream 600 601 -o > bbc1.mpeg

The values "600 and 601" are, respectively, the video and audio PIDs for the channel BBC ONE, as derived from the channels.conf file. So this is why it's important that you have your personal channels.conf file with all the PIDs so you can look them up.

Method 2: Alternatively, instead of using a combination of *zap and dvbstream, you can use dvbstream alone provided you pass which frequency to tune and list the correct PIDs. For example:

 dvbstream -f 578000 600 601 -o >bbc1.mpeg

Wait a few seconds and then press Ctrl+C to stop. You should then be able to open/playback the recorded file with any of your favourite media players (like Mplayer, (g)xine, noatune, etc. etc ) provided you have the correct decoders installed on your system (which, in general regards to DVB transmissions, are usually going to be MPEG-2, but can now also be MPEG-4).

If the file is rather small, e.g. smaller than 1 MB after a minute of recording, then you can't receive this TV channel - maybe the reception is bad (too weak antenna signal) - or maybe your card's frequency is not tuned for the right sender? Watch out, some PIDs come up a few times (but for different frequencies).

This might not be what you wanna do every day (unless you only watch BBC1 or you can easily memorise all your channels with their two PIDs) - but it's very fast and easy to do these steps for testing purposes.

Next steps - More feature rich viewing software

It is not the intention of this page to provide a detailed description of the use of DVB hardware with more complex Linux viewing software applications. Suffice it to say that you will have some choice. For example:

  • for light TV watching with a DVB device under Linux, MPlayer, Xine, Kaffeine, Klear and a few others are often selected.
  • alternatively, for "Media Center" type applications, the usual first suspects are Freevo, MythTV, and VDR, but there are others as well
  • you could use the streaming facilities of dvbstream, Mumudvb, dvblast, etc... and then watch the MPEG-2 stream (even possible on a different computer) with programs like Xine, MPlayer etc.

For some further inspiration on what's possible with more advanced software usage see:



(note: you'll need to install the VDR Software Decoder Plugin if you want to use VDR for watching with a software decoding card).

  • Digital Video Broadcasting – A practical guide by Hugo Mills [1]