dvbsnoop - FAQ
Some questions and answers...
- Q: What is dvbsnoop?
dvbsnoop is a mpeg analyzer for
viewing/debugging mpeg or dvb based stream information, send via digital TV.
You may also use dvbsnoop to analyze mpeg compliant streams stored on
filesystem or other media... dvbsnoop analayzes and displays mpeg, dvb dsm-cc,
mhp, etc. data and structures in human readable form. dvbsnoop is not designed
to be fault tolerant - damaged or braindead stream information could lead to
- Q: What do I need to run dvbsnoop?
dvbsnoop runs on Linux -
supporting DVB API 1 or DVB API 3. (DVB API 3 is part of Linux kernel
To use the realtime sniffing mode you need a dvb card installed into
your system. To analyze a stream file, you just need Linux (or Cygwin for
- Q: Under what license is dvbsnoop?
dvbsnoop is published
- Q: May I re-use dvbsnoop code or ideas for my own
dvbsnoop is published under "GPL". So yes, you may recycle
dvbsnoop code, if you are publishing your project under GPL, too. If you are
using dvbsnoop (basics, ideas, code), please place a link/note to the dvbsnoop
homepage in your project.
- Q: What is DVB and digital TV?
Have a look at
Google is very helpfull for
- Q: What features does dvbsnoop provide?
Have a look at the
- Q: Is there a BBS or newsgroup/maillist to ask
Well, you might use the
linuxtv maillinglist (or
post a question to the tuxbox forum
(German BBS, but you may also post questions in English).)..
- Q: I found a bug, what to do?
Interaction between standards
organizations (ETSI, ITU, ISO, ...) and also between standards itself sometimes
is very complex, especially when standards are enhanced or collide with other
drafts. So bugs are very likely (also programming bugs...). Due to missing or
proper test streams, some features are implemented without possible real life
testing... Please report any bug or odd behavior.
- Q: How do I know the PIDs to sniff on?
The PAT section
("dvbsnoop -nph 0x01") provides the necessary information. Use program PIDs in
the PAT to decode the PMT section.
To see if there are any "hidden" PIDs,
use "dvbsnoop -s pidscan".
- Q: How do I tune into a frequency with dvbsnoop?
doesn't do tuning. It's only designed to sniff...
Use dvbtune, or a GUI like
dbox2's "Neutrino" to tune into a transponder or frequency...
- Q: Why can't I snoop the PID 0x1FFF?
PID 0x1FFF is a NULL
packet, used for stuffing. The availablity of this PID depends on the firmware
(ucodes) of your dvb hardware.
- Q: Why can't I snoop some PIDs?
Depending on your DVB card
firmware or driver, a PID which is already occupied by another process may not
be available to dvbsnoop. In this case close all dvb applications (TV-,
- Q: Can I snoop multiple PIDs?
Currently not (DVB-API 1 and
DVB-API 3). But there is a workaround: depending on your DVB hardware you may
save a complete transport stream (raw binary data) or a multiple pid transport
stream as file. You can analyze this transport stream using "dvbsnoop -s ts
-tssubdecode -if filename ..."
- Q: Can dvbsnoop "follow" PIDs?
Yes. Use the option
"-spiderpid". This will enable dvbsnoop to recursivly follow PIDs. Use also
option "-n <count>" to limit PID read cycles...
- Q: Why can't I see any data analyzed by dvbsnoop?
tune into a valid transponder/frequency containing a DVB stream? Use dvbtune,
szap, VDR, Neutrino, Enigma or any other tool to tune to a DVB service
(program)... Use "dvbsnoop -signal" to check if you are tuned and locked into a
transponder and are in-sync.
- Q: What to do on "read error , buffer overflow"?
data stream on the selected PID is too fast for dvbsnoop to decode. Packets are
lost. The reason for this might be high PID bandwidth, slow cpu (e.g. a set top
box - PCs should have sufficient cpu power), or output is sent to a "slow"
terminal (e.g. via network connection). To avoid this, save the binary stream
to file (option -b) and analyze the stream file. If the buffer overlow still
consists while saving the stream to a file, try to save the stream to a fast
media (e.g. virtual disk/ram disk, - on many systems /tmp might be such a ram
As of version 1.3.69 you might use the command line
option "-buffersize xxxx" to set a larger demux buffersize. Size will be given
in KBytes (see usage description or feature list). dvbsnoop's default
buffersize is 256 KBytes.
- Q: I get strange output on SECTIONs...
Use the option -crc
to enforce valid data. If a packet is delivered in sync to dvbsnoop, depends on
your DVB hardware/firmware. Also I observed that some firmware is clearing the
"scrambled" flag in TS packets, even if the transport stream or PES is
scrambled or wrongly descrambled (e.g. because you didn't subscribe to this
channel). dvbsnoop tries to analyze the stream as unscrambled stream (which
will lead to odd analyzing reports, of course).
- Q: Why is the command option "-sync" default and otherwise on
SECTIONs mode "-nocrc" default?
Unsynced TS or PES is useless, because
decoding will be completly gaga. On sections -nocrc is default, because there
might be private sections (e.g. ECM) or DSM-CC sections with no or different
CRC calculations (e.g. dsm-cc datagram). Software packet sync is default as if
1.4.10 and cannot be switched off.
- Q: Can I filter or customize the dvbsnoop output?
you may find many tools to tweak or filter the output of dvbsnoop, using
"grep", "nawk", "perl" or other stuff.. (e.g.: dvbsnoop -nph 0x00 | grep -i
- Q: Can I filter dvb input?
Currently you only can filter
dvb stream input, using PID filters on sections and when reading from a
transport stream file. But plans are to enhance input filter capabilities.
There are requests by different persons: positive/negative filter mask,
filtering "bytes" on specified packet positions, and also requests for really
enhanced content (output) filters.
- Q: Can dvbsnoop decode private/user defined
Basically: Yes. You have to tell dvbsnoop which provider's private
scope to use. (e.g. commandline option: "-privateprovider premiere.de"). If
dvbsnoop is aware of this provider, it will decode the private data
- Q: Can dvbsnoop decode the private data of provider/service
Try "dvbsnoop -help", to see if the provider name is listed. If
not, someone has to send information about the private descriptors and tables
to the author.
- Q: Does dvbsnoop analyze MPEG video/audio stream
dvbsnoop decodes meta information about dvb and mpeg streams,
but does not analyze video or audio stream content in detail, which is
described outside ISO/IEC 13818-1 / ITU H.222.0. There are other good tools
available to analyze e.g. mpeg video I-frame rates, compression rates, mpeg
vectors, etc.. You may use dvbsnoop in combination with these tools. Latest
versions of dvbsnoop are doing a rough ISO/IEC 13818-2 analyze of a mpeg
- Q: Can I use dvbsnoop to do remote sniffing of DVB over a
Yes! Using special network programs like netcat (nc) or
dvbstream/rtpdump, dvbsnoop may also be used to do remote sniffing and
decoding. Basically, you may use unix "pipes" to push a dvb data stream over a
network and use a receiving program piping the data stream to dvbsnoop. Please
see the examples on the man page.
- Q: Will there be a XML output option for dvbsnoop?
Planned... But it needs major rewriting of some dvbsnoop routines and
- Q: Why is dvbsnoop command line based (pure text
You can use some easy perl-/shellscripts and tools like
GNU-PLOT or MRTG to create fancy graphics from dvbsnoop output (e.g. bitrate
figures, pid usage, etc.). For post-processing dvbsnoop output, you may use the
full range of unix tools and scripting languages (grep, perl, python, mrtg,
Also you might review the dvbsnoop output - saved to a file
- with a simple text editor and search for certain information in the stream.
Basically said: command line based programs offers you a whole punch of
postprocessing possibilites - e.g. for expert usage and data post
- Q: Will there be a graphical interface for dvbsnoop?
planned. But when XML output is implemented, there might be some future options
the implement an GUI-Addon.
- Q: Will there be a Windows port?
Currently no plans,
because you would need the DVB-API on Windows (One of the major problem on
Windows is: there is no standard api for dvb devices...).
But you may use
dvbsnoop as offline analyzer (option: -if filename) using e.g. CYGWIN. CYGWIN
based dvbsnoop will run in a commandline window (cmd.exe) or in an CYWIN
- Q: Can I use dvbsnoop without DVB cards installed?
can. But without dvb reception hardware, you will not able to do realtime
sniffing of the dvb traffic, of course.
But you may use dvbsnoop as offline
analyzer (option: dvbsnoop -if filename).
- Q: Future development of dvbsnoop?
I'm also involved in
other projects and too bad for my software projects: there is also a "real"
So, future development of dvbsnoop depends on my sparetime for
But if you are interrested in enhancing dvbsnoop, any help is