[linux-dvb] Streams recognized by dvbnet

Christian Prähauser cpraehaus at cosy.sbg.ac.at
Sun Oct 14 18:23:33 CEST 2007


Michael Harpe schrieb:
> I have been working on debugging reception of a datacast for a while now.
>
> I have determined that the data I am interested in is in PID 0x1af3. Here's
> what I get from a dvbsnoop pidscan...
>
> [...]
>
> The section ID is 0x3F (decimal 63) and as you can see it's ISO/IEC 13818-6
> reserved. The data is mostly ASCII text files and I can see them clearly in
> dvbsnoop dumps. The data is IP/UDP data. 
>
> Is this why I get no packets from dvbnet? 
>
>   
Hello Michael!

This section ID refers to so-called "DSM-CC Addressable Sections", which
are used in ATSC systems
for carrying (asynchronous) datagrams such as IP. Essentially, the
section format is the same as in Multiprotocol
Encapsulation (MPE) commonly used for IP-over-DVB, and implemented by
dvbnet. However, MPE datagram
sections have a table id of 0x3e, and the MPE dvbnet implementation
filters on that (among other things), which means
that it will (silently) discard other DSM-CC sections, like the one
mentioned above.

So without patching the code, you won't be able to receive the network
traffic with dvbnet.

Cheers,
Christian.

-- 
Christian Praehauser <cpraehaus at cosy.sbg.ac.at>
|| //\\//\\ || Multimedia Communications Group,
||//  \/  \\|| Department of Computer Sciences, University of Salzburg
http://student.cosy.sbg.ac.at/~cpraehaus/
http://www.network-research.org/
http://www.uni-salzburg.at/





More information about the linux-dvb mailing list