[linux-dvb] Re: TS tables doubts

[Nico <sabbi@cs.unibo.it>]

Very clear explanations.

Thanks very much to all of you.

		Nico

On Fri, 18 Jul 2003, Robert Schlabbach wrote:

> From: "Nico" <sabbi@cs.unibo.it>
> > 1) read the PAT to find the list of programs ids
> > 2) read the PMT to find the list of ES streams
> (audio/video/teletext/subs)
> > associated to a given program id
> >
> > Is it correct?
>
> Yes, but this is only ISO-MPEG2.
>
> > Now I wonder
> > 3) what's the use of NIT and SDT?
>
> Those are the extensions that DVB makes to ISO-MPEG2. It defines additional
> tables and "abstracts" the information from MPEG-2. While MPEG-2 only knows
> "programs" and refers to them by "program numbers", DVB calls these things
> "services" and refers to them by service identifiers (SIDs). MPEG-2 has no
> means to specify a transport stream (multiplex), DVB introduces the
> Original Network Identifier (ONID) and the Transport Stream Identifier
> (TSID) to address a stream.
>
> So in DVB you can fully address a service with an ONID:TSID:SID triple.
> ONID:TSID uniquely identifies a transport stream. The required tuning
> information for each ONID:TSID is transmitted in the DVB NIT (Network
> Information Tables). The services (SIDs) for each transport stream are
> described in the SDTs, including e.g. broadcaster, network and channel
> name. AFAIK, MPEG-2 has no means to transmit such information.
>
> Consider MPEG-2 as only a _base_ for a digital broadcasting system, which
> _needs_ to be extended to become a fully functional system. Two such
> extensions are ATSC (North America) and DVB (Europe), of which DVB appears
> to be the more complex and powerful one.
>
> Regards,
> --
> Robert Schlabbach
> e-mail: robert_s@gmx.net
> Berlin, Germany
>
>



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