[linux-dvb] DVB file formats

Andrew de Quincey adq_dvb at lidskialf.net
Sun Jun 19 03:13:30 CEST 2005


On Saturday 18 June 2005 21:29, Gavin Hamill wrote:
> On Sat, Jun 18, 2005 at 09:06:13PM +0100, Andrew de Quincey wrote:
> > Just a quick question... is DVB-C like DVB-S or DVB-T
> >
> > What I mean is: DVB-S has multiple satellites, but the
> > services/multiplexes from one particular satellite can be guaranteed to
> > be the same no matter where you receive them (as its the same signal).
> >
> > However, DVB-T is more complicated because the same services are
> > transmitted at different frequencies in different places (unless you have
> > an SFN of course).
> >
> > Which of these two does DVB-C match closest?
>
> Hehe nothing is ever simple..
>
> In each cable region, you will get the same freqs and muxes in use,
> that's guaranteed (although the cable co will typically broadcast the
> NITs for *all* regions even though 95% of them are useless information),
> but each region will also use a different set of frequencies...
>
> So in that respect, it's a little like both DVB-S and DVB-T, depending
> on where you're viewing from :)


Arrgh :) I'm beginning to think we need something like the following for DVBT 
to deal with this sort of thing:

<source_network>-<source_region>-<source_locale> 

<source_network> giving the broadcast network (e.g. "uk")
<source_region> giving the general region the source is available in (e.g. 
"scottish", "borders", "grampian" etc) since some services are only available 
in certain regions.
<source_locale> giving the local physical location of the source. For DVBT, 
this would be used to indicate the transmitter. Since multiple transmitters 
are used to cover a region they will have to transmit on different 
frequencies (well unless they're in a SFN).

This stuff is used in different places in the library:

<source_network> and <source_network>-<source_region> is used in the presets 
file to identify the broadcaster of a particular service.

<source_network>-<source_region>-<source_locale> is used in the adapters file 
in order to say what sources a particular DVB adapter can receive.. 

So for example my DVBT adapter would have "Tuk-scottish-blackhill". Therefore 
I know services in a presets file can be received if they have either just 
"uk" or "uk-scottish" as their source. 

Do you think this would cover DVBC as well?

Obviously DVBS only needs the <source_network> bit as there is no regional 
programming, and everyone receives the same signal from the same satellites.

Does anyone know about ATSC? I'm assuming since it is similar to DVBT, it will 
likely be supported by the above as well.




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