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DVB-C broken - update FAQ ?

 

 

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kiu at gmx

Jun 24, 2008, 3:36 PM

Post #1 of 4 (444 views)
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DVB-C broken - update FAQ ?

Hi List,

there are several bug reports about broken channel scanning for dvb-c
with some smaller providers.

Could you give a small explanation why it is broken ? We could use
these information to update the FAQ on the mythtv.org wiki and save
users like me several hours of scanning transponders, reading bug
reports, etc.
This would be a huge step forward in the user point of view.

As far as i understand it, some small providers send bogus data inside
the dvb-c stream which mythtv doesnt like (because its not dvb-c
compliant), correct ?

Why is w_scan/dvbscan/czap working without any problems then ?

Thanks in advance...

PS: How do you define small providers ? Eg the provider for Munich
(Population: 1.3M) is broken :)

--
kiu
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janne-mythtv at grunau

Jun 25, 2008, 1:21 AM

Post #2 of 4 (411 views)
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Re: DVB-C broken - update FAQ ? [In reply to]

On Wednesday 25 June 2008 00:36:53 kiu wrote:
>
> there are several bug reports about broken channel scanning for dvb-c
> with some smaller providers.

Not necessarily related to small providers but providers which don't
follow the DVB standard.

> Could you give a small explanation why it is broken ? We could use
> these information to update the FAQ on the mythtv.org wiki and save
> users like me several hours of scanning transponders, reading bug
> reports, etc.
> This would be a huge step forward in the user point of view.
>
> As far as i understand it, some small providers send bogus data
> inside the dvb-c stream which mythtv doesnt like (because its not
> dvb-c compliant), correct ?

There a too different cases.

Some provider change the modulation of satellite feeds for DVB-C but
don't modify the dervice information. I think (hope) this should be
handled gracefully by MythTV. One have to scan each frequency manually
but there is no way around it.

The other case is a wrong Network Information Table. These providers
have different regional channel lineups burt generate the SI in a
central place. They transmit for each region one NIT all the time. The
DVB standard has a flag to indicate whether a NIT is for the actual
network or for an other network. This information is not correct for
all but one of the regional networks. One has to know the network id to
get the correct network information table.

> Why is w_scan/dvbscan/czap working without any problems then ?

They aren't trusting the NIT.

> PS: How do you define small providers ? Eg the provider for Munich
> (Population: 1.3M) is broken :)

as I said above, not necessarily related to small providers


Janne
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kiu at gmx

Jun 25, 2008, 2:07 AM

Post #3 of 4 (411 views)
Permalink
Re: DVB-C broken - update FAQ ? [In reply to]

Quoting Janne Grunau <janne-mythtv[at]grunau.be>:
> On Wednesday 25 June 2008 00:36:53 kiu wrote:

>> Could you give a small explanation why it is broken ? We could use
>> these information to update the FAQ on the mythtv.org wiki and save

I will write a FAQ entry with your information thx.

> Some provider change the modulation of satellite feeds for DVB-C but
> don't modify the dervice information. I think (hope) this should be
> handled gracefully by MythTV. One have to scan each frequency manually
> but there is no way around it.

How can a user recognise this situation ? Eg QPSK modulation in
channel list instead of QAM64 ?

Scan each frequency means:
1. add all transponders from "w_scan -x" into mythtv and scan existing
transponders
OR
2. you have to add all channel information from "w_scan -X" into mythtv


> The other case is a wrong Network Information Table. These providers
> have different regional channel lineups burt generate the SI in a
> central place. They transmit for each region one NIT all the time. The
> DVB standard has a flag to indicate whether a NIT is for the actual
> network or for an other network. This information is not correct for
> all but one of the regional networks. One has to know the network id to
> get the correct network information table.

This means modifying the netword id in mysql and NOT do a rescan ?

How can a user recognise this situation ?

The pefect solution would be "talk to you provider, they should fix
it", right ?

Thx for your help...
--
kiu
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mythtv at colin

Jun 28, 2008, 11:20 AM

Post #4 of 4 (345 views)
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Re: DVB-C broken - update FAQ ? [In reply to]

Janne Grunau wrote:
> One has to know the network id to
> get the correct network information table.

I'm sure you know but this ticket is an important one here:
http://svn.mythtv.org/trac/ticket/3640


--

+------------------------+
| Colin Guthrie |
+------------------------+
| myth(at)colin.guthr.ie |
| http://colin.guthr.ie/ |
+------------------------+
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