[mythtv-users] Anyone with a MythTV and Free-to-air satellite setup in the United States?

[Karl Dietz]

On 13.07.2012 16:47, Another Sillyname wrote:
> On 13 July 2012 13:37, Robert Kulagowski<rkulagow at gmail.com>  wrote:
>> On Fri, Jul 13, 2012 at 1:38 AM, Another Sillyname
>> <anothersname at googlemail.com>  wrote:
>>> When you did your scan the BBC HD channel would be set a chanid of
>>> 6940 as that's the number that would get assigned by the satellite
>>> source, have a look here.
>>>
>>> http://www.lyngsat.com/Eutelsat-28A-and-Astra-1N-2A-2B.html
>>>
>>> Go down to BBC HD channel on 10847 V on transponder 50 read across to
>>> BBC HD UK and you'll see in the SID (service identifier) column the
>>> value of 6940.
>>
>> OK, I think that helps. The list that I was looking at didn't include
>> service identifier. A SID is going to be unique on a per-satellite
>> basis, or is it truly unique in that satellite providers coordinate to
>> ensure that there is no SID collision?
>
> Generally the SID will be unique within a satellite group rather then
> just one satellite (for example there are a number of satellites at
> 28.2E where BBC HD is transmitting from and they work in conjunction
> to not transmit the same SID for channels in that location).

While that's the case most of the time you should not rely on this
definition.

The service_id (which happens to be also the program_number, a concept
that is part of all MPEG transport streams be they DVB/ATSC/ISDB/DTMB)
must be unique per transport. Violation of this rule will result in a
transport that does not work for either program.

But the service_id must also be unique per original_network_id.
Violating this rule results in a setup that works a bit, but has funny
issues on some equipment. (As could be seen when the rule was violated
in early german DVB-T networks)

SES Astra happens to use ONID 1 for 19.2° E and ONID 2 for 28.8° E. But
on 19.2° E you also have some transponders from Sky/Premiere which use
their own ONID 133. (see http://www.lyngsat.com/Astra-2C.html )

(there are 2 or 3 collisions of service_id on 19.2° E with different
original_network_ids, but I forgot which.)

Btw, the original_network_id identifies the creator of the transport
multiplex while the network_id identifies the network that delivers the
transport to your receiver. As some early projects got the ONID/NID
mixed up you will find lots of places where they are mixed up.
(Cleaning this mess up in MythTV is on "my list")

Regards,
Karl

PS: Channel Number generator is here 
https://github.com/MythTV/mythtv/blob/master/mythtv/libs/libmythtv/channelscan/channelimporter.cpp#L424
and the channel_id generator is at 
https://github.com/MythTV/mythtv/blob/master/mythtv/libs/libmythtv/channelutil.cpp#L1490