[mythtv-users] multiple transmitters - same channel

[John Pilkington]

On 19/03/14 07:40, Karl Dietz wrote:
> On 19.03.2014 04:08, my thtv wrote:
>> Can mythtv show the same channel (2 channels with identical transportid,
>> networkid and serviceid)but on different frequencies?
>
> No, this mandatory feature of a DVB-T receivers has not yet been
> implemented in MythTV.
>
>> If not how can you choose which transmitter between multiples
>> transmitting the same channels?
>
> Pick one of the transmitters and manually scan only this one frequency
> after the full scan. Basically "last save/scan wins".
>
> Regards,
> Karl

If you want to select a set of muxes from just one transmitter the 
'linked scan' feature starting from a known good transport-frequency 
might be worth trying.

>
> PS: Here are some standard references in case someone wants to come up
> with an implementation of this missing feature.
>
>  From ETSI TR 101 211 V1.9.1 section 4.5.2
> For optimization of the network coverage, operators can broad cast the
> same transport stream in a network on alternative frequencies using
> different modulation parameters. The modulation parameters in the
> terrestrial_delivery_system_descriptor apply to the frequency indicated
> in the terrestrial_delivery_ system_descriptor
> and may not always apply to alternative frequencies. When the IRD uses
> an alternative frequency to tune to a transport stream it should not
> rely on those modulation parameters indicated in the
> terrestrial_delivery_system_descriptor.
>
> ETSI TR 101 211 V1.9.1 section 4.5.4.6 - Receiver guidelines
> has some variants for "If the signal strength decreases" depending on
> the network rollout.
>
> Also of interest (because of the clarity) is NorDig-T2 V1.0 section
> 3.4.4.4 - Installation mode: Automatic search, best service
> The IRD shall only display a service once in the service list (i.e.
> avoiding duplicate of the same services), even if the same service (1)
> (same triplet original_network_id, transport_stream_id and service_id)
> is received from multiple transmitters. If the same service can be
> received from several transmitters, the one with best reception quality
> shall be selected. The criteria for selection of the best received
> service (i.e. best reception quality) shall be based on the combination
> of the signal strength and signal quality according to sections 3.4.4.6
> and 3.4.4.7. An example of a possible selection algorithm is described
> in Annex E.
> Note 1: A service is uniquely identified by its DVB triplet
> (original_network_id, transport_stream_id and service_id) in all NorDig
> compliant terrestrial networks, except for the Norwegian terrestrial
> network, where only original_network_id and service_id are used to
> identify a service.