[mythtv-users] multiple transmitters - same channel

Karl Dietz dekarl at spaetfruehstuecken.org
Wed Mar 19 07:40:22 UTC 2014

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".


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 

ETSI TR 101 211 V1.9.1 section - 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 - 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 
and 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.

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