[mythtv-users] multiple transmitters - same channel - DVB Australia

myth mythtv at cain.id.au
Wed Mar 19 04:41:15 UTC 2014

> I have been using Mythtv for some years, however, recently here in
> Sydney Australia they have been retuning the digital (DVB) transmit
> frequencies.So I took the opportunity to re-scan my channels.However, I
> am in range of a number a transmitters and in some instances they are
> carrying the same services but signal strength and quality varies
> between them.
> I allocated different channels for the different transmitters in order
> to compare the quality of my reception from each source.However, I
> believe myth is not tuning to each but defaulting to a particular
> transmitter, regardless of the channel selected.
> So I had a look at some of the tables in mythconverg to try to
> determine why that may be.When checking channelscan_channel and
> channelscan_dtv_multiplex it appears that the latest scan correctly
> identify the same channel information with multiple entries for each
> frequency.I also checked dtv_multiplex, however, this table did not
> have all the available frequencies listed.It would seem that where
> transportid and networkid are identical for two different frequencies
> then only one of the frequencies is shown.
> So my questions are;
> Can mythtv show the same channel (2 channels with identical
> transportid, networkid and serviceid)but on different frequencies?
> If not how can you choose which transmitter between multiples
> transmitting the same channels?
> -Andrew

I'd like to re-clarify the statement above as it may be confusing.

I have 2 sources of the same channel. (Same technology - DVB - same tuner -
same source)

For instance, 
Here in Sydney I can receive the ABC1 channel from the Gore Hill transmitter
on a frequency of 226500000, it has a transportid of 545 and a networked of
4112.  During the myth-scan I assign this as channel 2 with it being
automatically assigned a callsign of ABC1.

An identical transmission is also broadcasts ABC1 from the South-West Sydney
transmitter on a frequency of 620500000, it also has a transportid of 545
and a networked of 4112.  During the myth-scan I assign this as channel 200
with it being automatically assigned a callsign of ABC1.

Both channel 2 and channel 200 can be selected and displayed by mythtv,
however, it appears to always set the tuner to 620500000 regardless of which
channel I choose.

When you check the database dtv_multiplex table there is no entry for
frequency 226500000.  

(I'm guessing the myth channel scanner sets the frequency to the last
scanned frequency where two channels have identical transportids?)

This is not a real problem if both channels are truly the same.  However,
although the content is the same, the reception quality is not.  Hence I
would like to be able to check both to see which is best and then select one
of them.


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