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

Mark Perkins perkins1724 at hotmail.com
Wed Mar 19 05:21:57 UTC 2014

On 19 Mar 2014, at 3:11 pm, "myth" <mythtv at cain.id.au> wrote:

>> 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.
> -Andrew
> _______________________________________________
There was a recent thread (maybe last 3 months) that detailed some peculiarities with myth in terms of handling this situation (at least if I recall correctly). But for the life of me I can't find it again. Hopefully the participants of that earlier thread will speak up again.

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