[mythtv-users] multiple transmitters - same channel

Michael Watson michael at thewatsonfamily.id.au
Fri Mar 21 08:50:58 UTC 2014

On 20/03/2014 12:07 AM, John Pilkington wrote:
> On 19/03/14 12:45, Mike Perkins wrote:
>> On 19/03/14 03:08, my thtv 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?
>> This is the same problem I face in the UK. The way I resolve it here is:
>> 1. Check online to find out what frequencies your preferred transmitter
>> is using.
>> 2. Do a scan-all and see if any of those frequencies are picked up. In
>> 'Transport Editor' keep one and delete the rest.
>> 2a. If your preferred transmitter isn't picked up (unlikely since it
>> will be the strongest signal) you'll have to edit one of the other
>> entries and try with that.
>> 3. In Channel Editor, delete every channel found. This will prevent
>> 'ghost' channels causing confusion later. (I have been known to do this
>> using mysqladmin but don't tell the devs.)
> Isn't this a single-box tick in the Channel Editor?  Agreed that it's 
> required, or at least a Good Idea.
> Note that tick/check is a prime example of UK/USA being 'divided by a 
> common language.'   Don't know about Oz.
Here its co-mingled.  Roughly depends on the state you went to school 
in.  Other oddities include the spelling of color / colour, disc / disk, 
and the pronunciation of castle.
>> 4. Do a 'Scan specific Transport' selecting the frequency you picked up,
>> ticking the box for using associated frequencies (I forget the wording).
> And the success of that will depend on correct transmitter-specific 
> data being inserted at source.  Mostly works for me in the UK.
>> 5. Profit!!
>> -> Another option you might consider is to visit your friendly aerial
>> installer and see if he has any band-pass filters. That could make your
>> problem less severe.
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