[mythtv-users] no channel lock

Rudy Zijlstra mythtv at grumpydevil.homelinux.org
Sat Nov 3 22:30:22 UTC 2007

Marcel Janssen wrote:
> Hello Rudy,
>> One other remark:
>> be very carefull with "scanning" the network. It will fail and destroy
>> the dtv_multiplex tables as @home (as many cable operators) is using a
>> different interpretation of the DVB standard with respect to NIT-Actual
>> and NIT-Other.
>> MythTv uses NIT-Actual to determine frequencies, and @Home is using
>> several NIT-Other where you need to know which one to use.
> How did you find the channels on your system ?
> I'm checking the database, but haven't found the cause yet.
> Regards,
> Marcel

Made a TS recording from the home frequency @home tells you, and 
analyzed the stream with dvbsnoop on the different NITs. The NIT-Other 
you need to have will tell you all the frequencies which are on your cable.

When you scan, you subsequently have to repair the tables. even when you 
scan only one TS. This is because Myth takes the info from the 
NIT-Actual - which in @home is almost always wrong. When doing this 
scan, you have to delete the bogus TS that are added when you scan a TS, 
and check that the relation between the mplexid mentioned in the channel 
table is correct with the dtv_multiplex table.

Christiaan van Dijk made a patch against svn 14207 which will scan 
@home, although it only works for a @home only setup. It makes a number 
of assumptions which break DVB-S. I have not checked whether it applies 
to current SVN or to 0.20-fixes.

i have attached it here. I used it by creating a separate source 
directory, installed that version for scanning of my network, and then 
re-installed the default SVN as i have a mixed DVB-S/DVB-C setup. As 
long  as the channels i am watching remain in the current TS, i need not 
scan again :)

Good luck,

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