[mythtv] [mythtv-commits] Ticket #1866: DVB Scanning - Remaining Issues

Rudy Zijlstra mythtv at edsons.demon.nl
Sun Aug 20 23:23:57 UTC 2006

Janne Grunau wrote:

>On Saturday 19 August 2006 12:27, MythTV wrote:
>> The old behaviour can be acheived by doing the
>> tuned scan, and then existing transport scan,
>> as the tuned scan will populate dtv_multiplex
>> from the NIT found on the first transport.
>This is for a first time user confusing and for anyone else impractical. 
>Most users of Full scan (tuned) use it since there is no full scan for 
>DVB-S and DVB-C.
>I looked into this 2 weeks ago and agree that it can't fixed easily. We 
>are probably not able to have the old behaviour in 0.20 but it should 
>be fixed sometime.
>> Alternatively, full scan is available to find
>> all the transports being broadcast, which will
>> work even if the transports do not provide any
>> information about other transports, as happens
>> in certain countries.
>There is no full scan for DVB-S and DVB-C. I don't think that an 
>equivalent to the DVB-T full scan is practical for DVB-S and DVB-C. 
>Astra 19.2E has about 100 transponders and I don't think it's a good 
>idea to maintain for several orbital positions lists of transponders in 
>the MythTV source code. For DVB-C we could scan the appropiate frecency 
>tables we have already. Although it is most of the time more effort 
>than needed.
For DVB-C using the frequency tables is not a good idea. Most of the 
European cable operators are not adhering  to any frequency table but 
there own. Which may be different for each city. German cable is slowly 
moving to a 8MHz raster layout. This is also not covered by any standard.

The best way to detect all streams on DVB-C is by a slow frequency scan, 
with 125MHz step size (or 250MHz, depending on tuner capability). yes, 
this takes time. It is the only way though. And please, please, do 
ignore NIT while you are doing this?? Because many cable operators do 
not provide a valid NIT-actual. They provide many NIT-Other, but no, or 
no valid NIT-actual..... And yes, i know Germany is the exception to the 
rule here, as the big three cable operators in Germany do provide a 
valid NIT-actual.



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