[mythtv-commits] Ticket #1485: DVB Scanning Issues

MythTV mythtv at cvs.mythtv.org
Wed Mar 29 08:38:55 UTC 2006

#1485: DVB Scanning Issues
 Reporter:  f.lange at hccnet.nl  |        Owner:  stuarta
     Type:  defect             |       Status:  new    
 Priority:  minor              |    Milestone:  0.20   
Component:  dvb                |      Version:  head   
 Severity:  low                |   Resolution:         
Comment (by stuarta):

 I believe the correct solution to the other_frequency list problem
 it to provide a method where we can throw a list of frequencies to
 check for a given tsid back up to the scanner. This can then be used
 for two things.

 1. Optimize scanning time by rewriting the scan list (this should be
 a new country specific scan

 2. Allow us to verify that the tsid we've tuned to is correct (since it
 is possible in fringe areas to recieve a signal from an adjacent area
 on one of the alternate frequencies given in the NIT, but for a different

 Also the correct way to handle these frequencies is to tune to each
 alternate frequency in turn, stopping once we find one where the tsid
 matches the tsid we know is associated with this transport.

 From the NIT at moely parc
 Transport_stream_ID: 4158
 Center frequency: 0x03412140 (= 546000.000 kHz)
 Other frequency descriptors:
                Centre_frequency: 0328f85b  (= 530166.067 kHz)
                Centre_frequency: 04724e40  (= 746000.000 kHz)
                Centre_frequency: 0303d725  (= 505833.033 kHz)
                Centre_frequency: 044daf40  (= 722000.000 kHz)
                Centre_frequency: 0410e75b  (= 682166.067 kHz)
                Centre_frequency: 04661940  (= 738000.000 kHz)
                Centre_frequency: 0328f85b  (= 530166.067 kHz)
                Centre_frequency: 04354540  (= 706000.000 kHz)

 The freq in use is 738000 kHz which is well down the list,
 and you can see that they are not ordered according to
 frequency but the most likely one you will use.

 Daniel, one thing I noticed while looking at this problem is
 the dvbdescriptor parsing code is not handling interdependecies
 between descriptors.

 In this specific case the alternate frequency descriptors are
 ONLY present iff the other_frequency_flag = 1, and each one only
 provides a new frequency, the rest of the information comes
 from the original terrestrial_delivery_descriptor which preceeded it.

Ticket URL: <http://svn.mythtv.org/trac/ticket/1485>
MythTV <http://www.mythtv.org/>

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