[mythtv] DVB/rotor tuning issues - found something interesting

Mark Buechler mark.buechler at gmail.com
Tue Apr 4 00:05:39 UTC 2006


I've gotten my DVB tuning issues down to almost nothing over the past few
version of Myth. Thanks! However, I still have a handfull of channels I
cannot go between. Keep in mind I'm using a rotor. I haven't really thought
about it much but tonight I looked into and found something interesting:

The follow mplex entries belong to the channels I can't tune to if I'm tuned
to the other.

mysql> select * from dtv_multiplex where mplexid = 313;
+---------+----------+-------------+-----------+-----------+-----------+------------+------+----------+------------+-----------+--------------+-------------------+----------------+---------+---------------+-----------+--------------+------------+----------------+---------------------+
| mplexid | sourceid | transportid | networkid | frequency | inversion |
symbolrate | fec  | polarity | modulation | bandwidth | lp_code_rate |
transmission_mode | guard_interval | visible | constellation | hierarchy |
hp_code_rate | sistandard | serviceversion | updatetimestamp     |
+---------+----------+-------------+-----------+-----------+-----------+------------+------+----------+------------+-----------+--------------+-------------------+----------------+---------+---------------+-----------+--------------+------------+----------------+---------------------+
|     313 |       11 |         104 |       257 |  12268000 | a         |
20000000 | auto | l        | qpsk       | a         | auto         |
a                 | auto           |       0 | auto          | auto      |
auto         | dvb        |             -1 | 2005-12-15 17:54:58 |
+---------+----------+-------------+-----------+-----------+-----------+------------+------+----------+------------+-----------+--------------+-------------------+----------------+---------+---------------+-----------+--------------+------------+----------------+---------------------+
1 row in set (0.00 sec)

mysql> select * from dtv_multiplex where mplexid = 3;
+---------+----------+-------------+-----------+-----------+-----------+------------+------+----------+------------+-----------+--------------+-------------------+----------------+---------+---------------+-----------+--------------+------------+----------------+---------------------+
| mplexid | sourceid | transportid | networkid | frequency | inversion |
symbolrate | fec  | polarity | modulation | bandwidth | lp_code_rate |
transmission_mode | guard_interval | visible | constellation | hierarchy |
hp_code_rate | sistandard | serviceversion | updatetimestamp     |
+---------+----------+-------------+-----------+-----------+-----------+------------+------+----------+------------+-----------+--------------+-------------------+----------------+---------+---------------+-----------+--------------+------------+----------------+---------------------+
|       3 |        2 |         205 |      4102 |  12282000 | a         |
20000000 | auto | r        | qpsk       | a         | auto         |
a                 | auto           |       0 | auto          | auto      |
auto         | dvb        |             -1 | 2005-11-22 18:13:11 |
+---------+----------+-------------+-----------+-----------+-----------+------------+------+----------+------------+-----------+--------------+-------------------+----------------+---------+---------------+-----------+--------------+------------+----------------+---------------------+
1 row in set (0.00 sec)


Notice the frequencies are very close. The DVB card/module is no doubt
searching for the nearest lockable frequency while tuning. Ordinarily that
isn't a problem (for my DVB card). However, notice the polarity. One is left
and the other right.

Does anyone here have experience enough to know if the DVB card/module will
alter the polarity IN ADDITION to searching for the nearest frequency? I'm
guessing that the card is locking the nearest frequency but the wrong
polarity. Once the card locks it never attempts to retune.

Here are the transponders between the first and last transports which the
card is probably locking on the way:

|     254 |       10 |           4 |       256 |  12268000 | a         |
20000000 | auto | l        | qpsk       | a         | auto         |
a                 | auto           |       0 | auto          | auto      |
auto         | dvb        |             -1 | 2005-11-28 12:57:37 |

|     260 |       10 |           5 |       256 |  12282000 | a         |
20000000 | auto | r        | qpsk       | a         | auto         |
a                 | auto           |       0 | auto          | auto      |
auto         | dvb        |             -1 | 2005-11-28 12:57:37 |

- Mark.
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