[mythtv-commits] Ticket #9765: Active EIT scanning permanently increases power consumption / feature request and workaround

[MythTV]

#9765: Active EIT scanning permanently increases power consumption / feature
request and workaround
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     Reporter:  bjoernv@…         |      Owner:  stuarta
         Type:  Developer Task    |     Status:  new
     Priority:  minor             |  Milestone:  unknown
    Component:  MythTV - EIT      |    Version:  Trunk Head
     Severity:  medium            |   Keywords:
Ticket locked:  0                 |
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 The option "Use DVB card for active EIT scan" is very helpful. This option
 ensures, that the EPG data for all configured channels is permanently
 updated. Switching off this option causes the problem, that only passive
 EIT scanning takes place. As far as I know, only recording streams and
 live TV streams were considered in passive EIT scan.

 Unfortunately the option "Use DVB card for active EIT scan" also increases
 the power consumption. Because the active scanning permanently takes
 place, also the power consumption increases permanently.

 The power management tool "powertop" shows this. With activated "active
 EIT scan" it shows, that the TV card and the MythTV backend cause a lot of
 kernel wakeups. In the example output, the TV card (Nove-T USB stick)
 causes 32.0% and mythbackend 2.9% of the wakeups. MythTV is idle in the
 example. No live TV or recoding takes place. The absolute values are not
 very relevant, because they chance quickly.

 {{{
 Top causes for wakeups:
   32.0% (601.2)   USB device 1-1.4 : Nova-T Stick (Hauppauge)
   27.0% (507.0)   [ehci_hcd:usb1] <interrupt>
   15.0% (282.3)   seamonkey-bin
    8.0% (150.1)   amarok
    5.9% (111.0)   [ahci] <interrupt>
    2.9% ( 55.3)   mythbackend
    2.1% ( 39.8)   npviewer.bin
 }}}

 I think, that both switching on and switching off the option "Use DVB card
 for active EIT scan" has pros and cons. I would prefer an option which has
 more intermediate levels. For instance something like "Use DVD card for
 active EIT scan every ...". The options may be 30 minutes, hour, 2 hours,
 12 hours, day etc.

 One problem is, that a normal user may not know, how often the EIT data
 changes in average.

 Because I want to save power consumption, but also want to have current
 EPG data, I currently use a workaround. A script does the following:

 1. Switch on dvb_eitscan in database table capturecard:
    update capturecard set dvb_eitscan=1 where cardtype='DVB';
 2. Restart mythbackend
 3. Sleeps 60 minutes
 4. Switch off dvb_eitscan
 5. Restart mythbackend

 I am not very comfortable with this workaround. One problem is, that
 restarting mythbackend interrupts live TV and recordings. It would be much
 better to have an option in mythfilldatabase which forces an active EIT
 scan also with option "Use DVB card for active EIT scan" turned off. But
 this still would be a workaround. I would prefer an option for mythbackend
 itself.

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Ticket URL: <http://code.mythtv.org/trac/ticket/9765>
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