Active EIT scanning permanently increases power consumption / feature request and workaround

[bjoernv@…]

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.

[Stuart Auchterlonie]

Thank you for your detailed feature request.

However you failed to read the TicketHowto? which says not to raise feature requests as tickets unless you have a patch to go with it.

Feel free to reopen when you have a patch...

Stuart