[mythtv-commits] Ticket #5754: Enhancement to make EIT Active Scanning end after a period, then restart later (a duty cycle)

[MythTV]

#5754: Enhancement to make EIT Active Scanning end after a period, then restart
later (a duty cycle)
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 Reporter:  simonwalls at yahoo.com  |        Owner:  stuarta   
     Type:  enhancement           |       Status:  new       
 Priority:  minor                 |    Milestone:  0.22      
Component:  eit                   |      Version:  0.21-fixes
 Severity:  medium                |   Resolution:            
  Mlocked:  0                     |  
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Comment(by simonwalls at yahoo.com):

 Well I have measured the power savings and they are worthwhile for me, I
 run a low-power mythtv backend and file server (24/7/100%) and am a reader
 of silentpcreview.com. We can be a bit obsessive about these things....

 I have 2 Nova-T PCI cards, one was always in active scan. Idle power
 consumed by the server reduced to 84Watts from 95Watts at the wall socket,
 during the active scan's 'rest' period, using the improved patch I attach
 today. That's about 8kWh or £1.00 saved per month, at current UK
 electricty prices. It corresponds to about 8.5 Watts before PSU
 inefficiencies. If both cards had been in active scan, I think the saving
 would be greater.

 To make it work, I added some new lines to the patch to close the card(s)
 when not in use, and I have set "Open DVB card on demand" for both cards
 in mythtv-setup.
 I now do a database query just like the one in eitscanner.cpp to find the
 number of dvb multiplexes, it avoids increasing the scope of the existing
 variable(s).

 I have revised the patch to scan on a one-hour cycle, and for 2 minutes
 per multiplex. Duty cycle is thus 12 minutes is 60 for my 6-mux reception
 conditions in the UK.
 To use this time setting, you must adjust (in mythtv-setup, General, "EIT
 Transport Timeout" a.k.a max_seconds_per_source) which controls the time
 per mux in the Active scan. This is 5 minutes by default, which means you
 would not cover all your muxes, but I have adjusted mine to 1 minute so
 each mux is 'seen' twice in the active eit period.

 Since you can see hundreds of EIT events in a few seconds, I believe this
 could work well.
 I will test the 2 mins per mux / 1 hour cycle to see how well the EPG is
 kept filled for 1 week. The power saving will only be for 4/5ths of the
 time, of course.

 This document looks like it has some useful information related to EIT
 delivery rate:
 http://www.bci.eu.com/library/articles/delivery.pdf

 Shortening the cycle time means that schedule changes have a greater
 chance of being picked up if they occur shortly before a programme. It's
 okay because tuner cards won't mind being enabled and disabled in short
 succession, unlike hard disc drives. Still, these timings are only for
 evaluation, and a week's trial may dictate changing them. Passive scan is
 still being done.

 I'm not posting a log this time as it was captured with a different set of
 cycle timings, but I'll post a summary log after my test.

 This improved patch might be more technically acceptable, but I note your
 views, janne. Given that my backend is never shut down, I think the power
 saving is worthwhile.

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Ticket URL: <http://svn.mythtv.org/trac/ticket/5754#comment:4>
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