[mythtv] RetuneMonitor generates significant load with DVB cards without hardware i2c support

Janne Grunau janne-mythtv at grunau.be
Tue Jul 25 22:13:53 UTC 2006


The cause is the FE_READ_STATUS ioctl in RetuneMonitor. It blocks for 
approximately 10ms on cards with a cx88 or bt8xx pci bridge and the 
pluto2 device. These devices have no hardware i2c support. For the cx88 
it's just not implemented yet. They use i2c bit banging instead.

This wouldn't be a problem if the signalmonitor is only for tuning 
checks before channel changes. But it isn't that good for the active 

I see two options to reduce the load:

1. don't call RetuneMonitor that often, 2-3 times per second is probably 
enough. This may slowdown tuning for rotors.

2. disable the RetuneMonitor after IsAllGood() is true. This removes the 
functionality but if I understand it correctly the main feature of the 
RetuneMonitor is to make tuning more reliable with rotors and 
diseq-switches. Currently the eitscanner is more reliable than 
live-tv/recordings since it has a continous LOCK check.


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