[mythtv-users] mythbackend random high cpu usage

Jeremy Green jrgreen at MIT.EDU
Mon Sep 19 01:14:23 UTC 2011

Michael T. Dean wrote:
> On 09/18/2011 06:14 PM, Jeremy Green wrote:
>> I am running MythTV 0.24.1 on Fedora 14, on a computer with a pcHDTV 5500 tuner,
>> 1.8GHz Core 2 Duo, and 2GB memory. For analog channels, the card is a
>> framegrabber and my recording profiles are set to encode MPEG-4.
>> When recording of an analog channel starts, one of the following two things
>> happens, seemingly at random:
>> 1. mythbackend uses around 50% of one core, and the recording is fine.
>> 2. mythbackend CPU usage is around 120% (and one of the threads is around 90%).
>> Usually audio sync in the recording is bad, and becomes worse over time (toward
>> the end of a 30 minute recording, audio sometimes lags a few seconds behind the
>> video). Sometimes a recording will have a few instances where about a second of
>> audio repeats itself.
>> If a recording starts with high CPU usage, and I stop and restart it a few
>> times, I am able to cause it to switch to the low CPU usage behavior.
>> Any help would be appreciated, as this is obviously quite annoying.
> Not just CPU frequency scaling?

No. Just now, I tried fixing both cores at 1.8GHz and starting a recording. One 
thread was consistently over 90% CPU usage. Then I stopped and restarted the 
recording, and usage was down to about 25%.


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