[mythtv-users] Lossless transcoding became really slow

Jim Stichnoth stichnot at gmail.com
Sat Jun 27 14:52:16 UTC 2009

Lately my lossless (commercial-removing) transcodes have become
exceptionally slow.  What used to finish in less than 5 minutes, now
takes about 2x realtime -- for example, a 30-minute recording may take
about an hour to complete.  During the transcode, the mythtranscode
process is consuming 1-2% CPU according to "top".  I don't know how to
evaluate disk I/O except by looking at the hard disk LED.  In the old
days, the LED would be pretty much solidly on; now it's mostly on but
you can see it flashing.  These are HDHR OTA recordings.  Nothing else
is going on on the system during the transcode.

The problem in diagnosing this is that I made a number of changes over
a short period of time, so it's hard to isolate which change led to
the slow transcodes.  Before, the system was running MythDora 5.
Since then, I upgraded to MythDora 10.21, built my own 0.21-fixes from
source (svn 20549), and patched it for VDPAU and HD-PVR.  I also moved
the backend from a dual-core 4450e system (GA-MA78GM-S2H, 2.3GHz
4450e) to a faster core 2 duo system (GA-E7AUM-DS2H, 2.5GHz E5200).

Any suggestions on what might might have slowed down the transcodes,
and how I might get the original speed back?


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