[mythtv-users] Why is h.264 seeking so slow?

Jim Stichnoth stichnot at gmail.com
Wed Sep 15 22:03:42 UTC 2010

I have noticed for a while that seeking in h.264 HDPVR recordings is
quite slow, compared to ATSC recordings.  It's most noticeable when
using the cutlist editor, skipping around a few frames or seconds at a
time trying to find the exact start/end of a commercial break.  It
seems to take 0.5-1 second per seek.  I can press a bunch of keys on
the remote in rapid succession to queue up a lot of seek operations,
then watch "top" on the frontend and backend.  The ION frontend is
using up to 15% of a CPU during this seeking, and the more powerful
backend doesn't go beyond about 3%.  I can't tell whether the disk is
thrashing during this, since the backend is in the garage.  I have
"Seek to exact frame" disabled in my settings.

On the other hand, seeking in ATSC files is quite reasonable, maybe
0.25 seconds or less per frame, about what I'd expect on the ION

Any ideas why this is the case, or suggestions on how to improve the
seeking performance?


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