[mythtv] EITScanner caused playback issues

Daniel Kristjansson danielk at cuymedia.net
Wed Jul 19 19:26:39 UTC 2006

On Wed, 2006-07-19 at 15:12 -0400, Tom Lichti wrote:
> >> Slightly OT, but if the DB is on a machine that is different from the 
> >> one doing the recording (and is not a MythBackend) would that pretty 
> Interesting. I would have thought it would help in all areas. I'm not 
> just talking about EIT stuff, but even regular PVR-x50 recordings as well.
Nope. I don't know why you would think that though. Sure the DB is now
using another hard-drive than the recording, which is good, but you also
need to get all that data marshaled and transmitted across the network.

Every 12 to 15 frames recorded by a PVR-x50 requires some data to be
written to the DB, and every 12 to 15 frames played on the frontend
requires some data from the DB, if something else is using the DB your
query usually need to get in line and wait, and wait, and wait, and
wait, sometimes for 40,000 milliseconds, well above the 25 ms you
might notice, or the 100 ms which will get you twiddling your thumbs
and considering a coffee break. Of course, MythTV batches up the writes
and the reads to the DB, but not too much because every little bit of
buffering slows down LiveTV startup. When you watch a prerecorded
program the buffering is much more aggressive so you don't need as
much DB performance... But all in all, good DB performance is pretty
central to MythTV working well.

-- Daniel

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