[mythtv-users] MythTV, seeking ahead / behind, NFS,
and bandwidth usage
blammo at dohboys.com
Sun Aug 1 16:40:43 EDT 2004
Two machines in this cluster, both Athlon XP 2400's, plenty of ram, both
running KnoppMyth R4V4, one backend with two PVR-250's, and a frontend with
Nvidia card hooked together on a 100M cisco switch. /myth mounted over NFS
from the backend.
When seeking forward / backward in MPEG2 streams, from recorded TV, I seem
to be running out of ethernet bandwidth. I don't notice this AT ALL in the
"Video" section with mplayer, just in the TV section. Anything over say 3X
seems to have diminishing returns. All the way up at 8x or 16x, checking the
switchports shows about 50 - 60meg of traffic running. The load on the
backend seems to be pretty low, as does the load on the front end. It just
seems like the frontend isn't getting data fast enough.
It appears to me, that the frontend has to read the whole file, to seek
ahead / behind in the file, at 1x, 1.5x 2x etc faster. It doesn't appear to
"seek" or "jump" at all ahead, rather reading the whole thing.
I'm just wondering if anyone else has run into this, and what they did to
fix it. Obviously transcoding to a low bit-rate MPEG4 would help. It makes
me wonder whether the front end couldn't be a little smarter about the file
reading, take less NFS bandwidth in the process. After all, mplayer has no
trouble skipping ahead, etc.
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