[mythtv-users] TCP performance issues

Eloy Paris peloy at chapus.net
Sun Sep 19 13:16:22 UTC 2010


Hello,

I'm running up-to-date 0.23-fixes and after moving my frontend to
Mythbuntu (it was running Debian and 0.23-fixes before) I started to
experience playback issues that I did not experience before. The exact
problem I am seeing are:

- It takes a few seconds (about 5) for a recorded show to start playing.
When I was running Debian, starting to play a show was a lot more
quicker.

- When the show starts to play there is stuttering for the first 2 or
3 seconds, like if the frontend is still filling up internal buffers.
Stuttering stops after the initial few seconds and playback then
proceeds normally. I did not experience this behavior when the frontend
was running Debian.

- Perhaps the most significant issue is that skipping forward (the
default; 30 seconds?) or backward (the default, 10 seconds?) takes a
long time (between 3 and 4 seconds) and the frotend seems to freeze
during this time. I did not experience this behavior when the frontend
was running Debian either

To me it is puzzling that I did not experience this problem when the
frontend was running Debian (and the corresponding mythtv packages from
Christian Marillat). Furthermore, the machine is diskless, and because
of this, the kernel used is exactly the same, i.e. I didn't even rebuild
it; I built it when the machine was running Debian and kept it for the
Mythbuntu install.

One final data point is that I configured the frontend to directly
access the recordings via NFS instead of using the Myth protocol and
connecting to the backend and all the problems went away -- immediate
playback, immediate response to skipping forward/backward, and no
stuttering the first few seconds of playback. To add to the mystery, NFS
is also using TCP, just as the Myth protocol.

Any thoughts, ideas, or suggestions?

Thanks in advance.

Eloy Paris.-



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