[mythtv-users] Stutter/pause and pixel debris when the programme moves from one to the next (Live TV)

[Ben Lancaster]

List,

I have a reasonably complex MythTV network:

 - Combined Tunerless Master backend + MySQL + storage in the loft
 - Diskless combined slave backend (with tuners) + frontend in the living room
 - Diskless combined slave backend + frontend in the bedroom

…all connected to a wired gigabit network.

All machines are running Mythbuntu (10.04 iirc) and Mythtv 0.24.1.

My video partition is formatted as XFS, run off a linux software RAID5 on the master backend, shared to the other slaves over NFS.

Now the problem I have is that when the programme changes when watching live TV (and the backend starts writing to a new file), I get a stutter or pause of a second or two, followed by pixel debris for a few more seconds.

On the master backend, my fstab looks like this:

UUID=e14288b2-2ce4-4f11-b31d-a45582dcc351 /srv/video xfs noatime,nodiratime,allocsize=512m 0 2

exports looks like this:

/srv/video    192.168.1.0/24(rw,async,no_root_squash,no_subtree_check)

On the slaves, fstab looks like:

192.168.1.98:/srv/video /srv/video nfs defaults,noatime,tcp 0 0

When the program changes, the master backend log says:

2011-08-10 23:15:01.357 AutoExpire: CalcParams(): Max required Free Space: 3.0 GB w/freq: 14 min
2011-08-10 23:15:01.865 MainServer::ANN Monitor
2011-08-10 23:15:01.874 adding: livingroom.local as a client (events: 0)
2011-08-10 23:15:01.883 MainServer::ANN Monitor
2011-08-10 23:15:01.890 adding: livingroom.local as a client (events: 1)

The slave backend with tuners says:

2011-08-10 23:15:00.700 LoadFromScheduler(): Error, called from backend.
2011-08-10 23:15:00.738 Finished recording Not Going Out "Life on Mars Bars": channel 1001
2011-08-10 23:15:01.135 TVRec(5): RingBufferChanged()
2011-08-10 23:15:04.092 MainServer::ANN Playback
2011-08-10 23:15:04.107 adding: livingroom.local as a client (events: 0)
2011-08-10 23:15:04.119 MainServer::HandleAnnounce FileTransfer
2011-08-10 23:15:04.129 adding: mythtv.benlancaster.co.uk as a remote file transfer
2011-08-10 23:15:07.547 RecBase(5:/dev/dvb/adapter5/frontend0): GetKeyframePositions(73,9223372036854775807,#2) out of 5
2011-08-10 23:15:07.663 RecBase(5:/dev/dvb/adapter5/frontend0): GetKeyframePositions(73,9223372036854775807,#2) out of 5

…and the playing frontend says:

Unknown ResidentProgram SBI
2011-08-10 23:15:04.179 RingBuf(myth://192.168.1.99:6543/1001_20110810231500.mpg) Warning: Not starting read ahead thread, already running
2011-08-10 23:15:04.187 Player(1): Forcing decode extra audio option on (Video method requires it).
2011-08-10 23:15:07.438 AFD: Opened codec 0x7f57c4646420, id(MPEG2VIDEO) type(Video)
2011-08-10 23:15:07.438 AFD: codec MP2 has 2 channels
2011-08-10 23:15:07.438 AFD: Opened codec 0x7f57c4646aa0, id(MP2) type(Audio)
2011-08-10 23:15:07.438 AFD: codec MP3 has 0 channels
2011-08-10 23:15:07.438 AFD: Opened codec 0x7f57c47faef0, id(MP3) type(Audio)
2011-08-10 23:15:07.438 AFD: Opened codec 0x7f57c451a2e0, id(DVB_SUBTITLE) type(Subtitle)
2011-08-10 23:15:07.570 AFD: Resetting byte context eof (livetv 1 was eof 0)

At first thought I wondered if it was IO related, but looking at the logs, I'm not so sure. Any ideas?

Ben