[mythtv-users] Ceton Based Recordings Failing

[Craig Huff]

I replaced my PVR-500 tuners awhile ago with a Ceton 6 ETH InfiniTV.  I was
having trouble with recordings that acted like they had dropped packets of
data.  The advice I got was to increase network stack buffers.  That seemed
to clear things up for awhile, but the problem has cropped up again.

Here are the values I changed and their current values:
net.core.rmem_max=1048576
net.core.rmem_default=1048576
net.ipv4.udp_rmem_min=1048576

and here are typical error messages from the mythbackend.log:
Jul 11 21:54:05 penguin mythbackend: mythbackend[2603]: E
CetonStreamHandler recorders/dtvrecorder.cpp:855 (FindH264Keyframes)
DTVRec[1]: PES start code not found in TS packet with PUSI set
Jul 11 21:54:10 penguin mythbackend: mythbackend[2603]: E
CetonStreamHandler recorders/dtvrecorder.cpp:881 (FindH264Keyframes)
DTVRec[1]: PES packet headers overflow to next TS packet, aborting keyframe
search
Jul 11 21:54:10 penguin mythbackend: mythbackend[2603]: E
CetonStreamHandler mpeg/mpegstreamdata.cpp:364 (AssemblePSIP)
MPEGStream[1](0x7f005401def0): Error: offset>181, pes length & current
cannot be queried

If I recall correctly other issues that were discussed as possible causes
for this behavior included the Ceton getting too warm/hot and network
architecture.

To keep the Ceton unit as cool as possible, I have it resting on top of a
140mm fan which is propped up on rubber feet providing good airflow up
through the Ceton.  My recording setup is in an upstairs area beside the
stairwell railing.  The stairs are open to air circulation on both floors.
Despite air conditioning, the air temperature around my MythTV system can
be about 75 F into the evening before coming back down.  At the moment, it
is 68 F ambient and the tuners are reporting temperatures just under 104
F.  I am currently recording a program and, while it appears to be working,
I am seeing errors logged like the last of the three listed above.  These
occur at intervals as short as 16 seconds or as long as 3+ minutes.

I have the backend and the Ceton connected to an 8-port Trendnet Gigabit
Switch along with other devices including a daisy chain to another one.  As
I understand it, anything other than traffic on this particular switch
should be irrelevant because it is a switch, not a simple hub.  I am not
certain what grade of ethernet cables I used to connect the backend and the
Ceton to the switch, but it seems likely that they are Cat 3.

If I have provided enough information to point to what is causing my
problems, I would appreciate any advice on fixing them.  If more
information is needed, you have but to tell me what you need (and if
arcane, where to find it).

Thank you for any assistance you can provide.

--
Craig.
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