[mythtv-users] Ceton Based Recordings Failing

Peter Bennett pb.mythtv at gmail.com
Thu Jul 12 16:53:53 UTC 2018

On 07/12/2018 07:24 AM, Craig Huff wrote:
> 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.
I have used a Ceton eth-6 for several years without this type of problem.
I suggest checking the coax cable from the cable company. Make sure it 
is tight and that there is no bad connector. I suggest if possible 
replace it with a new cable to see if that helps. Also you could try Cat 
5e or Cat 6 ethernet cable. Since you have a gigabit switch you can 
support gigabit speed. If you are recording several channels at the same 
time you will need gigabit speed.

I had a problem like this years ago with a HD Homerun Prime, and 
eventually found that the router it was going through was dropping 
packets. If all else fails you may want to try a different switch or 
router, to eliminate the switch as being a possible cause.


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