[mythtv-users] A little help clarifying dummy tuners and HD ringbuffers

Fri Aug 7 01:48:49 UTC 2015

> On 7 Aug 2015, at 7:40 am, Cody Hofstetter <codyhofstetter at gmail.com> wrote:
> 
> Hello all!
> 
> Still trying to fix a LiveTV "error opening jump program file buffer" when switching programs and am hoping for a little clarification on dummy tuners and HD ringbuffers. 
> 
> I'm using Mythbuntu 14.04 and .27 with a HDHomeRun Prime in CableCard mode.
> 
> First, my searching through the forums/archives has led me to find that dummy tuners were originally designed for use as a development tool for those without the hardware wishing to contribute to Myth (e.g. on a laptop, no tuner card, etc) and for use on backends with no tuners. 
> 
> I've come across some errors indicating dummy tuners (I believe) that I was unaware were set up. Which lead me to wonder if MythTV automatically sets up dummy tuners and if so, why? 
> 
> E CoreContext fileringbuffer.cpp:300 (OpenFile) FileRingBuf(/var/lib/mythtv/livetv/1043_20150805170925.mpg): OpenFile(): File too small (0B).
> E CoreContext mythplayer.cpp:2718 (JumpToProgram) Player(1):
> JumpToProgram's OpenFile failed (card type: HDHOMERUN).
> E CoreContext mythplayer.cpp:2719 (JumpToProgram) LiveTVChain has 6 entries#012 DUMMY: 1026 (17:08:58 to 17:08:58)#012 HDHOMERUN: 1026 (17:08:59 to 17:09:06) discontinuous#012 DUMMY: 1028 (17:09:06 to 17:09:07) discontinuous#012 HDHOMERUN: 1028 (17:09:07 to 17:09:24) discontinuous#012 DUMMY: 1043 (17:09:24 to 17:09:24) discontinuous#012* HDHOMERUN: 1043 (17:09:25 to 18:30:00) discontinuous
> E CoreContext mythplayer.cpp:2960 (EventLoop) Player(1):
> Unknown recorder error, exiting decoder
> 
> The MythWiki "Dummy Tuner" page says it's been outdated since .24 and Myth now has a dedicated "demo tuner". Hence the wondering if they automagically setup or I'm getting this error because of the Prime tuner. 
> 
> 
> Second, I understand the HD ringbuffers are, to paraphrase " to weather moments of stress and too large a ringbuffer will result in swapping" (description used in backend). So my question after searching through everything is, let's say most modern systems have at least 2/4gb of memory. Even if the swappiness is set to 60 as the default for most Linux distros, you still have plenty you could add before running into a problem (since the default is 9600kb). Please correct me if I'm wrong, but increasing the ringbuffer size won't increase the amount of time between switching programs in LiveTV (it should actually decrease it if switching for example from channel 2 to channel 3 and then back to channel 2?). From one of the many many posts I read somewhere I got that the live-tv chain ID is sent from the frontend to the backend and this is when the ringbuffer is assigned. Then the frontend loads the first channel in the chain to the ringbuffer. When the program guide data is changed (when you switch channels), it automatically creates a new file/chain entry. Is the only possible issue that would result from setting the ringbuffer higher is that it could get swapped? 
> 
> With the "RingBuf: Taking too long to be allowed to read.." error, where would you increase the timing to allow it to wait longer?  Unless I'm completely off and that's not the way you solve this error.
> 
> http://pastebin.com/rWvzir9s --- Backend/Frontend Logs
> 
> If anyone could even give me a partial answer it would help so frigging much! It's a nightmare trying to troubleshoot things after spending hours searching and still not finding a simple answer as I'm sure everyone can attest to. You guys are immensely helpful when stuck!
> 
> Thanks again!
> 
> P.S. Gary already helped me solve one previous error and I find the troubleshooting guide with the errors section of the MythWiki easiest to understand when looking for a particular error. I know there has been talk of restructuring the wiki and I would like to put the errors I have as I solve them in the troubleshooting guide to help anyone else who has the same issue. I wouldn't mind lending a hand in helping reorganize the wiki either if someone has taken a lead and can point me who to talk to. 
> _______________________________________________

I don't think the issue is in the ring buffer. The presence of a dummy tuner suggests to me that the tuners have not been setup correctly because MythTV doesn't create dummy tuners by itself. Waiting longer won't help if nothing is coming from the tuners.

I don't have a HDHomeRun so won't be able to help troubleshoot but if it were me I would delete all capture cards on all hosts in mythtv-setup and redo the HDHomeRun setup from the wiki.
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