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

Fri Aug 7 02:47:06 UTC 2015

Thanks Mark!

I am receiving channels and can view them completely fine using the Prime's
GUI/VLC. I can open LiveTV and watch channels in LiveTV. The issue only
occurs when watching a channel and I switch to another (only some of them
though which is what I find weird). Mythfrontend then gives the "error
opening jump program file buffer" and completely crashes. I got the thought
about the dummy tuners after reading this post:
http://www.gossamer-threads.com/lists/mythtv/users/504473 in which Mitchell
Gore says

"Also, if you follow those instructions (he is referring to the
HDHomerunPrime setup instructions in the MythWiki - the one you just
mentioned) you first attach the tuner to a dummy recorder. That way you can
fetch the listings. WHen doing this it will pause for a bit and look like
nothing is happening. but if you goto the channel editor you can see the
channels it grabed. Next you attach the tuner to the Prime and delete the
dummy."

The OP goes on to say "On that page it said that using the dummy was for
0.24-fixes but I'm using the 0.25 branch. I'll give that process a shot
though and see if it makes a difference."

Next post by OP: "In case anyone following along ran into the same issue
despite the fact that you are running Master or 0.25 go ahead and follow
the instructions for 0.24-fixes and it should work. Even in 0.25/Master (at
least from the mythbuntu repos) the channel numbers will not be fetched
unless you first configure the dummy recorder."

I couldn't find any reference to a dummy recorder whatsoever in the
MythWiki Prime install guide or when looking for the .24-fixes. This leads
me to believe it was there at one point but has since been removed. I've
searched through the last 20+ mailing list archive pages, plus forum
posts/pages and still couldn't find anything. My guess is perhaps that the
"virtual" Prime tuners are these dummy tuners, but I don't know for sure
because I can't find any other references.

As for the ringbuffer question, if you know how it works and can explain it
to me in detail it would be *greatly* appreciated. I'm relatively new to
Myth and trying to understand as much as possible in as much detail as
possible. I also try to research as much as possible before asking any
questions because I feel it helps me learn better by having to go through
the wiki/archives first and try to figure it out myself (trial by fire
so-to-speak). Which, unfortunately on the only hand means that if I'm
asking questions it's because I couldn't find the answer myself after quite
a bit of digging haha. That's one of the reasons I appreciate *any* input
anyone has so much. Maybe I just missed something really simple.

Thanks again Mark. I've already deleted and re-added the tuners, but if no
one else has any suggestions I might just try it again.

On Thu, Aug 6, 2015 at 9:48 PM, Mark Perkins <perkins1724 at hotmail.com>
wrote:

>
>
>
>
> 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 <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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>
>

-- 
If you have any questions feel free to contact me at this email, or at the
phone number listed below.

Thanks,
*Cody Hofstetter*
*CodyHofstetter at gmail.com <CodyHofstetter at gmail.com>*

*CodyHofstetter.com <http://www.CodyHofstetter.com> *
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