[mythtv-users] Strange Playback behaviour

[Allen Edwards]

On Tue, Oct 9, 2018 at 6:31 AM Stephen Worthington <stephen_agent at jsw.gen.nz>
wrote:

> On Tue, 9 Oct 2018 13:39:14 +0100, you wrote:
>
> >On Mon, 8 Oct 2018 at 15:27, Peter Bennett <pb.mythtv at gmail.com> wrote:
> >>
> >> The speed up and slow down problem is likely related to the audio. It
> >> tries to vary the video rate to keep in sync with audio. If it is
> >> getting bad audio timestamps or bad information from the audio driver
> >> this can happen. Run with -v playback and look at the log for
> >> confirmation. If this is the case I suggest trying different audio
> >> settings. Also there is a setting you can try. Run mythfrontend with -O
> >> AVSyncAveraging=60. The minimum and default value is 4. You can try
> >> different values. Higher values will smooth out the speed changes but
> >> may cause lip sync problems.
> >
> >Thanks for the tip, I turned on the playback logging and here is a
> >link to part of the log during a couple of minutes of watching a
> >pre-recorded program. http://paste.ubuntu.com/p/4c6nPpYTwC/
> >
> >Not sure what all these messages indicate, some, like this one :-
> >
> >Oct  8 21:34:03 mustard mythfrontend.real: mythfrontend[18401]: W
> >CoreContext audio/audiooutputalsa.cpp:243 (IncPreallocBufferSize)
> >ALSA: Try to manually increase audio buffer with: echo 128 | sudo tee
> >/proc/asound/card1/pcm7p/sub0/prealloc
> >
> >are obvious and I have attended to this now but not yet tested.
> >Others such as this one could be fixed (the device is owned by root
> >and mode 600) so that is where I was going to go next (1 step at a
> >time right ?)
> >
> >Oct  8 21:34:05 mustard mythfrontend.real: mythfrontend[18401]: E
> >CoreContext vsync.cpp:358 (TryInit) VSYNC: RTCVideoSync: Could not
> >open /dev/rtc: #012#011#011#011eno: Permission denied (13)
>
> This is what I did to fix the /dev/rtc problem.  The /dev/rtc device
> is a link to /dev/rtc0, so I created a file
> /etc/udev/rules.d/10-local-rules and put this in it:
>
> # Allow MythTV (mythtv group) access to the rtc hardware for
> mythfrontend to use it for timing.
> KERNEL=="rtc0", GROUP="mythtv", MODE="0660"
>
> So now my rtc devices look like this:
>
> root at mypvr:/etc/udev/rules.d# ll /dev/rt*
> lrwxrwxrwx 1 root root        4 Oct  8 04:30 /dev/rtc -> rtc0
> crw-rw---- 1 root mythtv 249, 0 Oct  8 04:30 /dev/rtc0
>
> and mythfrontend is happy:
>
> mythplayer.cpp:1832 (InitAVSync) Player(11): Video timing method: RTC
> _______________________________________________
>

Can you enlighten me as to how widespread this problem is?  Specifically,
would my new Mythbuntu 14 have this problem?  Watching DWTS last night the
playback was terrible.  Much worse than the same hardware with Mythbuntu 8,
my pre upgrade version.  I thought it might be fixed with the new 750 video
card which I plan to give another try at installing today but this post
makes me wonder.  Some of the dance moves were impossible, nobody can move
that fast without "special powers". Do I need to do something to my system
to fix timing?

Allen
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