[mythtv-users] Strange Playback behaviour

[Peter Bennett]

On 10/09/2018 10:03 AM, Allen Edwards wrote:
>
>
> On Tue, Oct 9, 2018 at 6:31 AM Stephen Worthington 
> <stephen_agent at jsw.gen.nz <mailto: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
>     <mailto: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
>
Run with -v playback and check for messages that say something like 
"video is xx frames behind audio, dropping frame to catch up". You can 
also try the setting mentioned above (-O AVSyncAveraging=60). I have 
written a new synchronization routine to help with some of these issues, 
but I don't know if it will help in your case. Let me know if you get 
the dropping frame messages or if the AVSyncAveraging works.

Peter
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mythtv.org/pipermail/mythtv-users/attachments/20181009/711c20e5/attachment.html>