[mythtv-users] Strange Playback behaviour

[Stephen Worthington]

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