[mythtv-users] mythfrontend lip sync problems?

John Pilkington johnpilk222 at gmail.com
Mon Oct 19 14:55:43 UTC 2020

On 19/10/2020 14:26, Greg Oliver wrote:
> On Mon, Oct 19, 2020 at 8:21 AM James Abernathy <jfabernathy at gmail.com 
> <mailto:jfabernathy at gmail.com>> wrote:
>     I have never had lip sync problems with mythfrontend until now. The
>     reason seems to be my FireTV Cube.
>     I do NOT have lip sync problems with mythfrontend on RPI4, FireTV 4K
>     Stick, Ubuntu PC, or Shield TV.
>     On all my Android devices, including the Cube I don't have problems
>     with lip sync on Leanfront or Kodi 18.8.
>     On the FireTV Cube only I have to edit the Audio Lip Sync to -400ms
>     so the picture and audio match.  Some days it's -200ms.  Since I've
>     never experienced this before, I'm wondering what could be the
>     problem?  Luckily, I can adjust to fix it, but it makes me think the
>     Cube isn't so good.
>     Is lip sync a common problem or is it just me and my Cube?
>     Jim A
> It's a definite problem with some hardware.  My AT&T TV (formerly 
> DirecTV Now) box had a pretty large skew.  Once I get the video 
> performing the way I like it with the playback profiles, I then match up 
> the audio sync.  I never have to touch it afterward.
> You are correct though - the leanback interfaces have always sync'ed 
> with no interaction.

I have no experience of the FireTV Cube, but the spec for the 2019 
device suggests that it should be OK.  IIUC lipsync drift in recent 
MythTV frontend has often resulted from frame dropping with greedy 
high-spec deinterlacers, and perhaps not having all available cores 
enabled.  I'm not sure if that's what you are getting.  Once set, again 
IIUC, the offset is remembered.


John P

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