[mythtv-users] mythfrontend lip sync problems?

Jim Abernathy jfabernathy at gmail.com
Mon Oct 19 15:15:55 UTC 2020

On 10/19/20 10:55 AM, John Pilkington wrote:
> 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.
> https://developer.amazon.com/docs/fire-tv/device-specifications-fire-tv-cube.html 
> John P

I appreciate all the help on this, but I finally realized that all my 
recent problems have been because I'm trying to make the Cube perform as 
well as my Nvidia Shield TV 2017 model.  I never really had a problem 
with the Nvidia on Mythtv-Frontend of Mythtv-leanfront. My only issues 
were on non-MythTV apps like Hulu+ and Netflix frame rate on European 
films. I solved those issue with beta fixes from Nvidia, so I really 
have no issues with Shield TV.

I solved my FireTV Cube problem this morning by returning it to Amazon 
for a full refund.

Jim A

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