[mythtv-users] frontend video smoothness

John Pilkington johnpilk222 at gmail.com
Tue May 19 11:08:43 UTC 2020


On 19/05/2020 08:54, Paul Gardiner wrote:
> On 18/05/2020 17:54, John Pilkington wrote:
>> On 18/05/2020 16:50, Jim Abernathy wrote:
>>> I now have an easy way to test multiple frontends very quickly 
>>> switching between them to compare which is best.
>>>
>>> And as all of you know the best can be different depending on which 
>>> video, which format, etc. I've found a short scene where the camera 
>>> pans past a number of people, and that motion makes the pan seem 
>>> slightly jerk, but not bad, certainly it doesn't prevent enjoyable 
>>> viewing of the program.
>>>
>>> Hardware:
>>>
>>> Backend common for all frontends. Core i7 Ubuntu 18.04 server Mythtv 
>>> v31. All video captured is MPEG2 USA OTA HD 1080i (1920x1080 at 30hz). 
>>> Average bit rate is 10Mb/s.
>>>
>>> Frontends:
>>>
>>> 1. Core i7 with Nvidia GT 1030 fanless GFX card
>>>
>>> 2. Nvidia Shield TV running mythfrontend and leanfront.
>>>
>>> 3. RP3B+ with MPEG2 license.
>>>
>>> I would have guess before hand that the PC with the GT1030 would be 
>>> the best, but it wasn't.
>>
>> Using DVB-T/T2 in the UK I find that the Leanfront on a 4K Firestick 
>> is excellent when it works, but it still seems to need purely 
>> progressive content and that often can't be guaranteed.  I have 
>> GT710s, which are less capable than your GT1030, and they lack 
>> smoothness in panning when using nvdec hardware decoding.  But with i5 
>> 4-core 3 GHz software decoding, playback is as smooth as I get from 
>> DLNA or the leanback on appropriate content.  I haven't seen what 
>> newer and cheaper devices can do, but I'm sceptical.  I think you 
>> ought to try software decoding on your i7.
> 
> That worries me a little. I still have an old nvidia ION based frontend 
> that seems to play everything I throw at it perfectly, but I'm still on 
> v29 and using vdpau. I hope the rendering rewrite hasn't caused any 
> regression.

No, this wasn't something that happened with the newer code.  It's just 
not like viewing an unchanging scene when a mask moves in front of it. 
Shapes are slightly unstable.  And everything is 25 Hz.
> 
>> And I recently noticed that the leanfront seems to work well with live 
>> DVB-T mpeg2 material, while recordings now have good audio but the 
>> video pauses briefly about once a second and sync is terrible...
> 
> That sounds like the TV being driven at the wrong frame rate, either a 
> 24fps movies played with the TV running at 25fps or vice versa. I'm 
> finding leanfront really very nice to use these days, but that is one 
> constant pain, having to do the strange vulcan nerve pinch on the 
> firestick control to get 24fps.

 > Paul G.

Yes, for leanfront it might be partially a framerate problem.  Firestick 
is natively 60 Hz and the content is 25 Hz.  My attempts at logging have 
given only a few lines, unlike Yeechang's from his Shield.  I'll look 
out for more options.  The 'live' behaviour came as a surprise.


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