[mythtv-users] NVDEC: is there something wrong with it?

Mark Kendall mark.kendall at gmail.com
Sun Nov 15 17:18:13 UTC 2020

On Tue, 10 Nov 2020 at 14:27, Jim Abernathy <jfabernathy at gmail.com> wrote:
> I just put together a new workstation where I will be watching TV with
> Mythtv-frontend when not using it for other things.
> It's a 6 core Ryzen 5 3600 with a Nvidia GT-1030 fanless GFX card.
> After the initial install of mythtv-frontend I started playing videos
> with the default settings of NVDEC.  That worked fine on HD 1080i
> content but when I tried a sub-channel where the video was 720x480 at 30, I
> immediately noticed that the video paused and played every few seconds
> and never got better.
> When I changed the video profile to High Quality OpenGL it worked
> perfectly on all video types.
> So I'll leave it that way, but why would NVDEC be so bad on 480i content??


A little late to the party but, thinking about it, there are 3 possible issues:-

- as others have mentioned the 'old' nvidia mpeg2 decoding problem.
You don't mention what the source material is other than the
resolution - but I would expect that to present itself as corrupted
video frames rather performance issues.
- deinterlacer. NVDEC has an awkward deinterlacer setup and there is
also the possibility it is falling over on a particular stream. I
would try going into the details of the video display profile and
disable the 'Prefer driver deinterlacers' option. That should give you
nvdec decoding with OpenGL shader deinterlacers - if that works then
the problem is in the deinterlacers.
- Stuarta A noticed an issue recently with some NVDEC problems which
we tracked down to the number of video buffers in use. We didn't
really finish the conversation but my testing with a 1030 works with
just about everything I can throw at it - whereas Stuart (with a
different nvidia card) had to make some source code adjustments to get
playback to work smoothly.

Can you post some 'mythfrontend -v playback' logs for a stream that
does not play well?

Thanks and regards

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