[mythtv-users] MythTV and 4K HDR TVs

Stephen Worthington stephen_agent at jsw.gen.nz
Fri Dec 29 09:59:14 UTC 2023

After 14 years with my old Sony 32" 1080p TV, I have ordered a new LG
C2 48" OLED TV.  This is mainly for downloaded and streamed
programming, which these days is typically 2160p and may be available
with HDR or Dolby Vision as well.  My recorded TV will still be 1080i
or worse.  I have a fanless Nvidia GT1030 card (DVI and HDMI 2.0b) in
my main MythTV box, and my laptop has a mobile Nvidia RTX2060
(Thunderbolt 3, mini DisplayPort 1.4 and HDMI 2.0b).  What I want to
do is set up both PCs to be able to play 2160p video files in the best
quality possible, but still have the <= 1080i recordings displayed
properly too.  So I was wondering what other people might have done to
make this work.

My understanding is that the GT1030 can do only 4K @ 60 Hz maximum,
and can not do RGB or 4:4:4 chroma subsampling at that frame rate, due
to it only having an HDMI 2.0b port.  So I will only get 4:2:0 or
maybe 4:2:2 chroma subsampling.  This causes problems with text on a
black screen, for example, so I would prefer to be able to do full
4:4:4 (which the TV supports).  To do that, I need either DisplayPort
1.4 or HDMI 2.1.  The next highest Nvidia chipset (1050) supports
DisplayPort 1.4, as does any higher Nvidia GPU.  With DP 1.4, I can
get a DP 1.4 to HDMI 2.1 adapter at a reasonable price, so that is the
cheapest route to full picture quality.  To get HDMI 2.1 directly on
the video card, I would need a minimum of a 3050 GPU and the prices
for them are horrible.  The plus side of 3050 and greater GPUs is that
they do AV1 decoding in hardware, which is likely to be more and more
important in the future.  The huge downside of any Nvidia GPU > 1030
is that the cards all have fans, which make annoying amounts of noise
and also tend to fail and kill the card.  So it would be good to know
if this is a real problem when using MythTV with such cards, as MythTV
does not push the GPU very much and the card may be able to run with
the fans stopped.  Does anyone have any experience of this?

For my laptop, I have ordered a mini-DP 1.4 to HDMI 2.1 adapter and
HDMI 2.1 cable, arriving mid-January.  That should make it able to use
the full specifications of the new TV (4K @ 120 Hz).  Has anyone used
this sort of setup with MythTV?

My understanding is that while some 4K video will play using VDPAU,
NVDEC will be required to support the full set of 4K formats.  So I
have tried switching both machines to use NVDEC instead of my normal
VDPAU High Quality setting.  But I have had problems with NVDEC - some
recordings do not play properly - they are all pixilated and the
colours are off also.  This happens on both PCs.  So is this likely to
be a MythTV problem, or an Nvidia one?  I can post a sample of a
recording that does this if anyone is interested.

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