4K - 4:2:0 option also for the lower fps - legacy AVR support

Hi there,

recently bought 4K LG TV to my parents. I noticed, that default CE behauviour is
4:4:4 when 30fps or lower
4:2:0 when higher fps

which could be overwritten by 4:2:2 CE option. My trouble is, that older receiver (Pioneer VSX 323) supports only 4:2:0 and only fps =<30. At least that my assumption from digging 4k specs from later pioneer models; for this mode from 2014 there is no reference according chroma at all, just mention about max 30fps. I know that default CE setting doesnt work for my 30fps test video.

Could I ask to add 4:2:0 option to the menu aswell, for the older receiver compatibility? Next time I visit parents Ill try 4:2:2 option, but I think 4:2:0 will be needed, and kinda makes sense as an option, when >30 fps have those by default and many videos using just 4:2:0.

I ordered also some expensive HDMI cables, but considering existing 50cm length, and especially after digging into Pioneer 2015 specs, 4:2:0 would be much appretiated.

I guess I could use some /sys/class/amhdmitx/amhdmitx0/attr attribute to trigger YUV420 for testing purposes? Maybe

echo '420,10bit' > /sys/class/amhdmitx/amhdmitx0/attr

or is it overriden by CE when starting video? I know its valid for all videos and it breaks autoswitch functionality, but for testing purposes, I think correct solution would be add 4:2:0 to switch for legacy devices (that AVR is brand new condition :slight_smile:

Have you actually tried this or are you asking after reading the specifications? Cause your AVR doesn’t support HDMI 2.0 which means that you won’t enjoy any HDR material. How big is your TV? If it’s less than say 65" you’ll have a hard time to see any differences between 1080p and 4K material as long as they are SDR - unless you are really close (under 1 meter or 3 ft).

If I were you, I would connect my AVR and CoreELEC device both to the TV and use ARC over HDMI for sound or just SPDIF. This way you’ll enjoy 4K and HDR and still have decent sound. You won’t get TrueHD / DTS-X etc, but the improvement in picture quality should be worth it. I guess your parents will buy a new AVR in the next years as it already is over 6 years old.

If you still want to connect your CE device to your AVR for TrueHD and DTS-X, enable 8-bit in CE settings and everything should be fine. There is no need for 10-bit as your AVR doesn’t support HDR.

You can place echo '420' > /sys/class/amhdmitx/amhdmitx0/attr in autostart.
This will force CE to always use 4:2:0.

HDR is not supported by AVR, that doesnt cross my mind when I ordered one VIM3L for them in future :slight_smile: Thats good point, and I am aware that HDR is much more beneficial than 4k. TV is 50, 1080 is otherwise fine, just want to ensure that at least feature is used, even when difference should be minimal.

The idea with ARC is interested, thanks for that! Must investigate, how is it with formats, if the TV would be capable output at least 5.1 (DTS/DD) for AVR, then its sufficient enough to try it, to possibly get HDR in future. And also, AVR doesnt have power off passthrough function, so that would be a nice addition to them also… But if it would be only 2.0 then its no go.

But at least 4k would be nice.

I will try both 4:2:2 and 4:2:0 (thanks Coolest) and see, how that Pioneer goes also. Anyway, is there any chance to 4:2:0 in options (still, and I confirm that ARC would be maybe better solution; more choices better user experience, and that one could be easy one and makes some sense)?

Which TV model do you have? Most likely you should not have a problem to output 5.1 with ARC. Check your TV’s audio settings and choose “bitstream” for ARC. Here is an informative site regarding ARC - What HDMI ARC (Audio Return Channel) Is. I would recommend to use ARC, but test both scenarios :slight_smile:

Its entry level LG 50UK6300, so I am not have high hopes… Manual is not very informative, only thing I can find for sure is that they implement DTS decoder. As you say, I am planning try and see method. Hopefully I will reach parents flat on weekend for a few moments.

Remember to update the TV to the latest firmware and use the HDMI port which has the additional “ARC” marked on it like “HDMI IN/ARC”.