LG C1 reads 25p content from Zidoo z9x as 24hz, but from the Ugoos it shows 25hz. Why?

So like the title says, I recently happened to notice that for 25p content, my LG OLED VRR Information menu reports 24hz over the Zidoo, even though the Zidoo reports that it's sending 25hz to the TV. However, on the Ugoos AM6B, it reports 50hz (assuming 25x2.) Does anyone know what's going on? Why would there be a difference in what my TV is getting (or thinks it's getting) from both of these devices? I tested differnet Chroma Subsampling rates as well as bit depths. It just seems to be a difference between the two boxes.

 

@Markswift2003 Do you know if the Zidoo Z9X has a built in "framerate sync" feature similar to the toggle on Kodi where it converts 25hz to 24hz, for compatibility reasons? It seems like the Zidoo is doing something like this as the TV reads 25p content as 24hz, but on other devices, this is not the case.

 

Auto framerate does exactly what it says - as long as EDID and legal HDMI modes allow, it will adjust to the framerate of the file.

Trust what the Zidoo says over the display - a lot of displays will say 24Hz when either 24 or 23 is output. Never seen one say 24 when the input is 25, but if the Zidoo says 25, it's 25.

 

The odd thing is, is that with the same signal type, the Ugoos makes the TV say 50hz. So there seems to be something between the devices that make the TV think it is getting different things.

 

It appears that with 25p content, YCBCR 444 10 bit makes the TV say 24hz. And YCBCR 420 12 bit makes the TV say 50hz (must be doubling it due to a legal hdmi mode) Not sure why the TV shows 24hz though. Very annoying and weird. I hope it's just a OSD bug.

 

Looks like it's the same issue as this person from early 2024:

https://forum.zidoo.tv/index.php?threads/z9x-pro-player-sets-24hz-for-25-fps-video-solved.97572/

From reading this thread, it seems like just a LG OSD bug, and that it's getting the correct signal and everything is fine. I wonder what causes this. It apparently works properly with a PC. And some devices report it correctly. Others don't. Idk what would cause the TV OSD to change haha. Weird.

 

Bad programming - it's common for TVs to display 24 for both 23.976 & 24 fps but not for 25 as well.

By the way, only 50-60Hz is legal at 4:2:0 which is why 25Hz content is frame doubled at 4:2:0.

 

Is there any reason that you can think of as to why it is reported as 25hz correctly from a PC, but not from certain streaming boxes?

And yea, the 50hz doubling to make the HDMI a legal mode makes sense! It also proves that the TV actually recognizes that it's getting a 25hz signal, because under those conditions, it doubles it properly to 50 and the OSD reads 50.

 

Not a clue - I don't know how the LG makes its determination of framerate - it's not as easy as you might think!