Unexpected TV HDMI resyncs after powering off C4

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Sinna
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Unexpected TV HDMI resyncs after powering off C4

Post by Sinna »

I recently replaced a Raspberry Pi 3 with a C4 as the hardware platform running Kodi. On the Raspberry Pi it was LibreElec, on the C4 CoreElec (because of boot issues when trying to boot from an LibreElec image). I can't get Kodi 19 to run smoothly on that Raspberry Pi, hence the switch.

Since the replacement, I notice that - when watching another HDMI source on my TV - the TV regularly goes black for a short time where it seems to choose a new resolution (1280x720 / 50p). In practice the resolution does not change. At the moment the TV goes black, sometimes the PWR LED of the C4 lights up.
This is quite annoying and never had this phenomenon with Raspberry Pi.

If I disconnect the HDMI cable from the Odroid or leave the Odroid shutdown but not unplugged from the mains, the problem does not occur. The C4 and the other HDMI source are connected to the TV using an HDMI switch (lack of ports on my TV).

What I have already tried myself: playing with CEC and HPD in /flash/config.ini and update the firmware of the board using armbian-config (booted from another µSD-card running Armbian). The problem however remains.
I searched for similar issues on the internet and found the thread [SOLVED] Issues, issues, issues on C4, but the solution mentioned there doesn't work out for me either.
Last edited by Sinna on Sun Jun 02, 2024 4:06 am, edited 2 times in total.

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Re: Unexpected TV HDMI resyncs after powering off C4

Post by Sinna »

I just realize it's not only after powering off the C4, but once the HDMI cable is connected to the HDMI switch. The topic title is in that way incorrect, but I can't change that any more.

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Re: Unexpected TV HDMI resyncs after powering off C4

Post by odroid »

In fact, we have no experience using the HDMI input switch, so it is difficult to determine the cause.

Anyway, what type of HDMI switch do you use?
And what is the native resolution and refresh rate of your TV?
What happens if you unplug the 12V DC plug from the C4?
Can you show us your modified /flash/config.ini in CoreELEC OS?

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Re: Unexpected TV HDMI resyncs after powering off C4

Post by mctom »

Perhaps this is an issue of HDMI switch trying to be smart and automatically switching inputs, albeit incorrectly?
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Re: Unexpected TV HDMI resyncs after powering off C4

Post by Sinna »

I reverted to the stock /flash/config.ini, see attachment.
The native resolution of my TV is 1920x1080 / 60p, the HDMI switch is an HQ 4port HDMI Switch (HQSSH100).

If the HDMI switch is the culprit, why didn't it happen with a Raspberry Pi 3 then?
Once the HDMI cable is attached to the HDMI switch, it happens with all other attached HDMI devices (DVD player and ISP decoder).
If I shutdown the C4 but leave the power supply plugged in, the phenomenon doesn't occur.
I have still have to test what happens when unplugging the 12V DC plug, but don't expect any difference with the power supply pulled from the mains power.
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Re: Unexpected TV HDMI resyncs after powering off C4

Post by odroid »

Try uncommenting line #124 and #135 in your config.ini file.
After cold booting, check what happens.

If it doesn't help, you might need to check the CEC options.
Do you use CEC feature in your TV?

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Re: Unexpected TV HDMI resyncs after powering off C4

Post by Sinna »

I've uncommented vout and frac_rate_policy as suggested but apart from CoreElec now stating it's on 1920x1080 60fps again instead of 50fps, the problem still occurs.
When I remove the 12V DC plug, the phenomenon is gone.
When I plug it back in (even while the adapter itself removed from the mains), I see some noise in the picture from the source currently playing and the phenomenon returns.

I already tried to switch off CEC from inside the CoreElec interface but to no avail either.
As far as I know, I don't have any CEC feature on the TV, a Samsung UE42F5000AWXXN, introduced in 2013.

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Re: Unexpected TV HDMI resyncs after powering off C4

Post by mctom »

Sounds like some kind of AC ground/earth witchcraft to me. After all you're dealing with a bunch of devices interconnected with HDMI cables that do not offer galvanic isolation.

I suppose that the video interruptions you see is the HDMI switch resetting itself, similarly to what many devices do after ESD zap. That's how you open locks by zapping intercom with a cigarette lighter.

If my diagnosis is correct, there are so many things that could have gone wrong.
I have a cursed socket at home, that is electrically close to the fridge socket. When its compressor started or stalled, my HDMI monitor would go blank for a few seconds. The solution - better HDMI cable.
If any of the HDMI-enabled devices you own happens to have an AC plug with Earth connection, try replugging it rotated 180 degrees (if Dutch sockets support it).
Sinna wrote:
Tue Jun 04, 2024 6:03 pm
When I remove the 12V DC plug, the phenomenon is gone.
When I plug it back in (even while the adapter itself removed from the mains), I see some noise in the picture from the source currently playing and the phenomenon returns.
This is disturbing to say the least. What else is your C4 connected to? Perhaps an Ethernet cable with nickel plated connectors?
Do you happen to have some other 12V PSU to test with?
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Re: Unexpected TV HDMI resyncs after powering off C4

Post by Sinna »

mctom wrote:
Tue Jun 04, 2024 8:58 pm
Sounds like some kind of AC ground/earth witchcraft to me. After all you're dealing with a bunch of devices interconnected with HDMI cables that do not offer galvanic isolation.
Sounds indeed familiar, but atm I don't know how to fix that. The power supply itself has no earth pin.
mctom wrote:
Tue Jun 04, 2024 8:58 pm
Sinna wrote:
Tue Jun 04, 2024 6:03 pm
When I remove the 12V DC plug, the phenomenon is gone.
When I plug it back in (even while the adapter itself removed from the mains), I see some noise in the picture from the source currently playing and the phenomenon returns.
This is disturbing to say the least. What else is your C4 connected to? Perhaps an Ethernet cable with nickel plated connectors?
It's indeed disturbing. I would expect no difference if the power is disconnected using the 12V DC plug or the power adapter itself.

The C4 is connected as follows:
  • 12V DC plug
  • ethernet port to a local network switch
  • HDMI port to the HDMI switch
mctom wrote:
Tue Jun 04, 2024 8:58 pm
Do you happen to have some other 12V PSU to test with?
I'll see if I have a spare PSU, but since smaller devices are all running on USB (so 5V) power...

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Re: Unexpected TV HDMI resyncs after powering off C4

Post by Sinna »

I thought I got it fixed by replacing the power supply from an old WD My Book External Hard Drive. Unfortunately phenomenon stays, but less often than before.
This is really weird.

@mctom: replugging 180° is not an option as it then blocks the power switch of the socket it's plugged into.

To summarize:
  • I've uncommented vout and frac_rate_policy as suggested.
  • CEC is switched off using the CoreElec CEC Adapter configuration page.
To be complete: I bought SOS Solutions' ODROID C4 Starter Kit (sorry, only available in Dutch), so I have the original 12V/2A power supply EU plug. I bought it at the end of August 2022.

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Re: Unexpected TV HDMI resyncs after powering off C4

Post by mctom »

If you see improvement then this is indeed some weird electrical problem.
Without tools and knowledge it may be hard to solve.

How many HDMI sources do you have connected to your HDMI switch? Have you tried leaving only two plugged in, The C4 and something else, to rule out that some other of your devices causes trouble?
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Re: Unexpected TV HDMI resyncs after powering off C4

Post by Sinna »

I have a Panasonic DVD player, a Proximus v5c decoder and the Odroid connected to the HDMI-switch. Both the DVD player and the decoder were already connected when swapping the Raspberry Pi for the Odroid.
So chances are very little one of those two is causing the issue. They both face the same phenomenon when the C4 is connected by HDMI or with the 12V DC plugged in.

It seems that current coming in from the HDMI port is flowing to the power supply. At some point (sooner with the official Odroid power supply, later with the power supply of the external hard drive) the power supply reaches a discharge which then causes the phenomenon.

Why I suspect this:
  • When the HDMI port is disconnected, the issue doesn't occur.
  • When the 12V DC plug is unplugged, the issue also doesn't occur.
  • When the 12V DC plug is plugged in to the board, but disconnected from the mains (using a power switch in the mains outlet), the issue does occur but time wise depending on the used power supply.
After rereading this reply, it looks like a grounding issue, but I don't know how to fix that properly: as far as I know, barrel plugs don't have grounding.

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Re: Unexpected TV HDMI resyncs after powering off C4

Post by mctom »

Uhh... not exactly. :?

First of all, your setup has a problem. A combination of devices you connected together has a problem.
If you remove the HDMI switch and connect C4 directly to a TV it will work fine as well. That doesn't mean the HDMI switch is faulty, right?
You can't rule out everything except C4 because it worked fine without it. It's a common investigation fallacy.
Sinna wrote:
Sat Jun 08, 2024 10:36 pm
(using a power switch in the mains outlet),
That's not equivalent of plugging the adapter out from the outlet. If the switch cuts just one of the two wires, strange things might happen, even if it's not the ground wire it's cutting.

Some things that you may want to try:
- Try plugging all the devices into the same extension cord with multiple outlets (to prevent many problems with electrical wiring your home might have),
- If you own a AC voltage probe (a screwdriver that glows when you touch the AC) and check if you don't get the AC voltage anywhere it shouldn't be:
-- Naked (not coated) metal parts of all appliances in question
-- Earth contacts in your wall outlets
My Odroid M1 server started zapping me after I moved it elsewhere and used an old socket with disconnected earth.. And my PSU required earth.
- Check again if ANY of your HDMI devices has a AC plug that has earth contacts and if so, try plugging it in, in reverse.
- Try again without DVD player or Proximus decoder and see if it improves the situation in any way.
- If your Ethernet cable has metal-plated jacks, disconnect it from C4 and see if it helps.
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Re: Unexpected TV HDMI resyncs after powering off C4

Post by Sinna »

mctom wrote:
Sun Jun 09, 2024 2:15 am
- Try plugging all the devices into the same extension cord with multiple outlets (to prevent many problems with electrical wiring your home might have),
That's already the case: the whole setup is behind an extension cord with multiple outlets. In the outlet the power supply of the C4 is plugged into, I plugged an additional switch to allow powering on/off the power supply itself (as the C4 has no power button itself).
mctom wrote:
Sun Jun 09, 2024 2:15 am
- If you own a AC voltage probe (a screwdriver that glows when you touch the AC) and check if you don't get the AC voltage anywhere it shouldn't be:
-- Naked (not coated) metal parts of all appliances in question
-- Earth contacts in your wall outlets
I don't have an AC voltage probe.
mctom wrote:
Sun Jun 09, 2024 2:15 am
My Odroid M1 server started zapping me after I moved it elsewhere and used an old socket with disconnected earth.. And my PSU required earth.
- Check again if ANY of your HDMI devices has a AC plug that has earth contacts and if so, try plugging it in, in reverse.
- Try again without DVD player or Proximus decoder and see if it improves the situation in any way.
- If your Ethernet cable has metal-plated jacks, disconnect it from C4 and see if it helps.
None of the devices have an earth contact and use a flat plug like the one in attachment.
I can disconnect one of the two other device so see if it improves, but not both as I otherwise don't have an HDMI source left. I have no cable TV.
The Ethernet cable has not metal-plated jacks.

And yes, I'm not an electrical technician but just an IT guy trying to solve this weird behavior.
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Re: Unexpected TV HDMI resyncs after powering off C4

Post by mctom »

Another idea for a test is to skip the power switch you're using for C4 and see how your setup behaves without it.
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Re: Unexpected TV HDMI resyncs after powering off C4

Post by Sinna »

I've moved the power supply of the C4 from the one extension cord with multiple outlets to another (also with a power switch) on the same electrical circuit and the phenomenon is gone.
By moving it, there's a chance I've rotated the power plug 180° without realizing.
Moving the power supply back to the original extension cord reintroduces the issue, even while not being powered on in the meanwhile.

Conclusion: I'm getting closer to a solution, but a solution I never expected to fix the root cause.
I'll try some other configurations with different power switches so I can centralize the power distribution again to one extension cord with multiple outlets.

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Re: Unexpected TV HDMI resyncs after powering off C4

Post by mctom »

Yeah, you probably swapped the plug contacts.
It shouldn't be happening at all in theory, but if I had to guess you could rotate a HDMI switch power plug to get a similar effect.
I suspect one of the PSUs involved is faulty. Since you tried replacing C4 PSU and it didn't solve the problem completely, I'd try replacing the HDMI switch PSU.

That's why I recommended checking with an AC probe if your appliances are even safe to use at this point. If the PSU has a galvanic leakage it may deteriorate further over time and do harm to someone.

I'm glad that my original diagnosis appears to be correct.
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Re: Unexpected TV HDMI resyncs after powering off C4

Post by Sinna »

I've replaced the power switch the power supply of the C4 is plugged into with a similar (but different) model and the problem seems to be fixed.
@mctom: thanks for the suggestions and pointing me to a solution.

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Re: Unexpected TV HDMI resyncs after powering off C4

Post by mctom »

This is great news, thanks for letting us know. :)
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