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Author Topic: HTPC Linux screen power issue - any advice welcome  (Read 535 times)

avid

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HTPC Linux screen power issue - any advice welcome
« on: September 18, 2023, 09:54:47 am »

I don’t believe I have a problem here with MC, but I am posting this here in the chance that I may catch someone’s curiosity, who then may suggest what I could look at or where else I might post.

My HTPC system comprises 4 significant hardware components.
  • A large TV screen on the wall – normally just used as a display.
  • An AV receiver responsible for selecting input source (from computer, streamer boxes or smart TV), routing audio (to 5.1 speakers for viewing, or multi-room speakers for listening) and audio controls (e.g. volume or DSP).
  • A server computer that runs both MC (used for all non-streamed media playing) and my own control software to manage everything - controlling the AV box, switching the screen on&off, controlling Spotify and Roku, and controlling MC via MCWS.
  • Phones and/or tablets for the UI to access the control software as a web app.
The wire from the computer to the AV box is a single HDMI, which carries the 4K video and 5.1 audio.

This hardware arrangement has worked well with a Windows OS for about 12 years. And it has also worked OK (with some minor teething issues) with a Linux OS for most of the last 2-3 weeks. Obviously, the OS is configured to inhibit power management (sleeping) and screen blanking. And I believe I have stopped all automatic updates to all firmware and software. The OS is Kubuntu in order to get an X-based DE; with Wayland on Ubuntu, none of the MCWS windows management commands would work.

Then yesterday, after no apparent changes, the computer started turning off the HDMI after 10 minutes when the physical screen was off. And this stops the audio signal as well. But this configuration is the normal mode for listening to music. And it was working on the same settings for 2-3 weeks beforehand.

I have checked and re-checked the Kubuntu KDE power management settings. I tried removing the Nvidia graphics card, reverting to on-board HDMI. My current work-around is to leave the TV screen on when just listening to music. But that is wasteful.

So …
  • Have I described the scenario and the problem clearly?
  • Has anyone got any ideas what I might try to fix this - or track down what might be causing the switch-off?
  • Can you suggest useful Linux forums that I might try posting for advice?
Thanks in advance … Brian
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bob

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Re: HTPC Linux screen power issue - any advice welcome
« Reply #1 on: September 18, 2023, 10:08:37 am »

There is a setting in MC to keep HDMI enabled when playing back on the local connection. Maybe turn that on? (search for HDMI in options).

Also, you can use xset from the command line to check the underlying state. Also, reporter in MC will tell you what state MC is in with regards to the screen.

HDMI has always been problematic with regards to audio when a monitor is involved. If you have 2 HDMI ports perhaps separating the audio into a different port would be useful.

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avid

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Re: HTPC Linux screen power issue - any advice welcome
« Reply #2 on: September 18, 2023, 10:33:20 am »

Thank you so much Bob,

I shall try each of these in turn (as soon as my wife stops watching her programme  ;D - the problem is only on the live system). The HDMI setting does look extremely relevant. And if I put the NVidia card back in and use a DisplayPort -> HDMI lead for video, then I could use the existing HDMI output for audio-only in parallel. Unfortunately the computer m/b doesn't have a separate digital out as an option.

I also have an old HDMI optical audio extractor available, but my AVR has no spare optical input - I am using it to replace an unreliable eARC from the (rarely used) Smart TV. But I have options I could trade-off here.

So ... lots to try here - I shall report back if I get anywhere.
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avid

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Re: HTPC Linux screen power issue - any advice welcome
« Reply #3 on: September 18, 2023, 01:13:33 pm »

Once again thanks Bob.

The HDMI option was all that it took. It now plays audio only without any screen display.

I shall experiment with xset to improve my understanding of the underlying Linux X technology. And I have replaced the NVidia card and will keep the separate HDMI port option as something to consider in the future.
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avid

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Re: HTPC Linux screen power issue - any advice welcome
« Reply #4 on: September 19, 2023, 02:51:22 am »

I think I can definitely confirm that the problem has gone away with this setting changed.

For the future, I have just spotted that the m/b has an SPDIF header that I can easily bring out to back-plate connectors. I am guessing that there is no real need to do this, because it would just carry the same digital audio signal that is currently going through HDMI. But, once again, it is good to have options.

Thanks for your help.
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mwillems

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Re: HTPC Linux screen power issue - any advice welcome
« Reply #5 on: September 19, 2023, 08:23:41 am »

I think I can definitely confirm that the problem has gone away with this setting changed.

For the future, I have just spotted that the m/b has an SPDIF header that I can easily bring out to back-plate connectors. I am guessing that there is no real need to do this, because it would just carry the same digital audio signal that is currently going through HDMI. But, once again, it is good to have options.

Thanks for your help.

So as a quick FYI in case you explore that in future, SPDIF can't carry 8 channels and can only carry 6 channels with lossy encoding, whereas HDMI can carry both in full fidelity.  If you have a stereo setup it shouldn't make a difference, but if you're doing multichannel, HDMI is meaningfully different.
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avid

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Re: HTPC Linux screen power issue - any advice welcome
« Reply #6 on: September 19, 2023, 08:51:10 am »

So as a quick FYI in case you explore that in future, SPDIF can't carry 8 channels and can only carry 6 channels with lossy encoding, whereas HDMI can carry both in full fidelity.  If you have a stereo setup it shouldn't make a difference, but if you're doing multichannel, HDMI is meaningfully different.
Thanks - that's useful to know. I had not realized that SPDIF was not the same spec as HDMI audio. If anything, I would have guessed that HDMI was the inferior.

It turns out that I have no need for separate audio cabling. But if I did, my AVR is configured for 5.1 with an optional down-grade for multi-room stereo. So the SPDIF would be enough - especially as my aging hearing can't now differentiate lossless and lossy content .
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