Server Version#: 1.40.3.8555
Player Version#:1.64.0.170-84278903
I have 2 Dell 3050 small form factor computers that I have installed Xubuntu 24.04 on, then plex-htpc (latest version). The audio is via line out on the Dell to line in on a small 2.1 channel 50 watt per channel audio amplifier. When I listen to music (using plex-htpc), volume level is normal, and controllable via remote keyboard. The problem occurs when I watch downloaded video content; the volume is extremely low. I have to turn the volume on plex-htpc all the way up, and then turn the volume all the way up on the amplifier. I also watch live streams using both VLC and SMPlayer, and the volume is very loud using those apps. I am struggling to figure out why this issue occurs. I might replace the amp with a more powerful one, but that does not explain why only certain media plays at a low volume. Any suggestions welcome!
In general:
Music (in the overwhelming majority of cases) is already in stereo (i.e. 2.0 channels).
And pretty much all of it is loudness-maximized.
Audio on a movie is not loudness-maximized.
And if on top of that your movie comes with a surround audio track, instead of stereo, it will be even quieter when it is automatically downmixed to stereo, to suit your speaker system.
First thing you should check is that Plex player knows that you have only stereo speakers. (The subwoofer can be disregarded in a 2.1 system, as it will always derive its signal from the Left and Right channels.)
Enter the settings, section Audio and verify that it’s only set to 2.0 channels.
Don’t set the audio interface to “Automatically selected”.
With that out of the way, try DISabling “normalization when downmixing to stereo”. Compare the loudness with it on and off. But keep in mind that it will only have an effect if the selected audio track has more than 2.0 channels.
If the above measures still don’t produce enough loudness for you, you will need to employ audio dynamics compression.
Some DVD/Bluray already bring a stereo audio track which has been compressed. So if you rip your own discs, make sure to keep that stereo track and not only the 7.1 surround version.
Items recorded from TV do also have usually already various levels of compression applied.
If your movie only comes with 5.1 or (worse) 7.1 channel audio, you will need to apply dynamic compression after the downmix to stereo.
You could produce an additional stereo audio track for your files. ffmpeg can produce these for you. But you will need to mux this audio track into the original video file, because Plex cannot use audio in a separate file. [How To] Downmix Surround Sound To AAC Stereo Properly (using FFmpeg Batch Converter)
Another way would be to look for a setting in your TV or speaker system, which can activate dynamic compression.
Often it is called “Night mode” or “Audio leveller” or similar.
If none of your devices has a compressor, you can activate one in Plex HTPC.
But you will need to re-activate it again after every restart of the app: An on-demand audio dynamics compressor for PMP and Plex HTPC
Thanks so much for the reply! I tried the options that were possible, none of them seemed to make a difference. Then I realized that the other plex-htpc box does not exhibit any of those symptoms…settings are the same on both, the only difference is the stereo amplifier that each is connected to. As it happens I have one of the stereos that works ok on order, so first I am going to swap out the amp and see if that fixes it. If not I’ll just completely reload Xubuntu 24.04 and plex-htpc on the affected box, although with the settings mirrored, not sure what that will do.
I couldn’t do the “Downmix Surround Sound to AAC” because the ffmpeg batch converter is a windows-only app, and I don’t have (nor will I ever) have a windows box around. I may mess with trying to do it on a linux box by trying to replicate the commands used, but that looks like a lot of work!
The “on-demand audio dynamics compressor” looked promising, but it seems the default location for the required file has changed so I’ll have to do a bit of poking around to see where it has moved to.
At the end of the day though, it works fine on one setup, yet doesn’t work on another setup with the exact same hardware, except the stereo amplifier. The new amp will be here in a couple days, so I may just blow away the non-working box for kicks in the mean time to see if it fixes the issue.
Please accept my thanks for the in-depth trouble shooting guide…while it didn’t fix the issue, I now have a better understanding of the audio processes going on behind the scenes, and any day I learn something is a good day!
Cheers!
Cliff
ffmpeg is an open source project. I think it even started on Linux. So you will be able to execute it on Linux for sure.
Whether there is a similar GUI for ffmpeg on Linux available, like the batch coverter, I don’t know. But chances are not bad.
You can’t find it in the locations mentioned in here? https://support.plex.tv/articles/plex-htpc-input-maps/
Yes, I’m pretty familiar with ffmpeg, I usually use it via command line, but interpreting what he’s doing in that link might be beyond me.
Ah, my bad, I didn’t notice (or assumed!) it was from the root dir, not from my dir. Sure enough, there it is, right where he said it’d be! Ok, cool, something to mess with this afternoon. Still curious as why the issue is only on one box though…
Made that change for the built-in compressor, no noticeable difference
You did press the key combo?
If so, you can verify via the player log that the command was executed.
If it was, and you still don’t hear a difference, then it might be that you have “HDMI passthrough” activated.
Go into the audio settings and remove those checkboxes from the various surround sound formats.
Yes, I did ctl-D, no apparent effect.
There is no option for hdmi passthrough, or passthrough of any kind in plex-htpc audio settings. Audio settings are configured as follows:
normalize multi-channel audio - unchecked
exclusive audio - unchecked
audio device - 2.1 surround output to front and subwoofer (i’ve tried “built-in analog stereo”, “default (alsa),” all to no effect.
audio device kind - basic
audio device channels - 2.1 (also tried 2.0 stereo to no avail)-
fixed audio offset - all set to 0ms
no option to remove checkboxes from surround sound formats.
plex-htpc for linux
client version - 1.64.170-84278903
platform version - 20
renderer - webgl
Have you ever pressed the Shift++
or - keys during playback?
Try inspecting the player log, whether the compressor command was actually triggered.
not knowingly, but i see that is a volume control, wasn’t aware of that. anyway, cranked that up to full vol, no effect.
whoa. so i went back into audio settings and reset them to match the other box that works, and magically it works now too. (normalize unchecked, exclusive audio unchecked, built-in analog stereo, audio channels 2.1).
gotta love it when stuff fixes itself!
Thanks for all the help, it’s much appreciated!
wow. now the box that was working fine is now having audio issues. i changed nothing, and now the normal vol up/down keys on the mini keyboard aren’t working. this is a real headscratcher. (the plex-htpc vol control that you enlightened me to, shift plus or minus works though, so not dead in the water.)
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