No sound for 4K+HEVC+EAC3 on desktop app. Web app has sound

Plex Players Desktop Players
1

Server Version#: 1.32.5.7328 but previous version also had this issue
Player Version#: now 1.70.2.3845-31e96af6 but also tried newest 1.74.1.3913-9baac009 and 1.73

Hello

I have encountered an issue where certain videos have no sound in the (Windows 11 x64) Plex desktop app but do have sound in plex web app on the same device in Chrome browser (well, Brave browser, Chromium-based). This is strange because usually, because of codecs, it’s the other way around. VLC media player also has sound for these videos, again on the same device

The file extension is MKV, the video codec according to the plex app is HEVC (so, x265) and the audio codec, again according to the plex desktop app is EAC3 with 5.1 sound. The plex server version is 1.32.5.7328 and the previous version had the same issue. The plex desktop app version is 1.74.1.3913-9baac009 and the previous version had the same issue as did the one before that. The videos without sound are all 2160p HEVC MKV with EAC3 5.1 audio. The audio bitrate is 256kbps and the sampling rate is 48000Hz

The android plex app on my TV also has sound. The plex desktop app also has sound for most of my other videos which aren’t 2160p HEVC EAC3 MKV. An example are 2160p HEVC DCA MKV videos, which do have sound. Another example of the same are 2160p HEVC AC3 MKV videos, which also have sound. I have confirmed with multiple, unrelated videos and so far it’s only 2160p+HEVC+EAC3 5.1 which has no sound

Anyone has any idea what might cause this? Exclusive audio mode is turned off in the desktop app, so it isn’t that. I’m also certain that these same video files used to play audio without any issues on this same device using the same plex desktop app before this issue started. Also, the issue happens both with sound output on speakers and sound output through BT headphones. I have no other sound issues with anything else on this device

Also, if I let it convert (transcode) from the original 2160p at 15.3mbps to “1080p HD” at 10mbps the sound starts playing again. If I let it transcode from 2160p to “1080p HD (High)” at 20mbps or “1080p HD (Medium)” at 12mbps it goes away again. Weird

If you want, I can provide debug logs. What I did to generate them: first play video which doesn’t have sound. Then start transcoding at “1080p HD” and sound returns, then play an x264 MKV video which does have sound as always. This so you have some context for the log files, if I provide them

Cheers

2

Go into the settings of the player. Disable audio bitstreaming (passthrough) for E-AC3 (“Dolby Digital Plus”).
Try again.

3

I have checked the player settings out but unless I’m misunderstanding you I can’t find that setting with how my audio devices are currently set up. If I change the “audio device kind” to “HDMI”, the setting “passthrough Dolby Digital Plus” does appear but is unchecked by default. However, my output is not HDMI, it is either 3.5mm jack for my PC speakers or Bluetooth for my headphones. For both, the only setting I can choose that seems valid is “basic” for “Audio device kind” since my speakers nor my headphones are “HDMI” or “Optical S/PDIF”

That said, I did try out both “HDMI” and “Optical S/PDIF” with Dolby Digital Plus passthrough disabled and for HDMI, it (unexpectedly) works as before, audio on all my files except 4K+EAC3 MKV files. For S/PDIF, Dolby Digital Plus passthrough is not a setting that appears and now all my files are without audio

Here are my settings as they were before, with the menu for device kind shown. Usually I left this top setting on “auto select device” but that produces the same issue. As you can see, for the “basic” device kind, no passthrough options appear
image

Here is what appears if I choose “HDMI” as the device kind for my (non-HDMI) speakers. The passthrough checkboxes are all unchecked by default but it doesn’t solve this issue
image

And here is what appears if I choose S/PDIF as device kind. Now I have no audio at all
image

4

I see, thanks for checking! Leave those settings as they were before, because “Basic” is the right choice if you have no HDMI or optical plug.

Please enable client logs, then play the file for ~ 30 seconds, then fetch the log and post it here.
Do also fetch the Plex media info XML of the video.

You might have to prepare a 30 seconds snippet of the video as a sample file, so the developers can try and recreate the issue.

5

I have played around 30 seconds of the file and have produced a desktop player log file, with the log settings on “Enabled” and not on “Verbose”. I have also prepared a sample file of that same 30 seconds + 10 seconds and have confirmed that it has audio when played through VNC player on the same device. The media XML data file together with log file is below. Should I also upload the video sample file here? If so, I will edit this reply and add it, though it will be in a zip file since MKV is not allowed. Note that I had to change the XML file extension to TXT, as XML is also not allowed apparently. I can also produce server log files if necessary and can provide samples of other, unrelated media with the same issue (all 4K HEVC EAC3 MKV though, as mentioned)
Video_File_XMLData.txt (11.7 KB)
Client_Logs_Nonverbose.txt (181.4 KB)

6

It would be great if you could upload the sample file to Google Drive and send me the download link per PM!

7

PM sent

1 Like
8

Have you confirmed that the sample file also exhibits the missing audio?
Because I cannot reproduce the issue on my side.

Did you connect the player to your Plex account?
Did you prevent internet access of the player by any means, like DNS filters or firewalls?

9

I hadn’t yet confirmed this, no. However now I have and indeed, it does not have audio unless I enable transcoding to “1080p (HD)”, at which point audio returns. It seems to be direct play which does not have audio for 4K HEVC EAC3. Note that I have made this sample with the plex transcoder through the command line

My player is connected to my plex account, yes

I have an enterprise firewall on my network periphery, though it allows any connection from inside to outside so it shouldn’t (and doesn’t) block the player trying to connect to the internet. Also, my plex server is local and the media is also played locally and from local NAS storage, confirmed by the fact that it continues playing if I completely block internet on my firewall. Apart from that, I am able to sign my plex account out and sign back in without issue, so the player is able to reach the internet and the plex account services

If the cause was internet access, wouldn’t it be expected that every video I have with every kind of codec would be missing audio in directplay mode, and not only 4K HEVC EAC3 MKV? Or am I mistaken?

[edit]
If you want to see what happens for yourself, I can also provide a screen capture of me playing a video without sound and after that one with sound, showing the video codec data for each one

10

Not necessarily. Some codecs need to be licensed by Plex per user and are as such not included in the player installation. Only when they are needed for the first time, they are downloaded and installed by the player (or server).

11

Understood. I have checked the firewall logs and nothing has been blocked coming from my PC’s IP or the Plex server’s IP and going to the internet for weeks on end, which is normal because of the rule allowing all outgoing traffic for any host inside the network. So I don’t think that this is the cause of this, especially so because it used to work for these files not too long ago and the firewall hasn’t been reconfigured for more than a year (I checked). And also because if I disable the firewall and just let everything through in both directions, open the gates (or rather, remove the gates) so to speak, it still doesn’t work

12

Solved it! Though I don’t know what caused it in the first place

First I found this
Then this
And then this
Which shows multiple people with the exact same issue, though it still seems pretty rare. The DLL files mentioned in those threads (DolbyDecMFT.dll in both System32 and SysWow64) were already in place on my PC, so I could not register them as described in those threads and also unregistering didn’t work, both actions gave me an error. I could also not remove or replace them because they are system files and are protected against tampering through file ownership by the TrustedInstaller system user, with very limited permissions for anyone else. I also noted then that those DLL files had a “date modified” property of just a few days ago, right around the time this issue started happening. So suspecting that I had likely found the cause, I decided to take a risk.

For anyone else reading, beware: tinkering with system DLL’s can be VERY RISKY. Do not proceed if you don’t have backups and/or aren’t really familiar with tinkering in windows to repair a damaged system and/or aren’t comfortable in the command line. Messing with the wrong DLL’s can and will brick your system or cause data loss or cause corruption, or… Downloading DLL files from the internet can also be risky and can lead to malware, incompatibility or damage

  • I first took a full image backup of my device.
  • Then I took ownership of both those DLL files and gave myself Full Control permissions on them
  • The previous step enabled me to delete them, which I did
  • Then I downloaded the DLL files found for instance in the comments of the second link above. You could also take them from another system where plex desktop doesn’t have this issue, which would be much better and safer. I didn’t have a second system though
  • I put those DLL files in the System32 and SysWow64 folders. See download link below
  • Then I registered those DLL files like so (in an elevated, administrator command prompt)

regsvr32.exe “C:\Windows\SysWOW64\DolbyDecMFT.dll”

and

regsvr32.exe “C:\Windows\System32\DolbyDecMFT.dll”

Then rebooted my device. Et voilà, direct play of HEVC EAC3 produces sound again, It’s fixed!

So either something damaged those DLL files or something else happened to them or their registration in windows. This could very well be a coincidence but I did update my plex desktop client around the time those DLL’s were modified. Does doing so change anything with those DLL files? Are those DLL’s some of the licensed codecs you were talking about? Is it possible a plex desktop update caused this, or perhaps I changed settings in the plex desktop app? Any other suggestions as to what could have caused this?

[edit]
Here is a link to those same DLL files but a much newer version than the ones linked in the threads above. Above are from 2017 (v10.0.10586.0) and these are from 2022 (v10.0.19041.1466). These newer ones also work, just tested them. I took them from this (archived) reddit thread. Also, this newer version has separate DLL’s for the sytem32 (32-bit) and SysWow64 (64-bit) folders, which the DLL’s linked in the above threads to not, those are just a single DLL file. Ignore the registry file in the zip, it is not needed.

13

Did you perhaps install one of the infamous “codec packs” that were all the rage a few years ago? (They can also come bundled with related software.) These can mess up Windows pretty bad.
My recommendation would be to remove them all, then reboot Windows and install the known-good LAVfilters package.

14

No, no codec package was installed nor did I install any other media-related software which might have come bundled with either such a package or with that Dolby-codec on its own. Nothing I did myself that could explain this, not within the given timeframe of the issue occurring. What could have happened is a windows update that did this, possibly, since I am on the insiders (beta) preview of windows 11, which can introduce some bugs from time to time, though I’ve never encountered it. Either that or a plex desktop update that went wrong are the only possible causes I can think of at the moment

Everything is working now, so I’m not going to mess with it anymore. So unless something else pops up I don’t think that LAVfilters package will be necessary, at least not at this point

Thank you for your help in any case. Still wondering what caused it though but I guess I’m never going to find out. I don’t like not knowing what caused a specific issue to occur though :thinking: which is a professional force of habit since I work in IT

15

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