Plex Web - NVidia HW Acceleration Bug w/changing transcode quality while video playing

Plex Players Desktop Players
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Server Version#: 1.18.7.2457
Player Version#: Plex Web App 4.26.1 - Chrome 80 & Tested in Edge
Player Version#: Plex Android App 7.28.0.15501

Very similar to the problem reported back in April 2019: Hardware acceleration problem only in plex web

I also have a NVIDIA GPU (GeForce 1050), and have hw acceleration turned on. It works fine with most players (Desktop App, Roku TV App), and changing Transcode Quality works fine from within the player while the movie is playing.

However in Plex Web, once you initially start the Video, it plays (either transcode or direct stream), but you can’t change to a different transcode setting, Plex Web just shows a black screen. The Plex server shows it as changed to the new Transcode Setting (Mbps), with (hw), and time going in the Plex Server Dashboard. But the Plex Web App just shows black, and won’t work after you change the Quality from within the video player.

Same as the link above, if you start on Direct Stream (works), but once you change to any transcode setting, you get a black screen, even though the Plex Dashboard shows it changed to the changed settings.
If you start the video on a Transcode (works), but once you change to a different transcode setting, it won’t. However you can change it to “Direct Stream” from this state, and it’ll work. But then you are stuck on Direct, if you change to any Transcode setting, it’ll just be a black screen again.

This happens in Plex Web. But seems like a pretty big bug if you have HW Transcode on, with a NVIDIA GPU. Unable to change to any other transcode setting once you start the stream… And seems like it may of been here since April 2019.

Android App has a similar issue, but doesn’t display a Black Screen, instead shows an error message that says to restart the App and the PMS (which I have multiple times).

Not too sure if this is related, but I do notice in other players (like Plex Desktop), if I change from Transcode setting -> Transcode setting, there is a “flicker” before it starts playing. Maybe the Plex Web is getting hung up on this and glitching out?

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OHHHHHHHH S(*T!!! Finally, someone else getting one of my issues. Yes, I am having the same issue (Plex Webapp can’t manually select a quality). For Android, PMS just fails to find the hw trancoders altogether.

Have you checked (in task manager) what happens to the HW ENC/DEC when you play a video in the WebApp? Specifically, start a file, let it run at “convert automatically”, then try to select a quality level? What I end up seeing is that, when converting automatically, the ENC/DEC and GPU memory are in use but, after switching to a quality level manually, the ENC/DEC and memory plummet to 0% use.

Also, does the webapp playing ever catch up and need to buffer? Mine would play for maybe 20 seconds then keep having to buffer to play a few more seconds.

Lastly, for me, when trying to play on Android, either the “transcoding” doesn’t seem to actually start (ie: it continues to direct stream, except for audio, as noted by the Plex dashboard) or it fails to find hw transcoders (in the PMS logs) and just reverts to CPU (again, as per the dashboard, but I’m not sure I even trust that info)

Ok, let’s play the “let’s gather data!” game, as I want to see if our issues line up:

  1. What is the resolution and encoder of the file you are trying to play? Is it 4K HDR encoded with HEVC/H.265?
  2. Is PMS running on Windows or a different OS?
  3. Is the OS on bare metal or in some sort of virtualization environment? If it’s a VM, what is your host/hypervisor?
  4. This is a multi-parter, as I’m not sure how familiar you are with Plex and troubleshooting this so I’m just detailing everything:
  • Turn off PMS, then restart it.
  • Make sure that verbose logging is NOT enabled but debug logging is (from the Plex Web App, go to Settings > General, click “Show advanced”, select “Enable Plex Media Server debug logging” and deselect “Enable Plex Media Server verbose logging”
  • Open up Windows Task Manager in the OS PMS is running in (if PMS is running in Windows), go to the “Performance” tab, and click on your GPU. Leave this open.
  • Return to your PC/wherever you are using the Plex WebApp. In the WebApp, go directly to your test file and play it. Let it start playing however it opens (presumably “convert automatically” but correct me if that’s wrong).
  • Once the playback has started, record of the utilization level of your GPUs Encoder, Decoder, and GPU memory usage of the PMS machine.
  • Once it’s played for a bit (10 seconds), try selecting any other manual quality setting. Record, again, the GPUs encoder, decoder, and memory usage/utilization levels from the PMS machine.
  • Once the stream fails to play for about 20 seconds, stop the playback. Immediately, from the Web Player, go to Settings > Troubleshooting and click Download Logs.
  • Extract the unnumbered (latest) “Plex Media Server.log” file and post it here along with the two sets of GPU data.
  1. Do #4 again, but try and play the same file from an Android device, preferably a cellphone using the Android App to keep it consistent with me. Note any errors or playback issues (such as stuttering) that you notice.
  2. Not sick of this yet? Repeat #4 but playback using the Plex Media Player Windows application. Note any errors or playback issues (such as stuttering) that you notice.

While I have not yet solved these problems for myself, at least I can see if we have the same problem and work towards a solution.

I shall wait with bated breath.

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For me, I’m also getting this issue, though as part of the much broader issue that I detailed above and that you, OP, are seeing. Of course, nothing was updated.

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haha very detailed!

  1. The main resolution I have is 1080p HEVC/x265. But I tested on a few files, like 480p MPEG, and some others and it had the problem on all the input sources I tried.
  2. PMS is the Windows version. Running on Windows Server 2012 R2 (similar to Win8.1).
  3. Bare Metal, no virtualization. Same with GPU, latest Win8.1 GeForce 1050 driver.
  4. (and 5/6) … On Windows Server 2012 R2, I don’t get the GPU utilization in Task Manager (like I get in Win 10). So I can’t do most of this. As for a “multi-parter”, they are single part shows. But yea I can’t seem to get any GPU utilization from WinServ2012R2… sry. I can try to get the .log files for the 3 players (Web, Android, Windows) when I get home.
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I can confirm this bug. Exact same symptoms. If you set your player transcode setting globally, GPU transcodes work fine. But if you change it after playback has begun then it never starts again.

Very confusing when trying to debug GPU issues.

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