PMS fails to transcode randomly




I'm running Plex Media Server version on headless Debian 9.3 with packages up to date. (kernel 4.9.0-5-amd64).

Whenever I try to play a movie in the Web Player (v. 3.31.1) which requires transcoding it randomly fails to transcode it. I can reproduce the issue with multiple files, it seems that it is not related to bad file encoding. The fail may occur at all length of the movie and it seems to be totally random.

When the playback stops I seek back to play that part again and it will fail to play at the same second. If I seek forward within the buffered area then it will continue to play the movie. If I seek outside the buffered area then back to the problematic part then the server tries to transcode that part again and it succeeds to transcode it and it wont fail.

I will attach the log (DEBUG mode enabled). I have also made a video about the issue. The playback is on the left and the Plex Media Server.log is tailed on the right. Maybe it helps to find the problem if you see the log in real time.

I have found two errors in the log which concerns me:
WARN - NAT: PMP, got an error: Not Supported by gateway.
ERROR - [Transcoder] [dash @ 0x2115140] Cannot use rename on non file protocol, this may lead to races and temporary partial files

Any help would be much appreciated!


May I see the XML please?

Also, did you purge the logs? There should be a lot more there


What kind of XML?

Also yes, I have stopped the server, deleted all the logs, started the server (as you can see in the video), then replicated the issue.


Hover over the item, expose the ellipsis (...) then “Get Info”

It will present “media info”. In the lower left will be 'View XML"

Copy/paste that text in your reply.

Before you ‘Post Comment’, highlight all of it and, using the Paragraph formatting at the top of the reply window, Paragraph Format -> Code. You’ll see it indent.
That prevents the forum from ‘eating’ it. :slight_smile:



What are these errors?

WARN - NAT: PMP, got an error: Not Supported by gateway.
ERROR - [Transcoder] [dash @ 0x2115140] Cannot use rename on non file protocol, this may lead to races and temporary partial files


So, noone knows what is the problem?


NAT-PMP is because your modem/router is not responding to UPNP and NAT-PMP requests to open a port.

The transcoder 'error' isn't an error. Dash is a streaming protocol and it knows that. It's falsely reporting. It's been addressed.

As for the file giving you problems:

  1. Xvid format
  2. AVI container.

I would like to suggest you perform a test encoding of this and try using it after converting to H.264.

ffmpeg -i  filename.avi  -c:v h264 -b:v 1500K -c:a copy  outputfilename.mp4

Copy the problem file to a test area, run the above command (editing as required), and put it in place of the AVI file (keep the AVI in your test directory as safe keeping.

Have PMS Scan your library again and update.

Now test playback.

I ask this because AVI files, especially XviD encoded, are very fragile. Re-encoding to H.264 and putting in a MP4 or MKV will correct any damaged values.

after playback complete and in position. test playback with PMS


I did what you asked above and the issue disappeared.
Now I see that the plex transcoder can't transcode this type of file properly.

But these files were playable without any issue before this "auto convert based on bandwith" feature was forced on us. It can't be turned off (unchecking it in the settings does nothing), also can't change transcoding to a specified bitrate, it jumps back instantly to auto convert. The bitrate drops drastically sometimes even at local area connection (gigabit) and the image becomes blurry.

This auto convert thing should not be released, at least shouldn't be forced to us. I get the idea, it is a great feature, but it is not tested properly with all file formats...