Hi,
I’m running Plex Server on Ubuntu on an HP Microserver (Gen9 - Dual-Core 2.30GHz Celeron CPU, 4GB RAM), which I believe should be capable of transcoding 1080p without problem - and indeed it used to…
For ages, everything ran fine, but recently I’m finding that for a lot of files, it buffers for a minute or so before anything plays, and then stops to buffer again every few seconds.
On these problem files, the logs show me a transcoding speed averaging about 0.4.
However, on other files of seemingly the same spec (ie, 1080p H264, AC3 5.1), the files play fine and I see a transcoding speed averaging around 10.
Any suggests what might be causing this or how I can debug this further?
I originally thought the problem was with files on my NAS as opposed to on the machine’s local drives, but I copied a problem file to the machine and the problem was the same.
I am running version 1.7.5.4035 - although I was having the same problem on 1.5.x.
Thanks
Pete
Sounds to me to be a file issue ie: the way it was encoded… could be the level or the reference frames, subs, container. Too little to go on though without the specs of the problem file or any logs.
Your log files (settings - server - help - download logs), 20 second after having seen the issue and stopping is the most helpful (post the ZIP file here).
The XML (hover over media -> Get Info -> View XML) shows us what PMS is seeing as the source material
Thank you for your replies.
I’m not sure it is a file issue though as it now happens on most files - including ones that played fine months ago.
Please find the requested info below
Log files
XML file
Also, Verbose mode log files if you need them.
Would it be useful to also provide logs for a file that does play back properly?
Yes, it helps but only 1 good example is needed and only a few seconds of the actual playback (enough to show it starts).
OK, here are the files from a working film:
Log files
XML file
Please let me know if there’s anything else that would help.
Regarding “La Gran Mentira”:
- Video: Transcoding is triggered by subtitles. Codec is H264 and bitrate is 9630
- Audio: Transcoding is triggered to downsample 5.1 to stereo
We have a guideline of 2000 passmark for 1080p/10Mbps H264 video, so your CPU, with a Celeron G1610T whose passmark is 2322, should be enough to transcode this film without subtitles. Subtitle transcoding uses only one core and your processor has two cores, so I suppose that a single core is not fast enough to encode subtitles for this bitrate. Can you please disable subtitles to test ?
When transcoding is necessary, the higher the bitrate the longer it takes to start a film. This is because the initial seconds are buffered to the device cache before playing starts, and caching continues during play (some devices are able to cache the whole film and continue playing even when PMS is stoped).
Thanks, that seems logical, but unfortunately turning the subs off doesn’t seem to make any difference.
See the log for playback without subs
The other thing to remember is that a month or two back I was able to play these files flawlessly, and the hardware hasn’t changed since.
I think that the problem can be triggered by one of the following:
- Roku parameters: did you specify a bandwith limit ?
- Router parameters: do you have DNS Rebinding protection active ?
Transcoding is being triggered because either the Roku is being considered “remote” or is parametrized to trigger transcoding when source has bitrate >10000Kbps (which is the case of “La Gran Mentira”)
I’ve noticed that in some logs you have used Roku3 and in others you have used PlexWeb. The rules to trigger transcoding are different for each. We need to compare “apples with apples”, therefore when I’ve asked you to disable subtitles I was also implying that you should use the Roku.
Also you should not use Make my CPU hurt in transcoding parameters.
Thanks. With regards to your questions:
1 - Roku ‘bit rate override’ is set to the default ‘automatic’ - is that what you mean? Or do you mean the selected playback quality? I noticed that the Roku’s Plex client’s quality settings for local files was set to ‘10mbps 1080p’ by default. I tried changing this to ‘Original’ - although it does say ‘not recommended’ and it now runs much better. Should I stick to this setting, or is there a good reason it’s not recommended? Thoguh the web player still doesn’t work properly even when ‘Original’ is selected and subtitles off.
2 - To be honest, I don’t know what that means but I can’t find any mention of it in my router settings.
Apologies for mixing the logs, will stick to Roku logs (though I’d been experiencing the issue on both).
Transcoder quality in Plex Server is set to Automatic.
As you may know there is a guideline to estimate the required passmark to transcode a film. But this is not rocket science.
In this case your processor with a 2322 passmark seems to not be powerfull enough to transcode “La Gran Mentira”, which has 1080p@10Mbps video and DCA audio. So I’ve tried to understand the reason why PMS decided to transcode:
- In the case of Roku3 was the local files ‘10Mbps limit’. If you increase this limit transcoding will not be triggered. How can this affect you ? Well, if your LAN connection is not fast enough it will become congested and viewing will suffer the same problems as before. The Roku3 may also have a bitrate limit (my AppleTV has a 20Mbps limit), and if you try to play too high bitrates without transcoding the device will hang and you will need to reset it
- I’m not an expert on Roku3, I don’t know if it can (and how) handle subtitles without transcoding, but you can ask this in the Roku forum. Subtitles usually trigger transcoding unless thay are in a certain format (usually srt external)
- About PlexWeb, I suspect that you are also limiting local quality to 10Mbps, such as, otherwise PMS thinks that your PlexWeb is remotely connected and transcodes because of it
It’s always better to play without transcoding. The quality will be preserved. Transcoding always impacts quality, but in several cases it’s a must. If you really need transcoding probably you should try to specify a target quality for local devices less than 10Mbps. It will lower the quality, yes, but maybe your CPU will be able to handle it, because target bitrate is one of the most influencing parameters on transcoding CPU usage.
Having tested it a bit, setting the Roku to ‘original’ and handling subs locally seems to have largely fixed the issue there.
The web player has ‘Home streaming’ set to ‘Original’ and seems OK unless I turn subtitles on. Perhaps a CPU upgrade is the only solution to that.
Thanks for your help.
@PeteWilliams said:
The web player has ‘Home streaming’ set to ‘Original’ and seems OK unless I turn subtitles on. Perhaps a CPU upgrade is the only solution to that.
Settings - Web - Player - ‘Burn Subtitles’ = “Automatic”
will at least prevent transcoding when you have text-based subtitles (SRT)
