Puzzlingly Perplexing PLEX Playback Problems on Synology DS-1019+

Plex Media Server NAS & Devices
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Server Version#: 1.15.3.876 (current version as of this post)
Player Version#: see below

I recently installed PLEX 64-bit on my Synology DS-1019+ (with Plex Pass and hardware transcoding turned on) and have been having a lot of issues with it, but they’re not very consistent. Right now the issue is playback on devices. I used Plex for years and years on Windows and found it to be quite stable, but I am really struggling to get stable usage of it on my Synology (which is depressing because it was the main reason I bought the 1019+).

Fire TV 4K (v.7.10.0.8875): won’t play the original (hardware limitation), but when set to transcode at 20mbps (I also tried 12mbps) it pauses playback every 10 seconds or so, freezes for 2-3 seconds, then resumes. Stopped Plex, restarted it, turned on debug logging, tried again. Got an error about the server not being powerful enough for playback. Repeat pausing issue again.

4K Apple TV (v.1.40.1.11962): plays original quality MKV without issue, when manually set to 20mbps it won’t play the movie at all. Exited the Apple TV app, killed it, restarted it, tried playback again at 20mbps. Black screen for a bit, then got a new error I’ve never seen before: “Couldn’t create the playback session for this item. Could not direct play because: App cannot direct play this item. Direct play is disabled. Could not transcode because: not enough bandwidth for any playback of this item. Cannot convert to below minimum bandwidth of 103kbps”.

I also tried the macOS desktop client and it worked without issue (though I suspect it was playing back the original quality file), though upon second attempt it says Plex is unreachable.

Throughout all this I was watching the CPU usage on the Synology NAS and it never went above 30%, so this doesn’t appear to be a CPU-dependant playback issue.

Here are the logs: Plex Media Server Logs_2019-04-05_19-24-17.zip (2.5 MB)

I think I filled in all the blanks on what is needed to report issues - please let me know if I missed anything.

EDIT: A few hours ago I installed two 512 GB M.2 SSDs into the 1019+ and created a read/write SSD cache…would that have anything to do with this? Would this impact the way Plex transcodes video? I wouldn’t think so, but I figured I’d mention it…

EDIT 2: I’ve done more testing and have another data point. Playback of h.264 MKVs work fine. Playback of older MKVs using VC-1 on the same hardware (Fire TV and Roku) has the pausing/buffering problem. On the Fire TV is pauses (freezes) for a few seconds, on the Roku it goes to a black buffering screen. So I’m wondering if this is really a transcoding of VC-1 MKVs problem…?

EDIT 3: Done more testing, digging up MKVs with VC-1 format videos and, yep, buffering every 20 seconds or so. MKVs with h.264 content, zero issues. So this really seems like a VC-1 related issue.

1 Like
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Wow! Thanks Trumpy81 for confirming that the log files back up my theory about the VC-1 files.

Here’s what I don’t get: playing back the VC-1 files, I’m watching the CPU usage and it never gets above 40%, with the Plex Media Server service never going past 26%. If the CPU truly couldn’t keep up, why wouldn’t it peg at 99%? That’s what my old Synology with an Atom CPU used to do when I asked it to transcode. @ChuckPa any thoughts here?

Is there a way to re-encode the VC-1 videos to h.264 while keeping them in the MKV container with subtitle support, etc.? Because transcoding them to MP4 h.264s is a non-starter - I’ll lose all the advantages of using MKV in the first place.

I may just have to go back to using Plex on my Core i7 Gigabyte BRIX, which means I dropped $1000+ on the 1019 + expansion unit for very little reason…the whole reason for the upgrade to the 1019+ was to run Plex on it with hardware transcoding. This VC-1 thing is a real kick in the nuts. :frowning: Never saw anyone talking about it as a known issue. Dang. :frowning:

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Really, really appreciate your input here Trumpy81! I am not wedded to MKV as a container, it’s simply what I’ve been using for years as I prefer to rip raw from the disc without going through the slowness of a transcode. I’m willing to trade storage size for time, but this VC-1 thing really threw me for a loop.

It seems to me there are two steps I need to do here to restore myself to Plex happiness: 1) find all VC-1 MKVs, then 2) transcode all these VC-1 MKVs to use h.264.

I’ve been searching these forums - and elsewhere - for how I’d locate all the VC-1 files and have struck out. I have probably 1600 MKV files in total ripped from my discs.

Is there a plugin/tool I can use to look at either the metadata in Plex and generate a list of all VC-1 files? Or is there a macOS or Windows tool that might also allow me to do that? I’ve spent a good hour going down the rabbit hole and as a non-developer non-Linux guy, whatever I found was beyond my ability to understand it.

Related to taking an MKV VC-1 and transcoding it into an h.264 file, I’ve found several guides. One thing that’s critical for me is maintaining forced subtitles so I can see non-English dialogue. Is there a solid guide for achieving this?

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Thank you - I got ExportTools installed and the exported CSV file is a glorious treasure trove of data! It looks like I have 170 movies I’d need to fix. That’s a lot, but at least now I know what I need to focus on. :+1:

I’ve looked at a few Handbrake guides and most seem to ignore the subtitle issue, which is really what I care most about. Are you aware of a guide for taking MKVs and converting them to MP4s while maintaining either full subtitle selections (I’m not sure that’s possible) or a way to always include the forced subtitle into the MP4?

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