I see part of what looks like the problem but because you turned on VERBOSE logging (which is off by default), I can’t see what PMS did (that information fell off the end of the logs buffer)
You have image-based (PGS) subtitles in the file. If you selected PGS, PMS will need to use the CPU (not the hardware) for this. The Samsung TV doesn’t accept PGS subtitles as an overlay.
It does accept SRT (Text-based) as an overlay.
HEVC is handled by the hardware but not the subtitles. Intel didn’t provide that capability in the CPU. Synology won’t license their proprietary hardware features for us to access.
My recommendation is to remove the PGS subtitles and replace with SRT if you need subtitles for English.
Please do turn VERBOSE logging off again until requested. A great deal of information we need for initial diagnosis is lost in almost every case.
Thanks for those logs.
The logs show why it stutters for you.
The CPU:
May 03, 2019 16:12:18.714 [0x7fc1639c5700] INFO - Plex Media Server v1.15.3.876-ad6e39743 - Synology DS718+ x86_64 - build: linux-x86_64 synology - GMT 01:00
May 03, 2019 16:12:18.714 [0x7fc1639c5700] INFO - Linux version: DSM 6.2.1.23824-6, language: en-US
May 03, 2019 16:12:18.714 [0x7fc1639c5700] INFO - Processor Intel(R) Celeron(R) CPU J3455 @ 1.50GHz
while great at HW transcoding because of the GPU ASIC built in, can’t handle subtitle burning back onto the image quick enough to keep up with the data rates.
• Codec HEVC
• Bitrate 50867 kbps
• Language English
• Bit Depth 10
• Chroma Subsampling 4:2:0
• Color Primaries bt2020
May 03, 2019 16:13:06.724 [0x7fc128652700] DEBUG - Found session GUID of k2s1ivqklbvmfgvido2ybgnp in session start.
May 03, 2019 16:13:06.724 [0x7fc128652700] DEBUG - Cleaning directory for session k2s1ivqklbvmfgvido2ybgnp ()
May 03, 2019 16:13:06.725 [0x7fc128652700] DEBUG - Starting a transcode session k2s1ivqklbvmfgvido2ybgnp at offset -1.0 (state=3)
May 03, 2019 16:13:06.731 [0x7fc128652700] DEBUG - TPU: hardware transcoding: using hardware decode accelerator vaapi
May 03, 2019 16:13:06.731 [0x7fc128652700] DEBUG - [Universal] Using local file path instead of URL: /volume1/video/Jurassic Park - UHD - 1993.mkv
May 03, 2019 16:13:06.731 [0x7fc128652700] DEBUG - TPU: hardware transcoding: zero-copy support present
May 03, 2019 16:13:06.732 [0x7fc128652700] DEBUG - TPU: hardware transcoding: not using zero-copy because subtitle burning is required
May 03, 2019 16:13:06.732 [0x7fc128652700] DEBUG - TPU: hardware transcoding: final decoder: vaapi, final encoder: vaapi
May 03, 2019 16:13:06.736 [0x7fc128652700] DEBUG - Job running: EAE_ROOT='/volume1/Plex/tmp_transcoding/pms-59206c01-f02b-4fe9-a7c5-d1914ac80172/EasyAudioEncoder' FFMPEG_EXTERNAL_LIBS='/volume1/Plex/Library/Application\ Support/Plex\ Media\ Server/Codecs/a22632d-2172-linux-x86_64/' XDG_CACHE_HOME='/volume1/Plex/Library/Application Support/Plex Media Server/Cache' XDG_DATA_HOME='/volume1/@appstore/Plex Media Server/Resources' X_PLEX_TOKEN='xxxxxxxxxxxxxxxxxxxx' '/volume1/@appstore/Plex Media Server/Plex Transcoder' '-codec:0' 'hevc' '-hwaccel:0' 'vaapi' '-hwaccel_fallback_threshold:0' '10' '-codec:1' 'dca' '-analyzeduration' '20000000' '-probesize' '20000000' '-i' '/volume1/video/Jurassic Park - UHD - 1993.mkv' '-filter_complex' '[0:3]scale=3840:2160[0];[0:0][0]overlay[1];[1]scale=w=1920:h=1080[2];[2]format=pix_fmts=nv12[3];[3]hwupload[4]' '-filter_complex' '[0:1] aresample=async=1:ocl='\''5.1'\'':osr=48000:rematrix_maxval=15.000000dB[5]' '-map' '[4]' '-metadata:s:0' 'language=eng' '-codec:0' 'h264_vaapi' '-b:0' '13682k' '-maxrate:0' '18243k' '-bufsize:0' '36486k' '-r:0' '23.975999999999999' '-force_key_frames:0' 'expr:gte(t,0+n_forced*1)' '-map' '[5]' '-metadata:s:1' 'language=eng' '-codec:1' 'aac' '-b:1' '687k' '-f' 'dash' '-min_seg_duration' '1000000' '-skip_to_segment' '1' '-time_delta' '0.0625' '-manifest_name' 'http://127.0.0.1:32400/video/:/transcode/session/k2s1ivqklbvmfgvido2ybgnp/a742c36a-bada-40dc-a225-86d93bfd3072/manifest' '-avoid_negative_ts' 'disabled' '-map_metadata' '-1' '-map_chapters' '-1' 'dash' '-start_at_zero' '-copyts' '-vsync' 'cfr' '-y' '-vaapi_device' '/dev/dri/renderD128' '-nostats' '-loglevel' 'quiet' '-loglevel_plex' 'error' '-progressurl' 'http://127.0.0.1:32400/video/:/transcode/session/k2s1ivqklbvmfgvido2ybgnp/a742c36a-bada-40dc-a225-86d93bfd3072/progress'
May 03, 2019 16:13:06.736 [0x7fc128652700] DEBUG - Jobs: Starting child process with pid 15781
My recommendations are:
Deselect the subtitles before playing.
Turn off “Always Burn”
Remove the PGS subtitles from the file (these must always be burned)
Thank you so much ChuckPA,
I have disabled the subtitles and I can search for subtitles with the Plex Pass. I was worried that I could not play the movies without subtitles because I live with mental health, and the subtitles help me understanding better. I can now play my movies as before, and I am very glad I can use my Plex Player as before but now without the subtitles that come with the movies. Thank you,
Many thanks for all your help it’s been working great ever since I turned off the subtitles. However I can’t understand why a NAS that is capable of playing a 70GB 4K movie fearlessly, cannot display simple lines of subtitles at the same time, on the Plex Player. I would suspect that it would not require as much power as it is required to play a movie, than it would require to play subtitles? By the way I miss a feature on Plex to show on Facebook the movie that we are watching on Plex to share with our friends. There could be a link pointing to a trailer? That could be awesome lol
The reason for that isn’t obvious unless you’re an engineer.
The TV isn’t capable of handling certain types of subtitles. Specifically, it can handle SRT, ASS, and SSA (Text-based) easily in the subtitle overlay but it can’t handle image-based (PGS, VOBSUB, and DVDRIP).
The NAS’ CPU has the hardware support for the video. This is what we use the most.
Intel didn’t provide a hardware assist for subtitles. This means the CPU itself has to do the work. NAS CPUs usually have a hard time with this task because, while streaming the video, it must also manually merge (burn) the subtitles onto each video frame at that high bit-rate resolution.
What we see is:
Without subtitles or with text-based subtitles, and a player which can handle text-based subtitles natively, there are no difficulties.
If burning subtitles into the video image, the CPU frequently don’t have enough power to keep up with the demands of real-time playback.
Thank you ChuckPA, it makes all sense, many thanks. So upgrading the hardware to a more capable CPU would be the solution? If that is the case, I would then replace the NAS for something of better quality since the Synology NAS can be replaced
I replaced my DS1815+ with something considerably bigger
I purchased the TVS-1282-i7 w/ 32 GB . This is overkill for most but I also use it for Plex development; several VMs, test media, etc.
The key to remember in any processor-centric upgrade for Plex is “Where is the deficiency?”
In the case of subtitles, raw CPU ‘crunch’ is needed because subtitles can’t be hardware accelerated.
In the case of more streams, higher bit rates, HDR → SDR, or simple quality of transcoded image, one of the smaller units with an Intel J3455 is more than enough for the average person 1-2 concurrent streams. Should you need more, you will need to step into the -7xxx class CPUs. The -7xxx class has a good price point for most.
I see no reason yet to step into the -8xxx and absolutely no reason for the -9xxx class processors. What I see of the 9xxx processors has been largely targeted for gamers.
I have a ds1019+ with 8gbs of ram. I do have plexpass lifetime membership. I can play 4k mkvs without any buffering via my nvidia shield tv wireless, so no ethernet wired connections.
4k movies play straight away as soon as i click on them. The size of the files range between 50-90gb mkvs.
The only time i have seen it struggle if i try and use a fire tv stick 4k. It seems to buffer quite a bit. So my advice is get a client that can cope, like a nvidia shield tv. This box plays everything with ease. Never had it ever buffer before.
I don’t have any more buffering since turning off the subtitles. other than the one off occasion, when the mkv file is corrupt and I can verify that buy playing another large movie as big as 80GB. That only when the file plays funny that Plex Player buffers but again it’s not Plex the issue here.
However my enjoyment stopped since I don’t have the subtitles available anymore.
I have mental health and the subtitles are important to me as they help me to understand the actors fully.
Nevertheless, I used to have subtitles before called something like “WebSubtile”
So I will be happy to upgrade to have a better NAS with enough CPU power to have the subtitles back.
There are times when I go back to the old good blu ray player because I miss so much the subtitles on Plex…
The Options available on Plex.tv are turned on based on the information Online, but they don’t seem to work.
So for these issues I don’t feel happy to support the Plex Pass at the moment unless someone could help with adding the subtitles on Plex Player for Samsung Smart-TV please?
I have a Synology Diskstation DS718+ with a quad core CPU with 6gb ram on an ethernet home network on Virgin Media Fibre 388M/S Up and 39M/S Up
Thank you for this, been really confused why my playback was struggling even with hw acceleration and I just assumed it was the CPU being weak.
This should really be prompted by the client if it notices buffering, the client I used simply told me that my CPU was too weak to handle the stream.
I even had external .srt file available and switching off the PGS and using that instead fixed the problem, no more buffering!
Might consider getting plex pass subscription just for the hw acceleration since my CPU cant handle 4k streams normally. (I am currently on a 30-days trail)
