Server Version#:1.25.4.5487
Player Version#: 4.73.3 (Plex Web) Same issue through Chromecast.
Synology 920+
DSM 7.0.1-42218
In the last few weeks almost all my streams from my Synology Plex server are buffering a lot. Initially I found the problem on my Chromecast. I tested its wifi in the room and was getting near 600mb/s. To be sure, though, I tested it on a computer wired to the same switch the Synology is on and got the same behavior. Anything over about 1 mb/s would buffer every 20 seconds or so. I watched the Synology while trying to transcode the bitrate down and it wasn’t breaking a sweat at all. CPU and memory stayed well below 30% utilization.
It just doesn’t seem to be feeding the chunks out to the player fast enough.
Can you help? Logs attached.
Plex Media Server Logs_2022-02-01_09-57-10.zip (5.3 MB)
Please turn DEBUG logging back ON, (you don’t save space by turning it off as the sizes are fixed length).
Now recreate the failure please and download a fresh set of logs.
Logs attached.
Plex Media Server Logs_2022-02-01_11-23-29.zip (5.3 MB)
Here’s a video at 4k and then transcoded to 720. They both buffer.
Indeed your Syno isn’t breaking a sweat at all. HW transcoding is engaged.
There is a network problem here somewhere.
Independent of internet speeds,
- Are both devices on the same subnet
-or- - Is there a direct connection (Remote Access enabled) to allow more than 2 Mbps to be sent?
-or- - Has a Remote Access upload limit been asserted ?
Feb 01, 2022 11:19:51.834 [0x7ff36d0ecb38] DEBUG - [Transcode] We're going to try to auto-select an audio stream for account 1.
Feb 01, 2022 11:19:51.834 [0x7ff36d0ecb38] DEBUG - [Transcode] Selecting best audio stream for part ID 5473 (autoselect: 0 language: en)
Feb 01, 2022 11:19:51.834 [0x7ff36d0ecb38] DEBUG - [Transcode] Audio Stream: 19922, Subtitle Stream: -1
Feb 01, 2022 11:19:51.835 [0x7ff36d0ecb38] DEBUG - [Transcode] Found session GUID of t2jaxy38c7x3i8rpnbkbclgl in session start.
Feb 01, 2022 11:19:51.835 [0x7ff36d0ecb38] DEBUG - [Transcode] Cleaning directory for session t2jaxy38c7x3i8rpnbkbclgl ()
Feb 01, 2022 11:19:51.835 [0x7ff36d0ecb38] DEBUG - [Transcode] Starting a transcode session t2jaxy38c7x3i8rpnbkbclgl at offset -1.0 (state=3)
Feb 01, 2022 11:19:51.836 [0x7ff36d0ecb38] DEBUG - [Transcode] TPU: hardware transcoding: using hardware decode accelerator vaapi
Feb 01, 2022 11:19:51.836 [0x7ff36d0ecb38] DEBUG - [Transcode] TPU: hardware transcoding: zero-copy support present
Feb 01, 2022 11:19:51.836 [0x7ff36d0ecb38] DEBUG - [Transcode] TPU: hardware transcoding: using zero-copy transcoding
Feb 01, 2022 11:19:51.836 [0x7ff36d0ecb38] DEBUG - [Transcode] [Universal] Using local file path instead of URL: /volume1/homes/plex/Disney Parks Ephemera/Haunted Mansion Singing Busts-upscaled.mp4
Feb 01, 2022 11:19:51.836 [0x7ff36d0ecb38] DEBUG - [Transcode] Codecs: hardware transcoding: testing API vaapi
Feb 01, 2022 11:19:51.837 [0x7ff36d0ecb38] DEBUG - [Transcode] TPU: hardware transcoding: final decoder: vaapi, final encoder: vaapi
Feb 01, 2022 11:19:51.838 [0x7ff36d0ecb38] DEBUG - [Transcode/JobRunner] Job running: FFMPEG_EXTERNAL_LIBS='/var/packages/PlexMediaServer/shares/PlexMediaServer/AppData/Plex\ Media\ Server/Codecs/62cc2bc-4226-linux-x86_64/' LIBVA_DRIVERS_PATH='/volume1/@appstore/PlexMediaServer/lib/dri' X_PLEX_TOKEN='xxxxxxxxxxxxxxxxxxxx' '/volume1/@appstore/PlexMediaServer/Plex Transcoder' '-codec:#0x01' 'mpeg4' '-hwaccel:#0x01' 'vaapi' '-hwaccel_fallback_threshold:#0x01' '10' '-hwaccel_output_format:#0x01' 'vaapi' '-hwaccel_device:#0x01' 'vaapi' '-analyzeduration' '20000000' '-probesize' '20000000' '-i' '/volume1/homes/plex/Disney Parks Ephemera/Haunted Mansion Singing Busts-upscaled.mp4' '-filter_complex' '[0:#0x01]hwupload[0];[0]scale_vaapi=w=2276:h=1280:format=nv12[1];[1]hwupload[2]' '-map' '[2]' '-codec:0' 'h264_vaapi' '-b:0' '1899k' '-maxrate:0' '2533k' '-bufsize:0' '5066k' '-r:0' '29.969999999999999' '-force_key_frames:0' 'expr:gte(t,n_forced*1)' '-map' '0:#0x02' '-codec:1' 'copy' '-copypriorss:1' '0' '-f' 'dash' '-seg_duration' '1' '-dash_segment_type' 'mp4' '-init_seg_name' 'init-stream$RepresentationID$.m4s' '-media_seg_name' 'chunk-stream$RepresentationID$-$Number%05d$.m4s' '-window_size' '5' '-delete_removed' 'false' '-skip_to_segment' '1' '-time_delta' '0.0625' '-manifest_name' 'http://127.0.0.1:32400/video/:/transcode/session/t2jaxy38c7x3i8rpnbkbclgl/6192f9d3-d753-4c6c-914a-16a005865d5e/manifest?X-Plex-Http-Pipeline=infinite' '-avoid_negative_ts' 'disabled' '-map_metadata' '-1' '-map_chapters' '-1' 'dash' '-start_at_zero' '-copyts' '-vsync' 'cfr' '-init_hw_device' 'vaapi=vaapi:' '-filter_hw_device' 'vaapi' '-y' '-nostats' '-loglevel' 'quiet' '-loglevel_plex' 'error' '-progressurl' 'http://127.0.0.1:32400/video/:/transcode/session/t2jaxy38c7x3i8rpnbkbclgl/6192f9d3-d753-4c6c-914a-16a005865d5e/progress'
Feb 01, 2022 11:19:51.838 [0x7ff36d0ecb38] DEBUG - [Transcode/JobRunner] Jobs: Starting child process with pid 10308
They are both on the same subnet, the same dumb switch even. Remote access has been enabled, but there is no upload speed set.
It definitely looks like it’s being throttled at 2mb/s for some reason, doesn’t it?
Check in the player quality settings
Next, check the WiFi and make sure it’s associated at the higher speed SSID
The debug I sent you was while I was watching through Plex Web which is on a PC hardwired to the switch. So no wifi is on.
The Plex-Web quality is set:
No “Automatically adjust quality”
Video quality maximum for internet streaming.
Yes “Play smaller videos at original quality”
Home Streaming-Yes “use recommended settings.”
For home streaming – use maximum / original. (recommend).
I don’t think you have a limit on your home LAN where you’d saturate gigabit ?
Yes, home streaming is set at “recommend”.
So if I go to the server that is running Plex and download the same file to the same computer that I was trying to watch it on, it came down in about 4 seconds. I know it’s not apples to apples, but we can see there’s no throttling. They’re both plugged in to the same dumb switch. You couldn’t turn on throttling if you wanted to.
Stupid question time
MTU == 1500 ?
Not a stupid question at all, but I checked the server and the network interface is set at MTU 1500.
It might be time to install iperf3 wherever you can and start running pure LAN network speed tests from devices → Server.
Confirm the base network is solid from point to point then we can backtrack through the media.
Here’s my iperf3 results.
Connecting to host 192.168.50.97, port 5201
[ 4] local 192.168.50.66 port 2441 connected to 192.168.50.97 port 5201
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-1.00 sec 106 MBytes 889 Mbits/sec
[ 4] 1.00-2.00 sec 112 MBytes 940 Mbits/sec
[ 4] 2.00-3.00 sec 112 MBytes 939 Mbits/sec
[ 4] 3.00-4.00 sec 109 MBytes 917 Mbits/sec
[ 4] 4.00-5.00 sec 112 MBytes 935 Mbits/sec
[ 4] 5.00-6.00 sec 111 MBytes 932 Mbits/sec
[ 4] 6.00-7.00 sec 111 MBytes 935 Mbits/sec
[ 4] 7.00-8.00 sec 112 MBytes 941 Mbits/sec
[ 4] 8.00-9.00 sec 112 MBytes 941 Mbits/sec
[ 4] 9.00-10.00 sec 111 MBytes 932 Mbits/sec
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-10.00 sec 1.08 GBytes 930 Mbits/sec sender
[ 4] 0.00-10.00 sec 1.08 GBytes 930 Mbits/sec receiver
Ok, so I tried a lot. I changed each cable in the transaction, tried a few different computers and experimented with taking movies off and on transcoding. This seemed to point to something. Even though the syno isn’t struggling with the transcoding at all, if I play something at original quality, it passes the traffic at super high speeds, 90 - 100+ mb/s, but as soon as I start it transcoding, even if the quality is almost the same, it drops dramatically to somewhere between 2 - 5 mb/s. What the heck?
Synology has TERRIBLY weak CPUs.
Audio transcoding is ‘meh’ OK.
Depending on what you’re doing with the video, it will work very nicely (the J4125 is strong with HW VIDEO transcoding.
The moment you introduce subtitle burning – GAME OVER.
Can you please capture one of these for me that fails.
May I also see the XML (hover over the video → Get Info → View XML – Attach only the <media> → </media> part.
The first set showed no subtitles. I need to see the same failure you do
I’m sorry, you’re asking for the XML and what else?
Logs which capture a failing playback (2-5 Mbps)
I think I found the issue… https://www.reddit.com/r/PleX/comments/gpp05s/synology_ds920_conversion_issues
Changing the preferences.xml to point at the VAAPI driver suddenly fixed my test video. It played through without buffering. Fingers crossed, that was it.
That’s only going to be temporary.
If you want it permanent,
add
VaapiDriver="i965"
to Preferences.xml, using the Synology Text Editor and Plex stopped.
Make 100% certain to preserve the spacing and format convention just as you see with the other preferences in there.
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