Hi, I got my Plex Server running on a QNAP TS-251+
I tried to play a 4K movie at 71Mbps on my TV and I got some buffering.
Lower bitrate like 60Mbps works flawlessly.
I thought the issue was caused by my TV, but I just tried to run a server on my PC, and the file is played perfectly.
How is this possible that my NAS is struggling to do this, as this is 100% direct playing ??
And yes, everything is wired via ethernet at 1Gbps, and my HDD got 0 problem. I just copy that movie from my NAS to my PC at 110MB/s. (And everything is running the latest update)
I would really appreciate some help !
Thanks
Sure it’s the QNAP? it might be the connection to the TV itself (wifi) ?
Yes, absolutely sure. My TV is wired. I just ran the movie for 30min and not a single buffering when streaming from my PMS PC.
I just tried to stream from my PMS NAS and it’s buffering every 20sec.
Edit : just checked the cpu and memory consumption of my NAS during the stream : 12% CPU – 60% RAM.
As expected, as direct playing requires very low power… I really don’t understand why it’s happening.
start running iperf3 on the LAN.
Something isn’t behaving up to spec or the tv is 100 Mbps only and dead-on spec.
Most TVs are only 100 Mbps, not gigabit. At 100 Mbps, a 71 Mbps video + audio + TCP/IP overhead will go over 100 Mbps. Also remember, 71 Mbps is the average bitrate, not the peak.
In the QNAP monitor, can you see the output data rate from the adapter?
12.83 MB/sec = 100 Mbps. See how close you get to that number.
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Okay, first of all, thank you for helping me !
Indeed, my TV is only 100Mbps (sadly), but that’s not the bottleneck here, as the file is playing perfectly when streaming from my PC.
I monitored the output data rate of both my NAS and PC when streaming the file : they are both exactly the same : It fluctuates between 5.5 and 10.1MB/s which is lower than what my TV is capable of. Every time I run a speedtest from it, I got a solid 98Mbps (no more, no less) which is 12.25MB/s.
I figured out by killing a lot of background process on my NAS that my file is now less buffering, but not perfect. How is this related, as there is a lot of memory and CPU power left, no matter what ?
I don’t know if I’ve done the correct thing but here are the test of an iperf3 I ran : The server is my NAS, the client my PC :
Connecting to host 192.168.1.42, port 5201
[ 4] local 192.168.1.99 port 54057 connected to 192.168.1.42 port 5201
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-1.00 sec 112 MBytes 944 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 112 MBytes 941 Mbits/sec
[ 4] 4.00-5.00 sec 111 MBytes 933 Mbits/sec
[ 4] 5.00-6.00 sec 112 MBytes 941 Mbits/sec
[ 4] 6.00-7.00 sec 112 MBytes 942 Mbits/sec
[ 4] 7.00-8.00 sec 112 MBytes 940 Mbits/sec
[ 4] 8.00-9.00 sec 112 MBytes 941 Mbits/sec
[ 4] 9.00-10.00 sec 112 MBytes 941 Mbits/sec
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-10.00 sec 1.09 GBytes 940 Mbits/sec sender
[ 4] 0.00-10.00 sec 1.09 GBytes 940 Mbits/sec receiver
iperf Done.
Good. That shows gigabit from PC - NAS.
Since you can’t run iperf on the TV, you have to “wing it”
- Pull open the QNAP desktop resource monitor.
- Start Playback at the TV.
- Look at the speed of bytes being sent. (blue) (12 MB/sec = 100 Mbits/sec )
- what does it show?
I’ve already done that, this is what I meant when I said :
I monitored the output data rate of both my NAS and PC when streaming the file : they are both exactly the same : It fluctuates between 5.5 and 10.1MB/s which is lower than what my TV is capable of. Every time I run a speedtest from it, I got a solid 98Mbps (no more, no less) which is 12.25MB/s.
Apologies… not enough 
QNAP shows us average rates. We will never see peaks.
I trust the TV’s results far more. It has verified it’s 100 Mbps capable.
I would like to see the XML (Hover over item → Get info → View XML) of one of the 70 Mbps video file which is causing problems.
The ethernet data rates for such a file would be approximately (assuming norms),
70 Mbps video w/ 10 Mbps audio (5.1 or better) puts us at 80 Mbps. Adding TCP/IP overhead brings us to ( 80 * 1.2 ) 96 Mbps average.
If this is the average bitrate, peaks are clearly going to be well over 100 Mbps. This is the vulnerability. Does the TV have enough internal memory to buffer through that ? It’s the unknown.
Haha, don’t worry 
Okay, I’ll get you that in a few hours when I’ll be home.
But how do you explain the fact it’s perfectly playing when streaming from the PC ?
I don’t really think the bottleneck of the TV is problematic here, as I’ve watched the whole movie yesterday night (MI: Fallout) without any buffering at all !
The PC, as you showed, is gigabit and not 100 Mbit. It can pull the data faster and not drop out.
Plus, PC’s (browsers) generally have much bigger buffers to work with.
No, that’s not what I meant.
I meant, the PC is my server, and it’s streaming to my TV. That’s what I meant from the beginning when I was comparing my NAS and my PC. Everytime, the client was the TV, only the servers were different.
Sorry if I was not clear 
Now I am confused.
Let’s go back to the beginning:
- Streaming to TV is OK (?) when the PC is the server
- Streaming to TV OK (?) when the QNAP is the server.
- Wherever it fails, please recreate the stutter (Stop it after the second one)
- wait 30 seconds
- Settings - Server - Download Logs
- Get the XML for the video played
- Attach the XML and the ZIP file here.
Supplemental:
What is the data flow path?
NAS (media) -> PC (server ) -> TV (client) ?
or
NAS (media & server) -> TV (client) ?
Okay so.
At first, my default setup is NAS (media/server) -> TV (client)
This is where the buffering is appearing
I don’t know why but an idea came to me : To test with PC (media/server) -> TV (client)
And this got 0 problem
So here are the logs from NAS -> TV. I struggled more than usual to find a buffering spot. I cleaned a lot of old install, not at all related to Plex, today. I don’t know if it’s related
Plex Media Server Logs_2019-04-05_21-27-39.zip (1.5 MB)
MIFallout.rar (4.4 KB)
As expected, there is only contention when PMS first starts (normal).
There has to be a networking problem in there somewhere.
Are Jumbo packets in use? (anything with a MTU > 1500 )
Currently, the MTU of my NAS is 1500.
Should I use Jumbo frames instead ? I heard it can increase speed but sometimes, causes instability issue.
I asked to confirm you are NOT using them.
Jumbo frames are only of use on certain cases like Block I/O devices (iSCSI target/Lun networks)
From all indications, your NAS isn’t capable of pushing the bits fast enough to the TV.
what is strange is that it can send the same media to the PC, which then retransmits it to the TV ok.
I would open a QNAP support ticket and arrange for their help.
Okay, thanx for the info !
Wow, yes, it’s really weird…
Thank you, keep me up if you have news !
In the meantime, I will probably by a larger HDD for my NAS in the coming weeks, and I will take the opportunity to do a fresh install of QTS, to see if it solves it or not.
A fresh install of QTS doesn’t do anything unless you’ve completely wiped the old from the internal flash.
QNAP keeps the OS and your CACHEDEV devices separate.
The only thing which is app related is the contents of /share/CACHEDEV1_DATA/.qpkg and that will have no impact on performance unless you have too many apps running in too little amount of memory.
Hi again.
I ran a couple more test, and I don’t think my NAS is the real problem here.
I tried to run the built-in DLNA server of my NAS, and play the movie on my TV over it. --> No buffering in one hour of testing.
The bug must be on the QNAP version of Plex because :
PC(Plex) --> Ok
QNAP(DLNA) --> Ok
QNAP(Plex) --> Not ok
What do you think ?
