Plex increasing bitrate causing problems

General Discussions
1

Hello,

I have been running plex for years and have just discovered a strange issue. My server is reasonably powered Xeon 1231v3, 16gb ram, Debian headless.

I have some TV shows that are 1080p and between 10-13mbit bitrate. When I play them from a browser they play fine at the original bitrate as reported by the server dashboard.

When I play this content via my Smart TV, the dashboard reports that its being transcoded to 19mbit bitrate. This causes the video to buffer randomly from 10 seconds to 30 seconds continuously.

I can limit the local bitrate on the TV to 10 or 12 mbit and it plays fine, but when I set ‘original’ as the quality it starts messing the bitrate up again causing buffering.

Any ideas or help would be greatly appreciated?

Thank you

2

Do you by chance have bitrate and the bandwidth reserve confused? If you’re setting quality to Maximum/Original, and it’s “DirectPlay” The bitrate is whatever the file is
 If you transcode it to a lower bitrate (your 10 to 12Mbit scenario) then it’s obviously lowering the bitrate. Plex, as far as I know, does not increase the bitrate, unless you’re doing something like going from a 1080p 4Mbit x265 file to a 1080p x264 file for codec compatibility, in this case, plex will artificially inflate the bitrate to like 10Mbit or something like that


The next question I have is, is the TV DirectPlaying or transcoding? If it’s DirectPlay you could have a couple of different issues.

  • The Decoder of the TV Is not working fast enough (seems unlikely but it IS a possibility)
  • The wifi connection to your smart TV is not fast enough for whatever bitrate you’re playing, but it IS fast enough for 10-12mbit
  • From what I understand, some older Samsung TV’s don’t like the multiple audio stream files so much
 anything more than 2 Audio Streams and it freaks out


If it’s transcoding, that could be a bunch of different things
 Your server should be fast enough to transcode I believe
 it’s got a 9,000 passmark so iirc that should be enough for 4x1080p transcodes (I think it’s 2,000 score per 1080p transcode).

More information and logs will likely be really helpful here to let the community see exactly what’s going on in that exchange


3

Can you give the exact video and audio specs of the file, and are you using subtitles?

4

I think I might be confusing the two.

I have a strange feeling that my Hisense Smart TV’s network is not capable, even though its ethernet. When I start a TV show and watch the Plex dashboard, the bandwidth will never exceed 20mbit via the TV, but other local devices will use 50-100mbit when starting.

One of the files the tv has problems with is as follows:

Media

Duration 1:02:27
Bitrate 12277 kbps
Width 1920
Height 1072
Aspect Ratio 1.78
Video Resolution 1080p
Container MKV
Video Frame Rate PAL
Video Profile high

Part

Duration 1:02:27
Size 5.36 GB
Container MKV
Video Profile high

Codec H264
Bitrate 11893 kbps
Language English
Bit Depth 8
Chroma Location left
Chroma Subsampling 4:2:0
Frame Rate 25 fps
Height 1072
Level 4.1
Profile high
Ref Frames 4
Scan Type progressive
Width 1920
Display Title 1080p (H.264)

Codec AC3
Channels 2
Bitrate 384 kbps
Audio Channel Layout stereo
Sampling Rate 48000 Hz
Display Title Unknown (AC3 Stereo)

5

That file checks out, and oddly, it’s a 12Mbit file, so I don’t think it’s a bandwidth issue if you’re able to successfully do 12Mbit 1080p with other files.

This XML Data only gives us more questions than answers
 So when you’re playing is the file DirectPlay or is it Transcode?

6

Now take a look at the real bandwidth requirements of this file in the Plex XML info
Because the number above is only a stupid average, calculated by taking the file size and divide it by its play time. For “streaming” purposes this can be misleading in a big way.

7

Server is probably transcoding

8

That is a weird conclusion to draw. It only means the file has either ‘25fps progressive’ or ‘50fps interlaced’ frame rate.

9

I didn’t think all tv were compatible with pal?

In any case, checking the reason for transcoding is the first thing to check.

10

I think the issue here is the opposite. Because OP said if he is limiting the bitrate, playback is smooth. Which means that direct-playing causes stuttering.

The bandwidth graph in the Dashboard can give you a clue:

  • stop all playback activity of other clients
  • start playback on the tv without restricting the bandwidth

Now wait ~60 seconds and then look at the bandwidth graph.
If you see a flat horizontal line, you have a network bandwidth restriction somewhere between the server and the TV. (but it could be caused by the TV itself as well)

If you however see “bursts” of data, the network bandwidth is probably not the issue.

11

Screenshot of the dashboard with the video playing would be useful too.

12

Thank you to everyone for your replies. It turns out that it was my smart TV’s inbuilt plex client and the TV’s throughput in general causing the problem. Can’t believe I have never noticed it before.

Got a new device to fix the problem as it definately wasn’t Plex related.

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