Plex Nine Troubleshooting test
Plex/Nine Troubleshooting Guide
Disclaimer: Not guaranteed to be 100% accurate, complete, or up to date, may or may not also have been written by drunken monkeys.
Defining Judders, Stutters and Stalls
Here are some common definitions for some of the AV playback issues you may see.
When the audio track and video track are not matching up, resulting in (most noticeable) mouths moving and the dialog not matching the facial movements
When a television doesn't refresh quickly enough or doesn't stitch frames properly resulting in a "hopping" motion when panning left to right or experiencing fast motion. Judder is usually at fairly regular intervals, its not a random stutter, but rather a regularized skip or motion instability, most noticeable usually in horizontal camera pans.
When audio continues, but frames are dropped, resulting in a pause, then a speed up of frame rate to catch up to the audio track.
When your network cannot keep up with the video file and the playback stops all together, then rebuffers to proceed. This results in a total pause of video/audio playback, then resuming
Juddery, Stalling, Stuttery playback - The Top 10 Major causes
There can be many causes for un-even playback of your media in Plex. There are a couple of major offenders that can cause your shows to play with little hiccups, pauses or even major glitches. This Guide should help you to work out what sort of 'judder' you have, some of the likely causes and hopefully rectify them.
#1 Cause of Judder - Media that has a mis-matched fps for your TV
This is the single most common cause for what people will variously call juddery, jerky or stuttery playback. When you're looking at 'judder' playback, you'll notice a regular pause in the picture motion. It may be a very subtly pause or a really jarring stop, but the key is that it's regular. If you notice a pause 1 minute into a video, then another in 5 minutes, you're seeing stutter - not judder.
Quick solution Set your TV refresh rate (Mac OS X Preferences > Displays > Refresh Rate) to one of: - The recommended setting for your TV - break out your manual and read it! - If your TV properly supports 24p, set it to 24p - If your TV supports 50/60/100/120Hz, set it to the closest match for the media you care the most about
Explanation Judder is caused by a mis-match between the fps of the media being played and the frequency your TV has been set to. Ideally, your TV should be set to the same or multiple of the fps of the media being played. Most media around today - particularly HD media has a frame rate of 24 fps. DVD media can have a frame rate of 25fps (PAL) or 29.97fps (NTSC).
Quite often, your TV will have a recommended setting
Here's the Quick-explanation:
Matching fps to Screen Frequency People generally know that a movie is a set of still images projected onto a screen many times each second. In the cinema, a projector displays 24 still frames each second on the screen and we see a movie. Your TV set is the same - it projects individual pictures many times each second on the screen. TV's are quite different to the cinema - especially today, but fundamentally, the two do the same job.
TV grew up differently to cinema. The world was divided into NTSC and PAL regions. they used similar but different technologies for displaying TV images. We don't really care too much about NTSC or PAL - except for one important part - the refresh rate. NTSC uses 29.97 fps and PAL uses 25.
#2 Causes of Judder - Motion correction features on your TV
#3 Causes of Judder - Badly encoded media
Note: most of these media problems can only be addressed when ripping and encoding the dvd. There is generally no way to fix most of these in an existing encode, in most cases you will need to re-rip the dvd.
Telecine (aka 3:2 or 2:3 pulldown)
Telecine video is the DVD era's greatest crime against cinema. (post letter-boxing maybe)
warning: contains lots of crap you probably dont really need to know.
tl;dr: When ripping/encoding try to restore your movie to its original framerate if you can.
Film is generally 24 frames per second, that is every 24th of a second the projector will display a new full frame image. The Majority (but not all) of movies are shot at 24 fps, but everything shot with Film is frame-based, which as you'll see soon is an important distinction.
NTSC Video however runs at 60 fields per second. NTSC video is the television standard widely used for decades in north america and Asia. The PAL video standard used mostly in Europe is similar at 50 fields per second.
huh? what's a field? i thought video was just sequence of still images called frames? oh you poor naive child born in the digital flat-screen utopia... For most of the lifetime of television technology, until quite recently, television was all interlace all the time. Those giant 100lb lead and glass boxes we used to microwave our retinas with are CRT tvs, and that was the technology for the vast majority of the existence of television. and CRTs dont refresh the whole image at once, but rather half the lines at a time, they switch beween the odd and even lines, becoming one smoothly moving picture in your eyeballs. so what you see as one image is actually 2 interlaced half height "Fields" (top and bottom) representing the intermittent odd and even lines of the screen.
So, when movies began to come to home video, first as vhs and then dvd, they needed to find a way to turn 24 frames into 60 fields for viewing on home TVs, and because 60 is not an even multiple of 24, they cant just split the lines and call it a day. no, indeed some darker voodoo would be required...
TO BE CONTINUED...
How to Fix
Other Framerate Conversions
HD Audio Tracks
Currently Plex has problems playing the 2 main HD audio codecs found on blurays, Dolby TrueHD and DTS-HDMA. (LPCM is fine). Trying to play one of these can result in either no audio at all, or really bad video stuttering.
How To Fix
thankfully this is one that is usually pretty easy to fix and wont require a re-encode of the video.
solution 1: Just switch to a different audio track. many times discs/rips (usually ones with the dolby format) come with a normal DD 5.1 audio track as well as the HD track. If your file does have an alternate audio stream in a format plex can handle fine, you can just switch to it in plex while playing. the option is under the audio pane (the speaker looking button) of the on screen display that comes up when you hit menu on the apple remote, or M on the keyboard. however if you'd like a more permanent solution for the file then:
solution 2: Remux the file without the HD audio. Assuming you have another audio track for the movie which plex can play (ac3, DTS, whatever), then you can use MKVMerge (mac gui builds here: ) to remux the video without the HD audio track that gives plex problems, mkvmerge is easy, really fast, and does not re-encode or in any way affect the video quality.
solution 3: Re-encode the audio to something plex CAN play properly. if you dont just happen to have a non-hd copy of the movie's audio just laying around, it is possible it re-encode the audio yourself. you see, these hd audio bluray formats are lossless, and that means they're perfect for this. I cant give you step by step instructions on what tools to use cause i havent done it myself, google around a bit, i think the current standard tool for converting bluray audio is eac3to (on windows) but dont quote me on that. If you want to keep the full quality audio, you can re-encode it to FLAC 5.1 (losslessly!) which plex plays great, or you can convert to normal DTS or ac3 (dolby digital), and afterwards use mkvmerge to remux it back to the video, replacing the soundtrack that was causing problems.
solution 4: don't download HD rips with these formats. I know it may sound obvious, but if you know that videos with one of these hd audio codecs cause problems for you, just avoid them in the future and choose something with plain DTS or AC3.
#4 Causes of Stutter - CPU overload
#5 Causes of Stutter - Other applications running
#6 Causes of Stutter - Settings on your Mac like Desktop Pics, Screen Savers
#7 Causes of AV Sync - CPU starvation
#8 Causes of AV Sync - A/V Receiver or Connection Problems
#9 Causes of Stalling - Network congestion
#10 Causes of Stalling - Overloaded Server
#11 Causes of ???
Stuttering Video - understanding some causes
There are many reasons why you might see video stutter or jerky playback. Ignoring software bugs and issues, there is an important concept - Frames per Second/Screen refresh mis-match - which is the number one contributor to ‘jerky’ playback on your TV.
When a show plays, it plays at a certain number of Frames per Second. A Blu-ray disk is usually 23.97fps, movies 24fps, PLA/SECAM 25 and NTSC 30fps. Why should you be worried about any of this? Because it’s a common source of ‘jerky’ playback problems when playing back media - especially today’s enormous screens! Here’s how it works.
Imagine that you have a pile of pictures and you’re standing next to a conveyer belt with boxes stuck to it. The conveyer belt moves so that every second, 30 boxes pass you by. Now, imagine that you’re fast enough to put 24 pictures down on the conveyer belt each second. There’s a mis-match - and 6 boxes are going to miss out on a picture. Imagine now that your 24 pictures are stored in a movie file, and the conveyer belt is your TV screen. The 6 missing pictures each second add up and create a problem called telecine judder. We call it ‘jerky playback’ and it’s really annoying!
Let’s apply this directly to Plex. You have a modern flat-screen panel - usually that means you can set it to 24, 50, 60, 100 or 120hz. Think of this as the conveyer belt. You’ve converted a Blue-Ray movie using a tool like MakeMKV, Handbrake or some other great piece of software and left it at the default setting. This usually means the movie rip will be encoded at the same rate as the source... Blu-Ray is usually 23.976fps.
So, what’s the ideal way to set up your panel? You need to choose a frequency as close to or a multiplier of the source. So, in this case the ideal setting the screen to 24Hz. If you don’t have that option, then choose the next nearest multiplier - 50/100Hz. If you have an NTSC source show, it’ll probably be 29.97fps... so the ideal would be 60/120Hz. Get the idea?
So, this is all very well and good, but it means that if you have a collection that is mixed - some 24, some 30fps movies. What are you supposed to do? You can’t set the panel to both - and that means that one or the other show will be jerky. There is no instant solution to this problem.
Media not being matched
Media being incorrectly matched
TV Show/Movie entries don't appear
Plex On-line/Help is empty
There is just one hardcoded change required when transferring libraries over to a new machine.
The file below needs to be edited and the Master user needs to be changed to reflect the new machines home directory:
In my example, I needed to change this line:
and everything booted up just fine :-)