Has anyone had the experience of using the new “Watch Together” feature and finding that it slowly goes out of sync? Last evening, a friend and I used this feature to watch a program and although it was synchronized at the start, by the end of a 30-minuted program we were a good 2-3 seconds apart. (This actually even happened prior to using this feature when a friend and I would cue up and start a program at the same time). Is Plex compensating for internet speed and video processing by playing the program at slightly less than 1x the speed on my friend’s device? Is there any way to correct this?
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Sounds more like a one-time hiccup that caused a little delay.
Not sure about your use case… a 2-3 seconds difference after 30 minutes playback doesn’t sound that horrible to me.
PS: I remember the actual broadcast delays during the Olympics or some world cup games, when there had been up to 20 seconds of delay between people receiving their tv program via cable, satellite or terrestrial (+ analog vs. digital) – screen 1: player approaches the penalty point, the audience gets excited… screen 2: audience already starts celebrating the goal.
Expecting ‘Frame Sync’, over the internet, in different networks, on different clients, in different states/provinces/counties/countries/continents - is a dream. As in, it’s not gonna happen.
If you guys are playing the same Show - consider it a win.
Expecting ‘Frame Sync’, over the internet, in different networks, on different clients, in different states/provinces/counties/countries/continents - is a dream. As in, it’s not gonna happen.
Tell that to the internet-synchronized clocks. NTP takes in to account internet latency so that both sides are in sync to less than a nanosecond.
Also: I don’t know if everyone is aware, but during playback the clients are reporting playback position very often.
The only thing left is keyframes, which make it difficult to reliably set the playback position for some media, but even that’s a solved problem via transcoding. Alternately everyone could just sync to the same keyframe at the same time.
TL;DR: Getting sync to under 10ms is doable.
Not entirely 
(from Network Time Protocol - Wikipedia)
NTP can usually maintain time to within tens of milliseconds over the public Internet, and can achieve better than one millisecond accuracy in local area networks under ideal conditions. Asymmetric routes and network congestion can cause errors of 100 ms or more.
It might be technically possible to push for a more strict sync – just not sure it’s worth the effort. Unless you want to add live interaction with the people you watch together with… what is a few seconds over a 90 minutes duration?!
Hah, were any jump scares or dramatic reveals ruined because of the drift? My sympathies. That’s such a first-world problem, and I would be totally irrationally annoyed too.
It’s possible to get clocks darn close! But they started at the same time. Even the cheapest clock around should be able to maintain accuracy of a couple of seconds over 30 minutes.
Still, different decoder engines take different liberties. After all, nobody ever compares them side by side, right?
One way to present 29.97fps content is “on 30”. If one of the players did it that way, it works out to about 2 seconds over 30 minutes. You probably don’t have 29.97fps content, but it’s an easy example. Or some decoders will skip over frames they can’t parse, jumping forward in time, while others will extend the ‘good’ frames and maintain monotonic progress.
The idea of using keyframes to synchronize would require both players to be using the same file, too - it would either mandate or eliminate transcoding for Watch Together.
I’m guessing “Watch Together” tells both players “start ASAP”. Does anybody know what it actually does?
We didn’t need Watch Together…
We’ve been doing it for years…
Group Text - “Play Now”!
Just as accurate as “Watch Together” across Continents when “Play Now!” won’t even work (for long) in the Same House!
but this thread is hilarious… Please… carry on…
(just remember “Watch Together” took development time away from:
The Plex Dance, The misplacement of Local Media Assets, A Letter Stack in Collections, or any one of the other million things that are broken in Plex, but we really needed Watch Together - time well spent)
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… isn’t live interaction the ideal?
Like I would never advocate for Plex to roll in video chat clients, but who is out there sitting at home and texting “play now” to someone, then watching the entire thing without some sort of realtime audio or video?
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Let’s remember that we’re literally talking about a very first-world tool. We’re always pushing for better and don’t need any of it. Better quality, more devices, better utilizations of resources to share with more people, better metadata so it looks better, etc, etc, etc.
I would even argue that keeping the compass pointed at “better”/“best” is what really defines a Plex fan.
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No … but never say never …
I might advocate for text chat, on the big screen, as an amazing “casual togetherness” feature. I already ignore movies while texting my BFFs.
It could be like “live subtitles”. Or do-it-yourself MST3K.
I like the positivity of “something isn’t perfect, maybe it could be awesome”. 
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This can have several reasons. Particularly when using completely different client types.
Each device can have slightly different frame rates. Some client types will sync the picture to the clock of the audio interface (to achieve lip-synchronity), which can be slightly different on different device types.
I wouldn’t expect Watch Together to be frame-perfect. This is outside of it’s scope. If you’d wanted to achieve frame-perfection, a lot more effort had to be made and a lot more software had to be changed and rewritten.
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I’ve been experiencing the same issue as well.
I tested this out with my iPad and iPhone (both playing original, with no transcoding and both on local network). Although the runtime counter seemed to have always been synched within a second, I noticed a 7-8 second gap between what was playing. Both devices would say 7:21, but one device was up to 8 seconds behind.
It would have assumed that 7:21 runtime in a video would be nearly identical (within a second) from anywhere you watch. How can the same runtime have such different gap?
That’s surprising to me. I’ve seen the runtime counter drift “a little bit” between different player types, but I’ve always felt the actual video playback was within 1-2 seconds of the runtime counter. I’d expect two iOS devices to be “very similar”. 
If you’re using Airplay for audio, there’s some magic video delay, but I think the runtime counter stays aligned. Just brainstorming.
Were you using the “new” player on both iPad and iOS?
Synchronized playback is most important for halloween. If the “scares” aren’t aligned, somebody will scream early! 
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totally agree, that is entirely the point. and assumed that some sort of vocal /video link is established among the viewers, otherwise why bother doing the darn feature.
might as well just tell your mates 'hey guys watching so and so tonight, 9 …ish." and them to reply “yeah … cool… us too … ish”
and bam done deal.
If there is a watch together feature it is ALL about watching it together and interacting.
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