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Audio Out of Sync


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#1 EddieA

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Posted 11 July 2012 - 04:16 PM

I noticed yesterday, when checking some of my recent encodes, that the audio was out of sync, which I hadn't experienced before.

After checking a couple of things, I tried changing the Audio settings, in the Playback options. Originally it was set to: AAC Stereo. Switching it to: AC3 5.1 appeared to have solved the issue, even though AFAIK,my Roku doesn't support 5.1 playback from Plex.

However, when checking some of the files I'd previously played perfectly, instead of finding that they were AC3 5.1, as I expected, they were also set to AAC Stereo. So it seems that just using AAC Stereo is not the issue.

Why are some AAC Stereo streams playing correctly, but not others. Some transcoded, others not ??

This is a 2100X Roku, 2nd model, 1st generation. Plex version: 0.9.6.5.178-5c3cf40

Cheers.

#2 schuyler

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Posted 12 July 2012 - 06:27 PM

For the ones that have issues, are they out of sync from the very beginning? Or do they slowly drift out of sync? Or is it only after doing some sort of pause/resume/seek?

The answer likely depends on that. If they're out of sync right off the bat, then the Roku must not like something about the file. The Roku can be a bit picky about how audio and video are interleaved. If it's possible to extract and share a small sample that has the problem, that'd be great.

#3 J.P.

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Posted 12 July 2012 - 07:19 PM

I have seen this periodically. Typically pausing the video, rewinding one or two seconds, then pressing play fixes it.

#4 EddieA

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Posted 13 July 2012 - 06:55 AM

For the ones that have issues, are they out of sync from the very beginning? Or do they slowly drift out of sync? Or is it only after doing some sort of pause/resume/seek?

The answer likely depends on that. If they're out of sync right off the bat, then the Roku must not like something about the file. The Roku can be a bit picky about how audio and video are interleaved. If it's possible to extract and share a small sample that has the problem, that'd be great.

They appear to be out of sync from the very start. No pause/resume/seek, nothing, just play.

On one, where the studio logo audio starts immediately, it plays about one second of audio, then drops for a second or so before resuming, but only the audio. There's no pause in the video. After that it's out of sync, but it seems like it's more off than the length of the stutter. The others, I haven't been able to discern a "gap" as it starts to play.

Let me see if I can slice off the first few minutes from one. Or maybe run an analyse program on the file to see if there's a difference in the way the AAC Stereo stream is encoded. They are all packaged the same as mkv containers.

Cheers.

#5 mrthepete

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Posted 16 July 2012 - 02:36 AM

They appear to be out of sync from the very start. No pause/resume/seek, nothing, just play.

On one, where the studio logo audio starts immediately, it plays about one second of audio, then drops for a second or so before resuming, but only the audio. There's no pause in the video. After that it's out of sync, but it seems like it's more off than the length of the stutter. The others, I haven't been able to discern a "gap" as it starts to play.

Let me see if I can slice off the first few minutes from one. Or maybe run an analyse program on the file to see if there's a difference in the way the AAC Stereo stream is encoded. They are all packaged the same as mkv containers.

Cheers.

If I ffwd a few minutes and then back up a minute or so, the sync issue is fixed for me. The problem is, I should be able to hit play and have it play in sync. It's a hassle to ffwd, then rewind. And if I screw up and rewind to zero minutes, the sync problem is not solved. This issue needs to be fixed, imo.

#6 EddieA

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Posted 16 July 2012 - 05:32 AM

If it's possible to extract and share a small sample that has the problem, that'd be great.

I sliced off the 1st 3 minutes, or so, from Predators that exhibits the out of sync when playing the AAC Stereo stream. The AC3 5.1 plays perfectly.

It's a tad under 40Meg and you can pull it from my ftp site: ftp://ftp.BogoLinux.net It's in the pub directory.

Cheers.

#7 macjohnmcc

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Posted 19 July 2012 - 07:38 PM

I experience this regularly on Plex (client on Roku 2 HD). All of the videos with this problem play normally on VLC and on my iPad when I use Air Video and Air Video Server. I typically have to resort to connecting my Apple TV then viewing on my iPad using Air Play to view the content.

I am more than happy to provide samples if required to squash this bug.

#8 EddieA

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Posted 25 July 2012 - 05:37 PM

Any further updates on this now that you have a sample.

Cheers.

#9 evilcooper

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Posted 25 July 2012 - 06:53 PM

I am getting a similar problem currently with an .mp4 encode. Watching from the beginning doesn't cause any problems, but if I stop and try to resume, the audio is significantly desynced.

I've tried changing video quality, transcoding, and audio settings to no avail. The ffwd/rew trick outlined above doesn't fix it either.

It's not a pressing issue, and I haven's seen it elsewhere, but I mostly watch x264 mkvs for everything else.

#10 Schmye Bubbula

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Posted 11 August 2012 - 11:46 PM

I don't recall ever having had video/audio sync problems when first playing a video. But more often than not, if I fast-forward it gets out of sync. Does that provide a clue? (I can only speak for the Let Me Watch This channel, because that's about all I use Plex for, but I'm led to understand that with any channel, once a video is played, it's out of the hands of the channel, and Plex itself has taken over.)

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Edit: Woops, just now had a TV episode begin with the video & audio out of sync. Nevertheless, it still happens much more often for me after a fast-forward.

More generally, why does this out-of-sync happen in the first place? I would think that in this day and age, locking the video & audio together would be a trivial task. Are videos stuck in some legacy shortcoming from 20 years ago?

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Plex client 2.6.7 channel on Roku 1 XD-S
Plex Media Server 0.9.9.7.429
Mac OS X 10.6.8 Snow Leopard

(updated from PMS 0.9.5.3 & Mac OS X 10.5.8 on Mar 17, 2014)
Firefox 28.0

MacBook Pro (5,2) "Mid 2009" — 2.8 GHz Intel Core 2 Duo


#11 Braddock187

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Posted 15 August 2012 - 03:17 PM

I am also experiencing this when I pause and/or leave the Roku Plex app to do something else and then log back in and try to pick the same video back up (Resume). The audio is out of sync and it takes several fast forward and rewind attempts before I can seem to get it resolved. It's certainly a hassle. I've gone as far as uninstalling the client entirely - also have it on two different ROKU 2 XD boxes and both experience this same issue.

Any help would be appreciated.

#12 nvrmore100

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Posted 11 September 2012 - 06:24 PM

I have similar issues with my files when I fast forward or resume from a stopped playback. In my case when I hit play after a resume I hear the audio before the video appears. When the video appears the audio is out of sync by the length of time where it was not displaying. Fast forwarding / rewinding several times, or stopping/resuming sometimes will get it in sync, but its fruitless in most cases. A play from the beginning always works for me though, no issue with audio out of sync in that case.

#13 dead.electric

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Posted 12 September 2012 - 08:28 PM

I have the problem where audio plays for a second, then drops, then comes back severely out of sync. Happens with all of my content that has to transcode and has an aspect ratio other than 4:3 (I suspect this to be related to the fact that my 4:3 content is lower quality/bitrate, but can't prove it.)

I "fixed" the problem by re-encoding everything to files that will direct play. Probably not the solution you're looking for, but it did work (and loads quicker and puts less stress on my server as well). I used the BatchEncoder Handbrake extension, which made it fairly painless.




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