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Audio sync errors after fast forwarding recorded TV


Rogero54

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When watching recorded TV, after fast forwarding (skipping commercials for example), The audio channel is out of sync with the video. The video is ahead of the audio by a second. Rewinding the show fixes the issue. 

Server is a QNAP NAS TVS-673 with 16G of RAM. Clients are Nvidia Shield's. It occurred at 12:56, which should be at the end of the attached log. According to my wife it is an intermittent issue. 

 

Thanks,

Roger

embyserver (2).txt

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bungee91

I have this same issue and it's been driving me insane. Been like this for months now. I rolled back the ATV app from beta to stable thinking it was changes to Exo, and it made no difference. I have two Shields but it only happens on the older 2015 model that has surround sound (HDMI to receiver, 5.1 setup), and not on the 2017 model that is direct to TV and downmix to stereo. I didn't test the 2017 with a 5.1 setup, but they're basically the same hardware wise. I even did a factory reset on it to rule it out, and zero difference. 

Here's the thing, it's unfortunately not just Live Tv, I've noticed it on other content as well but certainly less frequent. It seems more obvious on DD 5.1 content audio output, I don't believe it happens with Tv streams that are 2 channel. You can even see it at times (if it's the same issue), video will literally pause on resume of play, audio will resume as normal and be off. Skipping back seems to resync it. 

I think this is very much related to the Shield and not the server, but that's just a guess at this point. I've just been living with it even though it happens for me on a daily basis on this particular setup. 

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pwhodges

I see this often, most seriously when playing recorded TV using a Roku, but also sometimes with other content; after jumping back or forth in a video, there is a good chance that audio and/or subs will be out of sync, not necessarily by the same amount.   Once this happens, the state is cached, and only playing from the start will fix it. 

I've not yet had time to sort out relevant logs (I've been away for a bit and am still catching up with stuff).  Using current beta server.

Paul

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bungee91

@ebr @Luke while I'm not the O.P. I'm fairly certain my issue is the same, and intend to get this resolved by providing as many examples as needed to pinpoint this issue. This issue is not new, it has been occurring for months. Wish I could pinpoint it, but it doesn't seem to be EXO from my previous attempts of rolling back to stable (weeks prior), and the issue being the same. Around 16:09 or 16:10 in this log the issue occurred.

What occurred: I skipped forward in the recording. Once it started again both audio and video started, a moment after then the video froze but the audio kept going. Audio was out of sync until I skipped back, then it was in sync again. This issue seems to happen during an in progress recording, and a direct stream is being processed. I sent an in app log as well, ~4:10CST user Home. I am not 100% certain the video always pauses and then out of sync, but I can say that does occur often enough to be noticeable.

 

embyserver (1).txt ffmpeg-remux-668cea34-118b-4cea-b412-4ce6281f5ef1_1.txt

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bungee91

One more example, same in-progress recording with the same issue occurring. 16:37, end of this remux log is when this occurred. I skipped forward, audio and video started for a second, then video froze for a second or two, then continued playback out of sync. Another app log sent as well at 16:37 CST.

I do NOT notice this issue when it is a completed recording and direct play.

ffmpeg-remux-b0ad3455-ac8c-4a13-83c1-7d4f8ce8611e_1.txt

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bungee91
2 hours ago, ebr said:

It is always an in-progress recording this happens with?

I'm fairly certain that's the case, as it's direct play when not in progress. I can say for certain it's much more frequent/noticeable/easy to make happen with an in-progress one. It may be more widespread than this though, I'll need to confirm. In the recent past I also was able to have sync issues with both an X264 DTS movie in my library as well as one with DD. I couldn't recreate that issue quickly though, so no assumptions here that's still the case. 

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bungee91

@ebr anything I can perform or test to help in diagnosing/resolving this issue? The primary telltale sign for me is the freezing of video and audio continuing as expected. Do you need to know if this happens on a full transcode (I can force that), or if enabling an in-app option (video stream copy, refresh rate switching, ....) makes a difference? I have a test stable Windows Emby server if its version of FFMPEG is different and worth testing against.

I wouldn't think this issue is very widespread given the lack of posts reporting it. Admittedly I had looked weeks back but assumed it was something with my setup. I even tested moving the Shield within 3' of my receiver to limit HDMI cable length. Suffice to say it made zero difference. I'm near certain forcing it to downmix to stereo would remove this issue as well, however didn't test that theory.

Thank you for your help.

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Rogero54
On 10/25/2020 at 6:17 AM, ebr said:

It is always an in-progress recording this happens with?

Not in my case. Always existing recordings.

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23 hours ago, bungee91 said:

I'm near certain forcing it to downmix to stereo would remove this issue as well, however didn't test that theory.

Can you test that theory?

Thanks.

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bungee91
On 10/27/2020 at 8:34 AM, ebr said:

Can you test that theory?

Thanks.

I was very incorrect, same exact issue with, or without pass-through. Also, it goes out of sync at times without the video visibly freezing and the audio continuing. This ONLY occurs when skipping forward, if playing consistently it isn't an issue. 

Since my issue is unique from the OP, should I create a new thread? 

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bungee91

I'm going to do some testing with the Shield hooked directly into the Tv, and using ARC to the receiver. I've been living with the absolutely obnoxious issue of an audio lag after play/pause condition that is apparently "as designed" by Nvidia with DD signals. Apparently they don't have the license for the DD decoding, and do not implement comfort noise on the output with pass-through and default back to PCM, which introduces the lag to occur. Using the Shield to Tv with ARC seems to remove this issue for me (amazing!), however severely limits the direct play audio formats in this configuration. However if it removes the lag issue from play/pause condition, AND fixes this issue, I no longer give a f*** due to it just working. We shall see, will report back.

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