Audio sync exists with 4.9.0 (how to reproduce)

[loopy750]

Audio sync is still an issue with 4.9.0, and tested using a few different network cards. The issue can be easily reproduced with both Normal and Low latency modes, although it may be less severe with the latter.

Please see the videos for how to reproduce, and the files used (linked/attached).

Latency: Normal - https://streamable.com/5p56f8
Latency: Low - https://streamable.com/b0dbsc

Over time, the audio/video may slowly drift out of sync. However, we can cause this effect immediately using the "static" image.

https://i.ibb.co/KGbPyPP/Image4.jpg - This is the expected result: frame "1" matches beginning of the 1kHz tone, hence in sync.

https://i.ibb.co/2Nch2Z6/Image3.jpg - The result after the "static" image has been shown: 1kHz tone begins at frame "54", 7 frames out of sync, or 116ms.

"Stress test" image file: https://i.ibb.co/SQhKMKQ/400pc-Gaussian-50pc-Grey.png
60 FPS Test mp4: 60 FPS TEST v2_1 START_AT_1.mp4_13MB.zip

[WiredUK]

I'd love to know if this is an NDI thing or an OBS thing. We're also seeing audio sync issues, though the low-latency mode appears to be a lot better. Even if I had a way to "reset" the sync, that would be enough for us, it's really starting to become a big problem.

[Anonymous2]

Hello, I also found a lot of audio/video desync with 4.9.0 that I never had on previous versions

[manuelnyc]

@WiredUK the problem is THIS palakis NDI plugin, when I use newtek tools I never have an issue, no drops no nothing, but when I use this palakis the problems, frame drops, out of sync, start to happen, sadly this is the only NDI plugin for OBS

[WiredUK]

@WiredUK the problem is THIS palakis NDI plugin, when I use newtek tools I never have an issue, no drops no nothing, but when I use this palakis the problems, frame drops, out of sync, start to happen, sadly this is the only NDI plugin for OBS

Not necessarily. It could still be OBS. We really need to understand this, it's really hurting the quality of our streams.

[manuelnyc]

@WiredUK the problem is THIS palakis NDI plugin, when I use newtek tools I never have an issue, no drops no nothing, but when I use this palakis the problems, frame drops, out of sync, start to happen, sadly this is the only NDI plugin for OBS

Not necessarily. It could still be OBS. We really need to understand this, it's really hurting the quality of our streams.

the only solution I found is this: (it's not a solution, it's a trick)

I produce the whole thing in OBS, skype calls etc, then from this computer I enable OBS's NDI output to my streaming computer, my streaming computer that receives my NDI stream is running Wirecast....... so to avoid the video/audio sync problems, every time there's a 1 or 2 seconds silence in the stream, I click reconnect in wirecast so the stream is fresh again...... doing this I never had a sync issue anymore, tested yesterday on a 2 hrs long stream

it is what it is,.......either this plugin or the whole NDI tech thing is still not well developed yet

[dgatwood]

One problem I just saw involved feeding 29.97/59.94 fps output from a Tricaster into OBS with OBS configured for 30 fps video. The video got farther and farther behind. What was interesting is that feeding 59.94 fps video into a 30 fps configuration drifted about the same amount as 29.97 fps video did.

So this seems to be a problem with some part of the NDI to OBS data path not handling the difference between drop-frame and non-drop-frame modes, but still getting the 30 fps vs 60 fps portion of the frame rate right.

Switching OBS to 29.97 fixed the problem.