Sync NDI video source with Audio-Interface source

[roenschg]

Hi there!

I work with two Logitech Mevo cameras via NDI and add them as an NDI source to my scenes.

I also have an external audio interface (Soundcraft Mixer) connected and added as an audio source where I gather the speakers voice from.

The NDI-Standard brings a delay of something up to a second to the video, but the audio interface just a few milliseconds.

This leads to the video and audio not being in sync.

Does anyone have an idea how to sync them. I tried just adding a delay to the audio from the sound interface, but I don't know the exact number how much the NDI-Stream is offset.

Best Regards,
Gerd

 

[AaronD]

Trial and error.

Or, you might have a look at Shotcut's automatic alignment feature:

Align To Reference Track

The Align To Reference Track tool allows multiple clips to be aligned to the audio in a reference track. This can be useful to align clips that were recorded at the same time from multiple camera angles. Align To Reference Track was added in version 22.06.23. Limitations This tool can only...

forum.shotcut.org

It's designed to take multiple audio sources, like from a bunch of simultaneous camera mics, and sync them all to the "good" audio. (and move the attached video with them) If you're using it at the start of a project that you're also going to finish in Shotcut, then that's all you really need to think about. But if you're using it for a measurement, then you may only be able to get a frame's worth of resolution, not milliseconds or samples. (unless you come up with some trickery that I haven't, which is entirely possible) It might be enough though.

In your case, see if you can record a single file with the "good" sound and the NDI sound on different tracks. Maybe panned hard left for one and hard right for the other. Load that recording into Audacity, and export each track as its own separate WAV file. Load those WAV files into Shotcut, leaving enough space at the start of the Timeline for them to move, and auto-align them. Now you have a difference in start times, when they used to be exactly the same. That's your offset.

If your NDI cameras don't do sound, then you can record a hand-clap or a hollywood-style clapboard (this is exactly what those are for) where each camera can see it well. Probably a separate recording for each camera. Load that recording twice into Shotcut, putting one of them in an Audio Track, mute the Video Track, and slide them back and forth on the Timeline until the audio spike lines up with the first frame of the clap being fully closed. Back up a bit and play it to confirm. As in the previous paragraph, you now have a difference in start times, when they used to be exactly the same. That's your offset.

 

[DukeTate]

Hi there!

I work with two Logitech Mevo cameras via NDI and add them as an NDI source to my scenes.

I also have an external audio interface (Soundcraft Mixer) connected and added as an audio source where I gather the speakers voice from.

The NDI-Standard brings a delay of something up to a second to the video, but the audio interface just a few milliseconds.

This leads to the video and audio not being in sync.

Does anyone have an idea how to sync them. I tried just adding a delay to the audio from the sound interface, but I don't know the exact number how much the NDI-Stream is offset.

Best Regards,
Gerd

Gerd,

Did you ever figure it out?