Fluctuating Audio Offset in OBS with PTZ NDI camera

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Pastor Adam

New Member
Our church has a live stream setup that we installed this past summer. We have a PTZ Optics 30X NDI camera that is mounted in the balcony about 25 ft from where our streaming computer is. The camera is using NDI for both power and video transfer. We also have our church sound system coming into a Focusrite Scarlett 2i2 (3rd Gen) USB Audio Interface which is also connected to our streaming computer that is running OBS. Since both audio and video are not coming in both through the camera we knew that we would need to have an audio offset however we have noticed that this offset seems to need to be changed for some reason. If we zoom in for a particular project we might need to change it from 233 ms to 500 ms or the video / audio is way off. We have had it at 233 ms for months and just this past Sunday we had to raise it to 350 ms to get it to line up. What are we missing. We have a lot of bandwidth in internet. Is there a reason that zooming in the camera would change the offset? Is there a setting we are missing that is causing it to fluctuate on its own? What can we do to correct it or do we just need to check the offset often?

We are currently broadcasting our livestream to Facebook on Sunday mornings and then pushing the recording to YouTube after the service is overwith. Thank you for your help.
 
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Lawrence_SoCal

Active Member
I'll be watching this thread, as I'm interested generally in NDI and USB interfaced sound system for House of Worship streaming (I'm in charge of our church's setup), though my camera is Panasonic vs PTZoptics

Also, just a side note. IF you Facebook schedule your live videos, non FB folks can watch (and see video library)
I personally don't have a FB account... and never have had one... no plans to change that... so I get avoiding FB
But, with livestream of services, and associated comments in FB, I advocated against also putting our services up in YouTube. The only reason I can think of to post to YouTube would be convenience for non-technical folks to easily be able to watch YouTube from Roku, Apple TV, Smart TV, or similar device (vs going to URL which almost all of those devices can do as well)
Just curious what the thinking is in your situation (as in should I re-consider)?

And thanks for the reminder... We just went from USB webcam to NDI video feed and I haven't done an audio sync yet (no one has complained yet.. but I should do so anyway).

On your PTZ optics, are you noticing the audio sync change when using Optical Zoom, or are you getting into digital zoom (digital zoom would entail PTZ camera's CPU, so it shouldn't change if well designed, but I if there was an audio sync difference, I could guess at camera CPU as possible technical cause)

Though... bandwidth to Internet shouldn't have anything to do with it? Now, other devices on your LAN causing local network traffic congestion certainly could cause a problem. Is your streaming PC directly plugged into same Ethernet switch as the camera? best practice would be to isolate the traffic (VLAN, etc) from NDI camera to streaming PC. Further, our streaming PC (and NDI camera) is firewalled off from the rest of the church network
 
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magicfriend714

New Member
Lawrence_SoCal said:
I'll be watching this thread, as I'm interested generally in NDI and USB interfaced sound system for House of Worship streaming (I'm in charge of our church's setup), though my camera is Panasonic vs PTZoptics

Also, just a side note. IF you Facebook schedule your live videos, non FB folks can watch (and see video library)
I personally don't have a FB account... and never have had one... no plans to change that... so I get avoiding FB
But, with livestream of services, and associated comments in FB, I advocated against also putting our services up in YouTube. The only reason I can think of to post to YouTube would be convenience for non-technical folks to easily be able to watch YouTube from Roku, Apple TV, Smart TV, or similar device (vs going to URL which almost all of those devices can do as well)
Just curious what the thinking is in your situation (as in should I re-consider)?

And thanks for the reminder... We just went from USB webcam to NDI video feed and I haven't done an audio sync yet (no one has complained yet.. but I should do so anyway).

On your PTZ optics, are you noticing the audio sync change when using Optical Zoom, or are you getting into digital zoom (digital zoom would entail PTZ camera's CPU, so it shouldn't change if well designed, but I if there was an audio sync difference, I could guess at camera CPU as possible technical cause)

Though... bandwidth to Internet shouldn't have anything to do with it? Now, other devices on your LAN causing local network traffic congestion certainly could cause a problem. Is your streaming PC directly plugged into jelp same Ethernet switch as the camera? best practice would be to isolate the traffic (VLAN, etc) from NDI camera to streaming PC. Further, our streaming PC (and NDI camera) is firewalled off from the rest of the church network
Click to expand...
Ptz has a great video that will help you sync your audio works perfect
 
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dfandrews

New Member
I'm using two PTZoptics NDI cameras at our church. The NDI feed is converted from NDI to HDMI (Magewell) and fed into a Atem Mini Pro. The house audio is also fed into a line level input on the Atem. The output of the Atem is connected to OBS (MBP) via USB-C connection. In OBS I introduce 400ms of delay. Works perfectly.
 

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mlcoz

New Member
Pastor Adam said:
Our church has a live stream setup that we installed this past summer. We have a PTZ Optics 30X NDI camera that is mounted in the balcony about 25 ft from where our streaming computer is. The camera is using NDI for both power and video transfer. We also have our church sound system coming into a Focusrite Scarlett 2i2 (3rd Gen) USB Audio Interface which is also connected to our streaming computer that is running OBS. Since both audio and video are not coming in both through the camera we knew that we would need to have an audio offset however we have noticed that this offset seems to need to be changed for some reason. If we zoom in for a particular project we might need to change it from 233 ms to 500 ms or the video / audio is way off. We have had it at 233 ms for months and just this past Sunday we had to raise it to 350 ms to get it to line up. What are we missing. We have a lot of bandwidth in internet. Is there a reason that zooming in the camera would change the offset? Is there a setting we are missing that is causing it to fluctuate on its own? What can we do to correct it or do we just need to check the offset often?

We are currently broadcasting our livestream to Facebook on Sunday mornings and then pushing the recording to YouTube after the service is overwith. Thank you for your help.
Click to expand...
Did you ever resolve this issue? I have the same problem. 3 x Birddog P100 NDI cameras into OBS, and I often need to vary the sync offset anywhere between 250ms and 650ms. It seems to be related to network traffic on our LAN, but I have never been able to isolate it. I may need to create an isolated network for just the cameras and a separate NIC on the livestream computer. It means that during a service I have someone constantly monitoring the livestream and letting me know when the offset needs to be tweaked.
 
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Lawrence_SoCal

Active Member
An isolated network is really important. Using VLANs will suffice if you have managed network gear (vs having to use separate physical switches if are type=Unmanaged). I also have streaming network behind its our router/firewall, and we make sure sure office computers and audience aren't using limited upstream Internet bandwidth during service

With varying latency @mlcoz is suffering, I'd think you be chasing your tail trying to address, vs isolating camera to OBS computer traffic
 
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