Inconsistent Audio delay creates sync issue in PTZ cameras [PLZ help]

[umitsedgi]

Hello all,

I have the below system for a place.
Multiple PTZ cameras are connected to a POE switch.
Audio and video get merged on the computer.

Whenever I start broadcasting, the delay amount changes. sometimes around 800ms sometimes goes all the way up to 6 whole seconds. When you set the right amount of delay for that particular broadcasting, it's usually good until the recording ends but when switch to another camera, the delay amount becomes not valid again.
I had a focusrite audio interface and had the same issue. Later on it malfunctioned and now the audio is directly plugged into the computer's line-in port (no audio interface is running currently )

When I ran a log report, this is what it says:

I don't mind buying new equipment to solve it but Just don't know where to start. I need a stable system where audio and video synchronization shouldn't be an issue.

I really appreciate if someone can help me.

 

[AaronD]

We have PoE-powered PTZ's at our church, and our finished soundtrack comes separately from the Front-of-House console. Our cameras do have a network stream that works, but we don't use it. We use the direct SDI output from each, with a separate run of coax back to the booth, which is also where the PoE switch is, and run the SDI video feeds directly into a 4-input PCIe card:

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OBS then does all of the switching, compositing, etc. No ATEM. OBS also drives a full-screen projector on a dedicated output of the GPU, and the Multiview on a different output of the same GPU. The third output is for the streaming dashboard in a web browser.

We're about 1/4-second latency, every time, and everything stays in sync.

We used to convert the SDI's to HDMI in the booth, and then feed those to a set of cheap HDMI -> USB captures. Those were random latency. Not as bad as you describe, but definitely noticeable, and different every time.

---

You should probably get the audio back off of the internal line-in. Yes, it works, but its performance is limited by being inside of an electrically noisy box. Stupidly-high spec "audiophool" audio is completely wasted in that environment, so don't believe that either.

Just getting the analog to digital converters outside of that noisy box does wonders, but it's also good to have something better than the same chip in a different chunk of plastic with a USB connector on it, like the cheap USB things are.

We use one of these:
https://www.amazon.com/Behringer-U-CONTROL-UCA202-Ultra-Low-Interface/dp/B000KW2YEI/
It's "only" 16 bits, but the low noise floor is still a big improvement! And if you've done your mastering well, before it gets there, 16 bits is plenty anyway. That's CD-quality, and OBS passes it straight through with no changes whatsoever.

 

[Lawrence_SoCal]

Going from PoE switch thru router to OBS PC is something I'd strongly advise against (I'd call that a 'no-no'). That can easily add varying latency depending on what else the router is doing, its config, performance level, etc.
our OBS PC is dedicated to OBS /streaming/video editing, and is direct connected to PoE switch with the NDI PTZ PoE cameras. The PoE switch, in our case, is connected to router (old router I had laying around which I donated) to protect Streaming environment. That router is then connected to site router and from there to Internet (fiber connection)
With a better PoE managed switch, or someone who knew that vendor better, might be able to handle security on the switch via ACLs. For me/us, a separate router was simply quick, dirty and effective

If the OBS Studio PC cannot be dedicated, (and in my case, secured against typical volunteer uneducated/mis-use), then separating from PoE network might make sense, but I'd still be inclined to go ACLs or similar route direct on PoE switch. Or be very careful with the router.. as that could easily be your entire problem

And if a digital mixer, I'd be inclined to USB connect to OBS PC and directly use audio signal from mixer without latency/translation with other 'interface' as show in your drawing. In our case, I put OBS PC in same space as mixer. I then use a 50ft fiber optic Display Port MST cable driving 2 monitors, and a similar length active USB cable for keyboard & mouse. The (physically secured) space with the mixer has an auto voltage regulating battery backup, the mixer, and the OBS PC, and the router and PoE switch.

Also, that H model CPU, is suspect means laptop, right? so beware thermal throttling and varying CPU performance levels, which could impact sync rates. And then there is the general background processes on that PC, which could easily be network and CPU impactful (the OBS Studio log won't show details on any of this).