OBS, Zoom & Extended Display to Projector

[jazzmonster]

Hello, I'd be very grateful for your advice.

I am the Zoom host at church for those who are unable to attend in person. I also livestream via Zoom to Youtube (so there's a copy of the service for anyone who wants to watch it later).

I use a MacMini to operate Zoom from. I have a laptop which runs Zoom and is connected to the projector (so that everyone in the room can see videos on the big screen that I'm playing). The audio from the lectern mic goes into the amplifier.

My problem is that I have a lip sync issue on the big screen. This is because the video runs from the MacMini into the laptop but the lectern audio goes into the amplifier/MacMini.

We can solve this problem by putting the lectern audio into the laptop as well as the video which works - except we get very loud howling feedback.

Can I use OBS to run the audio and video with Zoom and Youtube Livestream? Instead of the laptop, use an extended display on a 2nd monitor and connect that to the projector?

We want the big screen to display either the lectern camera or a video I'm showing. We don't want it to show things being moved around, and videos being queued.

I've set up OBS and starting to learn it but getting a bit mind boggled with it all! Before I go any further, it would be great to know if it's possible to do what I want with it. (No feedback, no lip sync issue).

Thanks so much!

 

[AaronD]

My problem is that I have a lip sync issue on the big screen.

No kidding! As you said, you have different paths for audio and video, and they have wildly different latency (processing delay).

Generally, I get the impression that this is a pile of band-aid fixes that has turned into a Rube-Goldberg machine. Even the first iteration might have been a premature latch onto the wrong tool for the job. It's hard to tell that for sure from what you said, but it does seem probable.

So, pare it back to a set of requirements with no tools specified at all, then rebuild everything to fit those requirements with nothing to do with what you had previously. Any similarity is purely by accident.

• Zoom is an interactive thing. Do you NEED that kind of interaction? Or would a one-way thing like YouTube work just as well?
  • YT, Twitch, Facebook, etc. are set up for remote viewing of fully-produced content. Online meeting platforms like Zoom and others, give you some more hoops to jump through to make it work.
• You have a big-screen projector. *Where* is it? Specifically, can you afford a round-trip server delay (10 seconds to a minute or so) so as to just grab the stream output from OBS? Or is there enough acoustic bleed through the building that it must be instantly real-time?
• What else are you doing? Are you talking over it in the remote setting? Is *that* what the lectern mic and camera are for?
• Etc.

...putting the lectern audio into the laptop as well as the video which works - except we get very loud howling feedback.

Feedback comes from having a complete loop in some form, with a total loop gain greater than 1. It could be purely electronic, or it could also have an acoustic component.

In your case, it sounds like you're driving some local speakers from the same laptop that also takes the mic. If the laptop sends that mic to those speakers, that's a complete loop when you consider the acoustic path from the speakers back to the mic. If the laptop has more amplification than what you lose through the air (and speaker inefficiency, and other settings throughout the system), that's a total loop gain greater than 1.

To fix feedback, the answer is always the same. Either:

• Eliminate the loop entirely (don't send that mic to that speaker at all) or
• Reduce the total gain of that loop to be less than 1 (turn it down and speak up, directly into the mic)

The second option can be done with any control that is included in the loop, but some have "nicer" side-effects than others.

• The master volume for a speaker will fix it just as well as the individual volume for that mic, but one affects everything that goes to that speaker and the other only affects that one source.
• The preamp setting for that mic will fix it just as well as an individual send, but one affects everywhere that the mic goes and the other only affects that one destination.

So...how is your rig laid out? How do signals flow through it? What does the complete internal diagram look like? Etc. For a good visual example, a large-format "sea of knobs" analog sound board is mostly individual sends arranged in a grid: columns are inputs, rows are outputs, and each intersection has a knob that only affects that one input going to that one output...

 

[Babs Johnson]

Hello, I'd be very grateful for your advice.

I am the Zoom host at church for those who are unable to attend in person. I also livestream via Zoom to Youtube (so there's a copy of the service for anyone who wants to watch it later).

I use a MacMini to operate Zoom from. I have a laptop which runs Zoom and is connected to the projector (so that everyone in the room can see videos on the big screen that I'm playing). The audio from the lectern mic goes into the amplifier.

My problem is that I have a lip sync issue on the big screen. This is because the video runs from the MacMini into the laptop but the lectern audio goes into the amplifier/MacMini.

We can solve this problem by putting the lectern audio into the laptop as well as the video which works - except we get very loud howling feedback.

Can I use OBS to run the audio and video with Zoom and Youtube Livestream? Instead of the laptop, use an extended display on a 2nd monitor and connect that to the projector?

We want the big screen to display either the lectern camera or a video I'm showing. We don't want it to show things being moved around, and videos being queued.

I've set up OBS and starting to learn it but getting a bit mind boggled with it all! Before I go any further, it would be great to know if it's possible to do what I want with it. (No feedback, no lip sync issue).

Thanks so much!

Your workflow is the problem.
The MacMini is sufficient for iMag and streaming to Zoom and YouTube simultaneously.
Connect the project's HDMI cable to the MacMini before launching OBS, then hover the mouse in the program window on OBS and right-click. You will then get an option to send that window out to the projector. That would cut the lip-syncing issue significantly if not altogether.
Multiple Out is a plugin for OBS that would allow you to push your stream to the likes of FaceBook and YouTube while using the virtual camera to push the stream to Zoom.
I assume your MacMini is a M1 otherwise it might struggle.

 

[jazzmonster]

Your workflow is the problem.
The MacMini is sufficient for iMag and streaming to Zoom and YouTube simultaneously.
Connect the project's HDMI cable to the MacMini before launching OBS, then hover the mouse in the program window on OBS and right-click. You will then get an option to send that window out to the projector. That would cut the lip-syncing issue significantly if not altogether.
Multiple Out is a plugin for OBS that would allow you to push your stream to the likes of FaceBook and YouTube while using the virtual camera to push the stream to Zoom.
I assume your MacMini is a M1 otherwise it might struggle.

Wowser, we hadn't even considered this, thank you! I'm not that techy (if you can't tell lol), I'm better with software and I struggle a bit with the hardware so we had a company come in and set it all up for us. While they are good at the hardware side of things they don't use Zoom at all and we couldn't find anyone familiar with Zoom who weren't trying to charge us £60K+, complete overkill for what we need.

The MacMini is an M1 - I will give this a try, thanks so much.

 

[Babs Johnson]

You're welcome, let me know how it went.