user4426: When I record video interviews over Hangouts / Skype / Zoom, I often ask the guest to record the audio locally using QuickTime Player, then get them to send me the audio file afterwards. I also record the video conference "in the cloud" using Google Hangouts record feature.
This means I get better quality audio that I can resync afterwards.
Is there a good way to do the same thing with video as I do with audio on a Mac? When I try to record their webcam in Quicktime Player, it stops the video stream working.
How can I let the guest record their webcam output while at the same time the webcam is streamed to Hangouts?

user2178: Problem interpretation
I'm interpreting the issue you're having as follows:
On the computer of the guest you want to record the audio and video stream from one or more devices. The same streams need to be available to the online meeting software (Skype/Zoom/Hangouts).
The issue you're running into with Quicktime is that a webcam can (often) only supply it's video stream to one program at a time. It first supplies it to Hangouts, but when you ask Quicktime to record, it switches the stream to Quicktime, stopping the video stream to Hangouts.
You need some way of "splitting" the signal.
Possible solution
You can use OSB Studio to achieve what you want. It allows you to record and stream the webcam video at the same time, the meeting software can then use OBS (not your webcam) as the video input device.
Rough steps are:

Install OBS Studio
In the sources panel, add a new "Video Capture Device":

In the properties window that pops up, select the webcam you want to use in the "Device" dropdown, leave the rest of the settings at their default:

Now OBS studio should show you what the webcam is seeing. You can move/scale the image and apply effects or corrections as needed.
Now you can let OBS start a "virtual camera". This will provide the video stream you see in the OBS screen as if it is coming from a "webcam" named "OBS Virtual Camera":

In the meeting software, go to the device settings and select "OBS Virtual Camera" (screenshot shows Teams as an example):

In OBS Studio you can now turn on the recording, it will record the webcam (and any other sources you've added in step 2):

When you start your online meeting, the meeting software will use "OBS Virtual Camera" as the camera. OBS Studio will record the webcam output in the background.

I've described the steps for the video part, but I imagine you can do something similar with the audio such that you get a synced recording right away. Then you don't need to re-sync the Quicktime recorded audio with the OBS recorded video.

4426: <p>When I record video interviews over Hangouts / Skype / Zoom, I often ask the guest to record the audio locally using QuickTime Player, then get them to send me the audio file afterwards. I also record the video conference &quot;in the cloud&quot; using Google Hangouts record feature.<br />
This means I get better quality audio that I can resync afterwards.</p>
<p>Is there a good way to do the same thing with video as I do with audio on a Mac? When I try to record their webcam in Quicktime Player, it stops the video stream working.</p>
<p>How can I let the guest record their webcam output while at the same time the webcam is streamed to Hangouts?</p>
 2178: <h3>Problem interpretation</h3>
<p>I'm interpreting the issue you're having as follows:</p>
<p>On the computer of the guest you want to record the audio and video stream from one or more devices. The same streams need to be available to the online meeting software (Skype/Zoom/Hangouts).</p>
<p>The issue you're running into with Quicktime is that a webcam can (often) only supply it's video stream to one program at a time. It first supplies it to Hangouts, but when you ask Quicktime to record, it switches the stream to Quicktime, stopping the video stream to Hangouts.</p>
<p>You need some way of &quot;splitting&quot; the signal.</p>
<h3>Possible solution</h3>
<p>You can use <a href="https://obsproject.com/" rel="nofollow noreferrer">OSB Studio</a> to achieve what you want. It allows you to record and stream the webcam video at the same time, the meeting software can then use OBS (not your webcam) as the video input device.</p>
<p>Rough steps are:</p>
<ol>
<li>Install OBS Studio</li>
<li>In the sources panel, add a new &quot;Video Capture Device&quot;:<br />
<a href="https://i.stack.imgur.com/P9ITD.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/P9ITD.png" alt="enter image description here" /></a></li>
<li>In the properties window that pops up, select the webcam you want to use in the &quot;Device&quot; dropdown, leave the rest of the settings at their default:<br />
<a href="https://i.stack.imgur.com/3W1H2.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/3W1H2.png" alt="enter image description here" /></a></li>
<li>Now OBS studio should show you what the webcam is seeing. You can move/scale the image and apply effects or corrections as needed.</li>
<li>Now you can let OBS start a &quot;virtual camera&quot;. This will provide the video stream you see in the OBS screen as if it is coming from a &quot;webcam&quot; named &quot;OBS Virtual Camera&quot;:<br />
<a href="https://i.stack.imgur.com/J56DL.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/J56DL.png" alt="enter image description here" /></a></li>
<li>In the meeting software, go to the device settings and select &quot;OBS Virtual Camera&quot; (screenshot shows Teams as an example):<br />
<a href="https://i.stack.imgur.com/8q3hk.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/8q3hk.png" alt="enter image description here" /></a></li>
<li>In OBS Studio you can now turn on the recording, it will record the webcam (and any other sources you've added in step 2):<br />
<a href="https://i.stack.imgur.com/wbNSW.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/wbNSW.png" alt="enter image description here" /></a></li>
<li>When you start your online meeting, the meeting software will use &quot;OBS Virtual Camera&quot; as the camera. OBS Studio will record the webcam output in the background.</li>
</ol>
<p>I've described the steps for the video part, but I imagine you can do something similar with the audio such that you get a synced recording right away. Then you don't need to re-sync the Quicktime recorded audio with the OBS recorded video.</p>
