iPhone as Mac video camera?

As to the possibility of using the iPhone as a video camera for the Macintosh, I am just following Apple's instructions: https://support.apple.com/guide/quicktime-player/record-a-movie-qtp356b55534/mac. As I said, this technique works with the MacBook but not the Mac Mini. Both Macs are running OS 10.15.4. The only difference, as far as I can tell, is that the Mini is a year or two older than the MacBook. I do not know if that age difference is enough to explain the difference in QuickTime Player's connectivity to the iPhone.

As to the purported lack of functionality of a third-party application, that is not true. I bought the iPhone because I need a webcam and the stores were all sold out of proper webcams. I am in a mixed-platform community. As much as I would prefer FaceTime, we have adopted Zoom as our standard. From what I have read, FaceTime does not cooperate with Zoom. Zoom needs a third-party application in order to connect to an iPhone. The third-party application most recommended is EpocCam. Apparently EpocCam had worked well with iPhone-as-webcam for a while, but sometime in April Apple changed its security settings. Now we have to modify Zoom each time a new upgrade comes out. See the description of the problem and the resolution at ¶7: https://www.kinoni.com/support-and-instructions/. I can report that the combination of Zoom and an enabled EpocCam perform quite well. EpocCam is a functional third-party application that does not appear in the App Store.

FWIW, here is a screen shot of my Sound preference pane:

In System Preferences>Security & Privacy>Privacy I have both Camera and Microphone set to allow QuickTime Player. QuickTime Player accesses my iPhone Camera, but the application registers no sound input.

I have to be missing something, but what?

On a different Mac, with the same iPhone, QuickTime Player works as advertised. I find a difference in the control panel:

On this Mac, QuickTime Player identifies the iPhone as "FaceTime HD Camera." On the Mac Mini, QuickTime Player identifies the same iPhone as "iPhone."

I expect that the difference means something.

In the Mac Mini I found an application named Audio MIDI Setup. In that application I found an option for enabling the iPhone. When I enabled the iPhone in Audio MIDI Setup, the iPhone appeared as an input device in the Mac's Sound pane:

Then I started QuickTime Player in the Mac. Immediately upon its opening, there were two changes in the "Audio Devices" window of Audio MIDI Setup. The USB line for iPhone, the one with the image of a microphone, disappeared. And the setting immediately below, also for iPhone, went back to "enable." At the same time, iPhone disappears as an input device in the Sound pane.

I repeated the process several times. Each time QuickTime Player turned off the iPhone as an audio input device.

I have no trouble getting video from the iPhone through QuickTime Player into the Mac, but audio does not work.

This is getting stranger as it goes along. After my post twenty minutes ago, I closed the application Audio MIDI Setup and opened Quicktime Player (both in the Macintosh.) This time iPhone remained as an input device in the Sound pane. But now QuickTime Player cannot connect to either video or audio through the iPhone:

I also tried just an audio recording in QuickTime Player through the iPhone. QuickTime Player did not record any audio with the first "iPhone" in the Microphone list. QuickTime Player reported that it could not record anything with the second "iPhone" in the Microphone list.

I think I am going backwards instead of forward.

I decided to try again on the MacBook Air. This time I connected the iPhone SE to the MacBook by two successive USB cables, one after the other. With both Lightning cables, I got the same, new problem. The Photos application opened unbidden, flashing on and off. I opened QuickTime Player, System Preferences, Audio MIDI Setup, and Safari. Photos would not let me use any of them; it kept flashing itself open over any other application that I tried to use on my Desktop. In Audio MIDI Setup the iPhone flashed on and off in the list of Audio Devices. In QuickTime Player, in between the intrusions of Photos, I could see that it did not list the iPhone under either Camera or Microphone (just as I reported in my post of May 15 at 8:10 P.M.) Here are the two different windows presented by Photos:

I have no idea what "unlock iPhone" means in this context.

Both of these screen shots show the iPhone as a device listed in Photos. I do not know how I got icon to appear twice like that. Pure luck. The iPhone flashes on and off in this window just as it does in Audio MIDI Setup.

I did not have this intrusive Photos on the Mini. I have never seen this phenomenon before. I have no idea what is going on.

At the time that I wrote my last report here, the iPhone was open and running. I know. I was looking at it. The problem was not what Photos said it was.

Eventually I was able to resolve the immediate problem. I moved to a different chair, and Photos got out of my way. I stopped getting the alternating windows that I reported in my last posting.

My iPhone still did not appear as an available device in the "New Recording" window of QuickTime Player. But QuickTime Player did accept my EpocCam as an available device. QuickTime Player then connected to the iPhone through EpocCam.

That was on the MacBook. Today, on the Mac Mini I repeat the experiment. Now I get the same report in QuickTime Player: it does not see the iPhone as an available device:

This experience is completely different from the screen shots that I posted yesterday at 10:41 A.M. and on May 13, 2020, at 8:46 A.M.

In the Security & Privacy pane, I found that I had the Camera set to allow QuickTime Player but Microphone was not so set. I set Microphone to allow QuickTime Player. I closed Preferences and started a new movie in QuickTime Player. My settings in QuickTime Player remain as before: set to iPhone. Now in QuickTime Player I can record video with my iPhone. But I am not recording audio at all.

It should be significant that in System Preferences>Sound I have only two choices for Input: line-in and EpocCam. The iPhone Camera and microphone do not appear at all in the Sound pane.

I expect that I am overlooking some setting somewhere. Where?

TIA

Today on the Mac Mini I tried again. QuickTime Player on the Mac brings in the video from the USB-connected iPhone. But QuickTime Player still removes the iPhone as an input item in the Sound pane of the Mac.