Image capture through Thunderbold 4 port on an M1 Mac

macOS specific usage questions
dmr
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Image capture through Thunderbold 4 port on an M1 Mac

Postby dmr » 02 Dec 2022 10:33

I'm using VLC Version 3.0.17.3 on an M1 Mac running Ventura 13.0.1.

I have a Blu-Ray player with an HDMI output going into a video and audio capture card with a USB-C output. When I plug the USB-C cable into a USB-C port on the Mac, VLC recognizes the capture card and everything seems to work fine. When I plug the the USB-C cable into a Thunderbolt 4 port on the Mac, VLC doesn't recognize that the capture card exists. Unfortunately, some M1 laptops only have Thunderbolt 4 ports - no USB-C ports. Thunderbolt 4 is supposed to be backward compatible with USB-C, but the capture card isn't recognized. Do you have any suggestions?

dmr
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Re: Image capture through Thunderbold 4 port on an M1 Mac

Postby dmr » 03 Dec 2022 00:36

My problem is now resolved. I think most (possibly all, I'm not sure) of the problem is due to macOS, not VLC. Although there are things that VLC could do to ameliorate the problem.

When I plugged the video capture card into the Thunderbolt 4 port, the system didn't react at all - the system acted as though nothing was plugged into the Thunderbolt 4 port. When I rebooted the system while the video capture card was plugged in, the system asked whether I wanted to allow the "accessary".

Possible amelioration: In the "Open Capture Device..." dialog, VLC could say something like "If your desired capture device(s) don't appear in the pulldown menus, try rebooting your computer with the 'desired capture device(s)' connected. If you are asked whether to allow them, do allow them."

The system also asked me to permit VLC to use the computer's camera and microphone. I think I had to agree. The video and audio source was the USB-C signal (converted from HDMI by the video capture card), so neither the computer's camera nor microphone were being used. I don't know whether there is code in VLC that was explicitly asking for access to the computer's camera and microphone. It shouldn't make such requests in this case.

Possible amelioration if the requests are an unavoidable consequence of getting access to the video capture card's signal through the Thunderbolt 4 port: VLC could advise users that they may be asked to grant VLC access to the computer's camera and microphone, even though they aren't being used in this situation. If VLC has to be granted that access in order to use the signal from the video capture card, the users should be advised of that.


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