Playing from Capture Card or Webcam, Video device not found even though listed

Important Information

Provide following Information:

• mpv 0.33.1
• macOS 11.1
• Source of the mpv binary or bundle: macOS builds by stolendata
• If known which version of mpv introduced the problem: unknown

Reproduction steps

Run in terminal:

mpv av://avfoundation:video="HD Pro Webcam C920"

"HD Pro Webcam C920" is derived from

ffmpeg -f avfoundation -list_devices true -i ""

Also tried ShadowCast (capture card), same thing. Goal is to achieve this on MacOS.

Expected behavior

mpv opens with view of webcam feed

Actual behavior

[ffmpeg] AVFoundation indev: Video device not found
[lavf] avformat_open_input() failed
Failed to recognize file format.

Log file

output.txt

When I try to capture the feed directly in ffmpeg, I have to specify a framerate -- is there a way to do that in mpv? The fps flag didn't seem to work -- thinking maybe it instead needs to be in the ffmpeg args?

Start with the reproduced command mpv av://avfoundation:video="HD Pro Webcam C920" and compare it with the linked ffmpeg device listing and output.txt. Trace the AVFoundation input path and determine why a listed webcam or capture card is rejected; done means the feed opens on macOS and the required framerate handling is understood.