うーん AVFoundation が微妙なのかキャプボが微妙なのか FFmpeg の処理が微妙なのか
nanka macOS no mondai na kiga shitekita
btw sometimes audio will gone for ~1 seconds (probably comes from capture device?), that is probably root issue
Result: in Asahi Linux, FFmpeg (V4L2+PulseAudio) recording works fine, so macOS AVFoundation implementation or FFmpeg AVFoundation device support is wrong i think (it might be able to workaround by copy capture device to loopback device, if some audio data was dropped by capture device)