Hi Richard,

I'm not sure where you've seen a spec for the USB Capture products that shows any of them capturing more than 2Ch (stereo) audio? I think it's the nature of UVC devices that the standard driver only supports 2 channels. The Pro Capture PCIe cards support 8 audio channels into vMix (and NewTek's NDI Connect), but that's because there's support in the Magewell driver (and vMix).

I will do a practical test for you tomorrow, since I have all the USB units and a test signal source with 8 audio channels. However, I suspect what they mean is that whilst the device will recognise 8 channels of audio, and maybe via the SDK or a different O/S it is possible to make use of them, the USB Capture SDI+ audio device that appears under Windows is only using Ch 1+2. I've just tested it with a USB Capture Plus HDMI, the only one from the USB Capture family that I have at home, and you can see in the screen grab that the Magewell utility shows that all 8 channels are present (although Ch 2-8 are muted with tone only on Ch 1), but vMix gets the audio via the Windows UVC driver, and that only carries Ch 1+2.

8ChAudio.PNG (78kb) downloaded 1 time(s).

I think the reason for showing all the channels in the Utility is that it's broadly a copy of the property panel for the Pro Capture cards, and I suspect the Tech Spec for the USB 4K SDI Plus on the web page has been copied & pasted from the Pro Capture SDI spec by someone in Marketing, unaware of the difference in the audio driver behaviour.

I think I did test it and, no, it doesn't offer a way to obtain more than Ch1+2 of the embedded audio via the UVC driver - which is the only driver currently available. As far as I can tell, the same "front end" is probably used in the Pro Convert NDI encoders, and they do convert 8 embedded audio channels, when available in the source signal.