In vMix settings, make sure the Default Audio Renderer is set to "Default DirectSound Device" if you are having issues with multiple DV cameras or audio sources in vMix.

Symptoms

One or more DV cameras may freeze or some inputs may not have any audio.

Cause

A Default Audio Renderer that does not support DirectSound was manually changed in Settings.
Windows does not support mixing audio for non-DirectSound renderers.

Solution

Ensure a DirectSound device such as "Default DirectSound Device" is selected in vMix Settings.

If after changing back to the DirectSound device, only one audio input can be heard, follow the steps below to reset vMix:

(Note the registry is an advanced system tool that may cause damage to your system if used incorrectly)

1. From the Start Menu, type in regedit and press enter.
2. Browse to HKEY_CURRENT_USER \ Software \ Microsoft \ Internet Explorer \ LowRegistry \ Audio \ PolicyConfig \ PropertyStore
3. Right click PropertyStore and select Delete, click Yes to confirm.
4. Run vMix and make sure the Default DirectSound Device is selected as the Default Audio Renderer.

Future version of vMix will remove the non-DirectSound sources altogether, to prevent them being selected accidentally.