You can use VIVE Facial Tracker to track the movement of the mouth.
* To apply the mouth movement to any VRM format models, VirtualCast combines five BlendShapes (A, I, U, E and O) from the preset BlendShapes of the VRM format to create corresponding mouth shapes.
As a prerequisite, you need to have SR_Runtime installed and the lip module must be recognized properly.
You need to change a setting from the settings in the title screen.
Turn on the check box: [Device] > [VIVE] > [VIVE Facial Tracker].
When everything is set properly, the lip module will be activated during the calibration and the tracking of the mouth will start.