My webcam show no image but has sound

[brats]

Hello,why my a4tech webcam show no image but has sound

 

[ksiemb]

Hello,why my a4tech webcam show no image but has sound

An update may have changed your driver, if it was working before.
In which case use device manager to Roll back the driver.

Or try using a generic driver, such as Yawcam.
http://www.yawcam.com/download.php