WhatsApp version 2.18.4 adds a new video call switch button that shows up during a voice call. People can click on the icon to switch to video call automatically, even when they’re on the voice call with a friend.
In this feature, if you click to switch your voice call to video the recipient will get a request for video call, which can either be accepted or rejected. WhatsApp will automatically switch from voice to video when the request is accepted. However, in case the user decides to reject the video call request, a voice call will normally continue. WhatsApp quick switch feature isn’t available for group calls.
Right now the feature is only available to Android beta testers or those who’ve signed-up for WhatsApp’s Beta Program. Those interested in becoming a beta tester for WhatsApp can head over to Google Play Store for now.