Google has finally enabled the video call option in the Phone call app. During the voice call if you click on the video button it will launch the duo video call both the ends and video camera automatically activated.
There aren’t any audio tones or clues that this is happening, so it’s easy for the recipient to miss if they’re not watching the screen. Once the video call via duo is connected the original call will be disconnected. Here the phone should be in unlocked status to switch for duo video call.
Switching to a video call in this way will leave two entries in your call log, one from the phone call and the other is from Duo. It will take couple of weeks to get the feature on their phone. Video call button isn’t available to anybody that doesn’t use Google’s Phone app.