With this one can directly initiate a video call from Android Messages, Contacts and Phone.The Google Duo makes use of a Technology called ViLTE which in essence is an extension of VoLTE and is used to enhance the voice channel along with the video component. However, Google is also working to being the feature to other Android devices as well.
Right after opening up the application, you can immediately notice a new category called 'Geometric Shapes, ' which has all the colorful images. "You can now start a video call directly from where you call or text message your friends, through your Phone, Contacts, and Android Messages apps".
Anyway, integrated video calling is being rolled out first to first-generation Pixel handsets and Android One and Nexus devices, Google says. So, for making a video call via Google Duo, the user of the Android phone needs to have the Duo application installed in their phone.
Duo is pretty easy to get (Google Play), so that requirement should be easy enough for both you and whoever you're video calling.
Also if both users are on carrier service that supports ViLTE video calling, the video calls will be routed through the carrier's ViLTE service.
As for supported devices, you and whoever you are video calling only have a handful to choose from.
This is an exciting new addition to Android, and you can see how it could eventually be integrated directly into Android.