The Google Cast SDK allows users to extend Android, iOS, and Chrome apps to direct their streaming audio and video content to a TV or sound system. Hidden within the flurry of announcements originating from Google I/O 2021, Google is adding in new functionality to the Cast Connect library, allowing users to transfer their streams across devices, and even add in devices to a stream.

Stream Transfer and Stream Expansion are two new features that are coming to the Cast Connect library. With Stream Transfer, users will soon be able to move playback between cast devices. Google says that users like to watch content across many screens, whether it is multiple TVs spread across the home in different rooms, or an array of tablets of tablets, smart displays, and mobile devices, users want the ability to transfer the content that they are casting from one device to another. Cast Connect's Stream Transfer feature makes this a reality.

Once a Cast Connect session is started, the user can switch the casted content from one device to another simply by using their voice. When a stream is in place, invoke Google Assistant and issue relevant commands such as "Move this to the Bedroom Display". This will transfer the content and the content progress to the relevant connected display device.

With Cast Connect Stream Expansion, users can add speakers to the content that is playing on the stream.

Developers do need to make certain small changes to their app to allow the ability to Stream Transfer and Stream Expand. Once the app supports the two features, users will have a better and streamlined experience, especially if they own multiple devices. Adding the ability to add more audio sinks is also great for augmenting the capacity of media consumption without needing to involve other complicated solutions.