US Patent 10235808 Communication system

A user device comprises a network interface, a rendering module, and a scene modification module. The network interface is configured to receive a video signal from another device via a network. The rendering module is configured to control display apparatus of the user device to display a virtual element to a user of the user device, the virtual element comprising a video image derived from the video signal. The modification module is configured to generate rendering data for displaying a modified version of the virtual element at the other device. The modified version does not include said video image. The network interface is configured to transmit the rendering data to the other device via the network. Alternatively or in addition, the rendering data can be modified at the other device to the same end.