Methods of operating a network server device are provided. The methods may include establishing a session with a client device. The methods may also include transmitting a first base segment providing first base content for a first time segment to the client device. The methods may additionally include transmitting a second base segment providing second base content for a second time segment to the client device. The methods may further include transmitting an additive segment including additive content for the second time segment to the client device. Also, the additive content may be synchronized with the second base content. Related methods of operating client devices are also described, as are related network server devices and related client devices.