Abstract: A transmission device includes a communication interface configured to perform communications with an external device and at least one display device, a memory configured to store analog data received from the external device, a signal processor, and a processor configured to control the signal processor to decode the analog data, separate the decoded analog data into analog audio data, analog video data, and analog additional data, convert the analog audio data, the analog video data, and the analog additional data, separated from one another, respectively, to digital audio data, digital video data, and digital additional data, configure a digital transport stream including a plurality of packets by separately packetizing the digital audio data, the digital video data, and the digital additional data, respectively, and transmit, using the communication interface, the digital transport stream to the at least one display device.