Patent ID: 8185792

Claim:
A data-transmission device that divides video data into packets and that transmits the packet to a data-reception device requesting the video data, the data-transmission device comprising: a generation unit configured to generate packets for transmission based on the video data; a setting unit configured to set importance for each of the generated packets; a storage unit configured to store information about the set importance in a first storage unit; a communication unit configured to transmit the generated packet to the data-reception device and receive a request for retransmission of the packet, the request being transmitted from the data-reception device; a saving unit configured to save the packet transmitted from the communication unit in a second storage unit; a calculation unit configured to calculate a loss rate of the packet based on the packet-retransmission request received by the communication unit; a determination unit configured to determine a retransmission packet which is retransmitted to the data-reception device based on the calculated packet-loss rate and the importance set for each of the packets, where the importance information is stored in the first storage unit; and a retransmission unit configured to read the determined retransmission packet from the second storage unit and transmit the read retransmission packet to the data-reception device via the communication unit. wherein the communication unit transmits the packet of the video data to a first data-reception device for which a first connection priority is set and a second data-reception device for which a second connection priority is set, and wherein in a case where the loss rate of the packet in the first data-reception device which is calculated by the calculation unit is equal to the loss rate of the packet in the second data-reception device which is calculated by the calculation unit, the determination unit determines that a first retransmission packet is to be transmitted and a second retransmission packet is not to be transmitted, the first retransmission packet being based on a packet-retransmission request from the first data-reception device for which the first connection priority is set, the second retransmission packet being based on a packet-retransmission request from the second data-reception device for which the second connection priority is set lower than the first connection priority, and the second retransmission packet having the same level of importance as the first retransmission packet.