Data transmission apparatus, data receiving apparatus, and data transmitting-receiving method

Abstract

Received packets are preserved in a receiving buffer 102; a playback decision section 103 decides whether the preserved packets are in time for the playback time or not; the playback orders and the preservation addresses of the preserved packets which have been decided to be in time are memorized in a pointer 104 for playback; the preserved packets are read and played back according to the pointer 104 for playback. And, the playback orders and the preservation addresses of the preserved packets are memorized in a pointer 106 for preservation; and a media conversion section 107 reads the preserved packets according to the pointer 106 for preservation, and memorizes them after conversion into packets with a form by which the packets may be memorized in a preservation memory 108.

1 . A data receiving apparatus comprising: 
 a reception section that receives packet data;    a loss decision section that decides whether or not there is missing packet data among the received packet data;    a playback time calculation section that calculates a playback time of the missing packet data;    a retransmission request decision section that decides whether to transmit an immediate retransmission request or a usual retransmission request for the missing packet data, based on a round trip time of data between the data receiving apparatus and a transmission side, a current time and the playback time; and    a retransmission request section that transmits the immediate retransmission request or the usual retransmission request.    
   
   
       2 . The data receiving apparatus according to  claim 1 , wherein the retransmission request decision section transmits the immediate retransmission request when a sum of the round trip time and the current time is smaller than the playback time, and transmits the usual retransmission request when the sum of the round trip time and the current time is larger than the playback time.  
   
   
       3 . The data receiving apparatus according to  claim 1 , further comprising a priority decision section that decides a priority of the missing packet data, 
 wherein the retransmission request section transmits the immediate retransmission request for the missing packet data whose priority is decided to be high when the sum of the round trip time and the current time is smaller than the playback time.    
   
   
       4 . The data receiving apparatus according to  claim 1 , wherein, when there is a small amount of transmission data at the transmission side, the retransmission request section transmits the usual retransmission request to the transmission side.