Abstract: A data transmission apparatus for sequentially transmitting data in units of packets each containing transmission data to the receiving end, comprises: a reception unit for receiving the transmission data as an input signal; a packet formation unit for receiving the transmission data received, and forming an uncompressed packet in which predetermined transmission data is stored as uncompressed data, and a compressed packet in which at least a portion of transmission data that follows the predetermined transmission data is compressed and stored as compressed data; a reference information management unit for holding and managing, as reference information, information relating to the uncompressed packet formed by the packet formation unit; and a transmission unit for transmitting the respective packets formed by the packet formation unit, as a transmission signal, to the receiving end.

Abstract: A data transmission apparatus for sequentially transmitting data in units of packets each containing transmission data to the receiving end, comprises: a reception unit for receiving the transmission data as an input signal; a packet formation unit for receiving the transmission data received, and forming an uncompressed packet in which predetermined transmission data is stored as uncompressed data, and a compressed packet in which at least a portion of transmission data that follows the predetermined transmission data is compressed and stored as compressed data; a reference information management unit for holding and managing, as reference information, information relating to the uncompressed packet formed by the packet formation unit; and a transmission unit for transmitting the respective packets formed by the packet formation unit, as a transmission signal, to the receiving end.

Abstract: A data transmission apparatus for relaying data transmitted from the transmitting end in units of packets, each packet having additional information relating to its sequence number, priority and data reproduction time, comprises: a receiving unit for receiving packets transmitted from the transmitting end; a priority decision unit for deciding the priority of each of the received packets; a retransmission packet storage unit for storing packets the priorities of which are equal to or higher than a predetermined value, as retransmission packets, on the basis of the priority of each packet decided by the priority decision unit; a retransmission instruction receiving unit for receiving a retransmission request from a terminal at the receiving end; a retransmission decision unit for deciding whether retransmission of the packet for which the retransmission request has been made should be performed or not, on the basis of the retransmission request and the storage status of the retransmission packets in the retran

Abstract: When an error is detected in a received header, in estimating reference information while assuming an error in a packet receiving interval, a header is decompressed using at least one value of another candidate sequence numbers used in correcting an erroneous sequence number, corresponding to a time that elapses between previously receiving a packet correctly and receiving a current packet and to the packet receiving internal. It is thereby possible to increase a possibility of estimating the reference information correctly and suppress the number of discarded packets at a receiving side, while suppressing increases in introduced processing amount in data transmission with header compression.

Abstract: A data transmission apparatus including a receiving unit for receiving transmitted packets; a priority decision unit; a retransmission packet storage unit; a retransmission instruction receiving unit for receiving a retransmission request from a terminal at the receiving end; a retransmission decision unit; a transmission queue management unit; and a transmission unit.

Abstract: In a normal operation state, a connection management section 21 writes data transmitted from a first processing section 13 to a data temporary storage section 22, and reads data to be received by the second processing section 14 from the data temporary storage section 22. Upon receiving control signals 31 and 32 which instruct a change of the subject of processing, the first processing section 13 and the second processing section 14 output a transmitting-end clear request 41 and a receiving-end clear request 42, respectively. The connection management section 21 reads data from the empty data storage section 23 after a transmitting-end clear request 41 is received and until a receiving-end clear request 42 is received, and writes data to the empty data storage section 23 after a receiving-end clear request 42 is received and until a transmitting-end clear request 41 is received.

Abstract: A data transmission apparatus including a receiving unit for receiving transmitted packets; a priority decision unit; a retransmission packet storage unit; a retransmission instruction receiving unit for receiving a retransmission request from a terminal at the receiving end; a retransmission decision unit; a transmission queue management unit; and a transmission unit.

Abstract: A data transmission apparatus for relaying data transmitted from the transmitting end in units of packets, each packet having additional information relating to its sequence number, priority, and data reproduction time, comprises: a receiving unit for receiving packets transmitted from the transmitting end; a priority decision unit for deciding the priority of each of the received packets; a retransmission packet storage unit for storing packets the priorities of which are equal to or higher than a predetermined value, as retransmission packets, on the basis of the priority of each packet decided by the priority decision unit; a retransmission instruction receiving unit for receiving a retransmission request from a terminal at the receiving end; a retransmission decision unit for deciding whether retransmission of the packet for which the retransmission request has been made should be performed or not, on the basis of the retransmission request and the storage status of the retransmission packets in the retra

Abstract: Method, transmitter and system for transmitting compressed header data in a packet stream from a transmitter to a receiver, the header data including a header data item, wherein the method comprises estimating a time period needed for performing a re-initialization process for reinitializing a value of said header data item, determining a time for starting the re-initialization process, the determined time being based on the estimated time period and starting the re-initialization process at the determined time.

Abstract: A method of transmitting data packets, in particular of real-time or near-real-time data over internet protocol (IP) networks using a real-time protocol (RTP) for media data products and a real-time control protocol (RTCP) for control data packets. Each protocol is allocated a fraction of the available transmission bandwidth. The method comprises the steps of measuring relevant characteristics of the network link, calculating from this measurement an optimized RTCP bandwidth and transmitting control data packets using the optimized RTCP bandwidth.

Abstract: A data transmission apparatus including a receiving unit for receiving transmitted packets; a priority decision unit; a retransmission packet storage unit; a retransmission instruction receiving unit for receiving a retransmission request from a terminal at the receiving end; a retransmission decision unit; a transmission queue management unit; and a transmission unit.

Abstract: A data transmission apparatus for relaying data transmitted from the transmitting end in units of packets, each packet having additional information relating to its sequence number, priority, and data reproduction time, comprises: a receiving unit for receiving packets transmitted from the transmitting end; a priority decision unit for deciding the priority of each of the received packets; a retransmission packet storage unit for storing packets the priorities of which are equal to or higher than a predetermined value, as retransmission packets, on the basis of the priority of each packet decided by the priority decision unit; a retransmission instruction receiving unit for receiving a retransmission request from a terminal at the receiving end; a retransmission decision unit for deciding whether retransmission of the packet for which the retransmission request has been made should be performed or not, on the basis of the retransmission request and the storage status of the retransmission packets in the retra

Abstract: SN examine section 101 monitors transmission data by way of monitoring an SN per packet, compares the SN in a packet that is to be transmitted with the SN in an immediately preceding packet, and outputs the comparison result to CID selection section 102 with transmission data. CID selection section 102 selects a CID based on the comparison result output from SN examination section 101 and appends the CID to the transmission data, and outputs the transmission data to header compression section 104. CRC bit calculation section 103 calculates a CRC bit from the header information. Header compression section 104 determines on a header compression format, compresses a header that contains an SN and a CRC bit, and connects the header with transmission data and transmit this to transmission section 106. Transmission packet storing section 105 that stores transmitted packets.

Abstract: When a received packet contains static information and a CRC section 104 detects an error, the static information alone will be read from a buffer 106 and replace the static information of the received packet. A header reproduction section 107 once again reproduces a header, and upon this reproduced header the CRC section 104 performs CRC. If a bit error is detected, the received packet will be discarded. If no error is detected, determining that the bit error was in the static information portion in the header of the received packet, the packet in which the static information has been replaced will be output as a received packet.

Abstract: In a sending device (100), a fragmenting portion (101) fragments a bit stream according to the predicted relationship of the frames, and the output of the fragmenting portion (101) is allocated to either a TCP (Transmission Control Protocol) or a UDP (User Datagram Protocol) port. In an IP (Internet Protocol) layer, an encrypting portion (102) executes an encryption process only on the port to which bit stream corresponding to the I (Intra) frames is transmitted. In a receiving device (110), a decrypting portion (112) decrypts data on the port to which the bit stream corresponding to the I frames is transmitted, and a reassembling portion (111) restores the data to the original bit stream. This restoration is carried out by lining up the packets in increasing order of TR (Temporal Reference) value. Thus, the amount of time required for encryption and decryption is reduced compared to a case in which encryption is performed on all frames.

Abstract: A data communication system capable of eliminating the retransmission of useless data that is too late for the playback time at the receiving side, and, accordingly, capable of eliminating the wasteful utilization of transmission band. In the system, round-trip time RTT of a packet between the server (data transmitting apparatus) 100 and the terminal apparatus (data receiving apparatus) 200 is calculated, and only when the sum of the round-trip time RTT and present time is less than the playback time of the packet, retransmission request for lost packet which has high priority is made.

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.

Abstract: An output controller 104 outputs coded data included in a packet arrived later than reproduction and display timing designated by a timestamp to a decoding section 105 together with coded data included in a packet designated by a timestamp next to the above timestamp. The decoding section 105 first decodes coded data included in the packet arrived later and updates the reproduced image that is one earlier than the above decoded reproduced image to the above decoded reproduced image, then decoding coded data included in the packet arrived before reproduction and display timing designated by the timestamp.

Abstract: In a bit counter 214, an amount of codes included in one transmission unit is counted; in a significance decision section 217, the amount of codes counted in the bit counter 214 is divided by the number of coded macroblocks included in the one transmission unit to calculate an average amount of codes per one coded macroblocks; and in a threshold comparing section 220, the significance of the pertinent transmission unit is decided by comparing the average amount of codes to the calculated threshold based on a frame rate and a bit rate.

Abstract: A data transmitting apparatus and a data receiving apparatus, which are capable of retransmitting a packet even when a retransmission request is made by a client after transmitting a session close notice packet to the client. A session is closed by a session closing means 105 when a predetermined period of time has passed after transmitting the session close notice packet, which is generated by a control command generating means 102 as the session close notice packet, from a packet transmitting means 103 to the client.