JP2002247134A - Communication control system, receiving device, and transmitting device - Google Patents

Abstract

(57) [Summary] [Problem] To perform error repair adapted to a user request,
Make effective use of network bandwidth. SOLUTION: On a receiving apparatus 100 side, a packet loss of received data is detected, a posting position on a window is specified with respect to data including a missing portion lost due to the packet loss, and a missing portion where the posting position is specified is identified. The data including the data is displayed on the window, and only the desired repaired part is selected. The transmitting device 200 creates repair data corresponding to the repaired part based on the selection information indicating the selected repaired part, and receives the data. On the device 100 side, based on the created repair data, only a desired repair portion of the packet loss data is restored and reproduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication system using a computer network.
The present invention relates to a communication control method, a reception device, and a transmission device capable of performing reception quality control adapted to a user request.

[0002]

2. Description of the Related Art With the recent development of broadband Internet or intranet (hereinafter, collectively referred to as a network), applications for transferring streaming media on a network have been spreading.

[0003] In the transfer of streaming media, it is necessary that the reproduction timing originally possessed by the data to be transmitted is faithfully reproduced on the receiving side, and RTP (Rea) is used as a transfer protocol for realizing this.
l-time Transport Protocol
l) is widely used.

[0004] The main features of RTP are described below.

[0005] The RTP includes a field for describing a time stamp and a sequence number in a packet header, and has a function of monitoring the quality of data transfer using such information.

[0006] However, a protocol framework for quality control of received data such as retransmission control is not specified, and an error control method according to individual requirements such as delay and degree of reception quality is implemented for each application. Must. In the payload field of the RTP packet, various types of encoded data are accommodated in a format defined for each system. As an RFC number for which a typical encoding method is defined, RFC2250 (MPEG1 /
2), RFC 2343 (MPEG-2A / Vbundl)
ed) and RFC2354 (Motion JPEG).

FIG. 10 shows an example of a protocol stack when streaming media is distributed using RTP.

[0008] RTP is a protocol implemented in the user area. As a transport layer protocol, UDP (User) suitable for distribution of real-time data is used.
Generally, Datagram Protocol is used (hereinafter, this configuration is referred to as RTP / UDP).

At present, many applications use RTP
Although streaming media is distributed in the / UDP configuration, unreliable trans
), the reception quality may be degraded due to packet loss.

[0010] As a method of restoring the deterioration of the reception quality, the following three methods are used in RFC2354 (Options f).
or Repair of Streaming Me
dia). Redundant transmission A technique that improves the reception probability by transferring copies of data that has already been transferred at different timings, or by transferring copies of data that has already been transferred at different timings using different encoding methods. Retransmission A method for requesting the transmission side to retransmit the data when a packet loss or error is detected on the reception side. Forward error correction (FEC) An error correction code is added and transmitted, and an error is corrected on the receiving side.

[0011] The streaming application is individually implemented by combining one of the above-mentioned restoration methods or the above-mentioned restoration methods.

[0012]

Among the above-mentioned repair means, reliable transmission (reli) capable of completely recovering an error.
Only retransmissions can provide an able transmit. As an example of realizing the retransmission method, RFC
793 (TCP)
On the other hand, a method using on control protocol is typical.

[0013] An ACK signal indicating that the receiving apparatus 100 of FIG.
And the transmitting device 200 transmits the ACK within a predetermined time.
If no data has been received, it is determined that the data did not reach the receiving device 100 normally, and the data retransmission process starts. When the network is not congested, the transmitting device 200 can continuously transmit data, so that the receiving device 100 can receive data with high response and low delay.

A problem arises when the network is congested and packet loss occurs. ACK is not delivered to transmitting apparatus 200 due to packet loss, and retransmission processing is started. At this time, the throughput decreases and the receiving device 10
There is a delay in receiving data at 0.

Another problem is that the transmitting device 200
In this case, when the reception of the ACK is greatly delayed, the data is retransmitted even though the data is normally received by the receiving apparatus 100, and the network bandwidth is wasted.

As described above, since retransmission has a problem of delay and a problem of waste of network bandwidth, a retransmission method is not suitable as a means for repairing deterioration of reception quality in a streaming application requiring a high response.

On the other hand, as described in RFC2354, FEC is effective as an error recovery means for reproducing streaming media with high response and low delay.

However, there is a limit to the degree of error that can be repaired by the FEC, and it is not possible in principle to guarantee 100% repair of deterioration like retransmission means, and it cannot meet the demand for reliable repair of deterioration. .

It is an object of the present invention to provide a communication control system, a receiving apparatus, and a transmitting apparatus capable of performing error recovery adapted to a user request and effectively using a network bandwidth. .

[0020]

SUMMARY OF THE INVENTION The present invention is a communication control method for exchanging data between a transmitting device and a receiving device via a network, and transmits data in packet units from the transmitting device to the receiving device. Data transmission means for transmitting;
A packet loss detecting unit configured to detect a packet loss of the received data, a specifying unit configured to specify a posting position on a window for data including a missing portion lost due to the packet loss, and the posting position; A posting means for posting on the window the data including the missing part specified by the user, a selecting means for selecting only a desired restoration part from the posted data, and a selection information indicating the selected restoration part. Retransmission requesting means for transferring to the transmitting device, repair data creating means for creating repair data corresponding to a repaired portion based on the transferred selection information by the transmitting device, Retransmitting means for retransmitting data to the receiving device; and the receiving device, based on the retransmitted repair data, By comprising a repair means to repair only the desired repair position of the scan data, and a communication control method.

Here, the receiving apparatus presents the data to be presented on the window without repairing the data including the lost portion where the packet was lost at the first reception, after the first posting, The missing part where data was lost due to packet loss is presented on the window,
The user selects only the repaired portion to be repaired from the displayed missing portions, requests retransmission to the transmitting device, receives the repairing data retransmitted from the transmitting device, and returns the retransmitted repairing data. The missing part at the time of the first reproduction may be restored using the data.

As the detection means, IETF (Inte
rnet EngineeringTask Forc
e) RFC (Request For Comment)
ts) RTP (Real-t) defined in 1889
im Transport Protocol) may be used as a transfer protocol, and packet loss may be detected using a sequence number described in the packet header.

In the payload field of the RTP packet, an extension header for storing information for specifying the presentation position of the encoded data on the window on the receiving side is provided, and the RTP packet is transferred to the receiving apparatus. You may.

[0024] The retransmitting means may be a TCP (Transmi- nation).
session control protocol) as a transport layer protocol, and the restoration data may be transferred to the receiving device.

The present invention relates to a receiving apparatus for exchanging data with a transmitting apparatus via a network,
Used in the communication control system, constituting the communication control system, the packet loss detection means, the identification means, the posting means, the selection means, the retransmission request means,
The receiving device is constituted by including the restoration means.

The present invention relates to a transmitting apparatus for exchanging data with a receiving apparatus via a network,
A transmission device is configured by including the data transmission unit used in the communication control system and configuring the communication control system, the restoration data creating unit, and the retransmission unit.

[0027]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Outline) First, the outline of the present invention will be described.

Generally, when receiving streaming media (reproduction of a program on the Internet in real time) represented by a moving image via a network,
When a packet loss occurs on the network, data presented to the user is partially lost.

According to the present invention, by associating a packet loss with a data loss portion on a window (display screen), a resendable loss portion is visualized and presented to the user, and only the portion that the user wants to repair is selected. Then, a retransmission request can be made.

That is, according to the present invention, in a communication system using a network, retransmission means for restoring data that has been lost during the first reception is not applied, and the present invention is designed to accept the degradation of the presentation information due to the packet loss while accepting the degradation.
Actively utilize the real-time nature of data transfer possessed by the DP. After this first playback is completed, the location where data was lost due to packet loss is presented on the window,
The user is allowed to select only the part to be repaired for the purpose of effective use of the network bandwidth.
It is characterized in that retransmission is performed by using a CP, and a selected portion is restored by the retransmitted data.

In other words, according to the present invention, the receiving apparatus detects a packet loss on the network from a discontinuous portion of the sequence number of the RTP header, and presents the position on the window of the encoded data missing due to the packet loss. Is specified, the specified portion is presented on the window, the user is allowed to select only the portion to be repaired, a retransmission request is made to the transmitting device for the selected portion, and the repair data retransmitted from the transmitting device is transmitted. It is characterized in that only a portion to be repaired is used for repairing and posting.

(Specific Example) Hereinafter, a specific example will be described.

An effective application of the communication system according to the present invention is video editing (including audio) using a network.

<System Configuration> First, the configuration of the present system will be described with reference to FIGS.

(Communication System) FIG. 3 shows the concept of a communication system applicable to the communication control system according to the present invention.

The present system, via the network 1,
The receiving apparatus 100 includes an editing terminal such as a network computer, and the transmitting apparatus 200 includes data 201 such as a hard disk and a server 202.

(Receiving Apparatus) FIG. 1 shows the configuration of the receiving apparatus 100.

The receiving apparatus 100 includes a user input interface 101 and a network interface 1
02, an OS (Operating System) unit 110, and an RTP (Real-time Transp).
(or Protocol) processing unit 120 and an application processing unit 130.

The user input interface unit 101
A signal which is connected to an input device 300 such as a mouse or a keyboard and sent from the user to the user input interface unit 101 via the input device 300 is transmitted to the OS unit 11.
Transfer to 0.

Network interface unit 102
Is connected to the network 1, transfers the data transferred via the network 1 to the OS unit 110,
The retransmission request signal A transferred from the OS unit 110 is transferred to the network 1.

(OS Unit) The OS unit 110 is provided with a user input processing unit 111 and an IP (Internet Protocol).
ol) processing unit 112 and UDP (User Datag)
ram Protocol) processing unit 113, TCP (T
transmission Control Proto
col) processing unit 114.

The user input processing section 111 transfers the signal transferred from the user input interface section 101 to the application processing section 130.

The IP processing unit 112 receives an RFC (Request)
(st For Comments), transfer the data to the UDP processing unit 113, and transfer the data transferred from the UDP processing unit 113 to the RFC.
After performing the protocol processing defined in the above, the data is transferred to the network interface unit 102.

The UDP processing unit 113 performs the protocol processing specified by RFC768, and
Transfer to 0.

The TCP processing unit 114 is used as a transport layer protocol for a retransmission request from the application processing unit 130.

The TCP processing unit 114 receives the retransmission request data transferred from the retransmission request processing unit 134 of the application processing unit 130, performs a protocol process specified by RFC, and transfers the data to the IP processing unit 112. Further, the IP processing unit 1
Receiving the retransmitted data transferred via
After performing the protocol processing specified in the above, the data is transferred to the application processing unit 130.

(RTP Processing Unit) The RTP processing unit 120
It comprises a packet loss detection unit 121 and a presentation position identification unit 122. Note that the processing unit that performs the protocol processing specified in the RFC relating to RTP is not related to the operation of the present invention, and thus the description thereof is omitted.

(Application Processing Unit) The application processing unit 130 includes a decoding unit 131 and a video reproduction unit 13.
2, the missing point presentation unit 133, and the retransmission request processing unit 134
And a restoration processing unit 135. The application processing unit 130 is connected to an external monitor 90 for displaying an image.

(Transmission Apparatus) FIG. 2 shows the configuration of the transmission apparatus 200.

The transmitting apparatus 200 includes a network interface unit 201, an OS unit 210, an RTP processing unit 2
20 and an application processing unit 230.

The network interface unit 2
01 and the OS unit 210 have the same functions as those of the receiving apparatus 100, and a description thereof will be omitted.

(RTP Processing Unit) The RTP processing unit 220
A prescribed protocol process is performed, and address information 500 indicating a presentation position on a window is written in an extension header 403 newly provided in the RTP packet 400, as shown in FIG. The address information 500 is notified from the presentation position address adding unit 231 of the application processing unit 230 at the time of data transfer.

(Application Processing Unit) The application processing unit 230 includes a presentation position address value adding unit 231.
And a retransmission processing unit 232.

The presentation position address adding unit 231 specifies the presentation position on the window and notifies the RTP processing unit 220 of the specified position.

As a method of specifying the presentation position, the stored data is decoded before transfer, the display position of the data is confirmed in advance, and the association between the encoded data and the presentation position when the encoded data is decoded is established. Can be applied.

For example, in the presentation position address adding section 231, the address information 5 indicating the presentation position on the window is displayed.
00, and notifies the RTP processing unit 220 of the address information 500 for specifying the presentation position. As a result, the RTP processing unit 220 converts the address information 500 into the header 401 and the payload 40 as shown in FIG.
2 is added to the newly provided extension header 403 in the RTP packet 400.

The retransmission processing unit 232 specifies data to be retransmitted from the time code of the frame containing the data to be retransmitted received from the receiving apparatus 100 and the address information 500 indicating the presentation position, and transmits the data to the OS unit 210. To the receiving device 100 via the

<System Operation> Next, the operation of the present system will be described with reference to FIGS.

(Transmitting Device Side) In the transmitting device 200,
The RTP processing unit 220 performs prescribed protocol processing, and transmits the data configured as the RTP packet 400 in packet units to the receiving device 100.

(Receiving Device: Packet Loss Detection Processing) FIG. 4 is a flowchart showing the processing in the packet loss detection unit 121.

First, in the standby state, the RTP processing unit 1
20 waits for reception of the RTP packet 400 (step S
1).

Next, the header part 4 of the RTP packet 400
The sequence number is extracted from 01 (step S2).

This sequence number is incremented by one each time one RTP packet 400 is transferred, as defined in RFC1889. Then, the extracted sequence number is set to Nnew (step S
3).

Next, the extracted sequence number is set to Nne
w is compared with the sequence number Nod of the RTP packet 400 received one packet before (step S
4).

If the difference is 1 as a result of the comparison, it is determined that there is no packet loss, and Nold is updated to Nnew (step S5).
Waits until (step S1).

On the other hand, if the result of the comparison indicates that the difference is not 1, it is determined that the packet has been lost, and FIG.
Is performed (step S6).
At the same time, Nold is updated to Nnew, and the process waits until the next RTP packet 400 arrives (step S1).

The sequence number is 16 bits (0 to 0).
65535), the sequence number is 65
When switching from 535 to 0, Nnew-Nol
Exception handling must be added when calculating d. Also,
In the packet loss detecting unit 121, an address value Ao indicating a presentation position on a window described later besides Nod
Store ld.

(Receiver Side: Presenting Position Specifying Process) FIG.
9 is a flowchart showing processing in the presentation position specifying unit 122.

After the packet loss detection unit 121 detects a packet loss, a process for specifying a presentation position is started.

First, in the standby state, a notification from the packet loss detector 121 is waited (step S11).

From the packet loss detecting unit 121, the address value Aold indicating the presentation position described in the RTP packet immediately before the missing RTP packet and a new RTP packet are displayed.
Address value An indicating the presentation position described in the packet
ew and the number Anum of addresses spanning a plurality of addresses described in the new RTP packet are received (step S12).

The above three parameters (Aold, An
ew, Anum), the missing presentation position is Aold +
It is specified that it is in the range of 1 to Anew + Anum-1 (step S13).

Finally, the specified result is notified to the application processing unit 130 and the processing is terminated (step S1).
4) Return to the standby state (step S11).

When data corresponding to one presentation position is divided into a plurality of RTP packets 400 and transferred, the extension information 403 of the plurality of RTPs includes address information 500 indicating the same presentation position. Is added. If at least one of a plurality of consecutive RTP packets 400 to which the address value indicating the same presentation position is added has been lost, the presentation position address is specified as a missing part according to the specification processing of FIG. Is notified to the application processing unit 130.

(Reception apparatus side: application processing) In the application processing section 130, the decoding section 131 decodes the encoded data transferred from the RTP processing section 120. In the case of using the data of the preceding and following frames during decoding (for example, MPEG-2
Then, I (Intra-frame) picture, P
(Prediction) Picture, B (Bi-di)
(P.pictures are decoded using the data of the previous frame, and B pictures are decoded using the data of the preceding and succeeding frames.) In the decoding unit 131, the following processing must be performed. is there.

That is, when decoding a certain part, if the data of the necessary preceding and succeeding frames is lost due to packet loss, the part cannot be decoded normally.
In this case, the information indicating the location of the location and the information necessary to decode the location but for identifying the location where the packet loss occurred are omitted as undecodable location information. Notify the presentation unit 133.

The video reproducing section 132 stores the data decoded by the decoding section 131 in a buffer memory, sequentially D / A converts the stored data, and outputs the converted data to a monitor. Also,
Output processing to the monitor is also performed on the video created by the missing portion presentation unit 133.

The missing portion presenting section 133 converts the image indicating the missing portion into an HTML (Hyp) based on the presentation position information notified from the presentation position specifying section 122 of the RTP processing section 120.
erText Markup Language),
XML (extensible Markup Lan)
g.), and transferred to the video playback unit 132.

FIG. 9 shows an image (one frame) 6 to be created.
00 shows a configuration example.

In the figure, the X portion 601 indicates a portion that has been lost due to packet loss. When the user clicks the X portion 601, the markup language notifies the retransmission request processing portion 134 of the retransmission request portion (presentation address). The video is created in.

When the decoding unit 131 is notified of the non-decodable portion information, the non-decodable portion is also indicated by x, and is associated with a portion that is necessary for decoding but has lost a packet. When an undecodable portion is clicked, a retransmission request is made for a portion that is necessary for decoding the packet but has lost the packet.

When retransmission request processing section 134 is notified of a retransmission request point from missing point presentation section 133, retransmission request packet including information for specifying the retransmission request point on transmitting apparatus 200 side is transmitted to transmitting apparatus 200. . As the information that allows the transmitting apparatus 200 to specify the retransmission request point, information that can be transmitted by combining the time code of the frame including the retransmission request point and the address value indicating the presentation position can be used.

(Transmitting Device: Address Addition Process) In the transmitting device 200, the retransmission processing unit 232
The data to be retransmitted is specified from the time code of the frame including the data to be retransmitted received from 00 and the address information indicating the presentation position.

The RTP processing unit 220 performs the prescribed protocol processing, and stores the address information 500 indicating the presentation position on the window in the extension header 403 newly provided in the RTP packet 400.

The process of adding the address information 500 to the extension header 403 is performed by the presentation position address value adding unit 231.

FIGS. 7 and 8 show the relationship between the presentation position 710 on the window 700 and the address value 720. FIG.

Since the missing range of the screen due to the packet loss differs for each encoding method, the relationship between the presentation position 710 on the window 700 and the address value 720 can be determined based on the range of the influence of the packet loss on the screen. I just need.

FIG. 7 shows a presentation position 710 and an address value 7 on the window 700 in a case where the influence range when one RTP packet is lost is limited to each block.
20 shows the relationship with 20.

FIG. 8 shows the relationship between the presentation position 710 on the window 700 and the address value 720 when the effect of losing one RTP packet affects one frame. The presentation position 710 in the case of FIG. 8 indicates the entire window. As the address value at this time, a time record value that is incremented by one for each frame of the moving image is used. In this example, the case where FIG. 7 is applied is described.

In the transmitting apparatus 200, when the data on the payload section 402 straddles a plurality of presentation positions as the address value indicating the presentation position in the newly provided extension header 403, the number of the straddled addresses (the aforementioned Anum ) And the last address value (Aold, Ane described above)
w).

For example, when the data on the payload section 402 corresponds to the position straddling “1” to “3” in FIG. 7, “3” is set as the number of straddling addresses, and the address value indicating the presentation position is set. "3" is written in the extension header 403.

On the other hand, RFC 2343 which defines the bundled MPEG payload format uses RT
It is recommended that data be accommodated in the payload section 402 of the P packet 400 in a unit that does not cause fragmentation in the lower layer. One macroblock (a unit of data for which motion compensation is performed is usually 16 pixels × 16 pixels) Is described as a unit to be contained in the payload, in most cases, fragmentation does not occur in the lower layer.

According to this recommendation, when the RTP payload length is set to a length that does not cause fragmentation in the lower layer, the data length corresponding to one presentation position may exceed the RTP payload length, and one presentation position Is accommodated and transferred across the payloads of the plurality of RTP packets 400. In this case, the extension header 403 of the plurality of RTP packets 400
The same presentation position address information 500 is added to all of them.

[0095] The data constituted by the RTP packet 400 to which the address information 500 has been added in this way is sent to the receiving apparatus 100 via the OS section 210.

(Receiving device side: restoration process) Receiving device 100
In the restoration processing unit 135, the data retransmitted from the transmitting device 200, that is, the RTP packet 400 to which the address information 500 is added is received via the OS unit 110, and the data and the first received data are The video playback unit 1 combines the video data in which the missing part has been repaired in combination.
32. Thereby, the restored video data desired by the user is reproduced.

As described above, the present communication system
At the time of the first playback of the video, it is necessary to ensure the continuity of playback without performing retransmission processing that may cause a delay, and after the first playback, the program editor needs to repair and confirm Since there is an advantage that only a portion can be selectively retransmitted, the video editing using the network 1 is not performed at the broadcast station, especially at the broadcast station.
This is particularly effective because importance is placed on high response equivalent to TR and continuous reproduction of a series of videos without interruption or freeze.

The communication system is also applicable to an on-demand streaming service, a still image distribution service, and a text distribution service.

[0099]

As described above, according to the present invention,
Detect the packet loss of the received data, specify the posting position on the window for the data including the missing part lost due to the packet loss, and post the data including the missing part with the specified posting position on the window to obtain the desired data. Select only the repaired part, create repair data corresponding to the repaired part based on the selection information indicating the selected repaired part,
Based on the created repair data, only the desired repaired portion of the packet loss data is repaired and reproduced, so at the first reception, retransmission means for repairing the packet loss data is applied. Instead, it is possible to use the real-time property of the data transfer of UDP positively while accepting the deterioration of the presented information due to packet loss, and to select only the part to be repaired and to surely restore the quality. The error can be corrected according to the request, and the network bandwidth can be effectively used.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a receiving device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a transmission device according to an embodiment of the present invention.

FIG. 3 is a block diagram illustrating a system configuration when a program is edited using a network.

FIG. 4 is a flowchart illustrating a packet processing detection process.

FIG. 5 is a flowchart showing processing in a presentation position specifying unit.

FIG. 6 is an explanatory diagram showing an extension header that stores an address for indicating a presentation position.

FIG. 7 is an explanatory diagram showing a configuration when a plurality of presentation position addresses are set on one window.

FIG. 8 is an explanatory diagram showing a configuration in a case where one presentation position address is set on one window.

FIG. 9 is an explanatory diagram illustrating an example of a video created by a missing portion presentation unit.

FIG. 10 is an explanatory diagram showing an example of a conventional protocol stack for data distribution using RTP.

[Explanation of symbols]

 1 Network 100 Receiving Device 101 User Interface Unit 102 Network Interface Unit 110 OS Unit 120 RTP Processing Unit 130 Application Processing Unit 200 Transmission Device 201 Network Interface Unit 210 OS Unit 220 RTP Processing Unit 230 Application Processing Unit 400 RTP Packet 401 Header Unit 402 Payload Part 403 extension header 500 address information 700 window 710 presentation position 720 address value

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K014 AA01 EA06 FA16 5K030 GA11 HA08 HB02 HC01 JA07 JT03 KA01 KA06 KA13 KA19 LA01 MB13 5K034 AA05 BB06 CC02 DD03 EE11 FF13 HH01 HH02 HH06 HH09 MM01 MM03

Claims (7)

[Claims] 1. A communication control method for exchanging data between a transmitting device and a receiving device via a network, comprising: a data transmitting means for transmitting data in packet units from the transmitting device to the receiving device; A receiving unit configured to detect a packet loss of the received data; a packet loss detection unit configured to specify a posting position on a window for data including a missing portion lost due to the packet loss; Posting means for posting data including the specified missing part on the window; selecting means for selecting only a desired repair point from the posted data; and selecting information indicating the selected repair point. Retransmission requesting means for transferring to the transmitting device; and the transmitting device corresponding to a repaired portion based on the transferred selection information. Repair data creating means for creating the repair data; resending means for resending the created repair data to the receiving device; and the packet loss based on the retransmitted repair data by the receiving device. And a repairing means for repairing only a desired repaired portion of the restored data. 2. The data receiving apparatus according to claim 1, wherein the data to be presented is not repaired at the first reception, and the data including the lost portion is presented on the window without being repaired. The missing part where data was lost due to the loss is presented on the window, and only the repaired part that the user wants to repair is selected from the posted missing parts, and a retransmission request is sent to the transmitting apparatus, and the retransmitted part is sent from the transmitting apparatus. 2. The communication control method according to claim 1, wherein the repair data is received, and the lost portion at the time of the first reproduction is repaired by using the retransmitted repair data. 3. The method according to claim 1, wherein the detecting means is an IETF (Internet).
net Engineering Task Forc
e) RFC (Request For Comment)
ts) RTP (Real-t) defined in 1889
3. The communication control method according to claim 1, wherein an image transport protocol is used as a transfer protocol, and a packet loss is detected using a sequence number described in a packet header of the transfer protocol. 4. An extension header for storing information for specifying a presentation position of a coded data on a window on a receiving side is provided in a payload field of the RTP packet, and the RTP packet is transmitted to the receiving apparatus. 4. The communication control method according to claim 1, wherein the data is transferred. 5. The transmission means according to claim 5, wherein said retransmission means is a transmission control (TCP).
The communication control method according to any one of claims 1 to 4, wherein the repair data is transferred to the receiving device by using (Protocol) as a transport layer protocol. 6. A receiving device for exchanging data with a transmitting device via a network, wherein the receiving device is used in the communication control method according to claim 1. A receiving device comprising: the packet loss detecting unit; the specifying unit; the posting unit; the selecting unit; the retransmission requesting unit; 7. A transmitting apparatus for exchanging data with a receiving apparatus via a network, wherein the transmitting apparatus is used in the communication control method according to claim 1. A transmission device comprising: the data transmission unit; the repair data generation unit; and the retransmission unit.