JP2001045098A - Data communication system, data communication unit, data communication method and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize excellent communication quality by allowing each recipient to select a reception rate and error immunity suitable for each reception environment and to distribute a moving picture medium in real time especially in a multicast environment in the case of simultaneous data communication by many recipients via a network. SOLUTION: A sender side terminal has a coder 1011 that hierarchically encodes data, an FEC data generating section 1013 that generates FEC data, a data transmission section 1012 that transmits both the data as different data series, and an FEC data transmission section 1014. A receiver side terminal has a received series selection section 1036 that selects a proper data series on the basis of a reception state, a data reception section 1031 that receives the selected data series and an FEC data reception section 1032.

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, a data communication device, a data communication method, and a storage medium. More specifically, the present invention relates to real-time transmission / reception of constantly generated data such as video and audio through a network.
The present invention relates to a data communication system, a data communication device, a data communication method, and a storage medium suitable for performing reception.

[0002]

2. Description of the Related Art Generally, when data communication is performed on a network whose quality is not guaranteed, such as the Internet, data loss due to an error occurring in the network is inevitable. In particular, H. 263 (international standard for full-color video coding) and MPEG (Moving Picture Experts Gro
up: Full color moving image compression method) When transferring a moving image compressed by a differential codec such as the one described above, since the effect of data loss propagates in the spatial and temporal directions of the image, it is a separate issue from controlling the transmission rate. Addressing errors is an important issue.

As a means for repairing this data loss, a method called Forward Error Correction (FEC: automatic error correction method) has been considered. In this method, data for error correction (FEC data) is redundantly transmitted in advance, and if an error actually occurs in a network, the FEC data is used to repair the lost data. It is considered to be particularly suitable for real-time communication of moving images in that the delay time required for error recovery can be suppressed relatively low as compared with the method of retransmitting data. FEC can be used in IETF (In
Internet Draft (An RTP Paylo) by ternet Engineering Task Force
ad Format for Generic Forward Error Correction) has been proposed.

[0004] In this case, how much the FEC data amount is added depends on the network conditions. Therefore, a method has been devised for adjusting the amount of redundant data for FEC depending on network conditions.
Such a technique is based on the premise that one type of data is not transmitted even when there are many terminals. However, in a situation where there are many receiving terminals, it is desired to adjust the amount of error correction data optimally for each receiving terminal.

[0005]

On the other hand, when transmitting continuous media such as video and audio simultaneously in real time to a plurality of receiving terminals via a network, the quality of the media to be transmitted becomes a problem. Especially when the network environment of each receiving terminal is different, high-quality media should be transmitted according to the terminal connected by the broadband network, or the quality should be adjusted to a terminal that has the ability to receive only low-quality media The problem arises. Therefore,
A method has been proposed in which media data is compressed by hierarchies, and each hierarchy is transmitted as another stream. Even if only the basic layer is received, it is possible to receive the minimum quality data, and by sequentially joining and receiving the data stream (data sequence) of the higher layer, high-quality media is gradually provided. Be able to receive.

As described above, a receiving terminal having a narrow effective band between transmission and reception can receive only a basic lower layer stream and obtain the minimum quality, and a receiving terminal having a wide band network can use a high quality medium. A method has been devised in which a stream of an upper layer that can be reproduced is received to obtain high-quality media. In such a method, data with various qualities can be adaptively transmitted to a plurality of receiving terminals. Further, in order to cope with networks having different transmission path reliability, it is desirable to adjust the additional amount of error correction data according to the network conditions of each receiving terminal.

By the way, networks of different communication systems such as the Internet (Ethernet (LX having a bus structure jointly developed by Xerox, DEC, and Intel Corporation of the United States)
AN), ISDN (Integrated Service Digital Netwo
rk: In a network in which various data flows into nodes on the way where mixed data and modems are mixed in the middle, and the same data is transmitted to a plurality of terminals in one packet) Broadcasting systems such as these have become widespread. In such a situation, when transmitting continuous media such as video and audio simultaneously to a large number of receiving terminals in real time, optimal quality and optimal error resilience are determined according to the network connection form of each receiving terminal and the amount of external traffic. It is necessary to realize a data transmission method in consideration of the above.

As described above, multicast communication for broadcasting media data such as a moving image to a large number of recipients via a network has begun to spread, but when such communications are performed, the communication environment greatly differs between the recipients. Is a problem. That is, if transmission is performed at a high rate according to a receiver connected with a sufficient bandwidth, excessive data flows into a communication path of a receiver connected with a narrow bandwidth, congestion occurs, and conversely, If transmission is performed at a low rate in accordance with a low-speed line, there is a problem that a wideband receiver cannot use the bandwidth. In order to cope with this problem, there is a method in which a transmitting side transmits a plurality of layered transmission data sequences (data streams) and a receiving side selects and receives only an appropriate sequence from these data sequences. Proposed. In this way, a receiver capable of using a wide band receives a high rate or a large number of sequences, and a receiver connected with a narrow band line receives only a low rate or a small number of sequences, so that individual receivers can receive signals. Communication at an appropriate reception rate can be realized.

[0009] When the communication environment between receivers differs greatly as in the case of multicasting, the state of error occurrence also differs for each receiver, and therefore, not only the reception rate but also the degree of guaranteed error resilience. In addition, it is necessary for the receiver to be able to select the receiver according to the communication environment in order to realize good communication quality.

[0010] The present invention has been made in view of the above points, and when performing data communication simultaneously with a large number of recipients via a network, each recipient receives a reception rate and an error suitable for the respective reception environment. It is an object of the present invention to provide a data communication system, a data communication device, a data communication method, and a storage medium that realize good communication quality by selecting a robustness, and in particular, enable real-time moving image media to be distributed in a multicast environment. .

[0011]

In order to achieve the above object, the invention according to claim 1 provides a method for transmitting data via a network between a data communication device on a transmission side and a plurality of data communication devices on a reception side. A data communication system for transmitting and receiving, wherein the data communication device on the transmission side encodes the data hierarchically to generate encoded data, and the encoding means hierarchically encodes the data. Correction data generating means for generating error correction data for each of the encoded data, and transmitting the hierarchically encoded data and the error correction data as different data sequences. Transmitting means, wherein the receiving-side data communication device is a selecting means for selecting an appropriate data sequence from the different data sequences based on a receiving state; and It characterized by having a receiving means for receiving-option data series.

[0012] To achieve the above object, the invention according to claim 2 is characterized in that the data sequence transmitted by the transmitting means is:
According to a basic sequence corresponding to a layer of the data encoding, one or more extension sequences which are higher layers of the basic sequence, and respective correction data generated for the hierarchically encoded data. A correction data series.

In order to achieve the above object, the invention according to claim 3 is characterized in that the basic sequence is always selected from the data sequence by the selecting means.

According to a fourth aspect of the present invention, the data communication apparatus on the transmitting side further comprises a step of packetizing the encoded data hierarchically encoded by the encoding means. A data packetizing unit for generating a packet, and a correction data packetizing unit for generating an error correction packet using the error correction data, wherein the correction data generation unit uses the data packet. The data for error correction is generated, and the transmitting unit transmits the data packet and the error correction packet as a data sequence of the encoded data and a data sequence of the error correction data, respectively. Features.

In order to achieve the above object, the invention according to claim 5 is characterized in that the transmitting means transmits data packets with data transmission time information and a sequence number added to each data packet in the data sequence. I do.

In order to achieve the above object, the invention according to claim 6 is characterized in that the correction data generating means refers to a data packet of the hierarchically encoded data and encodes the encoded data portion of the data packet. The error correction data is generated by using only the error correction data packetizing means, the correction data packetizing means generates a payload header including only the minimum necessary information at the time of error correction, and generates the error correction data and the payload header. Is used to generate the error correction packet.

[0017] In order to achieve the above object, the invention according to claim 7 is characterized in that the data communication device on the receiving side further comprises a status acquisition means for acquiring the reception status.

In order to achieve the above object, the invention according to claim 8 is characterized in that the state acquisition means acquires a data loss rate, a transmission rate, and a reception rate as the reception state.

In order to achieve the above object, the invention according to claim 9 is characterized in that the selecting means is such that the data loss rate is smaller than a predetermined threshold and the ratio between the transmission rate and the reception rate is larger than a predetermined threshold. In the case of further receiving an extended sequence that is a data sequence of the encoded data of the upper layer, if the data loss rate is smaller than a predetermined threshold and the ratio between the transmission rate and the reception rate is smaller than a predetermined threshold, the reception is performed. Reduce the data sequence for correction that is, if the data loss rate is greater than a predetermined threshold and the ratio between the transmission rate and the reception rate is greater than a predetermined threshold, further receive a data sequence for correction, the data If the loss ratio is larger than a predetermined threshold and the ratio between the transmission rate and the reception rate is smaller than a predetermined threshold, the received extension sequence is sequentially reduced from the upper layer. That.

[0020] In order to achieve the above object, the invention according to claim 10 is characterized in that the state acquisition means acquires a data loss rate as the reception state.

In order to achieve the above object, the invention according to claim 11 is characterized in that the selecting means receives the error correction data sequence when the data loss rate is smaller than a predetermined threshold and the error correction data sequence is being received. Receiving an extended sequence that is a data sequence of coded data of an upper layer by reducing the error correcting data sequence, and receiving the error correcting data sequence in which the data loss rate is smaller than a predetermined threshold. If not, further receive an extended sequence that is a data sequence of the encoded data of the upper layer, if the data loss rate is receiving an extended sequence greater than a predetermined threshold, reduce the received extended sequence The data sequence for error correction is further received, and when the data loss rate is larger than a predetermined threshold and an extended sequence is not received, the data sequence for error correction is further received. And wherein the door.

In order to achieve the above object, the invention according to claim 12 is characterized in that the predetermined threshold value is determined according to a coding method of the coded data.

In order to achieve the above object, the invention according to claim 13 is a device for transmitting data such as a moving image from the data communication device on the transmitting side to a plurality of data communication devices on the receiving side via a network such as the Internet. It is applicable to multicast communication for reporting.

In order to achieve the above object, an invention according to claim 14 is a data communication device for transmitting data to a plurality of data communication devices on the receiving side via a network, wherein the data is hierarchically transmitted. Encoding means for encoding to generate encoded data, correction data generating means for generating error correction data for each encoded data hierarchically encoded by the encoding means, And transmitting means for transmitting the hierarchically encoded data and the error correction data as different data sequences.

In order to achieve the above object, the invention according to claim 15 is characterized in that the data sequence transmitted by the transmitting means is a basic sequence according to a hierarchy of the data encoding and an upper layer of the basic sequence. One or more extension sequences and a correction data sequence corresponding to each correction data generated for the hierarchically encoded data.

In order to achieve the above object, the invention according to claim 16 is characterized in that the basic sequence is always selected from the data sequence by the data communication device on the receiving side.

To achieve the above object, the invention according to claim 17 further comprises a data packetizing means for packetizing the encoded data hierarchically encoded by the encoding means to generate a data packet. Correction data packetizing means for generating an error correction packet using the error correction data, wherein the correction data generation means generates the error correction data using the data packet. The transmitting unit transmits the data packet and the error correction packet as a data sequence of the encoded data and a data sequence of the error correction data, respectively.

[0028] In order to achieve the above object, the invention according to claim 18 is characterized in that the transmission means transmits data packets with data transmission time information and a sequence number for each data packet in the data sequence. I do.

In order to achieve the above object, an invention according to claim 19 is characterized in that the correction data generating means refers to a data packet of the hierarchically encoded data and encodes the encoded data portion of the data packet. The error correction data is generated by using only the error correction data packetizing means, the correction data packetizing means generates a payload header including only the minimum necessary information at the time of error correction, and generates the error correction data and the payload header. Is used to generate the error correction packet.

In order to achieve the above object, the invention according to claim 20 is applicable to multicast communication for broadcasting data such as moving images to a plurality of data communication devices on the receiving side via a network such as the Internet. There is a feature.

To achieve the above object, an invention according to claim 21 is a data communication device for receiving data from a data communication device on the transmission side via a network,
Selection means for selecting an appropriate data sequence based on a reception state from data sequences transmitted from the transmission-side data communication device, and reception means for receiving the data sequence selected by the selection means It is characterized by.

In order to achieve the above object, the invention according to claim 22 is characterized in that the data sequence transmitted from the data communication device on the transmitting side is a basic sequence corresponding to a layer of the data encoding, It is characterized in that it is a correction data sequence corresponding to one or more extension sequences which are higher layers of the sequence and each correction data generated for the hierarchically encoded data.

In order to achieve the above object, the invention according to claim 23 is characterized in that the basic sequence is always selected from the data sequence by the selection means.

[0034] In order to achieve the above object, the invention according to claim 24 is characterized in that it further comprises a status acquisition means for acquiring the reception status.

In order to achieve the above object, the invention according to claim 25 is characterized in that the state acquiring means acquires a data loss rate, a transmission rate, and a reception rate as the reception state.

[0036] In order to achieve the above object, the invention according to claim 26, wherein the selecting means is configured such that the data loss rate is smaller than a predetermined threshold and the ratio between the transmission rate and the reception rate is larger than a predetermined threshold. In the case of further receiving an extended sequence that is a data sequence of the encoded data of the upper layer, if the data loss rate is smaller than a predetermined threshold and the ratio between the transmission rate and the reception rate is smaller than a predetermined threshold, the reception is performed Reduce the data sequence for correction that is, if the data loss rate is greater than a predetermined threshold and the ratio between the transmission rate and the reception rate is greater than a predetermined threshold, further receive a data sequence for correction, the data When the loss rate is larger than a predetermined threshold and the ratio between the transmission rate and the reception rate is smaller than a predetermined threshold, the received extended sequences are sequentially reduced from the upper layer. To.

[0037] In order to achieve the above object, the invention according to claim 27 is characterized in that the state acquisition means acquires a data loss rate as the reception state.

[0038] In order to achieve the above object, the invention according to claim 28, wherein the selecting means receives the error correction data sequence when the data loss rate is smaller than a predetermined threshold and the error correction data sequence is being received. Receiving an extended sequence that is a data sequence of coded data of an upper layer by reducing the error correcting data sequence, and receiving the error correcting data sequence in which the data loss rate is smaller than a predetermined threshold. If not, further receive an extended sequence that is a data sequence of the encoded data of the upper layer, if the data loss rate is receiving an extended sequence greater than a predetermined threshold, reduce the received extended sequence The data sequence for error correction is further received, and when the data loss rate is larger than a predetermined threshold and an extended sequence is not received, the data sequence for error correction is further received. And wherein the door.

[0039] In order to achieve the above object, the invention according to claim 29 is characterized in that the predetermined threshold value is determined according to an encoding method of the encoded data.

In order to achieve the above object, the invention according to claim 30 is applicable to multicast communication in which data such as moving images is broadcast from the data communication device on the transmission side via a network such as the Internet. There is a feature.

[0041] In order to achieve the above object, an invention according to claim 31 is a data communication system for transmitting and receiving data between a data communication device on the transmitting side and a plurality of data communication devices on the receiving side via a network. A data communication method applied to the data communication apparatus, wherein the transmitting-side data communication apparatus hierarchically encodes the data to generate encoded data; A correction data generating step of generating error correction data for each of the encoded data, and transmitting the hierarchically encoded data and the error correction data as different data sequences. And the receiving-side data communication apparatus selects an appropriate data sequence from the different data sequences based on a reception state. A selection step that is characterized by having a reception step of receiving the selected data series in said selection step.

[0042] In order to achieve the above object, the invention according to claim 32, wherein the data sequence transmitted in the transmitting step is a basic sequence according to a hierarchy of the data encoding, and an upper layer of the basic sequence. One or more extension sequences and a correction data sequence corresponding to each correction data generated for the hierarchically encoded data.

In order to achieve the above object, the invention according to claim 33 is characterized in that the basic sequence is always selected from the data sequence in the selecting step. In order to achieve the above object, the invention according to claim 34, wherein the data communication apparatus on the transmitting side generates a data packet by packetizing the encoded data hierarchically encoded in the encoding step. Data packetizing step, and a correction data packetization step of generating an error correction packet using the error correction data, the correction data generation step,
The data packet is used to generate the error correction data, and in the transmitting step, the data packet and the error correction packet are respectively divided into a data sequence of the encoded data and a data sequence of the error correction data. Is transmitted.

In order to achieve the above object, the invention according to claim 35 is characterized in that in the transmitting step, data transmission time information and a sequence number are added to each data packet in the data sequence and transmitted. I do.

In order to achieve the above object, the invention according to claim 36, wherein in the correction data generating step, a data packet of the hierarchically encoded data is referred to by referring to an encoded data portion of the data packet. The error correction data is generated by using only the error correction data packetizing step. In the correction data packetizing step, a payload header including only information necessary at the time of error correction is generated, and the error correction data and the payload header are generated. Is used to generate the error correction packet.

In order to achieve the above object, the invention according to claim 37 is characterized in that the data communication device on the receiving side further comprises a status acquisition step for acquiring the reception status.

In order to achieve the above object, the invention according to claim 38 is characterized in that in the state acquiring step, a data loss rate, a transmission rate, and a reception rate are acquired as the reception state.

In order to achieve the above object, in the invention according to claim 39, in the selecting step, the data loss rate is smaller than a predetermined threshold and a ratio between the transmission rate and the reception rate is larger than a predetermined threshold. In the case of further receiving an extended sequence that is a data sequence of the encoded data of the upper layer, if the data loss rate is smaller than a predetermined threshold and the ratio between the transmission rate and the reception rate is smaller than a predetermined threshold, the reception is performed. Reduce the data sequence for correction that is, if the data loss rate is greater than a predetermined threshold and the ratio between the transmission rate and the reception rate is greater than a predetermined threshold, further receive a data sequence for correction, the data If the loss rate is larger than a predetermined threshold and the ratio between the transmission rate and the reception rate is smaller than a predetermined threshold, reduce the extended sequences to be received in order from the upper layer. And it features.

[0049] In order to achieve the above object, the invention according to claim 40 is characterized in that in the status obtaining step, a data loss rate is obtained as the reception status.

In order to achieve the above object, the invention according to claim 41, wherein, in the selecting step, when the data loss rate is smaller than a predetermined threshold value and the error correction data sequence is being received, the data loss rate is determined. Receiving an extended sequence that is a data sequence of coded data of an upper layer by reducing the error correcting data sequence, and receiving the error correcting data sequence in which the data loss rate is smaller than a predetermined threshold. If not, further receive an extended sequence that is a data sequence of the encoded data of the upper layer, if the data loss rate is receiving an extended sequence greater than a predetermined threshold, reduce the received extended sequence When the data sequence for error correction is further received and the data loss rate is larger than a predetermined threshold and no extended sequence is received, the data sequence for error correction is further received. Characterized in that it.

[0051] In order to achieve the above object, the invention according to claim 42 is characterized in that the predetermined threshold value is determined according to a coding method of the coded data.

In order to achieve the above object, according to the invention of claim 43, the data such as a moving image is transmitted from the data communication device on the transmitting side to a plurality of data communication devices on the receiving side via a network such as the Internet. It is applicable to multicast communication for reporting.

In order to achieve the above object, the invention according to claim 44 is a data communication system for transmitting and receiving data between a transmitting data communication device and a plurality of receiving data communication devices via a network. A computer-readable storage medium storing a program that executes a data communication method applied to the data communication method, wherein the data communication method includes: an encoding step of hierarchically encoding the data to generate encoded data; A correction data generation step of generating error correction data for each of the encoded data hierarchically encoded in the encoding step; and the hierarchically encoded data and the error correction. And a transmission step of controlling to transmit data for each as a different data sequence, from among the different data sequences A selection step of selecting an appropriate data sequence based on signal conditions, and having a receiving step of controlling so as to receive a selected data series in said selection step.

[0054] In order to achieve the above object, the invention according to claim 45 is characterized in that a data sequence to be transmitted and controlled in the transmitting step is a basic sequence corresponding to a layer of the data encoding, and an upper layer of the basic sequence. It is a correction data sequence corresponding to one or more extended sequences and each correction data generated for the hierarchically encoded data.

In order to achieve the above object, the invention according to claim 46 is characterized in that the basic sequence is always selected from the data sequence in the selecting step.

In order to achieve the above object, the invention according to claim 47 further comprises a data packetizing step of packetizing the encoded data hierarchically encoded in the encoding step to generate a data packet. And a correction data packetizing step of generating an error correction packet using the error correction data. In the correction data generation step, the error correction data is generated using the data packet. In the transmitting step, the data packet and the error correction packet are controlled to be transmitted as a data sequence of the encoded data and a data sequence of the error correction data, respectively.

In order to achieve the above object, in the invention according to claim 48, in the transmitting step, control is performed such that data transmission time information and a sequence number are added to each data packet in the data sequence and transmitted. It is characterized by the following.

In order to achieve the above object, the invention according to claim 49, in the correcting data generating step, refers to a data packet of the hierarchically encoded data, and refers to an encoded data portion of the data packet. The error correction data is generated by using only the error correction data packetizing step. In the correction data packetizing step, a payload header including only information necessary at the time of error correction is generated, and the error correction data and the payload header are generated. Is used to generate the error correction packet.

[0059] In order to achieve the above object, the invention according to claim 50 is characterized by further comprising a state obtaining step of obtaining the reception state.

In order to achieve the above object, the invention according to claim 51 is characterized in that, in the state obtaining step, a data loss rate, a transmission rate, and a reception rate are obtained as the reception state.

In order to achieve the above object, in the invention according to claim 52, in the selecting step, the data loss rate is smaller than a predetermined threshold and a ratio between the transmission rate and the reception rate is larger than a predetermined threshold. In the case, control is further performed to receive an extended sequence which is a data sequence of the encoded data of the upper layer, and the ratio between the transmission rate and the reception rate is smaller than a predetermined threshold, and the data loss rate is smaller than a predetermined threshold. In this case, the correction data sequence being received is reduced, and when the data loss rate is larger than a predetermined threshold and the ratio between the transmission rate and the reception rate is larger than a predetermined threshold, the data sequence for correction is further received. Extended system for receiving when the data loss rate is larger than a predetermined threshold and the ratio between the transmission rate and the reception rate is smaller than a predetermined threshold. And wherein the reducing sequentially from the upper layer.

[0062] In order to achieve the above object, the invention according to claim 53 is characterized in that in the state obtaining step, a data loss rate is obtained as the reception state.

In order to achieve the above object, the invention according to the fifty-fourth aspect, in the selecting step, when the data loss rate is smaller than a predetermined threshold and the error correction data sequence is being received, the reception is performed. Control to receive an extended sequence which is a data sequence of higher-layer encoded data by reducing the data sequence for error correction, and wherein the data loss rate is smaller than a predetermined threshold value and the data sequence for error correction is controlled. Is not received, control is further performed to receive an extended sequence that is a data sequence of higher-layer coded data, and if the data loss rate is larger than a predetermined threshold and an extended sequence is being received, reception is performed. If the data loss rate is greater than a predetermined threshold and no extended sequence is received, control is performed to reduce the extended sequence that is being performed and further receive the data sequence for error correction. It is characterized by controlling so as to further receive a data series for the error correction.

In order to achieve the above object, the invention according to claim 55 is characterized in that the predetermined threshold value is determined according to a coding method of the coded data.

In order to achieve the above object, the invention of claim 56 relates to a method for transmitting data such as a moving image from a data communication device on the transmitting side to a plurality of data communication devices on a receiving side via a network such as the Internet. It is applicable to multicast communication for reporting.

[0066]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment and a second embodiment of the present invention will be described in detail with reference to the drawings.

[First Embodiment] FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration of a data communication device according to the embodiment. The data communication device according to the first embodiment of the present invention includes a transmitting terminal 1-1 and a plurality of receiving terminals 1-2.
Are communicable with each other via a network 1-3. FIG. 1 is a block diagram showing data transmitted by a transmitting terminal 1-1 through a network 1-3.
1, 1-22... Show the internal configuration and connection relationship of each terminal when receiving.

Further, the transmitting terminal 1-1 includes a data generating unit 1-11, a layer 1 transmitting unit (BaseLayer).
1) 1-121, layer 2 transmission unit (FECLayer)
1) 1-122, Layer 3 transmitting section (Enhanceme
nt Layer 2) 1-123, Layer 4 transmitting section (FEC Layer 2) 1-124, Layer 5 transmitting section (Enhancement Layer 3) 1-1.
25. Further, the above receiving terminal 1-21
Data receiving section 1-21, data processing section 1-212, receiving layer selecting section 1-213, receiving state monitoring section 1-12
4 is provided. The other receiving terminals 1-22... Have the same configuration as the above-mentioned receiving terminals 1-21, and their illustration is omitted.

Here, the network 1-3 in the first embodiment of the present invention refers to the network L operated in the organization.
It includes everything from an AN (Local Area Network) to a large-scale network in which an unspecified number of networks such as the so-called Internet are connected, and does not specify the form.

The above-described configuration will be described in detail together with the operation. Specifically, the data transmitted by the transmitting terminal 1-1 may be, for example, video data captured by a video camera, etc. It is not limited. In the transmission terminal 1-1, the data generation unit 1-11
Encodes the media to be transmitted hierarchically. Since hierarchical coding is used, when the data is reproduced only with the Base layer (basic sequence), the quality is poor but the medium can be reproduced at a minimum. By using the upper enhancement layer (extended sequence) together with the Base layer, media can be reproduced with higher quality. For example, in the case of a video, an image having a high resolution and a high frame rate is obtained. The hierarchically encoded data is packetized for transmission, and FEC data for error correction is generated for each layer based on the packetized data. A parity packet or the like is used as the FEC data.

Base layer and each enhancement
The t layer and the error correction layer for each are sent to different layer transmission units (data transmission units) 1-121 to 1-125 as separate streams. Layer transmission units (data transmission units) 1-112 to 1-125 add information of a sequence number and a time at which data is transmitted for each packet, and transmit each layer as a separate stream to the network 1-3. Multicast (distributing the same information to specific destinations). Which layer is to be received can be selected by the receiving terminals 1-21, 1-22,.

On the other hand, each of the receiving terminals 1-21, 1-22,.
Receives only the appropriate one of the layers being transmitted. The received data is sent to the data processing unit 1-212.
To be processed. For example, if the data is video,
Processing for displaying video (decoding and display processing, etc.)
Is performed by the data processing unit 1-212. Each receiving terminal 1-
21, 21, 22..., During data reception, the reception status monitoring unit 1-214 monitors the reception status such as packet loss and transmission delay, and transmits the information to the reception layer selection unit 1-213.
Send to The reception layer selection unit 1-213 determines a layer to be received according to the received reception status. The reception layer selection unit 1-213 reports to the data reception unit 1-211 to perform reception on the determined layer, and the data reception unit 1-211 continues to receive the specified layer.

Next, the first embodiment of the present invention configured as described above is described.
The operation of the transmitting terminal 1-1 and the receiving terminals 1-21, 1-22... Of the data communication apparatus according to the embodiment of FIG.
This will be described with reference to FIG. FIG. 2 is a flowchart showing data transmission processing on the transmission terminal side of the data communication apparatus according to the first embodiment of the present invention, and FIG. 3 is a reception terminal side of the data communication apparatus according to the first embodiment of the present invention. FIG. 4 is a flowchart showing a data receiving process of the data communication apparatus according to the first embodiment of the present invention.
It is a flowchart which shows the receiving layer selection process in 1-22 ....

First, the transmitting terminal 1-1 of the data communication device
Will be described based on the flowchart of FIG.

First, the transmitting terminal 1-1 captures data to be transmitted (step S201), and hierarchically codes the data (step S202). Enhanc based on the lowest Base layer using hierarchical coding technology
By adding the element layers sequentially from the bottom, compression is performed so that the quality is gradually improved. Data of each layer is packetized, and a stream of the Base layer and a stream of each Enhancement layer are generated (step S203). For example, when encoding is performed on three layers, one Base layer stream and two Enhancement layer streams are generated.

The data packet of each layer is referred to to generate a packet for error correction, and the data stream of the FEC layer is generated one by one for each layer (step S20).
4). A parity packet or the like can be used for error correction. In this way, the layered media data and F
A layer of the data stream is generated from the EC data, and is sent out on the network 1-3 as separate data streams (step S205). When data is sent to the network 1-3 (step S20)
5) The packet is provided with information on a sequence number managed for each stream and a time stamp of the transmission time.

Next, the operation of each of the receiving terminals 1-21, 1-22... Of the data communication apparatus according to the first embodiment of the present invention will be described with reference to the flowchart of FIG.

Each of the receiving terminals 1-21, 1-22,... Receives the data transmitted from the transmitting terminal 1-1 via the network 1-3 by the data receiving section 1-211 (step S301). The data sent from the transmitting terminal 1-1 is processed by the data processing unit 1-212 (step S302). For example, when video data is transmitted from the transmission terminal 1-1, video display is performed.

Each of the receiving terminals 1-21, 1-22... Periodically monitors statistical information of the transmission / reception status (step S303). The transmission / reception status at this time includes a packet loss rate, a transmission rate, a reception rate, and the like.
The packet loss rate can be measured from the number of missing sequence numbers among the sequence numbers assigned to the transmission data. The transmission rate can be estimated from the time stamp and the sequence number given to the transmission data. The reception rate can be easily calculated from the log of the packet size and time of the reception data. Then, based on the transmission / reception status, the data layer to be received by the receiving terminal is selected (step S3).
04). If the receiving layer is changed by the selection, the layer to be actually received is changed (step S30).
5) After the change, data reception is continued for the data of the layer to be received.

Next, the receiving layer selection processing in the receiving terminals 1-21, 1-22,... Of the data communication apparatus according to the first embodiment of the present invention will be described with reference to the flowchart of FIG.

First, the packet loss rate is checked and compared with a threshold (for example, 5%) (step S401), and then the ratio of the reception rate to the transmission rate is compared with a threshold (for example, 0.9) (step S402). If the loss rate is smaller than the threshold value and the transmission / reception rate ratio is larger than the threshold value, it means that there is a margin in the bandwidth and the loss is small, so that the enhancement layer of the higher layer is received (step S403). When the loss rate is smaller than the threshold value and the transmission / reception rate ratio is smaller than the threshold value, it is considered that the loss is small and the quality of the communication channel is good, but the transmitted data is not sufficiently received and the amount of transmitted data is small. It seems that there is not enough bandwidth to receive enough. In this case, there is no need to receive redundant FEC layers unnecessarily, so the number of FEC layers being received is reduced (step S4).
04).

If the loss rate is larger than the threshold and the transmission / reception rate ratio is sufficiently larger than the threshold, the network 1-3
Is sufficient, but the communication path is considered to be unreliable, so the FEC layer starts to be newly received (step S406). On the other hand, when the loss rate is larger than the threshold and the transmission / reception rate ratio is smaller than the threshold, it is considered that the bandwidth is fundamentally insufficient.
The number of the “ncement” layers is reduced in order from the higher layer (step S407). At this time, the reception is stopped.
If the FEC layer related to the interference layer has also been received, the reception of this FEC layer is also stopped.

By repeating the above steps, the transmitting terminal 1-1 sends out the generated data streams of a plurality of layers to the network 1-3 by the hierarchically encoded data and the FEC for error correction. I do. The receiving terminals 1-21, 1-22,... Select and receive data of an appropriate layer as described above according to the receiving situation.

FIG. 5 is an explanatory view showing a hierarchical data transmission / reception state which can be realized by the above method according to the first embodiment of the present invention. In the figure, the upper side is an example of hierarchical data prepared by hierarchical encoding and error correction on the transmitting side. In this example, the Base layer and two Enh
An ancement layer has been generated. Three FEC layers for error correction are prepared for each of the three data streams, one layer each. A receiving terminal (client) with a narrow network band receives only the Base stream as shown in A in the figure.

On the other hand, a receiving terminal (client) having a wide network bandwidth to some extent receives three data streams, for example, B and C in the figure, but is connected by an unstable network with a large packet loss. The receiving terminal receives the FEC stream as shown in B in the figure. On the other hand, a receiving terminal connected by a reliable network with little packet loss does not receive the FEC stream as shown in C in the figure, but receives the media data stream up to the highest quality layer.

FIG. 6 is a block diagram showing a specific example in which the data communication apparatus according to the first embodiment of the present invention is applied to a data communication system. The data communication system according to the first embodiment of the present invention includes a camera server 10
And the client 20. Further, the camera server 10 includes a camera 100, a capture unit 101, an interface 102, a CPU 103, a ROM
104, RAM 105, external storage device 106, keyboard 107, display device 108, communication interface 109
It has. Further, the client 20 is
3, ROM 204, RAM 205, external storage device 20
6, a keyboard 207, a display device 208, and a communication interface 209. In the figure, reference numeral 300 denotes a network.

The above configuration will be described in detail.
Transfers video data captured by the camera 100 to the client 20 via the network 300. The correspondence between the configuration in FIG. 6 and the configuration in FIG. 1 above is that the camera server 10 corresponds to the transmission terminal 1-1, and the client 20 corresponds to the reception terminal 1
It will be understood that this corresponds to -21. Further, a plurality of the clients 20 exist in different places connected by the network 300.

Now, the camera server 10 and the client 2
The hardware difference of 0 is a difference between whether or not the camera and the capture unit are provided, and both the camera server 10 and the client 20 can be realized by, for example, a personal computer. That is, reference numerals 103 to 109
And 203 to 209 have substantially the same configuration, each of which can be realized by a general-purpose computer (for example, a personal computer).

On the other hand, in terms of software, the camera server 10 compresses the captured video data, generates error correction data, and transfers the data to the client 20 (stored in the external storage device 106 and RAM).
The client 20 receives the video data and displays it on the client 20 (stored in the external storage device 206 and stored in the RAM 20).
205 is loaded and executed). Data compression can be performed by hardware using a capture card or by software. However, the fact that data can be compressed by using a hierarchical encoding technique in order to realize the first embodiment of the present invention. Is the condition.

However, in this example, for convenience, the camera server 1
0 and the client 20 are only shown separately, and when a video capture function is added to both of them, both can function as a camera server and a client.

Now, the operation when the above-described operation of the data communication apparatus of FIG. 1 is applied to the data communication system of FIG. 6 will be described with reference to the flowcharts of FIGS. FIG. 7 is a flowchart illustrating transmission processing in the camera server according to the first embodiment of the present invention;
FIG. 8 is a flowchart showing a data receiving process in the client according to the first embodiment of the present invention, and FIG. 9 is a flowchart showing a receiving layer changing process in the client according to the first embodiment of the present invention.

First, the operation of the camera server 10 will be described (FIG. 7). First, the camera server 10 captures an image captured from the camera 100 by the capture unit 101 according to the capture interval (step S70).
1). The video captured by the capture unit 101 is
Layer coding is performed on a plurality of layers (step S702).
Next, the packet is divided into packets of an appropriate size for each layer (step S703). Further, a parity packet for error correction is generated for the packetized media data of each layer (step S704). One parity packet is added to several packets of media data.

The data of each layer generated in this manner is rate-adjusted in time for the next capture timing, and transmitted on the network 300 as separate data streams (step S705).
As described above, the camera server 10 periodically repeats the process from capture to transmission of the video.

On the other hand, the processing of the client 20 is as follows.
First, the data reception processing (FIG. 8) will be described. First, the client 20 receives the data of the receiving layer arriving from the camera server 10 (step S80).
1). When one frame of data arrives, a packet loss is checked, and if there is a loss, recovery is performed using an error correction packet (step S802). Next, an image is generated by decoding the data after the error correction (step S803) and displayed on the display device 208 (step S803).
804).

Next, the reception layer change processing (FIG. 9) in the client 20 will be described. First, in the client 20, an initial receiving layer is determined at the time of startup (step S811), and an initial layer change timer is set (step S812). Next, it is checked whether the time of the initial layer change timer has expired (step S81).
3) If the time of the initial layer change timer has passed, the reception status statistical information is checked (step S8).
14). Next, the receiving layer is determined and changed according to the above-described method (FIG. 4) from the receiving state (step S81).
5). This change in the reception layer has an effect as a change in the designated reception layer in the above-described reception processing. Thereafter, the reception layer change timer is set again (step S816), the process returns to step S813, and the processes from step S813 to step S816 are repeated.

As a result of the above, simultaneous data transfer to a plurality of receiving terminals via a network is performed by generating a plurality of streams by hierarchical coding and error correction on the transmitting terminal side, and according to the network conditions of each receiving terminal. Thus, the receiving terminal selects the most suitable received data stream, so that the most suitable data transfer can be performed.

When the Internet is assumed as the target network in the above embodiment, the method of sending data to the network is IETF (Internet Engine
IP (Internet) standardized by ringTask Force
Protocol) multicast can be used.
In this case, as a method for the receiving terminal to select a stream to be received from a plurality of layers, IGMP (Internet G
Join and leave messages to a multicast group using the Roup Membership Protocol) can be used.

The data rates of the Base layer and the Enhancement layer in the above-described embodiment are desirably set as appropriate according to the type of network and the type of interface connected to the network. For example, if the above system is built in-house, Ethernet (Ethern)
et: A LAN with a bus structure jointly developed by three companies, Xerox, DEC, and Intel, with a transmission speed of 10 Mbps and 1
00 Mbps), so a high transfer rate could be set.

As described above, according to the data communication apparatus of the first embodiment of the present invention, data generation section 1-1 that hierarchically encodes data of a transmission target medium.
1. A transmission terminal including layer transmission units 1-112 to 1-125 for transmitting hierarchically encoded data as different data streams, generating error correction data for each data stream, and transmitting the data as separate streams. 1-1, a reception status monitor 1 for monitoring the reception status
-214, a receiving layer selecting unit 1-213 for selecting an appropriate data stream based on a receiving situation, and a receiving terminal 1-21 having a data receiving unit 1-211 for receiving the selected data stream. Such functions and effects are provided.

In the above configuration, in the transmitting terminal 1-1,
Layer coding of transmission target data, packetization of data of each layer, Base layer stream and each enhancement
generation of a stream of the ment layer, generation of a packet for error correction for data of each layer, generation of a data stream of the FEC layer one by one for each layer, generation of a data stream layer by layered media data and FEC data. And sends them to the network 1-3 as separate data streams. A packet is provided with information of a sequence number managed for each stream and a time stamp of a transmission time.

The receiving terminals 1-21, 1-22... Periodically monitor statistical information of the transmission / reception status, select a data layer to be received based on the transmission / reception status, and change the reception layer based on the selection of the reception layer. , The reception of the data of the changed reception layer is continued.

[0102] In the receiving terminals 1-21, 1-22, ..., when the packet loss rate is smaller than the threshold value and the transmission / reception rate ratio is larger than the threshold value, Enhancem of the upper layer is further increased.
If the loss rate is smaller than the threshold and the transmission / reception rate ratio is also smaller than the threshold, the FEC layer is reduced.If the loss rate is larger than the threshold and the transmission / reception rate ratio is sufficiently larger than the threshold, the FEC layer is changed. When a new reception is performed and the loss rate is greater than the threshold value and the transmission / reception rate ratio is smaller than the threshold value, the enhancement layers to be received are reduced in descending order of the enhancement layers.

Thus, according to the first embodiment of the present invention, when data is transmitted from a transmitting terminal to a plurality of receiving terminals via a network, an optimum state is determined according to the state of an intervening network that differs for each receiving terminal. It is possible to transmit data having high quality and optimal error tolerance. Therefore, an excellent effect is obtained, which is particularly effective when a real-time property is required such that live video taken by a camera is simultaneously relayed to a large number of viewers.

[Second Embodiment] FIG. 10 is a block diagram showing a configuration of a data communication apparatus according to a second embodiment of the present invention. The data communication device according to the second embodiment of the present invention includes a transmitting terminal 1001, a receiving terminal 1002
Are configured to be communicable via the network 1021. Further, the transmission side terminal 1001 includes an image capture device 1010, an encoding device 1011, a data transmission unit 1012, an FEC data generation unit 1013, and an FEC data transmission unit 1014. Further, the receiving terminal 1002 includes a data receiving unit 1031, an FEC data receiving unit 1032, an error correcting unit 1033, and a decoding device 103.
4. An image display device 1035 and a reception sequence selection unit 1036 are provided.

The general function of each unit of the above-mentioned transmitting terminal 1001 and receiving terminal 1002 will be described.
In 001, the image capture device 1010 captures the image of the display screen as a file. Encoding device 10
11 generates a hierarchical data sequence from the input video signal. The data transmitting unit 1012 generates a data packet based on the encoded data, forms a basic sequence and an extended sequence according to the coding hierarchy, and sends the data to the network 1021. The FEC data generation unit 1013 generates FEC data based on the data packets of each stream. The FEC data transmission unit 1014 packetizes the FEC data and sends the packet to the network 1021.

On the other hand, in the receiving terminal 1002, the data receiving section 1031 receives the encoded data via the network 1021. FEC data receiving unit 1032
Receives FEC data via the network 1021. The error correction unit 1033 performs restoration processing of a lost packet. The decoding device 1034 decodes the encoded data. The image display device 1035 displays the received image. The reception sequence selection unit 1036 switches the reception sequence at regular time intervals based on the packet loss information.

The functions of the main parts of the transmitting terminal 1001 and the receiving terminal 1002 will be described in detail together with the operation. First, the function and operation of the transmitting terminal 1001 will be described. The encoding device 1011 generates a hierarchical data sequence from the input video signal. As for the hierarchical method, one encoder outputs a plurality of encoded data having different resolutions and SN ratios, and a plurality of encoders outputs encoded sequences having different frame rates. Can be used, but the method is not specified here. The encoded data is sent to a data transmission unit 1012, where a data packet is generated,
A base sequence and an extended sequence are formed according to the coding layer and transmitted to the network 1021.

For example, in multicast, one transmission sequence corresponds to one multicast group.
At the same time, the data packet is
, And FEC data is generated based on the data packets of each series, and the FEC data is
4 and transmitted to the network 1021. Also one FEC in multicast
The data sequence corresponds to one multicast group. In the data transmission unit 1012, a sequence number (sequence number) and a time stamp (data transmission time information) are added to the data packet independently for each stream, and the FE
In the C data generation unit 1013, the sequence number and the number of packets of the data packet used for the FEC data are added as header information.

Next, the function and operation of the receiving terminal 1002 will be described. Only the sequence selected by reception sequence selecting section 1036 is received by data receiving section 1031. Here, a packet loss is detected from the sequence number added to the packet and reported to the reception sequence selection unit 1036.
The reception sequence selection unit 1036 totals the information of the reported packet loss, and switches the reception sequence at regular time intervals based on the information. The received data is sent to the error correction unit 1033 when FEC data is received, and restoration processing of a lost packet is performed. After the decoding device 1034 reconstructs the data packet into a decodable unit (for example, one frame), it decodes it into a video signal.

FIG. 20 is an explanatory diagram showing a conceptual example in which the program and related data of the present invention are supplied from a storage medium to the apparatus. The program and related data of the present invention are stored in a storage medium 2001 such as a floppy disk or a CD-ROM.
3 to be supplied. Thereafter, the program and related data of the present invention are temporarily installed from the storage medium 2001 to the hard disk, and
Or by directly loading the program into the RAM without installing the program on the hard disk, the program of the present invention can be executed.

In this case, when the program of the present invention is executed in the data communication apparatus according to the second embodiment of the present invention, the data communication apparatus (transmitting terminal 1001 , Receiving terminal 100
The program can be executed by supplying the program and related data of the present invention to 2) or storing the program and related data of the present invention in advance in the data communication device (the transmitting terminal 1001 and the receiving terminal 1002). Becomes

FIG. 19 is an explanatory diagram showing a configuration example of the storage contents of the storage medium storing the program and related data of the present invention. The storage medium of the present invention is, for example, volume information 1
901, directory information 1902, program execution file 1903, program-related data file 190
4 and the like. The program of the present invention
This is program-coded based on a flowchart shown in FIG.

The correspondence relationship between each component in the claims of the present invention and each unit of the data communication apparatus (transmitting terminal 1001, receiving terminal 1002) according to the second embodiment of the present invention is as follows. It is as follows. The encoding unit corresponds to the encoding device 1011 of the transmitting terminal 1001, the correction data generating unit corresponds to the FEC data generating unit 1013 of the transmitting terminal 1001, and the transmitting unit corresponds to the transmitting terminal 1001.
Data transmission unit 1012, FEC data transmission unit 1014
And the data packetizing means corresponds to the transmitting side terminal 1001.
The data packetizing means for correction corresponds to the FEC data transmitting unit 1 of the transmitting side terminal 1001.
014, the selection means corresponds to the reception sequence selection unit 1036 of the reception side terminal 1002, and the reception means corresponds to the reception side terminal 1
002 data receiving unit 1031, FEC data receiving unit 1
032, the status acquisition unit corresponds to the function of the reception sequence selection unit 1036 of the receiving terminal 1002. Further, the data communication device on the transmission side corresponds to the transmission side terminal 1001, the data communication device on the reception side corresponds to the reception side terminal 1002, and the network corresponds to the network 1021.

Next, the second embodiment of the present invention configured as described above is described.
Regarding the process of generating data for error correction in the data communication apparatus according to the embodiment of the present invention, Motion JPEG (Joint Photographic Experts
Group: color still image compression method), parity data as FEC data, and RT as the communication protocol.
P (Rapid Transport Protocol: high-speed protocol of transport layer) / UDP (User Datagram Protocol: one of multimedia protocols) / IP (Internet Pro
Tocol: a protocol of the third layer network layer of the OSI reference model) will be described with reference to FIGS.

Coding apparatus 1011 of transmitting side terminal 1001
Is input with one frame of video data, and JPEG compression is performed. The encoded data is packetized for transmission, where the packet size is the minimum MT of the channel.
U (Max Transfer Unit: Ethe
If the packet size is larger than 1500 bytes (rnet), a fragment is generated. Therefore, a plurality of packets are generated by dividing the encoded data in advance so that the generated packet size does not exceed the MTU. At this time, in order to minimize the overhead due to the header added at the time of transmission, division is performed from the beginning of the encoded data so that the packet size after division becomes equal to the MTU. An 8-byte RTP JPEG payload header (FIG. 1)
1) and a 12-byte RTP header (FIG. 12) are added to form one RTP packet (payload: information transferred in a cell).

The XOR (ex
One or a plurality of FEC data is generated by performing a bit operation such as exclusive OR). At this time, when the operation is performed on the entire RTP packet divided into MTU units as described above, the generation is performed. RTP to FEC data
By adding the FEC payload header and the RTP header, the FEC packet exceeds the MTU size and a fragment is generated (FIG. 13). In order to avoid this, FEC data having the same size as the original data is generated using only the JPEG data portion of the data packet (FIG. 1).
4). Therefore, the header size that can be added to this FEC data is the same 20 bytes as that of the original data, that is, the same 8 bytes as the JPEG payload header.
What is necessary is just to design the FEC payload header of e. The method will be described below.

First, header information required on the receiver side to reconstruct original coded data from data divided into a plurality of packets is as follows: RTP header: data length, marker bit, time stamp RTP JPEG Payload header: Image size, Q
Value and offset. These information must be restored when the lost packet is restored. Further, information necessary for restoring a lost packet using FEC is a sequence number and the number of packets for identifying a packet used for generating FEC data. These eight pieces of header information need to be restored.

First, among these information, the image size,
The Q value (parameter indicating the image compression ratio (the ratio of the data amount of the original still image to the compressed still image)) and the time stamp are constant within the same frame, and the values of the packets before and after the packet are received. Do not include it in the header because the value is available. Next, the offset is not included in the header if the data length and marker bit of the preceding and succeeding packets are obtained and can be restored using these. Therefore,
The information that needs to be included in the header is the data length, marker bits, the sequence number of the original data, and the number of packets.
Here, since the data length and the marker bits need to be equal to all the packets used for generating the FEC data, these XOR
Is included in the header. FIG. 15 shows the configuration of the FEC payload header. Note that this FEC packet generation technique is also applicable to the first embodiment.

Next, a method of selecting a reception sequence on the reception side in the data communication apparatus according to the second embodiment of the present invention will be described with reference to FIG. 16 taking as an example a case where layering is performed for a frame rate. This will be described in detail.

First, when starting the reception of the video, the receiver receives only the basic sequence (step S1601). In the case of multicast, this corresponds to joining a multicast group to which the basic sequence is transmitted, and transmission of a join message of IGMP is used for this. After starting the reception of the basic sequence, the receiving terminal 1002 (recipient) measures the packet loss rate at regular intervals (step S160).
2). If the packet loss rate is lower than the predetermined threshold value (NO in step S1603), the communication path is in a good condition, and the reception can be performed at almost the required reception rate. In consideration of increasing the reception rate, one of the extension sequences is newly received (steps S1607 to S1609). In step S1607, it is determined whether the FEC sequence is currently received. If it is determined that the FEC sequence is being received, the received FEC sequence is reduced by one (step S160).
8) One of the extended sequences is newly received (step S16)
09) On the other hand, if it is determined in step S1607 that no extension sequence has been received, one of the extension sequences is newly received (step S1609).

At this time, hierarchies are performed on the transmission side so that the frame data of the basic sequence is interpolated by the frame data of the extension sequence. In this case, the effective frame rate can be increased. Note that a time stamp added to a packet can be used to determine the frame order in merging.

On the other hand, if the measured packet loss rate exceeds the threshold (YES in step S1603), the requested reception rate is not achieved, and the effect of increasing the data reception rate by receiving the extended sequence is weakened. . Therefore, by newly receiving one FEC data sequence (steps S1604 to S1606), error resilience can be increased, and the effective reception rate can be increased by repairing the packet loss rate. Step S1604
It is determined whether or not an extension sequence is currently being received. If it is determined that the extension sequence is being received, the received extension sequence is set to 1
In step S1605, one of the FEC sequences is newly received (step S1606). On the other hand, when it is determined in step S1604 that the FEC sequence has not been received, the FE
One of the C sequences is newly received (step S160)
9).

As described above, by switching between increasing the reception data rate and increasing the error resilience at a certain threshold, the receiver can achieve appropriate reception quality.

Next, a method for determining the threshold value of the packet loss rate in the data communication apparatus according to the second embodiment of the present invention will be described with reference to FIG.

Factors for determining this threshold include the encoding method, compression ratio, frame size, MTU of communication channel, FE
For example, the redundancy of C and the like can be mentioned. Here, as the determination method, the transmitting side notifies the receiving side of parameters such as the frame size, the compression ratio, and the FEC redundancy, and the receiving side uses the notified parameters based on the notified parameters, for example, as shown in FIG. A corresponding threshold value is selected with reference to each table. It is assumed that such a table is created based on an actual measurement value or a simulation in an actual network and prepared in advance by the receiver.

Next, an example of grouping of transmission sequences in the data communication apparatus according to the second embodiment of the present invention will be described with reference to FIG.

In practicing the present invention, the number of basic sequences is not limited to one, but the multicast becomes large-scale and the bandwidth of the communication path to which the receiver is connected differs within a range of several digits. In the situation, as shown in FIG.
64 kbps, 384 kbps, LA for DN (Integrated Service Digital Network)
A plurality of groups such as 10 Mbps for N are formed for each line, and a transmission data sequence and an error correction data sequence are hierarchized in each group. The present invention is also practiced by each receiver participating in a group suitable for the communication environment in advance, and then appropriately selecting and receiving a sequence in the group.

As described above, according to the data communication apparatus of the second embodiment of the present invention, the transmitting terminal 10
01 is an encoding device 101 that encodes data hierarchically
1. FE for each hierarchically encoded data
An FEC data generation unit 1013 for generating C data; a data transmission unit 1012 for transmitting hierarchically encoded data and FEC data as different data sequences;
C data transmitting unit 1014, and a receiving side terminal 1002
Is a reception sequence selection unit 1036 that selects an appropriate data sequence from different data sequences based on the reception state, a data reception unit 1031 that receives the selected data sequence, and F
Because of the EC data receiving unit 1032, the following operations and effects are achieved.

In the above configuration, data transmitting section 1012 of transmitting terminal 1001 adds data transmission time information (time stamp) and sequence number (sequence number) to each data transmission unit in the data sequence and transmits the data. . In this case, the data sequence transmitted by the data transmission unit 1012 includes a basic sequence according to the layer of data encoding, one or more extended sequences that are higher layers of the basic sequence, and hierarchically encoded data. FEC generated for
This is an FEC data sequence according to the data.

The receiving terminal 1002 acquires the data loss rate (packet loss rate) as the receiving state. When the data loss rate is smaller than the predetermined threshold and the FEC data sequence is being received, the reception sequence selection unit 1036 of the receiving terminal 1002 reduces the received FEC data sequence and further receives the extension sequence, Is smaller than a predetermined threshold value and F
If the EC data sequence is not received, a higher extension sequence is received. If the data loss rate is larger than a predetermined threshold and the extension sequence is being received, the received extension sequence is reduced to reduce the FEC data sequence. Is received, and if the data loss rate is larger than the predetermined threshold and the extended sequence is not received, the FEC data sequence is further received.

Thus, in the second embodiment of the present invention, when performing data communication simultaneously with a large number of recipients via a network, each recipient responds to the communication environment and the instantaneous reception situation. In this case, good communication quality is realized by adaptively selecting the reception rate and the FEC data addition rate, that is, by selecting the reception rate and error tolerance suitable for each reception environment by each receiver. The excellent effect that can be obtained is obtained. This is particularly effective when delivering real-time moving image media in a multicast environment.

[Other Embodiments] The first embodiment of the present invention described above.
In the second to second embodiments, the type of network is not specified, but the present invention is highly effective when applied to a large-scale network such as the Internet.
The present invention is also applicable to data communication via various networks such as LAN other than the Internet.

In the above-described first embodiment of the present invention, a camera server has been described as an example of a transmitting terminal, but the present invention is not limited to this. For example, the present invention is also applicable to a case where a moving image file stored in an external storage device is played to provide services to a client.

Further, in the above-described second embodiment of the present invention, the case where one transmitting terminal and one receiving terminal are connected to the network as shown in FIG. 10 has been described as an example. The present invention is not limited to the configuration shown in FIG. 10 described above, and can be applied to a case where an arbitrary number of transmitting terminals and receiving terminals are connected to a network.

Note that the present invention is not limited to only the apparatus and method for realizing the above-described embodiment, but realizes the above-described embodiment on a computer (CPU or MPU) in the system or the apparatus. The present invention also includes a case where the above-described embodiment is realized by supplying a program code of software for operating the computer or the computer of the system or apparatus according to the program code to operate the various devices.

In this case, the program code of the software implements the functions of the above-described embodiment, and the program code itself and means for supplying the program code to the computer, specifically, the program A storage medium storing the code is included in the scope of the present invention.

As storage media for storing such program codes, for example, floppy disks, hard disks, optical disks, magneto-optical disks, CD-ROMs,
A magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

In addition to the case where the computer controls various devices in accordance with only the supplied program code to realize the functions of the above-described embodiment, the computer code is used to execute the OS running on the computer. Such a program code is also included in the scope of the present invention when the above-described embodiment is realized in cooperation with an (operating system) or another application.

Further, after the supplied program code is stored in a memory provided in a function expansion board of a computer or a function expansion unit connected to the computer, based on the instruction of the program code, the function expansion board, The present invention also includes a case where a CPU or the like provided in the function expansion unit performs part or all of the actual processing, and the above-described embodiment is realized by the processing.

[0140]

As described above, according to the data communication system of the first to thirteenth aspects, when performing data communication simultaneously with a large number of recipients via a network, each recipient has a different receiving environment. By selecting a reception rate and an error resistance suitable for the communication, an excellent effect that good communication quality can be realized can be obtained. This is particularly effective when delivering real-time moving image media in a multicast environment.

According to the data communication device described in claims 14 to 20, and the data communication device described in claims 21 to 30, a data communication system is constituted by the data communication device on the transmission side and the data communication device on the reception side. Thus, an excellent effect that good communication quality can be realized is obtained as described above. This is particularly effective when delivering real-time moving image media in a multicast environment.

According to the data communication method described in claims 31 to 43, the data communication method is applied to a data communication system (a data communication device on the transmission side and a data communication device on the reception side). In addition, an excellent effect that good communication quality can be realized is obtained.
This is particularly effective when delivering real-time moving image media in a multicast environment.

According to the storage medium of the present invention, the data transmission method is read from the storage medium and executed by the data communication system (the data communication device on the transmission side and the data communication device on the reception side). As described above, an excellent effect that good communication quality can be realized is obtained. This is particularly effective when delivering real-time moving image media in a multicast environment.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a data communication device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a data transmission process on the transmission terminal side of the data communication device according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing a data receiving process on the receiving terminal side of the data communication device according to the first embodiment of the present invention.

FIG. 4 is a flowchart showing a reception layer selection process in the reception terminal of the data communication device according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a transmission / reception state of hierarchized data according to the first embodiment of the present invention.

FIG. 6 is a block diagram showing a specific example in which the data communication device according to the first embodiment of the present invention is applied to a data communication system.

FIG. 7 is a flowchart illustrating data transmission processing in the camera server of the data communication system according to the first embodiment of the present invention.

FIG. 8 is a flowchart showing data reception processing in a client of the data communication system according to the first embodiment of the present invention.

FIG. 9 is a flowchart showing a reception layer changing process in the client according to the first embodiment of the present invention.

FIG. 10 is a block diagram illustrating a configuration example of a data communication device according to a second embodiment of the present invention.

FIG. 11 is an RTPJP according to the second embodiment of the present invention.
FIG. 4 is an explanatory diagram showing a configuration of an EG payload header.

FIG. 12 is an explanatory diagram showing a configuration of an RTP header according to a second embodiment of the present invention.

FIG. 13 is an explanatory diagram showing a case where a fragment occurs at the time of generating FEC data according to the second embodiment of the present invention.

FIG. 14 is an explanatory diagram illustrating an FEC data generation method according to a second embodiment of the present invention.

FIG. 15 is an explanatory diagram showing a configuration of an FEC payload header according to the second embodiment of the present invention.

FIG. 16 is a flowchart showing processing for selecting a reception sequence according to the second embodiment of the present invention.

FIG. 17 is an explanatory diagram showing a table for performing threshold value selection according to the second embodiment of the present invention.

FIG. 18 is an explanatory diagram showing an example of grouping of transmission sequences according to the second embodiment of the present invention.

FIG. 19 is an explanatory diagram showing a configuration example of storage contents of a storage medium storing a program and related data of the present invention.

FIG. 20 is an explanatory diagram showing a conceptual example in which a program and related data of the present invention are supplied from a storage medium to an apparatus.

[Explanation of symbols]

 1-1 Sending terminal 1-21, 1-22 Receiving terminal 1-3, 300 Network 1-1 1 Data generating unit 1-121 Layer 1 transmitting unit 1-122 Layer 2 transmitting unit 1-123 Layer 3 transmitting unit 1-124 Layer 4 transmitting section 1-125 Layer 5 transmitting section 1-211 Data receiving section 1-212 Data processing section 1-213 Receiving layer selecting section 1-124 Reception status monitoring section 10 Camera server 20 Client 100 Camera 103, 203 CPU 109, 209 Communication interface 208 Display device 1001 Transmission terminal 1002 Reception terminal 1010 Image capture device 1011 Encoding device 1012 Data transmission unit 1013 FEC data generation unit 1014 FEC data transmission unit 1031 Data reception unit 1032 FEC data reception unit 1033 Error correction 1034 decoder 1035 image display device 1036 receives sequence selection unit 1903 program execution file 1904 program associated data file 2001 storage media

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuki Futaki 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term (reference) 5C059 KK00 MA31 PP04 RB02 RB09 RC04 RC22 RF04 SS06 SS20 TA39 TA76 TC21 TD12 UA01 UA04 UA38 5K030 GA01 GA11 HB02 HB12 HB15 HB19 HC01 JA05 KA02 LA01 LD06 MB01 MB13 5K034 AA02 AA05 CC02 MM01 MM18 QQ08 9A001 CC04 CC06 EE04 HH27 JJ27 LL05

Claims (56)

[Claims] 1. A data communication system for transmitting and receiving data between a data communication device on a transmission side and a plurality of data communication devices on a reception side via a network, wherein the data communication device on the transmission side comprises: Encoding means for hierarchically encoding data to generate encoded data; and correction data generation for generating error correction data for each of the encoded data hierarchically encoded by the encoding means. Means, and transmission means for transmitting the hierarchically encoded data and the data for error correction as different data sequences, respectively, wherein the data communication device on the receiving side comprises: Selecting means for selecting an appropriate data series from the series based on the reception state; and receiving means for receiving the data series selected by the selecting means. Over data communication system. 2. A data sequence to be transmitted by said transmitting means, comprising: a basic sequence according to a hierarchy of encoding of said data; one or more extension sequences which are higher layers of said basic sequence; 2. The data communication system according to claim 1, wherein the data communication system is a correction data sequence corresponding to each correction data generated for the corrected data. 3. The data communication system according to claim 2, wherein said basic sequence is always selected from said data sequence by said selection means. 4. The data communication device on the transmitting side,
Data packetizing means for packetizing the encoded data hierarchically encoded by the encoding means to generate a data packet, and a correction data packet for generating an error correction packet using the error correction data The correction data generation means generates the error correction data using the data packet, and the transmission means converts the data packet and the error correction packet to the codes respectively. 2. The data communication system according to claim 1, wherein the data transmission is performed as a data sequence of coded data and a data sequence of the error correction data. 5. The data communication system according to claim 4, wherein said transmission means adds data transmission time information and a sequence number to each data packet in the data sequence and transmits the data packet. 6. The correction data generating means generates the error correction data by referring to a data packet of the hierarchically encoded data and using only an encoded data portion of the data packet, The correction data packetizing means generates a payload header including only information necessary at the time of error correction, and generates the error correction packet using the error correction data and the payload header. The data communication system according to claim 4, wherein 7. The data communication device on the receiving side further includes:
2. The data communication system according to claim 1, further comprising a status acquisition unit for acquiring the reception status. 8. The data communication system according to claim 7, wherein said status acquisition unit acquires a data loss rate, a transmission rate, and a reception rate as said reception status. 9. The data sequence of encoded data of a higher layer when the data loss rate is smaller than a predetermined threshold and the ratio between the transmission rate and the reception rate is larger than a predetermined threshold. Receiving an extended sequence, if the data loss rate is smaller than a predetermined threshold and the ratio between the transmission rate and the reception rate is smaller than a predetermined threshold, reduce the received data sequence for correction, and If the ratio of the transmission rate to the reception rate is greater than a predetermined threshold is greater than a predetermined threshold, further receive a data sequence for correction, the data loss rate is greater than a predetermined threshold and the transmission rate and the reception 9. The data communication system according to claim 8, wherein when the ratio with the rate is smaller than a predetermined threshold, the received extension sequences are sequentially reduced from an upper layer. 10. The apparatus according to claim 7, wherein said state obtaining means obtains a data loss rate as said reception state.
A data communication system as described. 11. When the data loss rate is smaller than a predetermined threshold value and the error correction data sequence is being received, the selection means reduces the received error correction data sequence and further increases the upper layer. When the extended sequence which is the data sequence of the coded data is received, and the data loss rate is smaller than a predetermined threshold and the data sequence for error correction is not received, the data sequence of the coded data of the higher layer is further Is received, and the data loss rate is greater than a predetermined threshold, and an extended sequence is being received, the received extended sequence is reduced to further receive the data sequence for error correction, and the data 11. The data communication system according to claim 10, wherein when the loss rate is larger than a predetermined threshold and an extension sequence is not received, the data sequence for error correction is further received. M 12. The data communication system according to claim 9, wherein the predetermined threshold is determined according to a coding method of the coded data. 13. A multicast communication for broadcasting data such as a moving image from a data communication device on the transmission side to a plurality of data communication devices on a reception side via a network such as the Internet. The data communication system according to claim 1. 14. A data communication device for transmitting data to a plurality of data communication devices on a receiving side via a network, comprising: an encoding unit configured to hierarchically encode the data to generate encoded data; Correction data generating means for generating error correction data for each of the encoded data hierarchically encoded by the encoding means; and the hierarchically encoded data and the error correction data. Transmitting means for transmitting the data for use as data sequences different from each other. 15. A data sequence to be transmitted by said transmitting means, comprising: a basic sequence corresponding to a layer of said data encoding, one or more extension sequences which are higher layers of said basic sequence, and said hierarchically encoded sequence. 15. The data communication apparatus according to claim 14, wherein the data communication apparatus is a data series for correction corresponding to each piece of correction data generated for the generated data. 16. The data communication device according to claim 15, wherein the basic sequence is always selected from the data sequence by the data communication device on the receiving side. 17. A data packetizing means for packetizing encoded data hierarchically encoded by said encoding means to generate a data packet, and an error correction packet using said error correction data. Correction data packetizing means for generating the error correction data, the correction data generation means generates the error correction data using the data packet, and the transmission means, the data packet and the error correction 15. The data communication apparatus according to claim 14, wherein a data packet is transmitted as a data sequence of the encoded data and a data sequence of the error correction data. 18. The data communication apparatus according to claim 17, wherein said transmission means adds data transmission time information and a sequence number to each data packet in said data sequence and transmits. 19. The correction data generating means generates the error correction data by referring to a data packet of the hierarchically encoded data and using only an encoded data portion of the data packet. The correction data packetizing means generates a payload header including only information necessary at the time of error correction, and generates the error correction packet using the error correction data and the payload header. The data communication device according to claim 17, wherein: 20. The method according to claim 14, wherein the method is applicable to multicast communication for broadcasting data such as a moving image to a plurality of data communication devices on the receiving side via a network such as the Internet. A data communication device according to claim 1. 21. A data communication device for receiving data from a data communication device on the transmission side via a network, based on a reception state from a data sequence transmitted from the data communication device on the transmission side. A data communication apparatus comprising: a selection unit that selects an appropriate data sequence; and a reception unit that receives the data sequence selected by the selection unit. 22. A data sequence transmitted from the data communication device on the transmission side includes a basic sequence according to a layer of encoding of the data, one or more extension sequences that are higher layers of the basic sequence, and 22. The data communication device according to claim 21, wherein the data communication device is a correction data sequence corresponding to each correction data generated for the hierarchically encoded data. 23. The data communication apparatus according to claim 22, wherein said basic sequence is always selected from said data sequence by said selecting means. 24. The data communication device according to claim 21, further comprising a status acquisition unit for acquiring the reception status. 25. The data communication apparatus according to claim 24, wherein said state acquisition means acquires a data loss rate, a transmission rate, and a reception rate as said reception state. 26. When the data loss rate is smaller than a predetermined threshold and the ratio between the transmission rate and the reception rate is larger than a predetermined threshold, the selection means is a data sequence of encoded data of a higher layer. Receiving an extended sequence, if the data loss rate is smaller than a predetermined threshold and the ratio between the transmission rate and the reception rate is smaller than a predetermined threshold, reduce the received data sequence for correction, and If the ratio of the transmission rate to the reception rate is greater than a predetermined threshold is greater than a predetermined threshold, further receive a data sequence for correction, the data loss rate is greater than a predetermined threshold and the transmission rate and the reception 26. The data communication apparatus according to claim 25, wherein when the ratio with the rate is smaller than a predetermined threshold, the received extension sequences are sequentially reduced from an upper layer. 27. The data processing apparatus according to claim 2, wherein the status acquisition unit acquires a data loss rate as the reception status.
5. The data communication device according to 4. 28. When the data loss rate is smaller than a predetermined threshold and the error correction data sequence is being received, the selection means reduces the received error correction data sequence and further increases the upper layer. When the extended sequence which is the data sequence of the coded data is received, and the data loss rate is smaller than a predetermined threshold and the data sequence for error correction is not received, the data sequence of the coded data of the higher layer is further Is received, and the data loss rate is greater than a predetermined threshold, and an extended sequence is being received, the received extended sequence is reduced to further receive the data sequence for error correction, and the data 28. The data communication apparatus according to claim 27, wherein when the loss rate is larger than a predetermined threshold value and an extension sequence is not received, the data sequence for error correction is further received. 29. The data communication device according to claim 26, wherein the predetermined threshold is determined according to a coding method of the coded data. 30. The method according to claim 21, wherein the transmission-side data communication apparatus is applicable to multicast communication in which data such as moving images is broadcast via a network such as the Internet. A data communication device according to claim 1. 31. A data communication method applied to a data communication system for transmitting and receiving data between a data communication device on a transmission side and a plurality of data communication devices on a reception side via a network, comprising: An encoding step of encoding the data hierarchically to generate encoded data,
A correction data generation step of generating error correction data for each of the coded data hierarchically coded in the coding step; and the hierarchically coded data and the error correction data. And a transmission step of transmitting the data as different data sequences, wherein the receiving-side data communication device selects an appropriate data sequence based on a reception state from the different data sequences, and Receiving the data sequence selected in the selecting step. 32. The data sequence transmitted in the transmitting step includes a basic sequence according to a layer of the data encoding, one or more extension sequences that are higher layers of the basic sequence, and the hierarchically encoded sequence. 32. The data communication method according to claim 31, wherein the data sequence is a correction data sequence corresponding to each correction data generated for the corrected data. 33. The data communication method according to claim 32, wherein the basic sequence is always selected from the data sequence in the selecting step. 34. The data communication device on the transmitting side, further comprising: a data packetizing step of packetizing the encoded data hierarchically encoded in the encoding step to generate a data packet; A data packetizing step for generating an error correction packet using the data of the data packet, wherein in the data generation step for correction, the data for error correction is generated using the data packet, and the transmission step 32. The data communication method according to claim 31, wherein the data packet and the error correction packet are transmitted as a data sequence of the encoded data and a data sequence of the error correction data, respectively. 35. The data communication method according to claim 34, wherein in the transmitting step, data transmission time information and a sequence number are added to each data packet in the data sequence and transmitted. 36. In the correction data generating step,
Referring to a data packet of the hierarchically encoded data and generating the error correction data using only the encoded data portion of the data packet; 35. The data communication method according to claim 34, further comprising: generating a payload header including only necessary information; and generating the error correction packet using the error correction data and the payload header. 37. The data communication method according to claim 31, wherein the data communication device on the receiving side further comprises a status acquisition step of acquiring the reception status. 38. The data communication method according to claim 37, wherein in the status acquisition step, a data loss rate, a transmission rate, and a reception rate are acquired as the reception status. 39. In the selecting step, if the data loss rate is smaller than a predetermined threshold and the ratio between the transmission rate and the reception rate is larger than a predetermined threshold, the data sequence is a data sequence of encoded data of a higher layer. Receiving the extended sequence,
If the data loss rate is smaller than a predetermined threshold and the ratio between the transmission rate and the reception rate is smaller than a predetermined threshold, reduce the data sequence for correction that is being received, and the data loss rate is larger than a predetermined threshold. When the ratio between the transmission rate and the reception rate is larger than a predetermined threshold, a data sequence for correction is further received, and the ratio between the transmission rate and the reception rate is larger than the data loss rate is larger than a predetermined threshold. 39. The data communication method according to claim 38, wherein, when the threshold value is smaller than the threshold value, the received extension sequence is sequentially reduced from an upper layer. 40. The data communication method according to claim 37, wherein in the status obtaining step, a data loss rate is obtained as the reception status. 41. In the selecting step, when the data loss rate is smaller than a predetermined threshold and the error correction data sequence is being received, the received error correction data sequence is reduced to further increase the upper layer. When the extended sequence which is the data sequence of the coded data is received, and the data loss rate is smaller than a predetermined threshold and the data sequence for error correction is not received, the data sequence of the coded data of the higher layer is further Is received, and the data loss rate is greater than a predetermined threshold, and an extended sequence is being received, the received extended sequence is reduced to further receive the data sequence for error correction, and the data 5. The method according to claim 4, wherein when the loss rate is larger than a predetermined threshold value and the extension sequence is not received, the data sequence for error correction is further received.
0 data communication method. 42. The data communication method according to claim 39, wherein the predetermined threshold is determined according to a coding method of the coded data. 43. Applicable to multicast communication for broadcasting data such as moving images from the data communication device on the transmission side to a plurality of data communication devices on the reception side via a network such as the Internet. Claim 31
43. The data communication method according to any one of claims to 42. 44. A program for executing a data communication method applied to a data communication system for transmitting and receiving data via a network between a data communication device on the transmitting side and a plurality of data communication devices on the receiving side. A storage medium readable by a computer, wherein the data communication method includes: an encoding step of encoding the data hierarchically to generate encoded data; and each of the encoding steps hierarchically encoded in the encoding step. A data generation step for generating error correction data for the encoded data, and transmitting the hierarchically encoded data and the error correction data as different data sequences. Controlling the transmitting step, and selecting an appropriate data sequence from the different data sequences based on a reception state. Steps and the storage medium characterized by having a receiving step of controlling so as to receive a selected data series in said selection step. 45. A data sequence to be transmitted and controlled in the transmitting step includes a basic sequence corresponding to a layer of the data encoding, one or more extension sequences that are higher layers of the basic sequence, and the hierarchically encoded code. The storage medium according to claim 44, wherein the storage medium is a correction data sequence corresponding to each correction data generated for the converted data. 46. The storage medium according to claim 45, wherein said basic sequence is always selected from said data sequence in said selecting step. 47. A data packetizing step of packetizing encoded data hierarchically encoded in the encoding step to generate a data packet, and an error correction packet using the error correction data. Generating a correction data packetizing step, wherein in the correction data generating step, the error correction data is generated using the data packet, and in the transmitting step, the data packet and the error correction data are generated. 45. The storage medium according to claim 44, wherein control is performed such that a packet for transmission is transmitted as a data sequence of said encoded data and a data sequence of said error correction data. 48. The storage medium according to claim 47, wherein in the transmitting step, control is performed such that data transmission time information and a sequence number are added to each data packet in the data sequence and transmitted. 49. In the correcting data generating step,
Referring to a data packet of the hierarchically encoded data and generating the error correction data using only the encoded data portion of the data packet; 48. The storage medium according to claim 47, wherein a payload header including only necessary information is generated, and the error correction packet is generated using the error correction data and the payload header. 50. The storage medium according to claim 44, further comprising a status acquisition step of acquiring said reception status. 51. The storage medium according to claim 50, wherein in the status obtaining step, a data loss rate, a transmission rate, and a reception rate are obtained as the reception status. 52. In the selecting step, when the data loss rate is smaller than a predetermined threshold and a ratio between the transmission rate and the reception rate is larger than a predetermined threshold, the data sequence is a data sequence of encoded data of a higher layer. Control to receive an extended sequence, if the data loss rate is smaller than a predetermined threshold and the ratio between the transmission rate and the reception rate is smaller than a predetermined threshold, reduce the correction data sequence being received, If the data loss rate is greater than a predetermined threshold and the ratio between the transmission rate and the reception rate is greater than a predetermined threshold, control is performed to further receive a data sequence for correction, and the data loss rate is a predetermined threshold. 6. The method according to claim 5, wherein when the ratio between the transmission rate and the reception rate is smaller than a predetermined threshold, the extension sequences to be received are sequentially reduced from an upper layer. The storage medium according to claim 1. 53. The storage medium according to claim 50, wherein in the status obtaining step, a data loss rate is obtained as the reception status. 54. In the selecting step, if the data loss rate is smaller than a predetermined threshold and the error correction data sequence is being received, the received error correction data sequence is reduced to further increase the upper layer. Control to receive an extended sequence which is a data sequence of the coded data, and when the data loss rate is smaller than a predetermined threshold and the data sequence for error correction is not received, the coding of the upper layer is further performed. Control to receive an extended sequence that is a data sequence of data, if the data loss rate is receiving an extended sequence greater than a predetermined threshold, reduce the received extended sequence to reduce the error correction data If the data loss rate is larger than a predetermined threshold and the extended sequence is not received, the data sequence for error correction is further received. The storage medium according to claim 53, wherein the storage medium is controlled as follows. 55. The storage medium according to claim 52, wherein said predetermined threshold value is determined according to an encoding method of said encoded data. 56. Applicable to a multicast communication for broadcasting data such as a moving image from a data communication device on the transmission side to a plurality of data communication devices on a reception side via a network such as the Internet. Claim 44
56. The storage medium according to any one of claims 55.