JP2001320407A - Data communication apparatus, data communication extension board and data communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data communication system that allows a host side to transmit/receive a RTCP(Real Time Control Protocol) packet even through the use of hardware such as a PCI(Personal Computer Interconnect) card or the like having a function of assembling/disassembling packets in compliance with the RTP(Real-time Transport Protocol). SOLUTION: An RTP card 60 is provided with an input output section 61 for real time data, a packet assembling/disassembling processing section 62 in compliance with the real time transport protocol, an RTP information management section 63 that manages RTP information with respect to the transmission/ reception of an RTP packet, and an interface section 64 that gives the RTP information managed by the RTP information management section 63 to a host side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a data communication apparatus for transmitting / receiving information via a network, an expansion board for data communication, and a data communication method.

[0002]

2. Description of the Related Art Conventionally, the Internet / Internet protocol has been used as a protocol for sharing resources on the Internet.
Protocol (IP: Internet Protocol), Transport
Control Protocol (TCP: Transport Control Pro
tocol) and User Datagram Protocol (UDP: User
Datagram Protocol) is used.

[0003] Connectionless (Con
IP, which is a packet transfer protocol, leaves the reliability assurance function, flow control function, and error recovery function to upper layers (transport layer and application layer). Therefore, packets in the IP layer may be lost or
The order may be wrong or duplicated. On the other hand, TCP having a reliability assurance function attaches a sequence number to each byte of the transferred data, and retransmits the data unless an acknowledgment (ACK) is sent from the receiving side. Furthermore, UDP, which provides a function of transmitting datagrams between applications, does not have a reliability assurance function for transferred data, a flow control function, and an error recovery function.
Instead, it is lighter than TCP and can transfer data with less overhead.

[0004] When an audio / video is viewed in a streaming manner such as a video conference or video on demand using an IP network, a transport protocol such as TCP for retransmitting at the time of an error cannot be generally used. Further, TCP is a protocol for one-to-one communication, and cannot transmit video to a plurality of parties. Therefore, UDP is used for such an application.

[0005] UDP is designed to allow an application process to transfer data to another application process on a remote machine with minimal overhead. Therefore, the information contained in the UDP header is only the source port number, the destination port number, the data length, and the checksum. Since there is no field for entering the number indicating the order of the packets in the TCP, different routes on the network are required. When the order of the packets is changed due to transmission through the network or the like, it is not possible to perform a process for returning the order to a correct state. In addition, neither TCP nor UDP has a field for entering time information such as a time stamp at the time of transmission.

Therefore, in an IP network such as the Internet, a real-time transport protocol (RTP: Rreal-time Transcription Protocol) is implemented as a transport protocol for realizing a real-time transport application for transmitting / receiving audio and video in real time.
sport Protocol) is recommended in RFC 1889.

[0007] RTP is located in the transport layer and is generally used over UDP with a real-time transport protocol (RTCP).

[0008] As shown in FIG.
It comprises a P header, a UDP header, an RTP header, and RTP data.

In the RTP header, version information (V: Ver
asion), padding (P: Padding), extension header (X: extens
presence / absence, transmission source (CRSC: Contoributing source)
Number, marker information (M: Marker), payload type (PT: Payl
oad Type), sequence number (Sequence Number), RTP
Timestamp, synchronization source (SSRC: Sychronization Sou
rce) identifier and contributing sender (CRSC: Contoributing so
urce) Each field for storing an identifier is provided.

[0010] Whereas RTP is a protocol for transmitting / receiving audio / video data itself, RTCP is
This is a protocol for periodically evaluating the line quality such as packet loss, delay jitter, round trip, etc., and transmitting / receiving information for realizing real-time communication corresponding to the band.

By using this RTCP, it is possible to perform dynamic processing such as estimating the state of the network and changing the transmission rate based on information fed back from the other party. In addition, since information indicating who is transmitting data and who is receiving it is also transmitted in the RTCP packet at the same time, it is possible to know the information of the current participant.

The RTCP packet is, as shown in FIG.
IP header, UDP header, RTCP header and RTC
It consists of P data.

The RTCP header contains version information (V: V
erasion), padding (P: Padding), report block
(RB: Report Block), RTCP type, report length, synchronization source of the sender of this packet (SSRC: Sychronization
Source) Each field for storing an identifier is provided.

The RTCP packet sent from the sender of the RTP data is, as shown in FIG.
As the RTCP data following the header, sender information (SR: Send) including a network time protocol (NTP) time stamp, an RTP time stamp, the number of transmitted RTP packets, and the number of transmitted RTP bytes.
ER Report) is stored, and recipient information (RR: Receiver
Report) is to be stored.

As shown in FIG. 11, the RTCP packet sent from the receiver of the RTP data is received information (RR: Receive) as RTCP data following the RTCP header.
er Report).

As shown in FIG. 12, the report block includes a synchronous sender (SSRC: Sychroniza
tion Source) Identifier, RTP loss rate, number of lost RTP packets, reception sequence number, average value of jitter of arrival time interval, transmission time of last received SR, time from last SR reception to transmission of this RR It is supposed to allow time.

Therefore, the sender manages the number of transmission RTP packets and the number of transmission RTP bytes when transmitting RTP data, and the receiver manages the number of reception RTP packets when receiving RTP data. It is necessary to manage information on the number of lost RTP packets and the jitter of arrival time.

Conventionally, RTP /
RTCP communication is performed by a host-side process 200 such as a personal computer, as shown in FIG. 13, for example. The host-side process 200 includes a network interface card 230 connected to a PCI bus 220 by a network card device driver 210.
Communication with an external network via the Internet.

In a personal computer, a PCI (Personal Computer Interconnect) bus,
An expansion board such as a SCSI (Small Computer System Interface) board or a network interface card can be connected via an SA (Industry Standard Archtecture) bus or the like, and thus can be used for various purposes.

[0020]

By the way, in order to process data at a higher speed, RTP packetization / depacketization processing is not performed by a host side process but by firmware on a PCI card. In the case of transmission / reception by the host side, RT
Since information relating to transmission / reception of the P packet cannot be managed, it is necessary to manage this on the PCI card side.

For example, in the case where the receiver of the RTP data can select whether to depacketize the RTP on the hardware side to reproduce a sound or a moving image or to save the data on the hard disk on the host side, etc. It is necessary that both the host side and the hardware side can manage information for RTCP and can appropriately acquire information.

In view of such a conventional situation, an object of the present invention is to transmit / receive RTCP packets on the host side even if hardware such as a PCI card having a function of packetizing and depacketizing RTP is used. It is an object of the present invention to provide a data communication device, a data communication expansion board, and a data communication method capable of performing communication using RTP / RTCP at a higher speed.

[0023]

A data communication apparatus according to the present invention comprises a host-side information processing apparatus, a real-time data input / output unit, and a real-time transport protocol (R).
A packetization / depacketization processing unit according to TP: Rreal-time Transport Protocol), an RTP information management unit for managing RTP information related to transmission / reception of RTP packets,
An interface unit for passing real-time data and RTP information to the host; and a data communication hardware connected to a bus of the host-side information processing device. It is determined whether the reception is performed by the host process or the data communication hardware. If the host process transmits / receives the RTP packet, the RTP information management database of the host process is updated while updating the RTP information management database. When the transmission / reception of the RTP packet is performed and the transmission time of the real-time transport protocol (RTCP: Rreal-Time Control Protocol) packet comes, based on the RTP information acquired from the RTP information management database on the host process side. Generates and sends RTCP packets, and RTP packets on the data communication hardware side When transmitting / receiving RTP packets, the RTP packet is transmitted / received while updating the RTP information management database on the data communication hardware side, and when the RTCP packet transmission time comes, the data communication hardware side Of the RTP information management database of the host process is copied to the RTP information management database of the host process, and the RTP information
It is characterized in that a TCP packet is generated and an RTCP packet is transmitted.

The present invention also relates to an expansion board for data communication connected to a bus of a host-side information processing apparatus, comprising: an input / output unit for real-time data; a real-time transport protocol (RTP: Rreal-time Transport Protocol)
Packetizing / depacketizing processing unit according to the above, and an RT for managing RTP information relating to transmission / reception of RTP packets
It is characterized by having a P information management unit and an interface unit for transferring the RTP information managed by the RTP information management unit to the host.

Further, the data communication method according to the present invention comprises:
Real-time transport protocol (RTP: Rreal
-time Transport Protocol) It is determined whether the transmission / reception of the packet is performed by the host-side process or the data communication hardware side. When the host-side process transmits / receives the RTP packet, the host process-side RTP
RTP packets are transmitted / received while updating the information management database.
When the transmission time of the protocol (RTCP: Rreal-Time Control Protocol) packet comes, the RT on the host process side
When an RTCP packet is generated and transmitted based on the RTP information obtained from the P information management database, and the RTP packet is transmitted / received on the data communication hardware side, the RTP information on the data communication hardware side is used. While updating the management database, transmission / reception of the RTP packet is performed. When the transmission time of the RTCP packet comes, the contents of the RTP information management database on the data communication hardware side are copied to the RTP information management database on the host process side. , RTP on the host process side
An RTCP packet is generated based on the RTP information acquired from the information management database, and the RTCP packet is transmitted.

[0026]

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

The present invention is applied to, for example, a network terminal device in a video conference system constructed by a plurality of network terminal devices 20A, 20B,... Connected via a network 10 as shown in FIG.

Network terminal device 20 according to the present invention
Is, for example, as shown in FIG.
0, PCI (Personal Computer Interconnect) bus 4
0 and a real-time transport protocol (RTP: Rreal-time T) connected to the host-side information processing device 20 via
(ransport Protocol) card 60.

The host-side information processing device 30 is a PCI
A network card device driver 35 and an RTP card device driver 36 for using the network interface card 50 and the RTP card 60 via the bus 40 are provided, and RTCP (RTP) is provided via the network interface card 50.
An RTCP / RTP transmission / reception processing unit 37 for transmitting / receiving packets is provided. RTCP / RTP above
In the transmission / reception processing unit 37, an RTP information management database 39 that manages RTP information related to transmission / reception of RTP packets is constructed.

As shown in FIG. 3, the RTP card 60 includes an input / output processing unit 61 for inputting / outputting real-time data such as audio and video.
And packetization / depacketization processing unit 6 according to RTP
2, an RTP information management unit 63 that manages RTP information related to transmission / reception of RTP packets, and a PCI interface unit 64 that passes the RTP packets and RTP information to the host side.

More specifically, as shown in FIG. 4, for example, the input / output processing unit 61 includes an MPEG (Moving Picture Exposure).
rts Group) Encoder 61A and MPEG decoder 62B
A video camera and a monitor device are externally connected to the MPEG encoder 61A and the MPEG decoder 62B. The packetizing / depacketizing processing unit 6
2 is M supplied from the MPEG encoder 61A.
An RTP packet generator 62A generates an RTP packet using PEG2 data as RTP data, and an RTP packet decomposer 62B decomposes the RTP packet supplied from the PCI interface 64. And
The RTP information management unit 63 updates the RTP information database each time one RTP packet is transmitted / received via the PCI interface unit 64.

In the network terminal device 20, the PTC mounted on the host-side information processing device 30 is used.
The processing is performed by the P module according to the procedure shown in the flowchart of FIG.

That is, when the PTCP module starts operation, first, the host-side information processing device 30
An RTP management information database 39 for P is created (step S1).

Next, the PTCP module acquires and holds information indicating whether the RTP packet is transmitted / received on the host side or the hardware side (step S).
2).

Next, the PTCP module determines whether transmission / reception of the RTP packet is performed on the hardware side based on the above information (step S3). Is used, the RTP information management unit 63 of the RTP card 60
Creates an RTP management information database (step S4).

Next, transmission / reception of the RTP packet is performed (step S5).

The PTCP module determines, based on the above information, whether the RTP packet is currently being transmitted / received on the hardware side (step S).
6).

When the result of the determination in step S6 is YES, that is, when the hardware is used, the PTCP module updates the RTP management information database of the RTP card 60 (step S7).
If the decision result in the above step S6 is NO, that is, if the host is used, the R
Update the TP management information database 39 (step S
8).

Next, the PTCP module determines whether or not the transmission time of the RTCP packet has come (Step S).
9) If the result of the determination is NO, that is, if the transmission time of the RTCP packet has not been reached, the process returns to step S5 to transmit / receive the RTP packet, and repeats the processing from step S5 to step S9.

When the result of the determination in step S9 is YES, that is, when the RTCP packet transmission time has come, the PTCP module determines whether or not the RTP packet transmission / reception was performed on the hardware side. (Step S10), and when the determination result is YES, that is, when the hardware is used, the contents of the RTP management information database of the RTP card 60 are stored in the RTP management information of the host-side information processing device 30. Copy to database 39 (step S1
1).

Further, the PTCP module acquires information from the RTP management information database 39 of the host-side information processing device 30, generates and transmits an RTCP packet (step S12). Thereafter, the process returns to step S5 to transmit / receive the RTP packet, and performs step S5.
Steps S5 through S11 are repeated.

That is, the network terminal device 20
When transmitting / receiving RTP packets in the host-side information processing device, the PTCP module in the RTP management information database 39 of the host-side information processing device 30
, While transmitting / receiving RTP packets,
When the transmission time of the RTCP packet comes, the RTP management information database 39 of the host-side information processing device 30
, And generates and transmits an RTCP packet.

In this case, as shown in FIG. 6, the RTP packet received by the host-side information processing device 30 via the network interface card 50 is
Audio and video information (MPEG data) included as data is stored in the information storage device 70 such as a hard disk by the host-side information processing device. In addition, the above R
The TP packet is sent to the PCI interface unit 64 of the RTP card 60 via the network card device driver 35 and the RTP card device driver 36. The RTP card 60 decomposes the RTP packet sent to the PCI interface unit 64 by an RTP packet decomposing unit 62B, and converts audio and video information (MPEG data) included in the RTP packet as RTP data into an MPEG decoder. The signal is decoded by 61B and output from a monitor device or speaker (not shown).

In the case where the RTP packet is transmitted / received by hardware, the PTCP module has:
RT by the RTP information management unit 63 on the RTP card 60 side
While updating the P management information database, transmission / reception of the RTP packet is performed, and as shown in FIG.
The contents of the RTP management information database on the host side are copied to the RTP management information database 39 of the host-side information processing device 30, information is obtained from the RTP management information database 39 of the host-side information processing device 30, and an RTCP packet is generated. To send.

In this case, the RTP card 60 generates MPEG data by the MPEG encoder 61A from audio and video information input by a video camera or the like (not shown), and converts an RTP packet having the MPEG data into RTP data into an RTP packet. Generated by the generation unit 62A. The RTP packet generated by the RTP packet generation unit 62A is sent from the PCI interface unit 64 to the network interface card 50 via the RTP card device driver 36 and the network card device driver 35, and is transmitted via the network interface card 50. Sent.
The RTP packet received via the network interface card 50 is sent to the PCI interface unit 64 of the RTP card 60 via the network card device driver 35 and the RTP card device driver 36. The above RTP card 60
Is the RT sent to the PCI interface unit 64
The P packet is decomposed by the RTP packet decomposing unit 62B, and audio and video information (MPEG data) included as RTP data in the RTP packet is decoded by the MPEG decoder 61B and output from a monitor device or speaker (not shown). .

[0046]

As described above, according to the present invention, the RTP
Even if hardware such as a PCI card having the function of packetizing and depacketizing the
RTP / RTC because P packets can be sent / received
Communication using P can be performed at higher speed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a video conference system constructed using a network terminal device to which the present invention is applied.

FIG. 2 is a diagram showing a configuration of a network terminal device according to the present invention.

FIG. 3 is a diagram showing a configuration of an RTP card provided in the network terminal device.

FIG. 4 is a diagram showing a specific configuration example of the RTP card.

FIG. 5 is a flowchart showing an operation of the network terminal device.

FIG. 6 is a diagram showing a communication state of the network terminal device.

FIG. 7 is a diagram showing a method of managing RTP information.

FIG. 8 is a diagram showing a configuration of an RTP packet.

FIG. 9 is a diagram showing a configuration of an RTCP packet.

FIG. 10 RTCP sent from a sender of RTP data
FIG. 3 is a diagram illustrating a configuration of a packet.

FIG. 11 RTCP sent from a receiver of RTP data
FIG. 3 is a diagram illustrating a configuration of a packet.

FIG. 12 RTCP sent from a receiver of RTP data
FIG. 4 is a diagram illustrating the contents of a report block stored in a packet.

FIG. 13 is a diagram showing a configuration of a conventional network terminal device.

[Explanation of symbols]

Reference Signs List 20 network terminal device, 30 host-side information processing device, 35 network card device driver, 3
6 RTP card device driver, 37 RTCP /
RTP transmission / reception processing units 37, 39 RTP information management database, 40 PCI bus, 50 network interface card, 60 RTP card, 61
Input / output processing unit, 61A MPEG encoder, 61B
MPEG decoder 62 Packetizer / depacketizer, 62A RT
P packet generator, 62B RTP packet decomposer, 6
3 RTP information management unit, 64 PCI interface unit, 70 information storage device

Claims (7)

[Claims] 1. A host-side information processing device, a real-time data input / output unit, and a real-time transport protocol (RTP).
l) a packetization / depacketization processing unit according to
An RTP information management unit that manages RTP information related to transmission / reception of P packets; and an interface unit that passes real-time data and RTP information to the host. The host-side information processing apparatus determines whether the transmission / reception of the RTP packet is performed by the host-side process or the data communication hardware, and the host-side process performs the transmission / reception of the RTP packet. To do so, the R on the host process side
RTP packets are transmitted / received while updating the TP information management database, and when the transmission time of a real-time transport protocol (RTCP: Rreal-Time Control Protocol) packet comes, the RTP information management database on the host process side When the RTP packet is generated and transmitted based on the RTP information obtained from the RTP information and the RTP packet is transmitted / received on the data communication hardware side, the RTP information management database on the data communication hardware side is updated. While the transmission / reception of the RTP packet is performed, when the transmission time of the RTCP packet comes, the contents of the RTP information management database on the data communication hardware side are copied to the RTP information management database on the host process side. RT on the side
A data communication device for generating an RTCP packet based on RTP information obtained from a P information management database and transmitting the generated RTCP packet. 2. The bus of the host-side information processing device has a P
The data communication device according to claim 1, wherein the data communication device is a CI (Personal Computer Interconnect) bus. 3. The data communication device according to claim 1, wherein the input / output unit of the data communication hardware includes an MPEG (Moving Picture Experts Group) encoder and an MPEG decoder. 4. An expansion board for data communication connected to a bus of a host-side information processing device, comprising: a real-time data input / output unit; a real-time transport protocol (RTP: Rreal).
-time Transport Protocol), an RTP information management unit that manages RTP information relating to transmission / reception of RTP packets, and an RTP information managed by the RTP information management unit to the host. An expansion board for data communication, comprising: an interface unit for transferring data. 5. The device according to claim 1, wherein the interface unit is a PCI (Per
5. The expansion board for data communication according to claim 4, wherein the expansion board is a sonal computer interconnect (BUS) interface. 6. The real-time data input / output unit includes an MPE
G (Moving Picture Experts Group) encoder and MPE
The expansion board for data communication according to claim 4, further comprising a G decoder. 7. It is determined whether transmission / reception of a real-time transport protocol (RTP) packet is performed by a host-side process or data communication hardware, and an RTP packet is determined by a host-side process. When transmitting / receiving RTP packets, while transmitting / receiving RTP packets while updating the RTP information management database on the host process side, the real-time transport protocol (RTCP: Rrea) is used.
l-Time Control Protocol) When the transmission time of the packet comes, an RTCP packet is generated and transmitted based on the RTP information obtained from the RTP information management database on the host process side, and the RTP packet is generated on the data communication hardware side. Send /
When performing reception, the data communication hardware R
The RTP packet is transmitted / received while updating the TP information management database, and when the transmission time of the RTCP packet comes, the contents of the RTP information management database on the data communication hardware side are transferred to the RTP information management database on the host process side. A data communication method, comprising: copying, generating an RTCP packet based on RTP information acquired from the RTP information management database on the host process side, and transmitting the RTCP packet.