JP2001186187A - Data communication equipment and communication control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide data communication equipment, capable of lowering the possibility that an RTCP control packet and an RTP data packet are discarded due to congestion. SOLUTION: When an RTCP control part 18 is notified from the a data communication quantity measuring part 6 that it is the time, when data communication quantity is small, the part 18 instructs an RTCP control packet generating part 10 for generating and transmitting a RTCP control packet, when the generation designated time of an RTCP control packet arrives. Meanwhile, when the part 18 is notified from the part 6 that it is the time, when the data communication quantity is large, the part 18 once holds the generation and transmission of the RTCP control packet, and instructs the part 10 to generate and transmit an RTCP control packet after being notified of the effect that it is the time, when data communication quantity is small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication apparatus and a communication control method for performing data communication by RTP via a network such as the Internet.

[0002]

2. Description of the Related Art In the Internet, audio and
RTP (Realtime Transp) is a standard protocol for real-time transmission of video and the like.
ortoProtocol).

[0003] RTP relates to a data protocol that defines a packet format for transmitting data such as audio and video, and transmission quality measured by using a time stamp and a sequence number given to an RTP data packet. Information (eg, packet round-trip time between sender and receiver, packet loss rate, jitter, etc.)
And a control protocol for exchanging information such as attribute information (e.g., name, address, mail address, telephone number, etc.) of the communication partner between the transmitting and receiving parties (the RTP control protocol is RTCP.
(Called RTP Control Protocol).

[0004] Note that RTP itself is not a protocol for guaranteeing QoS, but an upper layer (for example, an application) of RTP determines that the state of the network is congested based on information from a receiver, for example, and determines that data is congested. QoS control such as limiting the transmission speed can be performed.

[0005] Now, based on the RTP standard specification, RTP
Is generally realized as shown in FIGS. 4 and 5. FIG. 4 shows a configuration relating to transmission processing of the RTP data protocol and the control protocol, and FIG. 5 shows a configuration relating to reception processing of the RTP data protocol and the control protocol.

[0006] The RTCP information base 108 is a database for storing and managing information such as communication statistical information and communication participant attribute information collected in the own device and transmitted by RTCP.

In the transmission process of the data protocol,
The RTP data packet generation unit 104 converts the data generated by the encoding unit 102 such as audio and video into RTP data.
An RTP data packet is generated by putting it in the payload portion of the data packet and adding an RTP packet header, and transmits it to the lower network layer 120. Thereafter, the RTP data packet is sent out to the network. Further, statistical information and the like regarding the transmitted packet are recorded in the RTCP information base 108.

In the data protocol receiving process, the RTP data packet analyzing unit 134 analyzes the header of the received RTP pad, extracts the data loaded in the payload of the packet, and decodes audio and video data. To the conversion unit 132. Then, the encoded data is returned to the original data such as audio and video by the decoding unit 132. Further, the RTP data packet analysis unit 134 records statistical information and the like regarding the received packet in the RTCP information base 108.

In the control protocol receiving process, the RTCP control packet analyzing unit 140 analyzes the received RTCP control packet,
The result is recorded in the RTCP information base 108.

In the transmission process of the control protocol, the RTCP control packet generator 110 generates and sends out an RTCP control packet at an appropriate timing. However, the standard specification of the RTP specifies that the transmission interval of the RTCP control packet is adjusted so that the bandwidth occupied by the RTCP control packet is 5% of the bandwidth of the entire data communication.

For this purpose, generally, in the implementation of RTCP, a timer unit 116 for setting a transmission interval is provided, and when the timer unit 116 reaches a predetermined time, information recorded in the RTCP information base 108 is transmitted. An RTCP control packet is originally generated, transmitted to the lower network layer 120, and then transmitted to the network.

More specifically, in order to adjust the transmission interval, the average packet length measuring unit 112 transmits the transmitted RT.
Measure the packet length of the CP control packet and the received RTCP control packet, and
The average packet length (for example, the number of bytes or the number of packets) of the TCP control packet is measured. Then, when a certain RTCP control packet is transmitted, the average packet length measuring unit 112 measures the packet length to obtain a new average packet length,
The transmission interval adjustment unit 114 sets the communication bandwidth of RTCP (including transmission and reception) to 5% of the bandwidth of the entire RTP data communication based on the new average packet length.
The transmission interval of the next RTCP control packet is calculated, and the time of the timer unit 116 is set after the interval. When the timer section 116 reaches a predetermined time, an RTCP control packet is generated and transmitted as described above.

[0013]

Generally, in the Internet, packets that are being transmitted in a network are often discarded due to congestion. When performing communication on the Internet, it is indispensable to control communication in a terminal so as to minimize congestion. That is, when the amount of communication data flowing over the network is large, it is necessary to avoid congestion by reducing the amount of data as much as possible.

By the way, with regard to transmission of data such as audio and video which is mainly applied to RTP, the amount of data generated by an encoding unit for audio and video may be a variable rate. For example, in the MPEG2 video compression encoding method (ISO / IEC13818-2), there is a mode (VBR) for generating codes at a variable rate, in addition to a mode (CBR) for generating codes at a constant rate. In addition, the MPEG4 video compression encoding system (ISO /
In IEC14496-2), codes are basically generated at a variable rate.

Then, such a variable rate code is represented by R
In the case of transmission by TP, when an RTCP control packet is generated and transmitted when there is a large amount of code generated by an encoding unit such as audio and video, RTCP due to congestion is generated due to congestion.
There is a problem that the possibility that the TCP control packet or the RTP data packet is discarded increases.

The present invention has been made in view of the above circumstances, and provides a data communication apparatus and a communication control method capable of reducing the possibility that RTCP control packets and RTP data packets are discarded due to congestion. With the goal.

[0017]

SUMMARY OF THE INVENTION The present invention is a data communication apparatus for performing data communication by RTP (Real Time Transfer Protocol) via a network, and a first communication apparatus for transmitting and receiving RTP data packets via the network.
Transmission / reception means, second transmission / reception means for transmitting / receiving an RTCP (real-time control protocol) control packet via the network, and analysis means for analyzing the data amount of an RTP data packet to be transmitted from the own apparatus; Based on the information indicating the result of the analysis notified from the analyzing means, the RT
Control means for controlling the transmission timing of the CP control packet.

[0018] Preferably, the analyzing means, when notified by the obtaining means of information indicating that the data amount of the RTP data packet is large, is determined by the RT.
The control for suppressing the transmission of the CP control packet may be performed.

Preferably, a measuring means for measuring an average packet length of the RTCP control packet transmitted / received in the own device, and a bandwidth of the RTCP control packet transmitted / received in the own device are suppressed within a predetermined range. Based on the average packet length, R
Determining means for determining a transmission interval of the TCP control packet, wherein the control means determines the transmission interval of the RTCP control packet determined by the transmission interval determined by the determining means based on the information notified from the analysis means. Control for delaying the transmission timing may be performed.

Preferably, the control means is determined by the transmission interval determined by the determination means when information indicating that the data amount of the RTP data packet is large is notified from the analysis means. When the transmission timing has been reached, the transmission of the RTCP control packet may be delayed until information indicating that the data amount of the RTP data packet is small is notified from the analysis unit.

[0021] Preferably, the control means may be configured to notify the information indicating that the data amount of the RTP data packet is large from the analysis means,
When a predetermined time has elapsed since the transmission timing determined by the transmission interval determined by the determination means has been reached, the RTCP control packet may be transmitted.

[0022] Preferably, the analysis means includes an RTP.
By referring to the identification information added in the upper layer of the RTP included in the data packet, it may be determined whether the data amount of the RTP data packet is large or small.

[0023] Preferably, the analysis means includes the RTP
By actually measuring the data amount of the data packet, it may be determined whether the data amount of the RTP data packet is large or small.

Also, the present invention provides an R
A communication control method in a data communication device performing data communication by TP, wherein when transmitting an RTP data packet through the network, an analysis is performed on the data amount of the RTP data packet, and based on a result of the analysis, , The transmission timing of the RTCP control packet is determined, and the RTCP control packet is transmitted via the network according to the determination.

Note that the present invention relating to the apparatus is also realized as an invention relating to a method, and the present invention relating to a method is also realized as an invention relating to an apparatus.

The present invention relating to an apparatus or a method is provided for causing a computer to execute a procedure corresponding to the present invention (or for causing a computer to function as means corresponding to the present invention, or for causing a computer to correspond to the present invention). The present invention is also realized as a computer-readable recording medium in which a program for realizing the function of performing the above is recorded.

According to the present invention, it is possible to suppress transmission of an RTCP control packet during transmission of an RTP data packet having a large data amount, whereby the RTCP control packet or the RTP data packet is discarded due to congestion. The likelihood of the event being reduced.

[0028]

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

In the present embodiment, a case where an MPEG4 video compression code is transmitted by RTP will be described as an example.

FIG. 1 shows an example of the configuration of the data communication device of the present embodiment relating to the transmission processing of the RTP data protocol and the control protocol. FIG.
2 shows an example of a configuration relating to reception processing of an RTP data protocol and a control protocol in the data communication apparatus according to the present embodiment (the configuration relating to reception processing is basically the same as that of the related art).

The data communication device shown in FIGS. 1 and 2 is constituted by using, for example, a computer. Further, the data communication device executes an RTP data protocol and a control protocol with a data communication device which is a communication partner connected via a network such as the Internet and a LAN.

As shown in FIGS. 1 and 2, the data communication apparatus according to the present embodiment includes an MPEG4 video compression encoder (hereinafter, abbreviated as an encoder) 2 for generating an MPEG4 video compression code from MPEG4 video data. , RTP data packet generation unit 4, communication data amount measurement unit 6, RTCP
Information base 8, RTCP control packet generator 1
0, average packet length measurement unit 12, transmission interval adjustment unit 14,
Timer section 16, RTCP suppression section 18, MPEG4 video compression code decoding section (hereinafter abbreviated as decoding section) 32 for generating original MPEG4 video data by decoding MPEG4 video compression code, RTP data packet analysis section 3
4. An RTCP control packet analyzer 40 is provided.

Configuration of parts related to reception processing of RTCP information base 8 and data protocol and control protocol (RTP data packet analyzing unit 34, decoding unit 32, average packet length measuring unit 12, RTCP control packet analyzing unit 40 Etc.) and the operation are basically the same as those in the related art, and the description thereof is omitted below.

In the transmission process of the data protocol, the encoding unit 2 generates MPEG4 video compression code data having a variable length, and the RTP data packet generation unit 4 converts the compression encoded MPEG4 video data into RTP data.
An RTP data packet is generated by adding the packet to the payload portion of the data packet and adding a predetermined RTP packet header, and transmitting the generated RTP data packet to the lower network layer 20. The RTP data packet has a variable length according to the code amount of the encoded data. Further, as will be described in detail later, in the transmission process of the data protocol, the communication data amount measuring unit 6 measures the data amount of the transmitted RTP data packet, and reports the result to the RTCP.
The suppression unit 18 is notified (that is, RT
The CP suppressing unit 18 controls transmission of the RTCP control packet to the network based on the notification.)

In the transmission process of the control protocol, the RTCP control packet occupies 5% of the entire data communication bandwidth so that the bandwidth occupied by the RTCP control packet is 5%.
The transmission interval of the TCP control packet is adjusted in the same manner as in the related art, but the transmission of the RTCP control packet to the network is further controlled by the RTCP suppression unit 18 to avoid congestion.

Hereinafter, the suppression control for transmitting the RTCP control packet according to the present embodiment will be described in detail.

First, MPEG4 video compression encoding used as an example of a variable rate encoding method in the present embodiment will be described.

In MPEG4 video compression encoding,
There are three types of encoding for compressing each image frame of a video image: I encoding, P encoding, and B encoding. In the present embodiment, I
Encoding and P encoding are used.
The I-encoding compresses and encodes a frame independently of other frames, and compresses the spatial redundancy of video information. On the other hand, P encoding is
The compression encoding is performed after a difference between motion compensation frames is performed from an I frame existing before in time, and the temporal redundancy and the spatial redundancy of video information are compressed. The frame encoded by the P encoding is I
Since the temporal redundancy is smaller than that encoded by encoding, the code amount is smaller. Note that MP
In EG4 terms, each image frame that constitutes a video image is referred to as a VOP (Video Object Platform).
ne), a VO encoded in I encoding
P is called an I-VOP, and a frame encoded by P encoding is called a P-VOP. It is assumed that the code for one VOP is transferred in one RTP data packet. When decoding the MPEG4 video compression code, the original frame can be restored using the I-VOP alone, but the original frame is restored using the information of another frame for the P-VOP. Will be.

When the above encoding is performed, the I-VOP
When transferring P-VOP, the data traffic increases.
When data is transmitted, the amount of data communication is reduced, so that the state of large data communication and the state of small data communication are repeated. For example, the video image input to the encoding unit 2 has a speed of 10 frames per second and the I-VO
Assuming that P is generated every 0.5 seconds, five VOPs
Of I-VOPs with a large code amount and four I-VOPs with a small code amount are generated (and transmitted) (four P-VOPs between the I-VOP and the I-VOP). Will exist). The number of frames per second of a video image and the frequency of I-VOP generation may be fixed or variable in advance.

Now, the RTP data packet generator 4
One RTP data packet is generated for one VOP code for the code generated by the MPEG4 video compression encoding unit 2.

As described above, comparing the code amounts of the I-VOP and the P-VOP, the code amount of the P-VOP is generally smaller than that of the I-VOP because the compression in the time axis direction is performed. In the present embodiment, utilizing this fact, the data communication amount measuring unit 6
, Whether the MPEG4 video data included in the transmitted RTP data packet is an I-VOP
It analyzes whether the data is a VOP and determines whether the data amount is large or small (determines that the data amount is large for an I-VOP, and determines that the data amount is small for a P-VOP). Then, the result is notified to the RTCP suppressing unit 18.

More specifically, the MPEG-4 video code included in the RTP data packet is an I-VO
The determination as to whether it is P or P-VOP is made by MP
This is performed by analyzing the header added to the EG4 video code. That is, the header of each VOP of the MPEG4 video first has a length of 32 bits and a vo
There is a bit field called p_start_code, and the next two bits are vop_coding_ty
There is a field called pe. vop_cod
ing_type indicates the type of encoding of the VOP. When the value of the two bits is “00” in binary, it indicates that the encoding is I encoding, and when the value of “01” is “01”, it indicates that the encoding is P encoding. I have.
In this case, the data traffic measuring unit 6 uses the above vop_
The coding_type is checked, and when the value is “00”, the fact that the communication data amount is large is notified to the RTCP suppressing unit 18, and when the value is “01”, the RTC
The P suppression unit 18 is notified that the communication data amount is small.

Next, in order to adjust the transmission interval of the RTCP control packet so that the bandwidth occupied by the RTCP control packet is 5% of the bandwidth of the entire data communication, the transmission interval adjusting unit 14 controls the next RTCP control packet. The point at which the packet generation time is obtained and set in the timer unit 16 is the same as in the related art. However, in the present embodiment, the RTCP suppression unit 18 performs the RTCP based on the above notification from the data traffic measurement unit 6. Control for temporarily delaying the control packet generation time (that is, RTC
Control for temporarily suppressing the transmission of the P control packet).

That is, in order to adjust the bandwidth of the RTCP control packet, the average packet length measuring unit 1
In No. 2, the packet lengths of the transmitted RTCP control packet and the received RTCP control packet are measured, and the average packet length for all transmitted and received RTCP control packets is measured. And a certain RT
When the CP control packet is transmitted, the average packet length measuring unit 12 measures the packet length to obtain a new average packet length, and the transmission interval adjusting unit 14
Based on this new average packet length (including transmission and reception)
The communication bandwidth of the RTCP control packet is RTP
The next R should be 5% of the total data communication bandwidth.
The packet transmission interval of the TCP control packet is calculated, and the time of the timer unit 16 is set after the interval time. When the timer section 16 reaches a predetermined time, the RTCP suppression section 18 is notified of this fact. At that time, the RTCP suppression section 18 sends a notification from the data traffic measurement section 6 to the communication data volume. Depending on whether the notification is that the communication data amount is large or not,
It controls whether to generate and transmit a control packet or to delay generation and transmission of an RTCP control packet until a notification that the amount of communication data is small is received.

Hereinafter, the generation and transmission control of the RTCP control packet will be described in more detail.

First, the RTCP suppression unit 18 has two flags (F1, F2). The flag F1 is a flag indicating that the data amount measuring unit 6 has notified that the data communication amount is large. On the other hand, the flag F2
This flag indicates that the specified time of generation and transmission of the TCP control packet has been reached.

Here, FIG. 3 conceptually shows the relationship between the transmission of the RTP data packet and the flags F1 and F2 (for explaining the movement of the flag and the control contents, and is not necessarily the timing along the time axis). Is not exactly written).

When the RTCP suppression unit 18 is notified by the data traffic measurement unit 6 that the data traffic is high, the value of the flag F1 is set to "1" (FIG. 3A). t1). Further, when the data traffic measuring unit 6 notifies that the data traffic is small, the value of the flag F1 is set to “0” (FIG. 3A).
T2).

Then, as described above, the timer section 16
Has reached the RTCP control packet generation specified time, and the RTCP suppression unit 18 is notified of this fact. If the value of the flag F1 is set to “0” at that time, the RTCP control packet generation unit 10 is instructed to generate and transmit an RTCP control packet (see t3 in FIG. 3A).

On the other hand, the timer section 16 has reached the specified time of generation of the RTCP control packet,
If the value of the flag F1 is set to "1" at the time when the notification is sent to the suppression unit 18, the flag F2 is set to "1" and no instruction is given to the RTCP control packet generation unit 10 ( (See t4 in FIG. 3B). In this case, the process waits until the value of the flag F1 becomes "0".

When the RTCP suppressing unit 18 receives a notification indicating that the data traffic is low from the data traffic measuring unit 6, the value of the flag F 1 is set to “0”. At this time, if the value of the flag F2 is set to "1", the RTCP control packet generator 10 starts generating and transmitting the RTCP control packet, and then sets F2 to "0" (FIG. T5 and t6 of 3 (b)
reference).

As described above, according to the present embodiment, it is possible to suppress the transmission of the RTCP control packet at the time of transmitting the I-VOP having a large data amount, whereby the RTCP control packet or the RTP data packet is transmitted. The possibility of being discarded due to congestion can be reduced.

In the above description, the communication data amount measurement unit 6 is provided between the RTP data packet generation unit 4 and the lower network layer 20 in order to notify the RTCP suppression unit 18 about the communication data amount. The communication data amount measurement unit 6 is provided between the MPEG4 video compression encoding unit 2 and the RTP data packet generation unit 4 and measures the data amount by directly observing the data generated by the MPEG4 video compression encoding unit 2. It is also possible to carry out.

In the above description, the MPEG4 video compression code has been described as an example. Of course, the present invention can be applied to other variable-rate coding systems that handle video and / or audio.

Next, variations of the data communication device shown in FIGS. 1 and 2 will be described.

In the above description, the RTCP suppressing unit 18 performs the
When the value of the flag F1 is “1” at the time when the notification that the designated time for generating the P control packet has been reached is given, the generation and transmission of the RTCP control packet is suppressed, and the value of the flag F1 is set to “0”. Wait until it becomes RTC
A P control packet is generated and transmitted. By the way, depending on the system to which the present invention is applied,
Packets with very large amounts of data can be transmitted. In such a system, the suppression of RTCP control packets can be long. Therefore,
Elapsed time from the time when it was notified that the specified time of generation of the RTCP control packet was reached or the time when the flag F2 was set to "1" (see t7 in FIG. 3C), that is, the generation and transmission of the RTCP control packet If the time during which is suppressed exceeds a certain reference time (see t8 in FIG. 3C), even if the value of the flag F1 does not become “0”, the suppression is released and the RTCP control is performed. A packet may be generated and transmitted.

There are various methods for setting the reference time. For example, the reference time may be a preset value. Further, for example, the reference time is set to R
You may make it set dynamically in connection with the transmission interval of a TCP control packet. As a specific example, there is a method of multiplying a transmission interval between an RTCP control packet to be transmitted from now and an RTCP control packet transmitted immediately before by a certain coefficient as the reference time.

Each of the above functions can be implemented as software.

The present embodiment is also directed to a computer which records a program for causing a computer to execute predetermined means (or for causing a computer to function as predetermined means, or for causing a computer to realize predetermined functions). It can also be implemented as a readable recording medium.

The present invention is not limited to the above-described embodiments, but can be implemented with various modifications within the technical scope.

[0061]

According to the present invention, an RTP having a large data amount is provided.
It is possible to suppress the transmission of the RTCP control packet when transmitting the data packet, thereby reducing the possibility that the RTCP control packet or the RTP data packet is discarded due to congestion.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example regarding a transmission process of an RTP data protocol and a control protocol in a data communication device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a configuration regarding reception processing of an RTP data protocol and a control protocol in the data communication device according to the embodiment of the present invention;

FIG. 3 is a diagram conceptually illustrating control in the data communication device according to the embodiment of the present invention.

FIG. 4 is a diagram showing a configuration example regarding a transmission process of an RTP data protocol and a control protocol in a conventional data communication device.

FIG. 5 is a diagram showing an example of a configuration relating to reception processing of an RTP data protocol and a control protocol in a conventional data communication device.

[Explanation of symbols]

 2 ... MPEG4 video compression encoding unit 4 ... RTP data packet generation unit 6 ... Communication data amount measurement unit 8 ... RTCP information base 10 ... RTCP control packet generation unit 12 ... Average packet length measurement unit 14 ... Transmission interval adjustment unit 16 ... Timer Unit 18 RTCP suppression unit 32 MPEG4 video compression code decoding unit 34 Received RTP data packet analysis unit 40 Received RTCP control packet analysis unit

Claims (8)

[Claims] 1. A data communication apparatus for performing data communication by RTP (Real Time Transfer Protocol) via a network, comprising: first transmitting / receiving means for transmitting / receiving RTP data packets via the network; A) second transmission / reception means for transmitting / receiving a control packet via the network, analysis means for analyzing the data amount of the RTP data packet to be transmitted from its own device, and Control means for controlling the transmission timing of the RTCP control packet based on the information indicating the result. 2. The control means according to claim 1, wherein
2. The data according to claim 1, wherein when information indicating that the data amount of the TP data packet is large is notified, control is performed to suppress transmission of the RTCP control packet. 3. Communication device. 3. The RTCP transmitted and received by the own device.
Measuring means for measuring an average packet length of the control packet; and a transmission interval of the RTCP control packet based on the average packet length so as to keep the bandwidth of the RTCP control packet transmitted and received in the own device within a predetermined range. Determining means for determining the transmission timing of the RTCP control packet determined by the transmission interval determined by the determining means, based on the information notified from the analyzing means. The data communication device according to claim 1, wherein the data communication device performs the following. 4. The control means according to claim 1, wherein
When information indicating that the data amount of the TP data packet is large is notified and the transmission timing determined by the transmission interval determined by the determination means has been reached, the RTP data is transmitted from the analysis means. 4. The data communication apparatus according to claim 3, wherein the transmission of the RTCP control packet is delayed until information indicating that the data amount of the packet is small is notified. 5. The control means according to claim 1, wherein
Even if the information indicating that the data amount of the TP data packet is large is notified, a predetermined time has elapsed since the transmission timing determined by the transmission interval determined by the determination unit has been reached. The RT
The data communication device according to claim 4, wherein the data communication device transmits a CP control packet. 6. The analysis means refers to identification information added in an upper layer of RTP included in the RTP data packet to determine whether the data amount of the RTP data packet is large or small. The data communication device according to claim 2, 4 or 5, wherein it is determined whether there is any data. 7. The method according to claim 1, wherein the analyzing means determines whether the data amount of the RTP data packet is large or small by actually measuring the data amount of the RTP data packet. Item 6. The data communication device according to item 2, 4 or 5. 8. A communication control method in a data communication apparatus for performing data communication by RTP via a network, wherein when transmitting an RTP data packet via the network, an analysis on a data amount of the RTP data packet is performed. A communication control method comprising: determining a transmission timing of an RTCP control packet based on a result of the analysis; and transmitting the RTCP control packet via the network according to the determination.