JP6738306B2 - Data transfer device and data transfer method - Google Patents

Description

The present invention relates to a data transfer device and a data transfer method.

Due to the sophistication of devices, the usage of transmitting data streams such as audio and video is increasing.

There are RTP (Real Time Protocol), RTSP (Real Time Streaming Protocol), WebRTC (Web Real-Time Communication), etc. as protocols and frameworks for transmitting data streams such as voice and video in real time. In such protocols, the data is fragmented and transmitted.

On the other hand, from the viewpoint of convenience, protocols and frameworks such as HTTP (Hypertext Transfer Protocol), MQTT (Message Queue Telemetry Transport), and ROS (Robot Operating System) are also used.

For example, in HTTP1.1, Content-type:multipart can be used to send data in a stream. Figure 1 shows the sequence when using Content-type:multipart in HTTP1.1. In this method, in response to one request from the client, the server represents a plurality of resources (for example, a plurality of video frames) by using a specific boundary, and the data length (Content- (length) can be specified to continuously transmit data of a plurality of resources (see Non-Patent Documents 1 and 2).

RFC 1341, "MIME (Multipurpose Internet Mail Extensions): Mechanism for Specifying and Describing the Format of Internet Message Bodies", June 1992 RFC 2616, "Hypertext Transfer Protocol-HTTP 1.1", June 1999

In the future, it is expected that devices with data streams will spread and diversify the purpose of using the data streams. It is assumed that a protocol or framework with excellent real-time characteristics such as RTSP, RTP, WebRTC, etc. is used in the source that transmits the data stream. On the other hand, in the sink that receives the data stream, it is assumed that protocols and frameworks with excellent convenience such as HTTP, MQTT, and ROS are used. In such a usage mode, a device for performing protocol conversion between the source and the sink is required.

FIG. 2 is a diagram showing an example in which protocol conversion is required between the source and the sink. For example, when a protocol such as RTP is used at the source and data such as a video frame is fragmented and transmitted in detail, a header is added to each fragment and a fragment length is given. For example, when a protocol such as HTTP is used in the sink, it is necessary to first specify the data length in order to transmit the data in a stream. However, in order to specify the data length, it is necessary for the device between the source and the sink to buffer the data from the source in the memory and determine the total length of the data.

As a result, in the device between the source and the sink, the amount of memory used increases, the delay corresponding to the buffer increases, and the peaky traffic may be generated.

It is an object of the present invention to realize reduction of memory consumption, low latency, and packet pacing by estimating an appropriate data length when protocol conversion is required between a source and a sink. To do.

A data transfer device according to an aspect of the present invention is
A data transfer device for transferring data from a source to a sink,
A first protocol related function unit for receiving a fragment of data transmitted from the source using a first protocol for fragmenting and transmitting data;
A header information output function unit that estimates the data length of the data transmitted from the source based on the received meta information of the fragment and outputs header information indicating the estimated data length;
A second protocol in which the output header information is added to the first fragment in the data transmitted from the source and the data is transmitted to the sink by using a second protocol that specifies the data length and transmits the data. Protocol related function part,
It is characterized by having.

A data transfer method according to an aspect of the present invention is
A data transfer method in a data transfer device for transferring data from a source to a sink, comprising:
Receiving a fragment of data transmitted from the source using a first protocol for fragmenting and transmitting the data;
Estimating the data length of the data transmitted from the source based on the meta information of the received fragment, and outputting header information indicating the estimated data length,
A step of adding the output header information to a head fragment in the data transmitted from the source and transmitting the header information to the sink by using a second protocol for transmitting the data by designating a data length; ,
It is characterized by having.

According to the present invention, when the protocol conversion is required between the source and the sink, it is possible to realize a reduction in memory consumption, a low delay, and packet pacing by estimating an appropriate data length. It will be possible.

This is a sequence when using Content-type:multipart in HTTP1.1. It is a figure which shows the example which requires protocol conversion between a source and a sink. 1 is a schematic diagram of a data transfer device according to an embodiment of the present invention. It is a functional block diagram of the data transfer apparatus which concerns on the Example of this invention. It is a sequence diagram which shows the process of the data transfer apparatus which concerns on the Example of this invention. It is a flow chart which shows processing in a header information output function part. It is a figure which shows the hardware structural example of the data transfer apparatus which concerns on the Example of this invention.

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

FIG. 3 is a schematic diagram of a data transfer device 100 according to an embodiment of the present invention.

The data transfer device 100 is a network device that is located between a source and a sink and transfers data from the source to the sink. Protocol A such as RTP is used for the source and protocol B such as HTTP is used for the sink. The combination of protocol A and protocol B is not limited to RTP and HTTP, and another combination of protocols may be used. The protocol A is a protocol for fragmenting and transmitting data such as a video frame, a header including meta information is added to each fragment, and a fragment length is given. The protocol B is a protocol for transmitting data by designating a data length, and data having a designated data length is continuously transmitted.

The data transfer apparatus 100 estimates the data length based on the meta information of the fragment received from the source using the protocol A. The meta information includes fragment attribute information. For example, when the source transmits a video frame using RTP, the data transfer apparatus 100 receives from the time stamp and the sequence number included in the meta information. It is possible to recognize which fragment of which video frame the fragment is. Further, the fragment length can be recognized from the meta information. For example, the data transfer device 100 obtains a data length statistical value for each video frame and estimates a data length that is long enough to transfer the data transmitted from the source.

The data transfer apparatus 100 adds the estimated data length to the first fragment and transmits it to the sink. Since the data length that is long enough to transfer the data has been estimated, a portion that is less than the estimated data length occurs. This portion may be filled with a predetermined byte string.

Next, a specific configuration and operation of the data transfer device 100 will be described. FIG. 4 is a functional block diagram of the data transfer apparatus 100 according to the embodiment of the present invention, and FIG. 5 is a sequence diagram showing processing of the data transfer apparatus 100 according to the embodiment of the present invention.

As shown in FIG. 4, the data transfer apparatus 100 includes a protocol A related function unit 101 for communicating with a source using the protocol A, and a protocol B related function unit 102 for communicating with a sink using the protocol B. A transfer function unit 103 for transferring the data from the source to the sink and a header information output function unit 104 for outputting the header information when transferring the data from the source to the sink. Further, the data transfer device 100 may further include an external information acquisition unit 105 for acquiring external information that affects the data length. Note that FIG. 4 is merely an example of the configuration of the data transfer device 100, and for example, the transfer function unit 103 and the header information output function unit 104 may be realized as the same function unit.

First, the protocol A-related functional unit 101 receives a fragment of data transmitted from a source using the protocol A (S101). Meta information for identifying which fragment of what data is attached to this fragment. The protocol A related function unit 101 removes the header information of the protocol A added to the fragment, and transmits the fragment and the meta information of the fragment used for estimating the data length to the transfer function unit 103 (S102). .. The transfer function unit 103 transmits the meta information of the fragment to the header information output function unit 104 (S103).

The header information output function unit 104 estimates the data length of the data transmitted from the source based on the fragment meta information, and outputs the header information indicating the estimated data length. The header information is returned to the transfer function unit 103 (S104). The processing in the header information output function unit 104 will be described below.

FIG. 6 is a flowchart showing processing in the header information output function unit 104. When the header information output function unit 104 receives the fragment meta information, the header information output function unit 104 obtains the fragment number from the fragment meta information by using the function f that outputs the number of the fragment in the data (S201). However, the fragment number of the first fragment in the data is set to 0. For example, when RTP is used as the protocol A, the data to which the fragment belongs and the fragment number in the data can be obtained from the time stamp and the sequence number.

If the fragment number is not 0 (S202: YES), that is, if it is not the first fragment, it is not necessary to add a data length to the header information, and therefore header information=Null (S203).

When the fragment number is 0 (S202: NO), that is, when it is the first fragment, the header information output function unit 104 inputs fragment meta information, external information, etc., and outputs header information to be added. Header information is obtained using the function g for (S204). As described above, the header information output function unit 104 can recognize which fragment of which video frame the received fragment is and the fragment length, based on the meta information of the fragment. it can. The header information output function unit 104 obtains a statistical value of the data length from the fragment lengths of the fragments transmitted in the past from the source, and estimates a data length that is long enough to transfer the data transmitted from the source. .. For example, the average value and variance of the data lengths of N pieces of data transmitted in the past from the source may be obtained, and the average value+variance may be estimated as the data length.

Further, in order to estimate the data length, the external information acquired by the external information acquisition unit 105 that affects the data length may be further used, and the time may be further used. For example, when the source is a surveillance camera, the data compression rate differs between daytime and nighttime, and the data length may change. When such external information or time that affects the data length is given, the estimation accuracy of the data length can be improved.

The header information output function unit 104 can also use machine learning to estimate the data length. In machine learning, a model is constructed in advance using learning data such as past data length, external information, and time, and each time a fragment is received, the meta information of the fragment, external information, time, etc. are input and data is input. The length can be estimated.

Referring again to FIG. 5, the header information output function unit 104 transmits the header information indicating the data length estimated as described above to the transfer function unit 103 (S104). The header information output function unit 104 transmits the header information and the fragment to the protocol B related function unit 102 (S105). If the fragment is the first fragment, the header information is transmitted to the protocol B related function unit 102. However, if the fragment is not the first fragment, the header information is Null. Not sent. The protocol B-related function unit 102 attaches header information indicating the data length to the first fragment in the data transmitted from the source and transmits it to the sink (S106). Also, the protocol-B related function unit 102 fills a portion less than the estimated data length with a predetermined byte string and transmits it to the sink.

As described above, even when the protocol A is not used in the sink, the real-time property of the protocol A can be enjoyed in the sink.

<Effects of Examples of the Present Invention>
According to the embodiment of the present invention, the data transfer apparatus 100 estimates the data length when transferring the data received from the source to the sink, and then slightly increases the data length in order to obtain the necessary and sufficient data length. Determine the length. Then, the data length is specified and the data is transmitted to the sink in a stream. Therefore, the data received from the source can be transferred to the sink almost in real time, the memory consumption in the data transfer apparatus 100 can be reduced, and low delay and packet pacing can be realized. ..

Further, when external information or time that affects the data length is given, the estimation accuracy of the data length can be improved.

<Hardware configuration example>
FIG. 7 shows a hardware configuration example of the data transfer device 100 according to the embodiment of the present invention. The data transfer apparatus 100 may be a computer including a processor such as a CPU (Central Processing Unit) 151, a memory device 152 such as a RAM (Random Access Memory) and a ROM (Read Only Memory), a storage device 153 such as a hard disk, and the like. .. For example, the functions and processing of the data transfer device 100 are realized by the CPU 151 executing data or programs stored in the storage device 153 or the memory device 152. Input of data to the data transfer apparatus 100 may be performed from the input/output interface apparatus 154, and output of data from the data transfer apparatus 100 may be performed from the input/output interface apparatus 154.

<Supplement>
For convenience of explanation, the data transfer apparatus 100 according to the embodiment of the present invention has been described using a functional block diagram. However, the data transfer apparatus 100 according to the embodiment of the present invention is not limited to hardware, software, or a combination thereof. It may be realized in combination. For example, the embodiment of the present invention is a program that causes a computer to realize the functions of the data transfer device 100 according to the embodiment of the present invention, and a program that causes a computer to execute each procedure of the method according to the embodiment of the present invention. And the like. Moreover, each functional unit may be used in combination as necessary. Further, the methods according to the embodiments of the present invention may be performed in a different order from the order shown in the embodiments.

The method for reducing the memory consumption, reducing the delay, and pacing the packet by estimating the appropriate data length when the protocol conversion between the source and the sink is necessary has been described above. However, the present invention is not limited to the above embodiments, and various modifications and applications are possible within the scope of the claims.

100 data transfer device 101 protocol A related function unit 102 protocol B related function unit 103 transfer function unit 104 header information output function unit 105 external information acquisition unit

Claims (6)

A data transfer device for transferring data from a source to a sink,
A first protocol related function unit for receiving a fragment of data transmitted from the source using a first protocol for fragmenting and transmitting data;
A header information output function unit that estimates the data length of the data transmitted from the source based on the received meta information of the fragment and outputs header information indicating the estimated data length;
A second protocol in which the output header information is added to the first fragment in the data transmitted from the source and the data is transmitted to the sink by using a second protocol that specifies the data length and transmits the data. Protocol related function part,
Data transfer device having. The header information output function unit estimates a data length that is long enough to transfer data transmitted from the source,
The data transfer device according to claim 1, wherein the second protocol-related function unit fills a portion less than the estimated data length with a predetermined byte string. The said header information output function part estimates the data length of the data transmitted from the said source based on the average value and dispersion|variation of the data length of the data transmitted in the past from the said source. Data transfer device. Further comprising an external information acquisition unit for acquiring external information that affects the data length of the data transmitted from the source,
The data transfer device according to claim 1, wherein the header information output function unit estimates the data length of the data transmitted from the source, further based on the external information. The data according to any one of claims 1 to 4, wherein the header information output function unit estimates a data length of data transmitted from the source using a model constructed using learning data. Transfer device. A data transfer method in a data transfer device for transferring data from a source to a sink, comprising:
Receiving a fragment of data transmitted from the source using a first protocol for fragmenting and transmitting the data;
Estimating the data length of the data transmitted from the source based on the meta information of the received fragment, and outputting header information indicating the estimated data length,
A step of adding the output header information to a head fragment in the data transmitted from the source and transmitting the header information to the sink by using a second protocol for transmitting the data by designating a data length; ,
A data transfer method having.

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