JP2021087027A - Communication device and program - Google Patents

Abstract

To provide a communication device and program that select a grand master that operates stably from a plurality of grand masters, and communicates in PTP time synchronization.SOLUTION: A communication device 15 according to the present invention includes a PTP message transmission/reception unit 151 that transmits and receives PTP messages to and from other devices for which communication has been established, a grandmaster candidate selection unit 152, and a grand master selection unit 153. Each PTP message transmission/reception unit 151 obtains a PTP message from the other device, and each grandmaster candidate selection unit 152 extracts a parameter for selecting one from a plurality of grandmaster candidates on the basis of the PTP message. The grand master selection unit 153 selects one grand master according to a predetermined algorithm on the basis of the parameter, synchronizes the time, and notifies each PTP message transmission/reception unit 151 of the corresponding parameter.SELECTED DRAWING: Figure 1

Description

The present invention is a communication device that selects a ground master that operates stably in a synchronous communication system using an IP (Internet Protocol) network that operates a plurality of grand masters, and communicates with time synchronization based on PTP (Precision Time Protocol). And about the program.

Conventionally, a synchronous communication system for transmitting video / audio / synchronization information has been configured by a signal transmission method using SDI (for example, see Non-Patent Document 1) which is an interface for video and MADI which is an interface for audio. .. As a typical example of a synchronous communication system in the SDI / MADI signal format, for example, equipment related to program production can be configured as shown in FIG.

FIG. 5 is a block diagram showing a typical example of a conventional SDI / MADI signal format synchronous communication system. A device that transmits an image such as a camera 131 transmits the image as an SDI format signal (SDI signal) to the SDI router 121, and distributes the image from the SDI router 121 to a designated device such as a display 133 or a video switcher 134 for transmission. .. Further, a device that transmits audio such as a microphone 132 transmits the audio as a MADI format signal (MADI signal) to the SDI router 121 via the audio router 122, and the SDI router 121 transmits the display 133, the audio mixer 135, and the like. It is distributed and transmitted to the specified device of. The camera 131, the microphone 132, the display 133, the video switcher 134, the voice mixer 135, the SDI router 121, and the voice router 122 can be synchronized by the synchronization signal from the synchronization signal generator 110.

On the other hand, in recent years, Ethernet (registered trademark) frames (hereinafter, also referred to as "E frames" in the present specification) and IP packets (in the present specification, E frames and IP packets are collectively referred to as "IP-based packets". It is being studied to construct a synchronous communication system so as to store and transmit video, audio, and synchronization information in). As a typical example of a synchronous communication system constructed by an IP network using IP-based packets, for example, equipment related to program production can be configured as shown in FIG.

FIG. 6 is a block diagram showing a typical example of a synchronous communication system constructed by a conventional IP network. A device that transmits an image such as a camera 13-1 stores the image in an IP-based packet, transmits the image to a certain network switch 12, and transmits the image from the network switch 12 via another network switch 12 (shown in the figure). Or directly, based on the header information in the packet, the route is selected to a designated device such as the display 13-3 or the video switcher 13-4, and the image of the camera 13-1 or the like is transmitted. Further, a device that transmits voice such as a microphone 13-2 stores the voice in an IP-based packet, transmits the voice to a certain network switch 12, and transmits the voice from the network switch 12 via another network switch 12 ( (Not shown), or directly, based on the header information in the packet, the route is selected to a designated device such as the display 13-3 or the voice mixer 13-5, and the voice such as the microphone 13-2 is transmitted.

The network switch 12 is used for other network switches 12 (not shown) or for each device such as a camera 13-1, a microphone 13-2, a display 13-3, a video switcher 13-4, and a voice mixer 13-5. For example, it is connected by communication via a wired or wireless LAN (Local Area Network), and has a transmission / reception port for packet communication with each device. Further, the grand master device 10 and the network switch 12 are communicated and connected by master / slave time synchronization according to PTP. That is, the grand master device 10 packet-transmits the grand master (GM) clock of PTP for synchronizing the time of the network switch 12 as a PTP message (also referred to as “PTP synchronization message” or “announcement message”). .. Then, the network switch 12 operates in synchronization with the GM clock in a slave operation with the grand master device 10 as the master according to the PTP message. Similarly, the network switch 12 and each device such as the camera 13-1, the microphone 13-2, the display 13-3, the video switcher 13-4, and the voice mixer 13-5 communicate by master / slave time synchronization according to PTP. Be connected. That is, the network switch 12 packet-transmits a PTP message for synchronizing the time of each device such as the camera 13-1. Then, each device such as the camera 13-1 operates in synchronization with the GM clock in a slave operation with the network switch 12 as the master according to the PTP message.

As described above, the network switch 12 is configured as a communication device 15 that functions as a boundary clock device that operates in time synchronization of PTP with respect to the GM clock of the ground master device 10, and is configured as a communication device 15 such as a camera 13-1. Each device is configured as a communication device 15 that functions as an Ordinary Clock device that operates in time synchronization of PTP with respect to the GM clock. That is, the synchronization communication system shown in FIG. 6 performs time synchronization based on PTP in three layers of a GM clock, a boundary clock, and an ordinary clock. As a result, the synchronous communication system shown in FIG. 6 can maintain the synchronization between the clocks of each communication device 15 with the GM clock.

As described above, in recent years, it has been studied to replace the synchronous communication system composed of SDI and MADI with an IP network using a general IP-based packet. Synchronous communication systems based on IP networks are expected to reduce equipment costs because they are inexpensive and can increase transmission capacity. Further, for synchronization of each device in the synchronization communication system as shown in FIG. 5, a Black Burst signal (see, for example, Non-Patent Document 2) or a ternary Sync signal (see, for example, Non-Patent Document 3) is used by using a coaxial cable. It was transmitted and kept in sync. On the other hand, in a synchronous communication system as shown in FIG. 6 in which a conventional communication system is replaced with an IP network, each communication device 15 can be maintained by time synchronization based on PTP using the IP network. Therefore, in the synchronous communication system as shown in FIG. 6, a plurality of local synchronous communication systems are connected via the communication device 15 to form one synchronous communication system, and a plurality of grand masters are connected between the local synchronous communication systems. It is also possible to maintain the time synchronization of PTP based on one grand master selected from (see, for example, Non-Patent Document 4).

In Patent Document 1, as a communication device that performs an operation of selecting one grand master candidate from a plurality of grand master candidates, a message indicating the grand master candidate and its priority is acquired from another communication device. , The acquired priority message is compared with the priority of the grand master of the own communication device, and when the priority of the grand master candidate obtained from the other communication device is higher, the time of the other communication device and the auto communication with the time of the other communication device. A technique for calculating a difference from the time of a device and controlling the other communication device to be switched to the ground master of the own communication device when the difference is smaller than the threshold value is disclosed (see, for example, Patent Document 1). ).

Patent No. 6523589

SMPTE ST 292-1, “1.5 Gb / S Signal / Data Serial Interface”, [online], IEEE Xplore Digital Library, [Searched October 21, 1991], Internet <https://ieeexplore.ieee.org / document / 7291770> SMPTE ST 170, “2004 Television Composite Analog Video Signal NTSC for Studio Applications”, [online], IEEE Xplore Digital Library, [Searched October 21, 1991], Internet <https://ieeexplore.ieee.org/ document / 7291416> SMPTE ST 240, “1999 SMPTE Standard For Television 1125-Line High-Definition Production Systems Signal Parameters”, [online], IEEE Xplore Digital Library, [Searched October 21, 1991], Internet <https: // ieeexplore .ieee.org/document/7291461> SMPTE ST 2059-2, “2015 SMPTE Profile for Use of IEEE-1588 Precision Time Protocol in Professional Broadcast Applications”, [online], IEEE Xplore Digital Library, [Searched October 21, 1991], Internet <https: //ieeexplore.ieee.org/document/7291608>

By the way, for example, when using an IP networked synchronous communication system as shown in FIG. 6, local synchronization based on PTP is performed between the on-site equipment and the broadcasting station equipment at the relay site outside the broadcasting station. A communication system can be constructed, and each local synchronous communication system can be communicated and connected to form one synchronous communication system based on PTP as a whole. In this case, the time synchronization of PTP can be maintained between each local synchronization communication system based on one grand master selected from a plurality of grand masters, and the program production of the on-site equipment from the broadcasting station equipment (or broadcasting from the on-site equipment) can be maintained. It is possible to realize remote production that performs program production of station equipment).

For example, FIG. 7 is a block diagram showing a typical operation example when the synchronous communication system 1 based on PTP assumed from the prior art is operated individually without a connection between the broadcasting station equipment and the field equipment. Is.

In the synchronous communication system 1 shown in FIG. 7, in the broadcasting station equipment, the ground master device 10A and the network switch that operates in time synchronization of PTP with respect to the ground master (GM) clock (clock A) of PTP in the ground master device 10A. The boundary clock device 12A such as the above and the ordinary clock device 13A such as a camera that operates in time synchronization of PTP with respect to the GM clock (clock A) are connected by an IP network using an IP-based packet. Here, in order to synchronize the GPS time of the GPS (Global Positioning System) satellite 20 via the communication antenna 11A, the grand master device 10A is set to 0x20 as the time source defined by PTP. As a result, a GM clock (clock A) synchronized with the GPS time of the GPS satellite 20 is generated. The clocks of the ground master device 10A and the communication devices 15A constituting the boundary clock device 12A and the ordinary clock device 13A are synchronized with each other by master / slave time synchronization between the devices, and the PTP in the ground master device 10A is synchronized. PTP time synchronization can be performed in three layers based on the GM clock (clock A).

Further, in the synchronous communication system 1 shown in FIG. 7, in the field equipment, the ground master device 10B and the bounce of a network switch or the like that operates in synchronization with the PTP GM clock (clock B) in the ground master device 10B. The daily clock device 12B and the ordinary clock device 13B such as a camera that operates in time synchronization of PTP with respect to the GM clock (clock B) are connected by an IP network using IP-based packets. Here, in order to synchronize the GPS time of the GPS satellite 20 with the GPS satellite 20 via the communication antenna 11B, the grand master device 10B is set to 0x20 as a time synchronization source (timeSource) defined by PTP, whereby the GPS satellite 20 is set. A GM clock (clock B) synchronized with the GPS time of is generated. The clocks of the ground master device 10B and the communication devices 15B constituting the boundary clock device 12B and the ordinary clock device 13B are synchronized with each other by master / slave time synchronization between the devices, and the PTP in the ground master device 10B is synchronized. PTP time synchronization can be performed in three layers based on the GM clock (clock B).

By the way, in the synchronous communication system 1 shown in FIG. 7, the ground master devices 10A and 10B that generate the GM clock synchronized with the GPS time are installed and operated in the field equipment and the broadcasting station equipment, respectively. If a failure occurs in the GPS synchronization of the grand master device, it is desirable to configure the backup operation by using the GM clock from the other grand master device.

Therefore, as shown in FIG. 8, the boundary clock devices 12A and 12B can be connected so as to perform PTP time synchronization. FIG. 8 shows a typical operation example when the synchronous communication system 1 based on PTP assumed from the prior art is in a connected state so as to enable remote production of a broadcast program between the broadcasting station equipment and the field equipment. It is a block diagram which shows.

In the example shown in FIG. 8, the boundary clock device 12A is used as a master, the boundary clock device 12B is used as a slave, and the devices in the broadcasting station equipment are time-synchronized based on PTP with the clock A, and the on-site equipment is used using this clock A. An example of time synchronization of the devices in the device is shown. In this case, in the field equipment, the grand master device 10B becomes a master that passively operates on the clock A, and the boundary clock device 12B and the ordinary clock device 13B also operate on the clock A as master / slave time synchronization between the devices. .. That is, in the example shown in FIG. 8, it is possible to realize remote production in which a program is produced from the broadcasting station equipment to the on-site equipment.

Further, in the SDI / MADI signal format synchronous communication system as shown in FIG. 5, since the video and audio from the on-site equipment are not synchronized with the devices in the broadcasting station equipment, the broadcasting station equipment is used from the on-site equipment. Resynchronization processing is required when receiving video and audio, and there is a problem that synchronization shift may occur when performing remote production of broadcast programs. In such a case, the synchronization deviation can be eliminated by constructing the synchronization communication system 1 as shown in FIG.

That is, for each device illustrated in FIG. 6, a synchronous communication system 1 is constructed as shown in FIGS. 7 and 8, and the field equipment and the broadcasting station equipment each use the GM clock of PTP synchronized with the GPS time. Therefore, since the video and audio from the on-site equipment can be used as a signal synchronized with the device of the broadcasting station equipment, there is an advantage that the resynchronization process becomes unnecessary.

By the way, BMCA (Best Master Clock Algorithm) is defined in the standard SMPTE ST 2059-2 as an algorithm for selecting one from a plurality of grand master candidates of a plurality of PTPs (see, for example, Non-Patent Document 4).

FIG. 9 is a flowchart showing BMCA defined by the PTP standard SMPTE ST 2059-2 as an algorithm for selecting one from a plurality of grand master candidates (that is, GM clock candidates) of a plurality of PTPs. First, the standard SMPTE ST 2059-2 stipulates that the following parameters are included in the PTP message as a data set in order to select one from a plurality of grandmaster candidates of a plurality of PTPs.
The "GM clock identifier (Identity)" is an identifier unique to the GM clock.
The "first priority (priority1)" is the first priority for each GM clock set by the administrator of the synchronous communication system.
The "GM class" is a value indicating the traceability for each GM clock.
The "GM clock accuracy" is a value indicating the accuracy of each GM clock.
The "GM clock stability (offsetScaledLogVariance)" is a value indicating the stability of each GM clock.
The "second priority (priority2)" is a second priority for each GM clock set by the administrator of the synchronous communication system.
The "time source" is a set value indicating a synchronization source for each GM clock, and in this example, 0x20 is set to indicate GPS time synchronization.
The "number of boundary clocks (stepsRemoved)" is a value indicating the number of boundary clocks (that is, the number of boundary clock devices) in the path from each grandmaster device to the boundary clock device.

In the synchronous communication system 1 to which the boundary clock devices 12A and 12B shown in FIG. 8 are connected, each communication device 15A and 15B has a GM clock (clock A) of the PTP in the ground master device 10A and a PTP in the ground master device 10B. When one is selected from a plurality of GM clock candidates of the GM clock (clock B), the BMCA algorithm shown in FIG. 9 is applied as follows.

When the communication devices 15A and 15B acquire the PTP message including the data set of the clock A and the PTP message including the data set of the clock B, respectively, and compare each data set, first, the clock A and the clock B are compared. It is determined whether or not the GM clock identifiers (Identities) of the two GM clock candidates are the same (step S1).

When the GM clock identifiers (Identities) of the two GM clock candidates are the same (step S1: Yes), the communication devices 15A and 15B form a synchronous loop (GPS satellites shown in FIG. 8), although detailed description is omitted. 20. In order to avoid (loop formation of the ground master device 10A, boundary clock device 12A, boundary clock device 12B, and grand master device 10B), loop avoidance processing based on the magnitude of the number of boundary clocks (stepsRemoved) is executed ( Step S2).

When the GM clock identifiers (Identities) of the two GM clock candidates are different (step S1: No), the communication devices 15A and 15B compare the first priority (priority1) of the two GM clock candidates (step S3). ), The GM clock candidate having a small value of the first priority (priority1) is selected. For example, when the priority 1 of the clock A shows a higher priority than the priority 1 of the clock B (step S3: “A> B”), the process proceeds to step S9 and the clock B is selected. When the priority 1 of the clock A shows a lower priority than the priority 1 of the clock B (step S3: “A <B”), the process proceeds to step S10 and the clock A is selected.

On the other hand, when the priority 1 of the two GM clock candidates is the same (step S3: “A = B”), the communication devices 15A and 15B then compare the GM class (class) (step S4) and perform the GM class. Select GM clock candidates with a small (class) value. For example, when the class of the clock A shows a value larger than the class of the clock B (step S4: “A> B”), the process proceeds to step S9 and the clock B is selected. When the class of the clock A shows a smaller value lower than the class of the clock B (step S4: “A <B”), the process proceeds to step S10 and the clock A is selected.

On the other hand, when the GM classes of the two GM clock candidates are also the same (step S4: “A = B”), the communication devices 15A and 15B then compare the GM clock accuracy (step). S5), GM clock candidates having a small GM clock accuracy value are selected. For example, when the accuracy of the clock A is larger than the accuracy of the clock B (step S5: “A> B”), the process proceeds to step S9 and the clock B is selected. When the accuracy of the clock A is lower than the accuracy of the clock B (step S5: “A <B”), the process proceeds to step S10 and the clock A is selected.

On the other hand, when the GM clock accuracy of the two GM clock candidates is also the same, the communication devices 15A and 15B then compare the GM clock stability (offsetScaledLogVariance) (step S6) and perform the GM clock stability (step S6). Select GM clock candidates with a small offsetScaledLogVariance) value. For example, when the offsetScaledLogVariance of the clock A shows a value larger than the offsetScaledLogVariance of the clock B (step S6: “A> B”), the process proceeds to step S9 and the clock B is selected. When the offsetScaledLogVariance of the clock A shows a smaller value lower than the offsetScaledLogVariance of the clock B (step S6: “A <B”), the process proceeds to step S10 and the clock A is selected.

On the other hand, when the GM clock stability (offsetScaledLogVariance) of the two GM clock candidates is also the same, the communication devices 15A and 15B then compare the second priority (priority2) of the two GM clock candidates (step S7). ), The GM clock candidate having a small value of the second priority (priority2) is selected. For example, when the priority 2 of the clock A shows a higher priority than the priority 2 of the clock B (step S7: “A> B”), the process proceeds to step S9 and the clock B is selected. When the priority 2 of the clock A shows a lower priority than the priority 2 of the clock B (step S7: “A <B”), the process proceeds to step S10 and the clock A is selected.

On the other hand, when the second priority (priority2) of the two GM clock candidates is also the same, the communication devices 15A and 15B then compare the GM clock identifiers (Identities) (step S8) and perform the GM clock identifiers (step S8). Select GM clock candidates with a small Identity) value. For example, when the Identity of the clock A indicates a value larger than the Identity of the clock B (step S8: “A> B”), the process proceeds to step S9 and the clock B is selected. When the identity of the clock A shows a lower priority than the identity of the clock B (step S8: “A <B”), the process proceeds to step S10 and the clock A is selected.

As a result, in a synchronous communication system including a plurality of grand master devices, only the GM clock supplied by one grand master device determined by the BMCA algorithm among the plurality of grand master devices is used for time synchronization. Therefore, as in the synchronous communication system 1 shown in FIG. 8, when the on-site equipment and the broadcasting station equipment are connected so that they can be synchronized with each other by PTP, all the ground master devices of either the on-site equipment or the broadcasting station equipment are connected. The device will be time synchronized.

However, during the production period of the relay program by remote production, it is assumed that the connection (Fig. 8) and disconnection (Fig. 7) of the line between the on-site equipment and the broadcasting station equipment are frequently switched. In the synchronous communication system 1 shown in the above, in a mode in which the communication devices 15A and 15B operate by applying the BMCA algorithm shown in FIG. 9, the connection / disconnection of the line between the field equipment and the broadcasting station equipment is switched. The grand master, which is the time synchronization destination, is switched every time, and there is room for improvement from the viewpoint of stable operation.

The technique shown in Patent Document 1 does not change the grandmaster even if it is selected by BMCA when a new grandmaster candidate is connected and the quality of the provision time does not meet the threshold value. Become. Therefore, since the behavior changes depending on the setting of the threshold value, it is difficult to apply it to the synchronous communication system 1 shown in FIG. 8, which is expected to be used in various environments.

Therefore, in view of the above problems, an object of the present invention is to select a grandmaster that operates stably from a plurality of grandmasters in a synchronous communication system using an IP network that operates a plurality of grandmasters, and to use PTP. It is an object of the present invention to provide a communication device and a program for communicating in time synchronization.

The communication device of the present invention is a synchronous communication system using an IP network including a plurality of grand masters, selects a ground master that operates stably from the plurality of grand masters, and uses a time based on PTP (Precision Time Protocol). A communication device that communicates synchronously, and is provided in each of a plurality of transmission / reception ports for transmitting / receiving PTP messages using IP-based packets to each of a plurality of other devices for which communication has been established. A message transmission / reception unit, a grand master candidate selection unit, and a grand master selection unit that selects one of the plurality of grand masters are provided, and each of the PTP message transmission / reception units is a PTP message from another device connected by communication. And output to the corresponding grandmaster candidate selection unit, and the grandmaster selection unit notifies the parameters of the selected grandmaster, and sends a PTP message containing the parameters of the selected grandmaster. Each of the grand master candidate selection units has a means for transmitting to other devices connected by communication, and each of the grand master candidate selection units decodes a PTP message acquired from the corresponding PTP message transmission / reception unit and selects a grand master candidate. Extract Identity, priority1, class, accuracy, offsetScaledLogVariance, priority2, timeSource, and stepsRemoved specified in the PTP standard as parameters for performing operation and selecting one from multiple Grand Master candidates of PTP. It has a means to output to the grand master selection unit, and the grand master selection unit compares two grand master candidates according to a predetermined algorithm based on the parameters, and finally selects one grand master. It is characterized in that it has means for notifying each of the PTP message transmission / reception units of the parameters of the selected grand master by synchronizing the time.

Further, in the communication device of the present invention, the grand master selection unit has a difference in identity as a comparison of parameters of two grand master candidates as the predetermined algorithm, and priority1, class, accuracy, offsetScaledLogVariance, and priority2 are the same. When the timeSource is, the identity comparison of timeSource is performed, and when the timeSource is the same, the magnitude of each stepsRemoved is compared to select the grand master candidate with small stepsRemoved, and there is a difference in timeSource, or the magnitude of stepsRemoved is compared. When there is no difference, one grand master candidate is selected by comparing the size of Identity.

Further, in the communication device of the present invention, each of the plurality of grandmasters is set with a value indicating GPS time synchronization as the timeSource, and operates based on different grandmasters in GPS time synchronization by the predetermined algorithm. It is characterized in that it is configured to enable connection / disconnection of a line to another device at an arbitrary time.

Further, the program of the present invention is configured as a program for causing the computer to function as the communication device of the present invention.

According to the present invention, in a synchronous communication system using an IP network that operates a plurality of grand masters, each communication device can select a grand master that operates more stably as GPS time synchronization, and is in the synchronous communication system. Stable operation will be achieved even when the connection / disconnection of the line is frequently switched.

It is a block diagram which shows the schematic structure of the communication apparatus based on PTP of one Example by this invention. A flowchart showing an improved algorithm of BMCA defined by the PTP standard SMPTE ST 2059-2 as an algorithm for selecting one from a plurality of PTP grandmasters in a communication device based on PTP according to the present invention. is there. As a synchronous communication system based on PTP of one embodiment according to the present invention, a typical operation example that enables remote production of a broadcast program even when one of the broadcast station equipment and the field equipment is in a GPS synchronization failure state. It is a block diagram which shows. As a synchronous communication system based on PTP of one embodiment according to the present invention, both the broadcasting station equipment and the field equipment are in a GPS synchronized state, and the connection / disconnection of the line between the broadcasting station equipment and the field equipment can be switched. It is a block diagram which shows the typical operation example which enables the remote production of a broadcast program by making stable operation even when it is performed frequently. It is a block diagram which shows the typical example of the synchronous communication system of the conventional SDI / MADI signal type. It is a block diagram which shows the typical example of the synchronous communication system constructed by the IP network which uses the conventional IP-based packet. It is a block diagram which shows the typical operation example when there is no connection between a broadcasting station equipment and field equipment, and it operates individually as a synchronous communication system based on PTP which is assumed from the prior art. As a PTP-based synchronous communication system assumed from the prior art, a block diagram showing a typical operation example when a connection state is established so as to enable remote production of a broadcast program between a broadcasting station equipment and a field equipment. is there. It is a flowchart which shows BMCA defined by PTP standard SMPTE ST 2059-2 as an algorithm which selects one from a plurality of grandmaster candidates of a plurality of PTPs.

Hereinafter, the PTP-based communication device 15 and the synchronous communication system 1 according to the embodiment of the present invention will be described in order with reference to FIGS. 1 to 4. Regarding FIGS. 1 to 4, the same components as those shown in FIGS. 6 to 9 are designated by the same reference numbers.

(Communication device)
FIG. 1 is a block diagram showing a schematic configuration of a communication device 15 based on the PTP of one embodiment according to the present invention. The communication device 15 can be used as the communication device 15 shown in FIG. 6 and can be applied as the communication devices 15A and 15B of the synchronous communication system 1 shown in FIGS. 7 and 8. This will be described with reference to FIGS. 3 and 4.

As shown in FIG. 1, the communication device 15 of this embodiment is a boundary clock device or an ordinary clock device that operates in time synchronization of PTP included in a synchronization communication system 1 constructed by an IP network, and is a communication device. To send and receive PTP messages using IP-based packets to each of the N (N ≧ 2) other devices such as the Grand Master device and the other devices that have established communication. The PTP message transmission / reception unit 151, the grand master candidate selection unit 152, and the grand master, which have N transmission / reception ports P1, P2, ..., Pn and are provided in the N transmission / reception ports P1, P2, ..., Pn, respectively. It includes a selection unit 153. Note that the communication device 15 shown in FIG. 1 shows only a functional unit related to time synchronization control based on PTP that can be applied to a boundary clock device such as a network switch or an ordinary clock device such as a camera. The functional parts related to the generation, transmission, reception, etc. of packets such as video or audio are not shown because they are not the gist of the present invention.

Each PTP message transmission / reception unit 151 acquires a PTP message from another device connected by communication and outputs the PTP message to the corresponding grandmaster candidate selection unit 152, and the grandmaster selection unit 153 selected from the grandmaster selection unit 153. It has a function of receiving notification of parameters and transmitting a PTP message including the parameters of the selected grandmaster to other devices connected by communication. The operation of transmitting and receiving PTP messages on each transmission / reception port Pn is the same as that of the prior art for performing PTP time synchronization defined by the PTP standard SMPTE ST 2059-2, and the description thereof will be omitted.

Each grand master candidate selection unit 152 performs an operation of decoding a PTP message acquired from the corresponding PTP message transmission / reception unit 151 and selecting a grand master candidate, and selects one from a plurality of PTP grand master candidates. GM clock identifier (Identity), first priority (priority1), GM class (class), GM clock accuracy (accuracy), GM clock stability (offsetScaledLogVariance) specified in the PTP standard SMPTE ST 2059-2 as parameters. ), The second priority (priority2), the time synchronization source (timeSource), and the number of boundary clocks (stepsRemoved) are extracted and output to the grand master selection unit 153. The operation of selecting a grand master candidate from the PTP message on each transmission / reception port Pn is the same as the conventional technique for performing PTP time synchronization specified in the PTP standard SMPTE ST 2059-2. Omit.

As described above, the standard SMPTE ST 2059-2 stipulates that the following parameters for selecting one from a plurality of grandmaster candidates of PTP are included in the PTP message as a data set.
The "GM clock identifier (Identity)" is an identifier unique to the GM clock.
The "first priority (priority1)" is the first priority for each GM clock set by the administrator of the synchronous communication system.
The "GM class" is a value indicating the traceability for each GM clock.
The "GM clock accuracy" is a value indicating the accuracy of each GM clock.
The "GM clock stability (offsetScaledLogVariance)" is a value indicating the stability of each GM clock.
The "second priority (priority2)" is a second priority for each GM clock set by the administrator of the synchronous communication system.
The "time source" is a set value indicating a synchronization source for each GM clock, and in this example, 0x20 is set to indicate GPS time synchronization.
The "number of boundary clocks (stepsRemoved)" is a value indicating the number of boundary clocks (that is, the number of boundary clock devices) in the path from each grandmaster device to the boundary clock device.

The grand master selection unit 153 grounds a plurality of grand master candidates obtained from each PTP message transmission / reception unit 151 according to an algorithm improved from BMCA defined in the PTP standard SMPTE ST 2059-2 based on the above parameters. Two master candidates are compared, and one grand master candidate is finally selected. Then, the grand master selection unit 153 sets one selected grand master candidate as the grand master, synchronizes the time with the grand master, and notifies each PTP message transmission / reception unit 151 of the parameters of the selected grand master. Upon receiving this notification, each PTP message transmission / reception unit 151 transmits a PTP message including the parameters of the selected grand master to other devices that have been communicated with each other.

Here, the grand master selection unit 153 is an improved algorithm of the BMCA defined by the PTP standard SMPTE ST 2059-2, which will be described later with reference to FIG. 2, as a comparison of the parameters of the two grand master candidates. , GM clock identifier (Identity), 1st priority (priority1), GM class (class), GM clock accuracy (accuracy), GM clock stability (offsetScaledLogVariance), 2nd priority (priority2) When the time synchronization sources (timeSource) are the same, the identity comparison of the time source (timeSource) is performed, and when the time synchronization sources (timeSource) are the same, the magnitude of each boundary clock number (stepsRemoved) is compared and the boundary clock number (boundary clock number) ( Select a grand master candidate with a small stepsRemoved) and compare the size of the GM clock identifier (Identity) when there is a difference in the time source (timeSource) or there is no difference in the size comparison of the number of boundary clocks (stepsRemoved). Select one Grand Master candidate with.

(Operation of communication device)
FIG. 2 shows the PTP standard SMPTE ST 2059 as an algorithm for selecting one from a plurality of grand master candidates (that is, GM clock candidates) of a plurality of PTPs in the communication device 15 based on the PTP of one embodiment according to the present invention. It is a flowchart which shows the algorithm which improved the BMCA specified by -2.

The processing of steps S1 to S7 in FIG. 2 is the same as that of BMCA shown in FIG.

That is, when the communication device 15 of the present embodiment acquires the PTP message including the data set of the clock A and the PTP message including the data set of the clock B, respectively, and compares each data set, first, the clock A and the communication device 15 It is determined whether or not the GM clock identifiers (Identities) of the two GM clock candidates of the clock B are the same (step S1).

When the GM clock identifiers (Identities) of the two GM clock candidates are the same (step S1: Yes), the communication device 15 of the present embodiment forms a synchronous loop (GPS shown in FIG. 8), although detailed description is omitted. In order to avoid the loop formation of the satellite 20, the grand master device 10A, the boundary clock device 12A, the boundary clock device 12B, and the grand master device 10B), the loop avoidance process based on the magnitude of the boundary clock number (stepsRemoved) is executed. (Step S2).

When the GM clock identifiers (Identities) of the two GM clock candidates are different (step S1: No), the communication device 15 of this embodiment compares the first priority (priority 1) of the two GM clock candidates (step). S3), a GM clock candidate having a small value of the first priority (priority1) is selected.

On the other hand, when the priority 1 of the two GM clock candidates is the same (step S3: “A = B”), the communication device 15 of this embodiment then compares the GM class (class) (step S4) and GM. Select GM clock candidates with a small class value.

On the other hand, when the GM classes of the two GM clock candidates are also the same (step S4: “A = B”), the communication device 15 of this embodiment then compares the GM clock accuracy (accuracy) (step S4: “A = B”). Step S5), a GM clock candidate having a small GM clock accuracy value is selected.

On the other hand, when the GM clock accuracy of the two GM clock candidates is also the same, the communication device 15 of this embodiment then compares the GM clock stability (offsetScaledLogVariance) (step S6), and GM clock stability. Select GM clock candidates with a small (offsetScaledLogVariance) value.

On the other hand, when the GM clock stability (offsetScaledLogVariance) of the two GM clock candidates is also the same, the communication device 15 of this embodiment then compares the second priority (priority 2) of the two GM clock candidates (step). S7), a GM clock candidate having a small value of the second priority (priority2) is selected.

The subsequent processing is a processing peculiar to the communication device 15 of the present embodiment, and when the second priority (priority2) of the two GM clock candidates is also the same, the communication device 15 of the present embodiment is next to two. It is determined whether or not both of the GM clock candidate time synchronization sources (timeSource) are 0x20 (GPS time synchronization) (step S7A).

When the time sources (timeSources) of the two GM clock candidates are both 0x20 (GPS time synchronization) (step S7A: Yes), the communication device 15 of the present embodiment then determines the boundaries of the two GM clock candidates. The number of clocks (stepsRemoved) is compared (step S7B), and GM clock candidates having a small boundary clock number (stepsRemoved) are selected. For example, when stepsRemoved of one of the two GM clock candidates shows a higher priority than stepsRemoved of one clock B (step S7B: “A> B”), the process proceeds to step S9 and clock B is selected. To do. When the stepsRemoved of the clock A shows a lower priority than the stepsRemoved of the clock B (step S7B: “A <B”), the process proceeds to step S10 and the clock A is selected.

On the other hand, when at least one of the two GM clock candidate time synchronization sources (timeSource) is not 0x20 (GPS time synchronization) (step S7A: No), the process proceeds to step S8. Further, even when the number of boundary clocks (stepsRemoved) of the two GM clock candidates is the same (step S7B: “A = B”), the process proceeds to step S8.

In step S8, the communication device 15 of the present embodiment compares the GM clock identifiers (Identities) in the same manner as the BMCA shown in FIG. 9, and selects GM clock candidates having a small GM clock identifier (Identity) value.

By configuring the communication device 15 of this embodiment as described above and applying it as a boundary clock device (may be applied as an ordinary clock device), there are a plurality of grandmaster candidates on the synchronous communication system 1. However, when the parameters other than the GM clock identifier (Identity) and the boundary clock number (stepsRemoved) are the same, a grand master candidate having a small boundary clock number (stepsRemoved) value can be selected. Further, even if a failure occurs in the GPS synchronization of one grand master device, the synchronization can be maintained at the GPS synchronization time of the other grand master device by comparing the GM class (class) or the like.

(Synchronous communication system)
FIG. 3 shows a typical example of the PTP-based synchronization communication system 1 according to the present invention, which enables remote production of a broadcast program even when one of the broadcasting station equipment and the field equipment is in a GPS synchronization failure state. It is a block diagram which shows a typical operation example.

The configuration itself regarding the device arrangement of the synchronous communication system 1 shown in FIG. 3 is the same as that of the synchronous communication system 1 shown in FIG. 8, but the communication devices 15A and 15B in the synchronous communication system 1 shown in FIG. 3 are shown in FIG. The difference is that the communication device 15 of this embodiment is applied. That is, in the synchronous communication system 1 shown in FIG. 3, the boundary clock device 12A and the ordinary clock device 13A, and the boundary clock device 12B and the ordinary clock device 13B all follow the algorithm improved from the BMCA shown in FIG. , Operates to select one from multiple PTP grandmasters.

In the example shown in FIG. 3, there is an IP network connection between the broadcasting station equipment and the field equipment, the boundary clock device 12A is used as a master, the boundary clock device 12B is used as a slave, and the device in the broadcasting station equipment is clocked A. Shows an example in which PTP time synchronization is performed with, and the device in the field equipment is time-synchronized based on PTP using this clock A, and a state in which a failure occurs in GPS synchronization of the grand master device 10B is shown. ing. In this case, the communication devices 15A and 15B can maintain synchronization at the GPS synchronization time of the other grandmaster device by comparing the GM class. Therefore, in the field equipment, the grand master device 10B becomes a master that passively operates on the clock A, and the boundary clock device 12B and the ordinary clock device 13B also operate on the clock A as master / slave time synchronization between the devices. .. That is, in the example shown in FIG. 3, as in the example shown in FIG. 8, remote production can be realized in which a program is produced from the broadcasting station equipment to the on-site equipment.

FIG. 4 shows the time of the line between the broadcasting station equipment and the field equipment in the GPS synchronized state between the broadcasting station equipment and the field equipment as the synchronous communication system 1 based on the PTP of one embodiment according to the present invention. It is a block diagram which shows a typical operation example which enables the remote production of a broadcast program by performing stable operation even when synchronization is performed and switching is performed frequently.

The synchronous communication system 1 shown in FIG. 4 is an example when one of the broadcasting station equipment and the field equipment as shown in FIG. 3 is not in a GPS synchronization failure state, that is, the synchronous communication system 1 shown in FIG. The configuration itself related to the device arrangement is the same as that of the synchronous communication system 1 shown in FIG. 8, but as the communication devices 15A and 15B in the synchronous communication system 1 shown in FIG. 4, the communication device 15 of the present embodiment shown in FIG. 1 is used. It differs in that it is applied. That is, in the synchronous communication system 1 shown in FIG. 4, the boundary clock device 12A and the ordinary clock device 13A, and the boundary clock device 12B and the ordinary clock device 13B all follow the algorithm improved from the BMCA shown in FIG. , Operates to select one from multiple PTP grandmasters.

In the example shown in FIG. 4, there is an IP network connection between the broadcasting station equipment and the field equipment, and PTP time synchronization is performed with the boundary clock device 12A as the master and the boundary clock device 12B as the passive master. An example is shown in which the device in the broadcasting station equipment is time-synchronized by the clock A based on PTP, while the device in the field equipment is time-synchronized by the clock B based on PTP. In this case, a plurality of ground master candidates (clock A and clock B as GM clocks) exist on the synchronous communication system 1, and the communication devices 15A and 15B have GM clock identifiers (GM clock identifiers (clocks B) according to an improved algorithm of BMCA shown in FIG. When the parameters other than the Identity and the number of boundary clocks (stepsRemoved) are the same, the operation of selecting the grand master candidate (that is, the GM clock) having a small value of the number of boundary clocks (stepsRemoved) is performed.

That is, in the example shown in FIG. 4, the boundary clock device 12A has the boundary clock number (stepsRemoved) value used for the comparison determination of the use of the clocks A and B, and the clock A is boundary from the ground master device 10A. The number of boundary clocks (that is, the number of boundary clock devices) in the path to the clock device 12A is "0", and the clock B is in the path from the ground master device 10B to the boundary clock device 12A. Since the number of boundary clocks in the above (that is, the number of boundary clock devices) is “1” because the boundary clock device 12B is interposed, the clock A is selected. When the boundary clock device 12A selects the clock A, the ordinary clock device 13A selects the clock A because there is only a path for selecting the clock A in this example.

Further, in the example shown in FIG. 4, the boundary clock device 12B has the boundary clock number (stepsRemoved) value used for the comparison determination of the use of the clocks A and B, and the clock A is boundary from the ground master device 10B. The number of boundary clocks (that is, the number of boundary clock devices) in the path to the clock device 12B is "0", and the clock A is in the path from the ground master device 10A to the boundary clock device 12B. Since the number of boundary clocks in the above (that is, the number of boundary clock devices) is “1” because the boundary clock device 12A is interposed, the clock B is selected. When the boundary clock device 12B selects the clock B, the ordinary clock device 13B selects the clock B because there is only a path for selecting the clock B in this example.

The GM clock identifier (Identity) of the clock A and the GM clock identifier (Identity) of the clock B are used to synchronize the PTP time with the clock A by using the boundary clock device 12A as a master and the boundary clock device 12B as a passively operating master. This is because a smaller value is preset. Therefore, when the GM clock identifier (Identity) of the clock B is preset to a value smaller than the GM clock identifier (Identity) of the clock A, the boundary clock device 12B is mastered and the boundary clock device 12A is passively operated. It is also possible to synchronize the time of PTP with the clock B as the master.

Further, in the example shown in FIG. 4, the device in the broadcasting station equipment operates with the clock A, the device in the field equipment operates with the clock B, and one of the devices in the broadcasting station equipment and the field equipment operates passively. Therefore, even if the connection / disconnection of the line between the broadcasting station equipment and the field equipment is frequently switched, the broadcasting station equipment and the field equipment should be independently maintained in time synchronization and operate stably. As a result, stable remote production of broadcast programs becomes possible.

In other words, each of the plurality of grand masters (clock A and clock B) has a value (0x20) indicating GPS time synchronization set as a time synchronization source (timeSource), so that the communication device 15 shown in FIG. Is able to synchronize the time with the clock A for the device in the broadcasting station equipment and the clock B for the device in the field equipment while following the algorithm shown in FIG. 2, and connect / disconnect the line between the field equipment and the broadcasting station equipment. Is possible at any time.

In the synchronous communication system 1 of the embodiment shown in FIGS. 3 and 4, only the boundary clock devices 12A and 12B such as network switches are used from a plurality of PTP ground masters according to an improved algorithm of the BMCA shown in FIG. If one of the communication devices is selected, the algorithmic clock devices 13A and 13B such as a camera will operate in the same manner as the communication device operated by the BMCA shown in FIG. 9 as in the prior art.

Therefore, the communication device 15 shown in FIG. 1 is replaced with a boundary clock device such as a network switch that selects one from a plurality of grandmaster candidates, thereby connecting / disconnecting the line state between the plurality of communication facilities. Regardless, the time synchronization in each communication facility can be stabilized. In particular, the communication device 15 shown in FIG. 1 uses the parameters of Identity, priority1, class, accuracy, offsetScaledLogVariance, priority2, timeSource, and stepsRemoved defined in the PTP standard as they are, and follows an algorithm improved from the BMCA algorithm. Since the grandmaster is selected, it can be easily replaced and applied to an existing synchronous communication system using PTP, and has a high affinity.

With respect to the above-described embodiment, the computer can be configured to function as the communication device 15. Specifically, each function of the communication device 15 can be realized by reading and executing a program stored in a storage unit inside or outside the computer by a central processing unit (CPU) in the computer. .. Further, the program for realizing the function of the communication device 15 can be configured as a part of the software on the OS used in the computer. Further, the program for realizing the function of the communication device 15 can be recorded on a computer-readable recording medium and carried. Further, each function of the communication device 15 can be configured as a part of hardware or software, and can be realized by combining each function.

Although the present invention has been described above with reference to examples of specific embodiments, the present invention is not limited to the examples of the above-described embodiments, and various modifications can be made without departing from the technical idea. For example, in the above-described embodiment, an example in which one is selected from two grandmaster candidates is mainly described, but by repeating the selection of one from two grandmaster candidates, three or more grandmaster candidates are selected. It is also possible to select one from the above. Therefore, the present invention is not limited to the examples of the above-described embodiments, but is limited only by the scope of claims.

According to the present invention, when operating a plurality of grand masters in a synchronous communication system using an IP network, each communication device can be used even when the connection / disconnection of lines in the synchronous communication system is frequently switched. Since a grand master that operates more stably can be selected for GPS time synchronization, it is useful for applications of communication devices used in a synchronous communication system that operates a plurality of grand masters.

1 Synchronous communication system 10, 10A, 10B Grand master device 10a Synchronous signal generator 11A, 11B Communication antenna 12 Network switch (boundary clock device)
12A, 12B boundary clock device 13A, 13B ordinary clock device 13-1 camera (ordinary clock device)
13-2 Microphone (Ordinary clock device)
13-3 display (ordinary clock device)
13-4 Video Switcher (Ordinary Clock Device)
13-5 Audio Mixer (Ordinary Clock Device)
15, 15A, 15B Communication device 151 PTP message transmission / reception unit 152 Grand master candidate selection unit 153 Grand master selection unit P1, P2, ..., Pn transmission / reception port 20 GPS satellite 110 Synchronous signal generator 121 SDI router 122 Voice router 131 Camera 132 Microphone 133 Display 134 Video Switcher 135 Voice Mixer

Claims (4)

In a synchronous communication system using an IP network equipped with multiple grand masters, a communication device that selects a grand master that operates stably from the multiple grand masters and communicates with time synchronization based on PTP (Precision Time Protocol). And
A PTP message transmission / reception unit and a grandmaster candidate selection unit provided in each of the plurality of transmission / reception ports for transmitting / receiving PTP messages using IP-based packets to each of the plurality of other devices for which communication has been established.
It is equipped with a grand master selection section that selects one of the plurality of grand masters.
Each of the PTP message transmission / reception units acquires a PTP message from another device connected by communication and outputs the PTP message to the corresponding grandmaster candidate selection unit, and the parameters of the grandmaster selected from the grandmaster selection unit. Receiving the notification of, having a means of transmitting a PTP message including the parameters of the selected grandmaster to another device connected by communication.
Each of the grand master candidate selection units performs an operation of decoding a PTP message acquired from the corresponding PTP message transmission / reception unit and selecting a grand master candidate, and selects one from a plurality of PTP grand master candidates. It has a means for extracting Identity, priority1, class, accuracy, offsetScaledLogVariance, priority2, timeSource, and stepsRemoved defined by the PTP standard as parameters of, and outputting them to the grandmaster selection unit.
Based on the parameters, the grandmaster selection unit compares two grandmaster candidates one by one according to a predetermined algorithm, finally selects one grandmaster and synchronizes the time, and sets the parameters of the selected grandmaster. A communication device having a means for notifying each of the PTP message transmission / reception units. The grand master selection unit compares the parameters of the two grand master candidates as the predetermined algorithm, and when there is a difference in identity and the priority1, class, accuracy, offsetScaledLogVariance, and priority2 are the same, the identity comparison of the timeSource. When the timeSource is the same, each magnitude of stepsRemoved is compared to select a grand master candidate with a small stepsRemoved, and when there is a difference in timeSource or there is no difference in the magnitude comparison of stepsRemoved, the magnitude of Identity The communication device according to claim 1, wherein one grand master candidate is selected by comparison. Each of the plurality of grandmasters is set with a value indicating GPS time synchronization as the timeSource, and a line is connected to another device operating based on a different grandmaster in the GPS time synchronization by the predetermined algorithm. The communication device according to claim 1 or 2, wherein the communication device is configured to enable disconnection at an arbitrary time. A program for causing a computer to function as the communication device according to any one of claims 1 to 3.

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