JP4747787B2 - Delay time difference measuring method and delay time difference measuring apparatus - Google Patents

Description

  The present invention relates to a delay time difference measuring method and a delay time difference measuring apparatus, and more particularly to a delay time difference measuring method and delay for measuring a propagation delay time difference between paths of the transmitted packet signal when the same packet signal is transmitted through a plurality of paths. The present invention relates to a time difference measuring apparatus.

  When packet signals of the same material are transmitted via multiple paths, and information transmitted via one path is synchronized and switched without interruption, between the paths of the transmitted packet signals. It is necessary to measure the propagation delay time difference. For example, in order to perform synchronous switching from the working line to the protection line, the above-described propagation delay time difference is measured, and based on the measurement result, a delay circuit that delays each packet signal transmitted between the working line and the protection line Conventionally, the delay time is adjusted (see, for example, Patent Documents 1 and 2).

  In the above case, conventionally, for example, the propagation delay time difference is measured using a delay time difference measuring apparatus as shown in FIG. FIG. 5 shows a block diagram of an example of a conventional delay time difference measuring apparatus. In the figure, in a system that transmits a transport stream (TS) signal obtained by compressing and coding the same material by the MPEG (Moving Picture Experts Group) method, the first transmission path (for example, working line) is transmitted. The first TS signal to be transmitted is supplied to the PAT packet trap circuit 31 and the delay adjustment memory 34, respectively, and the second TS signal transmitted through the second transmission path (for example, the protection line) is the PAT packet trap circuit 32. And the delay adjustment memory 35 respectively. The first TS signal and the second TS signal are signals obtained by compression-coding the same material (video, audio, etc.).

  Each of the PAT packet trap circuits 31 and 32 detects a PAT packet from the input TS signal, and transfers only the detected PAT to the PAT packet time difference detection circuit 33. The PAT packet time difference calculation circuit 33 calculates the difference in time when the PAT is trapped from each input system, and sets the delay time in the delay correction memories 34 and 35 so that the difference becomes zero.

Japanese Patent Laid-Open No. 5-219027 JP-A-8-237230

  However, the conventional delay time difference measuring apparatus described above is basically premised on delay measurement at the same TS, and fixed such as PAT (Program Association Table) and PMT (Program Map Table). The delay is measured by the difference in the time at which TS packets having a pattern are received. For this reason, when the TS multiplexing process is performed only in a certain system in a plurality of transmission paths, or when the multiplexing process is different for each system, the TS multiplexing apparatus enters on the transmission path, and the packet PID (Packet Identification: If PAT regeneration processing is entered by packet identification) or program number reassignment processing, the contents of the PAT packet will be rewritten, so that there is a problem that the same packet cannot be recognized between the systems. .

  In addition, since the PAT and PMT are normally sent at a unique timing in the TS multiplexer, the PAT and PMT packets are sent at a unique interval different from the transmission interval of the original PAT and PMT. There is also a problem that timing information cannot be transmitted.

  The present invention has been made in view of the above points, and provides a delay time difference measuring method and a delay time difference measuring apparatus capable of measuring a delay time difference of a transmission path even when TS packet multiplexing processing is performed on the transmission path. The purpose is to do.

In order to achieve the above object, a delay time difference measuring method according to a first aspect of the present invention receives an MPEG transport stream including the same information transmitted by a plurality of transmission systems as an input, and the plurality of transmission systems In a delay time difference measuring method for measuring a relative delay time difference between transmitted transport streams, the method is used for measurement in a first transport stream input through a first transmission system among a plurality of transmission systems. The first step of passing only the first packet having the PID which is the packet identification information to be transmitted, and the first packet passed in the first step is a TS packet including the head data of the compressed data a second step of detecting the first payload unit start indicator bit in the header portion of the first packet indicating A third step of storing the first packet having a first payload unit start indicator bit detected in the second step in the storage means, the detection time of the first payload unit start indicator bit in the second step The fourth step of latching the count value indicating the arrival time of the packet from the counter that counts the clock with a constant frequency, and the first transformer input via the second transmission system among the plurality of transmission systems. A fifth step of allowing only a second packet having a PID which is packet identification information used for measurement in a second transport stream having the same information as the port stream and the same transmission source; the second packets passed in step is a TS packet including the head data of compressed data A sixth step of detecting a second payload unit start indicator bit in the header portion of the to the second packet, the first comparison reference payload portion of a packet stored in the storage unit, detected by the sixth step A second step of comparing the payload part of the second packet having the second payload unit start indicator bit as a comparison target and outputting a coincidence signal when the two coincide with each other, and when the coincidence signal is outputted The first transport stream and the second transport stream are obtained from the eighth step of latching the count value from the counting means, and the difference values of the values latched in the fourth step and the eighth step, respectively. And a ninth step of obtaining a delay time difference of

In order to achieve the above object, the second invention receives an MPEG transport stream including the same information transmitted by a plurality of transmission systems as an input, and is transmitted by the plurality of transmission systems. In a delay time difference measuring apparatus for measuring a relative delay time difference between transport streams, counting means for counting a clock having a constant frequency and outputting a count value indicating arrival time of a packet, and a first of a plurality of transmission systems A first packet trap means for passing only a first packet having PID which is packet identification information used for measurement in a first transport stream inputted through one transmission system; and a first packet it first packets passed by the trap means is TS packet containing head data of compressed data First packet having a first detecting means for detecting a first payload unit start indicator bit in the header portion of the first packet, the first payload unit start indicator bit detected by the first detecting means shown storage means for storing a first latch means for latching a count value from the counting means at the detection time point of the first payload unit start indicator bit of the first detecting means, a second of the plurality of transmission systems A second packet having a PID which is packet identification information used for measurement in a second transport stream that is input through the transmission system and includes the same information as the first transport stream and the same transmission source Is passed by the second packet trap means and the second packet trap means. Second detecting means for the second packet detecting a second payload unit start indicator bit in the header portion of the second packet indicating that the TS packet including the head data of the compressed data, stored in the storage means The payload portion of the first packet is used as a reference for comparison, and the payload portion of the second packet having the second payload unit start indicator bit detected by the second detection means is compared as a comparison target. The comparator means for outputting the coincidence signal, the second latch means for latching the count value from the counting means when the coincidence signal is outputted, and the first latch means and the second latch means, respectively. The difference in delay time between the first transport stream and the second transport stream is obtained from the difference value of the obtained values. And calculating means.

According to the present invention, the payload unit indicator bits indicating that the packet is a TS packet including the head data of the compressed data are compared with each other in the payload part of the two packets, and the delay is caused by the difference in reception time when the two match. By calculating the time difference, the delay time difference can be calculated regardless of the contents of the PAT and PMT, so the PID can be changed in the middle of the route, the transmission interval of the PAT and PMT packets can be changed, and the program number can be changed. Even if they occur, it is possible to detect whether or not they are the same packet, and as a result, a delay time difference can be detected.

Further, according to the present invention, the measurement of the delay time difference, PAT, because it uses Bae Lee load unit indicator bit of the header portion of the regenerated it is not packet multiplexer such as the PMT packet, a payload unit comparison The delay time can be measured stably within a range of variation in multiplexing processing time when the packet passes through the multiplexer by greatly reducing the frequency .

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of an embodiment of a delay time difference measuring apparatus according to the present invention. In the figure, a constant frequency reference clock oscillated from an oscillator (OSC) 1 is supplied to a time counter 2 where it is counted and used as a count value indicating the arrival time of a TS packet used for delay time measurement. The This count value is supplied to the first latch circuit 3 and the second latch circuit 4.

  The latch circuit 3 latches the count value when the payloads in the two TSs transmitted by the two transmission systems that perform delay measurement match based on a payload match signal described later, Output to 5. On the other hand, the latch circuit 4 performs the above operation when the TS packet having the PID used for the delay time difference measurement is trapped in the dual port memory 9 in the transmission system serving as a reference for the delay time difference measurement based on the copy completion signal described later. The count value is latched and output to the control circuit 5.

  The packet trap circuit 6 passes only the TS packet having the PID used for measurement out of the first TS packet input through the first transmission system, and supplies it to the comparison circuit 7. Further, the packet trap circuit 8 passes only the TS packet having the PID used for measurement out of the second TS packets input through the second transmission system, and outputs it to the latch circuit 4 as a copy completion signal. On the other hand, it is stored in the dual port memory 9.

  The comparison circuit 7 stores the payload portion of the TS packet of the second transmission system that is stored in the dual port memory 9 and serves as a reference for the delay time difference measurement, and the measurement target output from the packet trap circuit 6. Compares the payload part of TS packet of 1 transmission system with CPU or hardware logic one byte at a time, and when both match, that is, when the same TS packet is detected, generates payload match signal and latches Output to the circuit 3 and the control circuit 5.

  The control circuit 5 calculates the difference between the count values latched by the latch circuits 3 and 4, respectively, and inputs the first TS packet input through the first transmission system and the second transmission system. The delay time difference from the second TS packet is measured, and the delay times of the delay control circuits 10 and 11 are controlled according to the delay time difference. As a result, the delay time difference between the first TS packet delayed by the delay control circuit 10 and the second TS packet delayed by the delay control circuit 11 is made substantially zero and supplied to the switching circuit 12. Based on the control signal of the control circuit 5, the switching circuit 12 switches the output from the TS packet that has been output so far to the other TS packet among the first TS packet and the second TS packet in the first transmission system. To do.

  As described above, in the present embodiment, a delay time difference is detected by selecting a TS packet having a specific PID other than the PAT and PMT packets and comparing the payload part excluding the header part of the TS packet. Therefore, TS delay measurement can be performed even if PAT, PMT data, transmission interval change, TS packet PID change, etc. that occur when a multiplex system enters in the middle of the transmission path. .

  FIG. 2 shows a block diagram of Embodiment 1 of the delay time difference measuring apparatus according to the present invention. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. FIG. 2 is an example applied to a TS diversity (4-input diversity) device. For example, one TS signal transmitted from a relay vehicle running in the city, such as a marathon relay, has four transmission paths composed of a plurality of different base stations. The received signals are received and input to different delay adjustment circuits 18 to 21.

  Each of the first selector 13 and the second selector 15 receives four TS signals and selects one TS signal different from each other. That is, the selector 15 selects one TS signal that is a reference for delay time difference measurement from the four input TS signals, and supplies the selected TS signal to the packet trap circuit 16, and the selector 13 selects the four TS signals that are input. Among them, one TS signal that is a measurement target (a counterpart side with respect to the reference system) other than that selected by the selector 15 is selected and supplied to the packet trap circuit 14. The selectors 13 and 15 perform the above selection by a system selection signal from the control circuit 17.

  The packet trap circuits 14 and 16 pass only TS packets having a PID used for measurement. The dual port memory 9 stores TS packets trapped from the reference system TS for delay measurement by the packet trap circuit 16. The comparison circuit 7 includes a payload portion of a reference TS packet for delay measurement stored in the dual-port memory 9 and a TS trapped by the packet trap circuit 14 from the measurement target system selected by the selector 13. The payload part of the packet is compared, and it is determined whether or not they are the same packet.

  The control circuit 17 calculates the difference in delay time between the two systems by calculating the difference between the counter value from the latch circuit 3 when the payload coincidence signal is input and the counter value from the latch circuit 4 when the trap completion signal is input. Then, timing adjustment is performed by setting a delay time for correction in the delay adjustment circuits 18 to 21. The delay adjustment circuits 18 to 21 are configured by a memory, and read the TS signals that are input by delaying them independently from each other for a time set based on a control signal for setting a delay time from the control circuit 17. Used to adjust the delay time.

  Next, the operation of this embodiment will be described with reference to the timing chart of FIG. In FIG. 3, (A) is a source TS signal, (B) is a TS signal transmitted and received via the first route, and another TS is multiplexed during transmission of the first route. Yes. On the other hand, (H) is a TS signal transmitted and received through the second route, and this is not multiplexed in the route. Here, the delay is measured using the V4 packet of the original TS signal shown in FIG. 3A, and the TS signal shown in FIG. In addition, a TS packet transmitted through the first route is a measurement target.

  In FIG. 3, the time axis is assumed to advance from right to left, and the time counter value shown in FIG. 3E is incremented by 1 as time elapses. Further, the TS signal transmitted through the first route is delayed from the TS signal transmitted through the second route. Also, in the TS packets shown in FIGS. 3A, 3B, and 3H, A is an audio packet, V is a video packet, and the numbers following V or A are included in the packet. Indicates the value of the number (Continuity Counter) for checking continuity for confirming whether or not it has been performed. TS packets are received and input in the order of A1, V1, A2, V2,.

  In FIG. 2, the selector 15 that performs reference system selection selects the second TS signal shown in FIG. 3H received via the second path and supplies it to the packet trap circuit 16. When the control circuit 17 performs switching using the V4 packet in the second TS signal, the packet trap circuit 16 converts the V4 packet in the second TS signal based on the switching designation packet from the control circuit 17. When detected (trapped), as shown in FIG. 3G, a high-level trap completion signal is generated and supplied to the control circuit 17 and also supplied to the latch circuit 4, and the timer counter at that time 2 causes the latch circuit 4 to latch the count value “8” shown in FIG. As a result, the output value of the latch circuit 4 becomes “8” thereafter, as shown in FIG. The packet trap circuit 16 supplies the V4 packet in the second TS signal to the dual port memory 9 for storage.

  On the other hand, the selector 13 selects the first TS signal shown in FIG. 3B transmitted and received through the first route, and supplies the selected signal to the packet trap circuit 14. The packet trap circuit 14 detects (traps) the V4 packet in the first TS signal according to the PID setting from the control circuit 17 and supplies it to the comparison circuit 7. When the comparison circuit 7 completes reception of the V4 packet from the packet trap circuit 14, the comparison circuit 7 compares the payload portion of the V4 packet with the payload portion of the V4 packet stored in the dual port memory 9 one byte at a time. When they match, a time-level payload match signal for one packet shown in FIG. 3C is generated and supplied to the control circuit 17 and supplied to the latch circuit 3 from the timer counter 2 at that time. The count value “11” shown in FIG. 3E is latched by the latch circuit 3. As a result, the output value of the latch circuit 3 thereafter becomes “11” as shown in FIG.

  The control circuit 17 calculates the difference between the counter value “11” of the latch circuit 3 when the payload match signal is input and the counter value “8” of the latch circuit 4 when the trap completion signal is input, and the obtained difference value “ 3 ”is determined as a delay time difference between the two systems, and the delay time of the second delay adjustment circuit to which the second TS signal selected by the selector 15 is supplied is selected from the delay adjustment circuits 18 to 21. The delay time of the first delay adjustment circuit to which the first TS signal selected at 13 is supplied is controlled to be relatively large by a time corresponding to the difference value “3”.

  As a result, the time difference between the first delay TS signal supplied from the first delay adjustment circuit to the selector 22 and the second delay TS signal supplied from the second delay adjustment circuit to the selector 22 is substantially zero. The selector 22 switches and outputs the second delayed TS signal to the first delayed TS signal based on the system selection signal from the control circuit 17.

  As described above, in this embodiment, a delay is achieved by selecting a TS packet having a specific PID other than the PAT and PMT packets, and comparing the payload portion excluding the header portion of the TS packet with the comparison circuit 7. Since the time difference is detected, TS delay measurement is performed even if PAT, PMT data, transmission interval change, TS packet PID change, etc. that occur when a multiplex system enters the middle of the transmission path. be able to.

  In FIG. 2, when measuring the delay time difference between the transmission lines of the four input TS signals TS1 to TS4, the selectors 13 and 15 use the TS1 and TS2, TS2 and TS3, TS3 and TS4, and TS4 and TS1. The delay time difference of four patterns is measured.

  FIG. 4 shows a block diagram of Embodiment 2 of the delay time difference measuring apparatus according to the present invention. In the figure, the same components as those in FIG. The basic configuration of this embodiment is the same as that shown in FIG. 1, but the same packet detection method is further devised.

  In FIG. 4, payload unit start indicator detection circuits 24 and 25 detect a payload unit start indicator (payload_unit_start_indicator) bit in the TS packet header output from the packet trap circuits 6 and 8. This embodiment is different from the first embodiment in that this payload unit start indicator bit is added to the trap condition of the TS packet. In FIG. 4, the delay control circuits 10 and 11 and the switching circuit 12 of FIG. 1 are not shown.

In particular, in the case of a material having a high transmission rate, it is necessary to perform packet comparison at high speed. However, if the comparison processing is not in time, a situation occurs in which missing data is generated and delay measurement cannot be performed. Therefore, in this embodiment, the payload unit start indicator bit is a flag that is found in the first packet of the data chunk generated as a result of compression processing by MPEG2 or the like of the video and audio signals, and the generation interval is once every 20 to 30 msec. When the comparison circuit 26 compares the payload portion of the TS packet having the payload unit start indicator bit , the payload portion comparison frequency of the TS packet is greatly reduced.

  As a result, in this embodiment, the payload unit start indicator bit of the TS packet header part is added to the packet trap condition, so the frequency of comparing the payload part of the TS packet can be greatly reduced, and the burden on the processing system can be drastically reduced. The effect of being able to be obtained. Therefore, in this embodiment, the comparison circuit 26 may be realized by software using a microcontroller or the like.

It is a block diagram of one embodiment of the present invention. It is a block diagram of Example 1 of the present invention. 3 is a timing chart for explaining the operation of FIG. 2. It is a block diagram of Example 2 of the present invention. It is a block diagram of an example of the prior art.

Explanation of symbols

1 Oscillator (OSC)
2 Time counter 3, 4 Latch circuit 5, 17 Control circuit 6, 8, 14, 16 Packet trap circuit 7, 26 Comparison circuit 9 Dual port memory 10, 11 Delay control circuit 12 Switching circuit 13, 15 Selector 18-21 Delay adjustment Circuit 22 selector

Claims (2)

A delay for receiving, as an input, an MPEG transport stream including the same information transmitted by a plurality of transmission systems, and measuring a relative delay time difference between the transport streams transmitted by the plurality of transmission systems In the time difference measurement method,
A first step of passing only a first packet having a PID which is packet identification information used for measurement in a first transport stream input through a first transmission system among the plurality of transmission systems; When,
Detecting a first payload unit start indicator bit in a header portion of the first packet indicating that the first packet passed in the first step is a TS packet including head data of compressed data; Two steps,
A third step of storing in the storage means the first packet having the first payload unit start indicator bit detected in the second step;
A fourth step of latching a count value indicating the arrival time of a packet from a counter that counts a constant frequency clock at the time of detection of the first payload unit start indicator bit of the second step;
Packet identification used for measurement in the second transport stream that is input through the second transmission system among the plurality of transmission systems and includes the same information as the first transport stream and the same transmission source A fifth step of passing only the second packet having the information PID;
Detecting a second payload unit start indicator bit in a header portion of the second packet indicating that the second packet passed in the fifth step is a TS packet including the head data of the compressed data; 6 steps,
Comparing the payload portion of the second packet having the second payload unit start indicator bit detected by the sixth step, using the payload portion of the first packet stored in the storage means as a comparison reference A seventh step of comparing as a target and outputting a coincidence signal when both coincide,
An eighth step of latching the count value from the counting means when the coincidence signal is output;
A ninth step of obtaining a delay time difference between the first transport stream and the second transport stream from a difference value between the values latched in the fourth step and the eighth step, respectively. The delay time difference measuring method characterized by the above-mentioned. A delay for receiving, as an input, an MPEG transport stream including the same information transmitted by a plurality of transmission systems, and measuring a relative delay time difference between the transport streams transmitted by the plurality of transmission systems In the time difference measuring device,
Counting means for counting a clock with a constant frequency and outputting a count value indicating the arrival time of the packet;
A first packet that passes only a first packet having a PID that is packet identification information used for measurement in a first transport stream input through the first transmission system among the plurality of transmission systems. Trap means;
Detecting a first payload unit start indicator bit in a header portion of the first packet indicating that the first packet passed by the first packet trap means is a TS packet including the head data of compressed data First detecting means for
Storage means for storing the first packet having the first payload unit start indicator bit detected by the first detection means ;
First latch means for latching the count value from the counting means at the time of detection of the first payload unit start indicator bit by the first detecting means;
Packet identification used for measurement in the second transport stream that is input through the second transmission system among the plurality of transmission systems and includes the same information as the first transport stream and the same transmission source Second packet trap means for passing only the second packet having the PID which is information;
Detecting a second payload unit start indicator bit in the header portion of the second packet indicating that the second packet passed by the second packet trap means is a TS packet including the head data of the compressed data Second detecting means for
The payload portion of the second packet having the second payload unit start indicator bit detected by the second detection means, using the payload portion of the first packet stored in the storage means as a reference. Comparison means for comparing as a comparison target and outputting a coincidence signal when both coincide,
Second latch means for latching the count value from the count means when the coincidence signal is output;
Calculating means for obtaining a delay time difference between the first transport stream and the second transport stream from a difference value between values latched by the first latch means and the second latch means, respectively. A delay time difference measuring apparatus.

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