JP2001024656A - Communication device, and method and medium thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To utilize a synchronous residual time stump(SRTS) method also for the transmission of data whose data rate is not fixed by converting 1st data, whose data rate is not fixed, into 2nd data whose data rate is fixed, and generating clock information based on the STRS method. SOLUTION: A data conversion part 62 converts MPEG transport packet data, whose data rate is not fixed, into data whose data rate is fixed. A program clock reference(PCR) adjusting part 63 rewrites a PCR previously added to a MPEG transport packet corresponding to the data converted so that its data rate is fixed. An SRTS processing part applies transmission side SRTS processing to the data inputted from the PCR adjusting part 63 and generates an ATM cell as a processing result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication apparatus and method, and a medium, and more particularly to an ATM (Asynchronous Transf
The present invention relates to a communication device and method and a medium that can transmit and receive audio data and video data digitized using a communication technology.

[0002]

2. Description of the Related Art FIG. 1 shows a configuration example of a conventional data transmission system. It is assumed that the network 3 to which each of the encoding side and the decoding side is connected uses a satellite, similarly to the transmission method in digital CS broadcasting. That is, data transmitted via the network 3 has a delay at a constant interval.

An encoder 1 converts video data and audio data as data to be transmitted, for example, into MPEG data.
Encode according to the -2 method and output to the system encoder 2. The system encoder 2 packetizes and multiplexes the input video data and audio data to generate an MPEG transport packet,
A time stamp is added and transmitted over the network 3. The timestamp in the MPEG-2 format is PCR
(Program Clock Reference) and at least 0.1
It is added to the MPEG transport packet so that it arrives at the decoding side at intervals of less than seconds (hereinafter, the MPEG transport packet with the PCR added is referred to as a PCR packet). As shown in FIG. 2, the PCR is counted at the encoding timing on the encoding side (encoder 1), and is counted on the encoding side (system encoder 2).
Represents the count value of the system clock in FIG.
In addition, this system clock, in the case of the MPEG-2 system,
It is 27 MHZ.

Returning to FIG. 1, data transmitted via the network 3 arrives at the decoding side and is input to the system decoder 4. Since the data transmitted via the network 3 has a constant delay, the PCR (PCR packet) has the same interval as the interval sent from the encoding side (the difference is the MPEG-2). +/- 5 of standard
(Within 00 ns).

[0005] As shown in FIG. 3, the system decoder 4 includes a system decoding unit 11, a time stamp extracting circuit 12, and a PLL circuit 13. The system decoding unit 11 depacketizes the input packetized audio data and video data, and outputs the resulting audio stream and video stream to the decoder 5.

[0006] As shown in FIG. 2, the time stamp extracting circuit 12 is provided with a PC included in an MPEG transport packet.
R is extracted and output to the PLL circuit 13. PLL circuit 13
Generates a system clock of 27 MHz using the input PCR and outputs it to the decoder 5.

[0007] The PLL circuit 13 is configured, for example, as shown in FIG. The subtracter 21 has a PCR extracted by the time stamp extracting circuit 12 and a counter 24.
Value (D / A converter and VCO2)
3) is input. The subtracter 21 calculates a difference between the PCR of the PCR packet and the count value, and performs a low-pass filter (hereinafter abbreviated as LPF).
22. The LPF 22 smoothes the input operation result from the subtracter 21 and outputs the result to a D / A converter / VCO (voltage controlled oscillator) 23. D / A converter and VCO23
Converts a digital signal input from the LPF 22 into an analog signal, and uses the analog signal as a control voltage to generate a clock having a frequency corresponding to the control voltage. This clock is used as a system clock on the decoding side (system decoder 4), is supplied to the decoder 5, and is input to the counter 24.

The counter 24 is a D / A converter / VCO
23, and counts the count value.
The signal is supplied to the subtractor 21 as a signal representing the phase of the frequency of the system clock at that time. That is, this
In the PLL circuit 13, the speed of the system clock is increased or decreased so that the difference between the PCR added to the MPEG transport packet and transmitted and the count value of the own system clock disappears. I do.

Returning to FIG. 1, the decoder 5 decodes the streams of audio data and video data supplied from the system decoder 11 of the system decoder 4 based on the system clock input from the PLL circuit 13 of the system decoder 4. I do.

[0010] As shown in this example, when the data is delayed at a fixed interval, the time stamp (PCR) transmitted from the encoding side arrives at the same interval at the decoding side. The system clock is generated (adjusted) using the time stamp so as to synchronize with the system clock on the encoding side. As a result, the data is properly reproduced. However, as in the case where the network 3 is an ATM (Asynchronous Transfer Mode) network, a delay (hereinafter, referred to as delay fluctuation) occurring in the range of 1 ms to 2 ms (hereinafter referred to as delay fluctuation) occurs in the data instead of a delay at a fixed interval. Occasionally, in the above-described conventional data transmission system, the delay fluctuation is not absorbed, and the data is not properly reproduced.

[0011]

Therefore, various methods for reducing delay fluctuation have been proposed, but SRTS (Syn.
The chronous Residual Time Stamp) method is one of them.

FIG. 5 shows a configuration example of a data transfer system to which the SRTS method is applied. In this system,
Data is transmitted from the transmitting device 31 to the receiving device 32 via the ATM network 30.

The SRTS processing unit 41 of the transmitting device 31
As shown in (A), one byte of synchronous data (sy in the figure)
nc) and the following 187-byte encoded data (hereinafter, 1-byte synchronous data and the following 187-byte encoded data when it is not necessary to individually distinguish them, MPEG Transport Packet Data) is DVB (Digital Video Broadca)
sting) -Input in synchronization with a clock having a clock speed conforming to the Parallell standard (hereinafter referred to as a transmission clock). That is, this data has a constant data rate.

[0014] MPEG conforming to the DVB-Paralell standard
The transport packet data is 13.
Since the signal is output at a frequency of 5 MHz and is synchronized with each clock (data exists for each clock) as shown in FIG. 6A, the clock speed of the transmission clock is 108 Mbit / s. (= 8 bits × 13.
5 MHz).

When complying with the DVB-Paralell standard,
As shown in FIG. 6B, the MPEG transport packet data is dummy data (in the case of the example of FIG.
Dummy data) (indicated by the dotted frame in the figure)
May be inserted, but if one piece of dummy data is used, the data always exists at each clock and the data rate is kept constant.

The MPEG transport packet data shown in FIGS. 6A and 6B is encoded by an encoder (not shown) and multiplexed by a system encoder (not shown), and PCR is set at predetermined intervals. Have been.

Returning to FIG. 5, the SRTS processing section 41 calculates a total of 4 bits of differential data, so-called clock information, based on the clock speed of the transmission clock and the clock speed of the ATM network 30. The SRTS processing unit 41 also performs ATM conversion from the input MPEG transport packet data.
Each time a cell is generated and eight ATM cells are generated, one bit of the calculated difference data is added to each of the four ATM cells. In this way, the ATM cell to which the difference data has been added is transmitted on the ATM network 30 in synchronization with the transmission clock. In the following, these processes executed by the SRTS processing unit 41 are referred to as transmission-side SRTS processes.

The transmitting device 3 via the ATM network 30
The ATM cell transmitted from 1 is received by the receiving device 32 and input to the SRTS processing unit 42.

The SRTS processing section 42 generates an MPEG transport packet from the input ATM cell and extracts difference data. The SRTS processing unit 42 reproduces a clock based on the extracted difference data, thereby establishing synchronization of the MPEG transport packet. The clock and the MPEG transport packet generated in this way are output to a decoder (not shown). In addition,
Hereinafter, these processes executed by the SRTS processing unit 42 are referred to as SRTS processes on the receiving side.

The decoder is a receiving device (SRTS processing unit 42)
The MPEG transport packet is reproduced based on the clock from the S.32, but since the clock supplied from the SRTS processing unit 42 is synchronized with the transmission clock, the MPEG transport packet is not affected by the delay fluctuation. Plays correctly.

When the SRTS method is used, the data to be transmitted needs to have a constant data rate as described above. When transmitting data with a non-constant data rate, the SRTS method is used. There was a problem that could not be done. The details of the SRTS method are described in ITU (Internatio
nal Telecommunication Union) -T I.363.1.

The present invention has been made in view of such a problem, and aims to use the SRTS method even when transmitting data having a non-constant data rate.

[0023]

According to a first aspect of the present invention, there is provided a communication apparatus comprising: conversion means for converting first data having a non-constant data rate into second data having a constant data rate; Generating means for generating clock information according to the SRTS method based on the converted second data;
A transmitting unit that transmits the clock information generated by the generating unit and the second data converted by the converting unit to a receiving device.

According to a second aspect of the present invention, in the communication device, the conversion unit includes a storage unit that stores the first data, a storage unit that stores the dummy data, the first data stored by the storage unit, The dummy data held by the holding means is read at a predetermined timing, and the read dummy data is inserted into the read first data to form a second data.
And a constant rate generating means for generating the data of (1).

According to a third aspect of the present invention, in the communication method, the first data having a non-constant data rate is converted into the second data having a constant data rate, and the second data converted in the conversion step is converted. SRTS based on the data of 2
A generating step of generating clock information according to the method, and a transmitting step of transmitting, to the receiving device, the clock information generated in the processing of the generating step and the second data converted in the processing of the converting step. And

According to a fourth aspect of the present invention, in the medium, the first data having a non-constant data rate is converted into the second data having a constant data rate, and the second data converted in the conversion step is converted. Generating the clock information according to the SRTS method on the basis of the data of the above, transmitting the clock information generated in the processing of the generation step, and the second data converted in the processing of the conversion step to the receiving device. And steps.

[0027] In the communication device according to the first aspect, the communication method according to the third aspect, and the medium according to the fourth aspect, the first data having a non-constant data rate is the first data having a non-constant data rate. 2, the clock information according to the SRTS method is generated based on the second data, and the generated clock information and the converted second data are transmitted to the receiving device.

According to a fifth aspect of the present invention, there is provided a communication apparatus comprising: receiving means for receiving data to which clock information generated according to the SRTS method is added and dummy data inserted so that the data rate is constant; A synchronization unit configured to establish data synchronization based on clock information added to the received data; and a removal unit configured to remove dummy data from the data synchronized by the synchronization establishment unit. Features.

According to a sixth aspect of the present invention, there is provided a communication method comprising the steps of: receiving data to which clock information generated according to the SRTS method is added and dummy data inserted so that the data rate is constant; Based on the clock information added to the data received in the processing,
The method includes a synchronization establishing step for establishing data synchronization, and a removing step for removing dummy data from the data for which synchronization has been established in the processing of the synchronization establishing step.

According to a seventh aspect of the present invention, there is provided an input step for inputting data in which dummy information is inserted so that clock information generated according to the SRTS method is added and a data rate is constant, and processing of the input step. A synchronization establishment step of establishing data synchronization based on clock information added to the data input in step S, and a removal step of removing dummy data from data synchronized in the processing of the synchronization establishment step. It is characterized by becoming.

[0031] In the communication device according to the fifth aspect, the communication method according to the sixth aspect, and the medium according to the seventh aspect, clock information generated according to the SRTS method is added, and the data rate becomes constant. The data in which the dummy data is inserted is input as described above, and data synchronization is established based on the clock information added to the input data, and the dummy data is extracted from the data for which the synchronization has been established.

[0032]

FIG. 7 shows a configuration example of a data transmission system to which the present invention is applied. In FIG. 5, FIG.
The same reference numerals are given to the portions corresponding to the case in. As shown in FIG. 8A, the transmission device 51 includes valid data (indicated by a solid frame in the figure) including 1-byte synchronization data and 187-byte encoded data.
DVB-ASI (Async) comprising N (= 1, 2,...) Bytes of invalid data (indicated by a dotted frame in the figure).
Among the data conforming to the hronous interface, only the valid data is input as MPEG transport packet data. That is, the MPEG input to the transmission device 51
The data rate of the transport packet data is shown in FIG.
As shown in (A), it is not constant.

The valid data is encoded by an encoder (not shown) and multiplexed by a system encoder (not shown), and PCRs are set at predetermined intervals.
In the case of the example of FIG. 9A, the MPEG transport packet 2
(In the figure, described as packet 2) has a PCR. In addition, when conforming to the DVB-ASI standard, the MPEG transport packet data may include invalid data at random as shown in FIG. 8B.

The transmitting device 51 converts the input MPEG transport packet data having a non-constant data rate into data having a constant data rate.
The data obtained by the conversion is subjected to SRTS processing on the transmission side, and the ATM cells generated as a result are transferred to the ATM network 3.
Transmit on 0.

The receiving device 52 receives an ATM cell transmitted via the ATM network 30. Receiver 5
2 performs SRTS processing on the receiving side for the received ATM cell, establishes synchronization of the MPEG transport packet generated as a result, extracts the dummy packet inserted therein, and outputs the dummy packet to a decoder (not shown). I do.

Next, an example of the configuration of the transmitting apparatus 51 and its operation will be described. As shown in FIG. 7, the transmission device 51 includes a dummy data supply unit 61, a data conversion unit 62, a PCR adjustment unit 63, and an SRTS processing unit 41. The dummy data supply unit 61 has a PID (Packet Identification)
The data (dummy data) of the dummy packet set to 1FFFh is supplied to the data conversion unit 62.

The data converter 62 comprises a FIFO 71, a constant rate generator 72, and a switch 73, as shown in FIG. For example, as shown in FIG. 9A, the input MPEG transport packet data whose data rate is not constant is input to the FIFO 71, and the FIFO 71 stores it. The constant rate generating section 72 controls the switch 73, connects to the FIFO 71 or the dummy data supply section 61, reads the MPEG transport packet data from the FIFO 71 when connected to the FIFO 71, and connects to the dummy data supply section 61. In this case, the dummy data is read from the dummy data supply unit 61. The constant rate generating section 72 inserts the dummy data (data for the dummy packet) read from the dummy data supply section 61 into the MPEG transport packet data read from the FIFO 71 so that the data rate becomes constant, and performs PCR adjustment. Output to the unit 63.

For example, in the case of FIG. 9A, 188 bytes of MPEG transport packet data of an MPEG transport packet 1 (denoted as packet 1 in the figure) is input to the FIFO 71 and stored therein. 9B, the constant rate generating section 72 converts the 188-byte MPEG transport packet data of the MPEG transport packet 1 from the FIFO 71 so that the data rate becomes a constant data rate T1, as shown in FIG. The data is read and output to the PCR adjustment unit 63.

When all of the 188-byte MPEG transport packet data of the MPEG transport packet 1 is read, and there is no data to be read remaining in the FIFO 71 (MP
It is assumed that the MPEG transport packet data of the EG transport packet 2 has not yet been input to the FIFO 71), the constant rate generation unit 72 controls the switch 73, connects to the dummy data supply unit 61, and connects to the dummy data supply unit. The dummy data (dummy packet) of 188 bytes from 61 is read and output to the PCR adjusting unit 63 at the data rate T1, as shown in FIG. 9B.

That is, the data conversion section 62 converts the input MPEG transport packet data having a non-constant data rate into data having a constant data rate, and outputs the data to the PCR adjustment section 63.

The PCR adjuster 63 is configured to add a PCR (in the example of FIG. 9, the MPEG transport packet) added to the MPEG transport packet in advance.
The PCR included in the transport packet 2 is rewritten according to the data converted so that the data rate becomes constant, and is output to the SRTS processing unit 41.

The SRTS processing unit 41 performs SRTS processing on the transmission side on the MPEG transport packet data input from the PCR adjustment unit 63, and converts the resulting ATM cell into an ATS.
The data is transmitted on the TM network 30.

Next, a configuration example of the receiving device 52 and its operation will be described. The receiving device 52 includes an SRTS processing unit 42 and a dummy packet extracting unit 81.

The SRTS processing unit 42 has an ATM network 3
The ATM cell transmitted via "0" is input. SRTS
The processing unit 42 performs SRTS processing on the receiving side on the input ATM cell, as in the case of the example of FIG.
The PEG transport packet data (FIG. 9B) is generated and output to the dummy data extracting unit 81.

The dummy data extracting unit 81 converts the MPEG transport packet data into which the dummy packet is inserted, which is input from the SRTS processing unit 42, as shown in FIG.
As shown in (1), a dummy packet is extracted and output to, for example, a decoder (not shown). Since 1FFFh is set in the PID (Packet Identification) of the dummy packet, the dummy packet is thereby identified.

As described above, since the data rate is made constant by inserting the dummy packet, the SRTS on the transmitting side is inserted.
Processing and SRTS processing on the receiving side can be executed. That is, the SRTS method is used even when transmitting data having a non-constant data rate.

The series of processes described above can be executed by hardware, but can also be executed by software. When a series of processing is executed by software, a program constituting the software is used by a PCR rewriting unit 64 as dedicated hardware.
It is installed in, for example, a general-purpose personal computer or the like, which can execute various functions by installing a computer incorporated in the PC or various programs.

Next, referring to FIG. 11, a program for executing the above-described series of processing is installed in a computer, and a computer used for making the computer executable is a general-purpose personal computer. The following is an example of the case.

As shown in FIG. 11A, a program is stored in a hard disk 102 or a semiconductor memory 1 as a recording medium built in a personal computer 101.
03 in advance.

Alternatively, the program is executed as shown in FIG.
As shown in (B), a floppy (registered trademark) disk 111, a CD-ROM (Compact Disk-Read Only Memory) 11
2. MO (Magneto-Optical) disc 113, DVD (Digit
al Versatile Disk) 114, a magnetic disk 115, a semiconductor memory 116, or other such storage media, which can be temporarily or permanently stored and provided as package software.

Further, as shown in FIG. 11C, the program is wirelessly transferred from the download site 121 to the personal computer 101 via the artificial satellite 122 for digital satellite broadcasting, or transmitted to the local area network or the Internet. Network 131
, And can be transferred to the personal computer 101 by wire, and stored in the built-in hard disk 102 or the like in the personal computer 101.

The medium in the present specification means a broad concept including all these media.

As shown in FIG. 12, for example, the personal computer 101 has a CPU (Central Processing Unit).
it) 142 built-in. The CPU 142 has a bus 141
An input / output interface 145 is connected via the input / output interface 145. When a user inputs a command via the input / output interface 145 from an input unit 147 including a keyboard, a mouse, and the like, the CPU 142 ROM (Read) corresponding to the semiconductor memory 103 of FIG.
(Only Memory) 143 is executed. Alternatively, the CPU 142 may transfer the program stored in the hard disk 102 in advance, the satellite 122 or the network 131 to the communication unit 148.
And the program installed on the hard disk 102 or the floppy disk 111, CD-ROM 112, MO
Disk 113, DVD 114, or magnetic disk 1
15 and installed in the hard disk 102 are stored in a RAM (Random Access Memory).
y) Load to 144 and execute. Further, the CPU 142
Sends the processing result to, for example, the input / output interface 1
An output is provided to a display unit 146, such as an LCD (Liquid Crystal Display), as necessary, via the LCD 45.

In this specification, the steps of describing a program provided by a medium are not limited to processing performed in chronological order in the described order, but are not necessarily performed in chronological order. It also includes processes that are executed individually or individually.

In this specification, the system is
It represents the entire device composed of a plurality of devices.

[0056]

According to the communication apparatus of the first aspect, the communication method of the third aspect, and the medium of the fourth aspect, the first data having a non-constant data rate is converted to the first data having a non-constant data rate. Is converted to the second data which is not equal to the SRTS.
It can be transmitted using the law.

According to the communication device of the fifth aspect, the communication method of the sixth aspect, and the medium of the seventh aspect,
Clock information generated according to the SRTS method is added, dummy data is inserted so that the data rate is constant.Dummy packets are received, and dummy packets are extracted from the data. hand
The SRTS method can be used.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a conventional data transmission system.

FIG. 2 is a diagram illustrating PCR.

FIG. 3 is a block diagram illustrating a configuration example of a system decoder 4 of FIG. 1;

FIG. 4 is a block diagram illustrating a configuration example of a PLL circuit 13 of FIG. 3;

FIG. 5 is a block diagram illustrating a configuration example of a data transmission system to which the SRTS method is applied.

FIG. 6 is a diagram showing a data configuration of data conforming to the DVB-Paralell standard.

FIG. 7 is a diagram illustrating a configuration example of a data transmission system to which the present invention is applied.

FIG. 8 is a diagram showing a data structure of data conforming to the DVB-ASI standard.

FIG. 9 is a diagram showing a timing chart of data transmitted and received.

FIG. 10 is a diagram illustrating a configuration example of a data conversion unit 62;

FIG. 11 is a diagram showing a medium.

12 is a diagram illustrating a configuration example of a personal computer 101 in FIG.

[Explanation of symbols]

41 SRTS processing unit, 42 SRTS processing unit, 51 transmitting device, 52 receiving device, 61 dummy data supply unit, 62 data conversion unit, 63 PCR adjustment unit, 7
1 FIFO, 72 constant rate generator, 73 switch, 81 dummy data extraction unit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroaki Seto 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Eisaburo Itakura 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F term (reference) 5K030 HA10 HB02 HB09 HB29 JA06 KA02 KA21 5K033 BA13 CB02 CB15 CC01 DB11 DB12 5K047 GG11 JJ01

Claims (7)

[Claims] 1. A communication device connected to a receiving device via a network, wherein said conversion means converts first data having a non-constant data rate into second data having a constant data rate, and said conversion means. Generating means for generating clock information in accordance with the SRTS method based on the second data converted by: the clock information generated by the generating means; and the second data converted by the converting means. ,
A communication device, comprising: transmission means for transmitting to the reception device. 2. The conversion means includes: storage means for storing the first data; holding means for holding dummy data; first data stored by the storage means; Reading the held dummy data at a predetermined timing, inserting the read dummy data into the read first data,
The communication device according to claim 1, further comprising: a constant rate generating unit configured to generate the second data. 3. A communication method for a communication device connected to a receiving device via a network, comprising: converting a first data having a non-constant data rate into a second data having a constant data rate; A generation step of generating clock information according to the SRTS method based on the second data converted in the processing of the conversion step, and the clock information generated in the processing of the generation step, and the processing of the conversion step. Transmitting the converted second data to the receiving device. 4. A program for communication processing for communicating with a receiving apparatus via a network, wherein the first data having a non-constant data rate is converted into the second data having a constant data rate. A generating step of generating clock information according to the SRTS method based on the second data converted in the processing of the converting step; and the clock information generated in the processing of the generating step; and the converting step And transmitting the second data converted in the process of (b) to the receiving device. 5. A communication device connected to a transmission device via a network, wherein the clock information generated according to the SRTS method is added, and the reception device receives data into which dummy data is inserted so that the data rate is constant. Means, a synchronization establishing means for establishing synchronization of the data based on the clock information added to the data received by the receiving means, and from the data established by the synchronization establishing means, A communication device comprising: a removing unit configured to remove the dummy data. 6. A communication method of a communication device connected to a transmission device via a network, wherein clock information generated according to the SRTS method is added, and data into which dummy data is inserted so that the data rate is constant. A receiving step of receiving; a synchronization establishing step of establishing synchronization of the data based on the clock information added to the data received in the processing of the receiving step; Removing the dummy data from the established data. 7. A communication processing program for communicating with a transmitting apparatus via a network, wherein clock information generated according to the SRTS method is added, and dummy data is inserted so that a data rate is constant. An input step of inputting the received data; a synchronization establishing step of establishing synchronization of the data based on the clock information added to the data input in the processing of the input step; and a processing of the synchronization establishing step. A medium for causing a computer to execute a program, comprising: a step of removing the dummy data from the data for which synchronization has been established in step (a).