JP2004112334A - Real time transmission system and real time receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a real time transmitter in which it is possible to switch to another transmission line such as an ISDN network before a transmission line becomes unfit for transmission of real time signals due to frequent transmission errors, by detecting the tendency of the increase of the transmission errors in a VIP network using an IP. <P>SOLUTION: The real time receiver 3 is connected with a real time transmitter via the IP network 61 and an ISDN line 62, and is provided with an ISDN line communication control means 31 to control connection by establishing the connection of an IP network communication control means 30, a BF 32-1, an IP network synchronization detecting means 33-1, the ISDN line 62, a delay control means 34 to control delay amounts of both BFs on the basis of a BF 32-2, an ISDN line synchronization detecting means 33-2, and the detection results of a synchronization detecting means 33. Further, the receiver has a transmission line abnormality detecting means 36 to detect the increase signs of the transmission errors by measuring a packet loss rate and a jitter of the real time signals via the IP network 61, a switching means 35 to output the real time signals from the IP network 61 or the ISDN network 62 by switching them, and a delay means 37 to adjust the timing for switching the real time signals via the IP network 61 to the ISDN line 62. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a transmission path in which the transmission cost is inexpensive, such as a virtual private network (VPN) network using IP (Internet Protocol), but transmission errors sometimes increase because the network is shared with other terminals. It is possible to reduce transmission cost and secure reliability by adaptively switching to a transmission line having high reliability but high transmission cost because the line can be occupied like an ISDN (Integrated Services Digital Network) network. Aim.
[0002]
[Prior art]
Transmission apparatuses for transmitting image signals captured by a television camera include those using an ISDN line and those using an IP network. In this transmission device, the transmission path is disconnected due to disconnection, and the video and audio after the disconnection are not transmitted. Also, the video and audio after the disconnection is not normally recorded and cannot be viewed (for example, see Patent Document 1).
[0003]
To cope with this problem, it was necessary to duplicate the line and switch it. Conventionally, in a transmission device, a line is duplicated or a line is manually switched (for example, see Patent Document 2).
[0004]
However, in a VPN network using IP, whose service has recently been started, it has been conventionally performed to convert an image signal into an IP packet and send it to the network (for example, see Patent Document 3).
[0005]
[Patent Document 1]
JP-A-5-7363 [Patent Document 2]
JP-A-8-79727 [Patent Document 3]
JP 2001-238160 A
[Problems to be solved by the invention]
In order to solve the above problem, an object of the present invention is to detect an increasing tendency of transmission errors in a VPN network using IP, and to detect an increase in transmission errors before it becomes unsuitable for transmitting real-time signals. It is an object of the present invention to provide a real-time transmission device capable of switching to another transmission path.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides means for encoding real-time signals such as video and audio input from a television camera or the like, and transmission of the encoded real-time encoded signals with high reliability such as ISDN. Means for sending to a low-cost transmission line such as a network and a VPN network, and the communication quality of a real-time coded signal received via a low-cost transmission line such as a VPN network, and the communication quality is degraded. Means for starting communication on a highly reliable transmission path such as ISDN, switching to a real-time coded signal transmitted via a highly reliable transmission path such as ISDN, and decoding the real-time coded signal after switching Means for reproducing the original image or audio signal.
[0008]
Here, as an inspection method of the communication quality, an index often used in the evaluation of the IP communication, such as a packet loss rate and fluctuation (jitter) of a packet arrival interval, can be considered.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a real-time transmission system including a moving image transmitting apparatus as a real-time transmitting apparatus and a moving image receiving apparatus as a real-time receiving apparatus according to the present invention will be described with reference to FIG. The video signal input from the television camera 21 and the audio signal input from the microphone 22 connected to the moving image transmitting apparatus 1 are converted into digital data by the moving image transmitting apparatus 1 as an IP network 61 or an ISDN line 62. Is transmitted to the moving image receiving apparatus 3. In this case, instead of the television camera and the microphone in this case, a video device such as a VTR may be connected.
[0010]
The transmitted data is received by the moving image receiving device 3 and output as video and audio to the television monitor 51 and the speaker 52 connected to the moving image receiving device 3. In this case as well, instead of the television monitor and the speaker, it may be connected to another video device such as a VTR.
[0011]
The internal configuration of the moving image transmitting device 1 will be described with reference to FIG. The moving image transmitting apparatus 1 includes a video analog / digital converter (A / D) 10-1, a video encoding circuit 11-1, an audio analog / digital converter (A / D) 10-2, an audio codec. Circuit 11-2, video / audio multiplexing unit (MUX) 12, buffer memory (Buf) 13, IP network interface (NIC) 14, ISDN line interface (NCU) 15, storage unit 16, storage It has a unit operation control unit 17 and a connector port 18.
[0012]
The video analog-to-digital converter 10-1 has a function of digitizing a video signal input from the television camera 21.
[0013]
The video encoding circuit 11-1 has a function of converting the digitized video signal into encoded data suitable for transmission and storage.
[0014]
The audio analog-to-digital converter 10-2 has a function of digitizing an audio input signal input from the microphone 22.
[0015]
The audio encoding circuit 11-2 has a function of converting the digitized audio signal into encoded data suitable for transmission and storage.
[0016]
The video / audio multiplexing unit (MUX) 12 has a function of multiplexing these coded video and audio coded data.
[0017]
The buffer memory 13 functions as a buffer for preventing data from being temporarily interrupted when switching between the IP network interface 14 and the ISDN line interface 15.
[0018]
The IP network interface (NIC) 14 takes an interface with the IP network 61.
[0019]
The ISDN line interface (NCU) 15 interfaces with the ISDN line 62.
[0020]
The storage unit 16 has a function of storing data when both the IP network 61 and the ISDN line 62 are disconnected.
[0021]
The storage unit operation control unit 17 has a function of monitoring the IP network interface 14 and the ISDN line interface 15 and controlling the operation of the storage unit 16.
[0022]
First, the video input signal input from the television camera 21 is digitized by the video analog / digital converter 10-1. The digitized video signal becomes encoded data in a form suitable for transmission and storage by the video encoding circuit 11-1. On the other hand, the audio input signal input from the microphone 22 is also digitized by the audio analog-to-digital converter 10-2. The digitized audio signal becomes encoded data suitable for transmission and storage by the audio encoding circuit 11-2. These encoded video and audio coded data become coded data multiplexed by the video / audio multiplexing unit 12.
[0023]
The multiplexed video / audio encoded data is temporarily stored in a buffer memory (Buf) 13. The stored data is immediately sent to the next IP network interface 14, the ISDN line interface 15, and each entry of the storage unit 16 at the same time.
[0024]
The internal configuration of the moving image receiving device 3 will be described with reference to FIG. The moving image receiving apparatus 3 includes an IP network interface (NIC) 30, an ISDN network interface (NCU) 31, an IP network buffer memory (Buf) 32-1, and an ISDN line buffer memory (Buf) 32-2. , An IP network synchronization detection unit 33-1, an ISDN line synchronization detection unit 33-2, a delay control unit 34, a switch 35, a network abnormality detection unit 36, a delay unit 37, and video / audio multiplexed data separation. (DMUX) 38, a video decoding circuit 39-1, an audio decoding circuit 39-2, a video signal digital / analog converter (D / A) 40-1, and an audio signal digital / analog converter ( D / A) 40-2.
The IP network interface 30 is an interface with the IP network 61.
[0026]
The ISDN network interface 31 is an interface with the ISDN line 62.
[0027]
The IP network buffer memory 32-1 has a function of temporarily storing the transmission data extracted by the IP network interface 30.
[0028]
The ISDN line buffer memory 32-2 has a function of temporarily storing the transmission data extracted by the ISDN line interface 31.
[0029]
The IP network synchronization detector 33-1 has a function of detecting synchronization of the IP network.
[0030]
The ISDN line synchronization detecting section 33-2 has a function of detecting the synchronization of the ISDN line.
[0031]
The delay control unit 34, based on the synchronization between the IP network and the ISDN line detected by the IP network synchronization detection unit 33-1 and the ISDN line synchronization detection unit 33-2, stores an IP network buffer memory 32-1 and an ISDN line buffer. By controlling the read timing of the memory 32-2, it has the function of controlling the delay amount and measuring the switching timing.
[0032]
The switch 35 has a function of switching and outputting transmission data from the IP network 61 and transmission data from the ISDN line 62 under the control of the delay unit 37.
[0033]
The network abnormality detection unit 36 monitors transmission data received via the IP network 61, measures a packet loss rate, a jitter, and the like, detects a sign that a transmission error further increases, activates the ISDN line interface 31, and activates the ISDN line interface 31. In addition to setting up a call at 62, the function of notifying the video transmission apparatus 1 of an abnormality on the IP network 61 via the IP network 61 and instructing switching to the IP network interface 14 or the ISDN line interface 15. Have. Further, the network abnormality detection unit 36 monitors the IP network 61 while transmitting the transmission data via the ISDN network 62, and when detecting that the abnormality of the IP network 61 has been recovered, the transmission from the ISDN network 62 via the IP network 61. It has the function of returning to.
[0034]
The delay unit 37 has a function of adjusting the switching timing of the IP network 61 and the ISDN network 62 at the time of transmission line switching.
[0035]
The video / audio multiplexed data separation section 38 has a function of separating video data and audio data from the multiplexed data.
[0036]
The video decoding circuit 39-1 has a function of decoding video data to obtain digital video data.
[0037]
The audio decoding circuit 39-2 has a function of decoding the audio data to obtain digital audio data.
[0038]
Transmission data coming from the IP network 61 is input to the IP network interface 30. The transmission data extracted by the IP network interface 30 is once input to the IP network synchronization detection unit 33-1 via the IP network buffer memory 32-1. Transmission data coming from the ISDN line 62 is input to the ISDN network interface 31. The transmission data extracted by the ISDN line interface 31 is once input to the ISDN line synchronization detecting section 33-2 via the ISDN line buffer memory 32-2.
[0039]
The IP network synchronization detector 33-1 and ISDN line synchronization detector 33-2 detect the respective synchronizations, control the timing of reading from the buffer, control the delay, and measure the switching timing.
[0040]
The network abnormality detection unit 36 constantly monitors the packet loss rate of the received transmission data and the fluctuation (jitter) of the intervals at which packets arrive, and controls the switch 35 according to the set values. The delay unit 37 adjusts the switching timing while checking each synchronization. On the other hand, the network abnormality detection unit 36 instructs the moving picture transmitting apparatus 1 to switch the IP network interface 14 or the ISDN line interface 15 through the IP network 61.
[0041]
Returning to FIG. 2, the moving image transmitting device 1 that has received the switching instruction from the moving image receiving device 3 switches between the IP network interface 14 and the ISDN line interface 15. The coded data during the switching period is temporarily stored in the buffer memory 13, so that the switching can be performed smoothly.
[0042]
Next, the flow of data after switching will be described with continuation of FIG. The data selected and output by the switch 35 is separated by the video / audio multiplexed data separation section 38 into video encoded data and audio encoded data. The separated video encoded data is converted into a digital video signal by the video decoding circuit 39-1. The digital video signal is converted into an analog video signal by the video digital / analog converter 40-1 and output to the television monitor 51.
[0043]
On the other hand, for audio, similarly, the encoded audio data separated by the video / audio multiplexed data separation unit 38 is converted into a digital audio signal by the audio decoding circuit 39-2. The digital audio signal is converted into an analog audio signal by the audio digital / analog converter 40-2 and output to the speaker 52. The video input from the TV camera 21 is displayed from the TV monitor 51, and the audio input from the microphone 22 is reproduced from the speaker 52.
[0044]
Next, a switching operation sequence of the image transmission apparatus 1 according to the present invention will be described with reference to FIGS. First, the network abnormality detecting unit 36 of the video transmitting / receiving device 3 monitors the data loss rate, the RTT jitter, and the like on the IP network 61 (Step S1), and determines whether or not the value has exceeded a first value (Step S1). Step S2). When values such as the data loss rate and the RTT jitter on the IP network 61 are equal to or greater than the first threshold, the ISDN line interface 31 is started up (step S3).
[0045]
The line state is monitored by the ISDN line interface 31 (step S4), and if the state is not suitable (step S5: No), an accumulation start command is issued to the transmission side (step S6). Based on this, the transmission side starts accumulation (step S7). The loss rate and the jitter are continuously monitored, and it is determined whether or not the values are equal to or less than the first threshold (Step S8). When the values are equal to or less than the first threshold (Step S8: Yes). Then, an accumulation stop command is issued to the transmission side (step S9). Based on this, the transmission side stops the accumulation (step S10). Thereafter, the process returns to the normal loss rate and jitter monitoring state in step S1.
[0046]
On the other hand, when the loss rate and the jitter are equal to or larger than the first threshold value (step S2: Yes), the ISDN line interface is started up (step S3), and the ISDN line state is good (step S5: Yes). Connect the ISDN line 62 (step S11).
[0047]
After the ISDN line 62 is connected, the loss rate and the jitter of the IP network 61 are monitored. If the loss ratio and the jitter become equal to or less than the first threshold value (step S12: Yes), the ISDN line 61 is disconnected and the loss rate and the jitter Return to monitoring state.
[0048]
Also, in step S12, when the difference does not fall below the first threshold and becomes greater than or equal to the second threshold (step S14: Yes), the synchronization of the transmission data of both the IP network 61 and the ISDN line 62 is detected (step S12). In step S15, the buffer amount is adjusted (step S16), and when the timing of the data matches, switching from the data from the IP network 61 to the data from the ISDN line 61 is performed (step S17). At the same time, an accumulation start command is issued to the transmission side (step S18), and the transmission side starts accumulation (step S19).
[0049]
Further, the network abnormality detecting unit 36 continuously monitors the loss rate and the jitter of the IP network 61, and when the values fall below the first threshold value (step S20: Yes), the synchronization of both transmission data is synchronized. When the data is detected (FIG. 5: step S21), the buffer amount is adjusted (step S22), and the timing of the data on the IP network 61 and the data on the ISDN line 62 match, the data on the ISDN line 62 is replaced with the data on the IP network 61. Is performed (step S23). At the same time, a switching command and a storage stop command are issued to the transmitting side (step S29), and the transmitting side stops storing (step S30). Thereafter, the ISDN line is disconnected (step S31), and the process returns to the normal loss rate and jitter monitoring state in step S1.
[0050]
The IP network 61 is always connected even when the ISDN line 62 is in use, in order to switch back to the IP network 61 when the IP network 62 is restored, and the loss rate and jitter of the IP network 61 must be monitored. Must.
[0051]
The transmitting side continues to transmit the transmission data to the IP network 61 even while the ISDN line 62 is in use.
[0052]
【The invention's effect】
When the communication line is interrupted, automatic switching to the call transmission path can be performed to continue moving image transmission without any trouble. When the protection line is also interrupted, the video / audio data is stored in the video / audio storage means. Can be stored so as not to be overlooked. In particular, it has a great practical effect as a moving image transmission device used for monitoring purposes.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a real-time transmission system of the present invention.
FIG. 2 is a block diagram of a moving image transmitting apparatus according to the present invention.
FIG. 3 is a block diagram of a moving image receiving apparatus according to the present invention.
FIG. 4 is a sequence diagram in the moving image transmission system of the present invention.
FIG. 5 is a sequence diagram continued from FIG. 4;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Moving image transmission apparatus 10-1 Video analog-to-digital converter 10-2 Audio analog-to-digital converter 11-1 Video encoding circuit 11-2 Audio encoding circuit 12 Video / audio multiplexing unit 13 Buffer memory 14 IP network Interface 15 ISDN network interface 16 Storage unit 17 Storage unit operation control unit 18 Connector port 21 TV camera 22 Microphone 3 Video receiving device 30 IP network interface 31 ISDN network interface 32-1 IP network buffer memory 32-2 ISDN line buffer Memory 33-1 IP network synchronization detection unit 33-2 ISDN line synchronization detection unit 34 Delay control unit 35 Switching unit 36 Network abnormality detection unit 37 Delay unit 38 Video / audio multiplexed data separation unit 39-1 Video decoding circuit 39-2 Audio decoding circuit 40-1 Video digital / analog Audio converter 40-2 audio digital / analog converter 51 television monitor 52 speaker 61 IP network 62 ISDN line

Claims (9)

The real-time transmitting apparatus and the real-time receiving apparatus share a line with another user, and a transmission error (packet loss) increases when traffic increases. In a video / audio real-time transmission system connected via two transmission paths of two transmission paths,
Real-time transmitter
First communication control means for transmitting a real-time signal to the first transmission path;
Second communication control means for controlling a call connection with the second transmission path and transmitting a real-time signal to the second transmission path,
Real-time receiver,
First communication control means for controlling connection with the first transmission path;
A first buffer memory for temporarily storing a real-time signal received from the first transmission path;
First synchronization detecting means for detecting synchronization of the first transmission path;
A second communication control unit that establishes connection of the second transmission line and controls connection with the second transmission line when the transmission line abnormality detection unit detects a sign that a transmission error further increases;
A second buffer memory for temporarily storing a real-time signal received from the second transmission path;
Second synchronization detecting means for detecting synchronization of the second transmission path;
Delay control means for controlling delay amounts of the first buffer memory and the second buffer memory based on detection results of the first synchronization detection means and the second synchronization detection means;
A transmission path abnormality detecting means for measuring a packet loss rate, a jitter, and the like of a real-time signal received via the first transmission path and detecting a sign that a transmission error further increases;
Switching means for switching and outputting a real-time signal from the first transmission path and a real-time signal from the second transmission path;
Delay means for adjusting timing for switching a real-time signal via the first transmission path to the second transmission path. The real-time transmission system according to claim 1, wherein the first transmission path is a VPN network using IP, and the second transmission path is an ISDN network. 3. The real-time transmission system according to claim 1, wherein the real-time signal is a video signal and an audio signal. The real-time transmission system according to any one of claims 1 to 3, wherein the real-time transmission device includes an encoding circuit that encodes a real-time signal. The real-time transmitting apparatus and the real-time receiving apparatus share a line with another user, and a transmission error (packet loss) increases when traffic increases. A first communication control unit for controlling connection with a first transmission line, in a real-time receiving device configuring a video / audio real-time transmission system connected through two transmission lines of two transmission lines;
A first buffer memory for temporarily storing a real-time signal received from the first transmission path;
First synchronization detecting means for detecting synchronization of the first transmission path;
A second communication control unit that establishes connection of the second transmission line and controls connection with the second transmission line when the transmission line abnormality detection unit detects a sign that a transmission error further increases;
A second buffer memory for temporarily storing a real-time signal received from the second transmission path;
Second synchronization detecting means for detecting synchronization of the second transmission path;
Delay control means for controlling delay amounts of the first buffer memory and the second buffer memory based on detection results of the first synchronization detection means and the second synchronization detection means;
A transmission path abnormality detecting means for measuring a packet loss rate, a jitter, and the like of a real-time signal received via the first transmission path and detecting a sign that a transmission error further increases;
Switching means for switching and outputting a real-time signal from the first transmission path and a real-time signal from the second transmission path;
Delay means for adjusting the timing of switching a real-time signal via the first transmission path to the second transmission path. The real-time receiving apparatus according to claim 5, wherein the first transmission path is a VPN network using IP, and the second transmission path is an ISDN network. 7. The real-time receiving device according to claim 5, wherein the real-time signal is a video signal and an audio signal. 8. The real-time receiving apparatus according to claim 5, further comprising a decoding circuit for decoding the real-time signal. 9. The transmission line abnormality detecting means for transmitting a real-time signal via the first transmission line when detecting that the increase in transmission errors has been restored. Real-time receiver.

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