JPH05292055A - Staff synchronizing device - Google Patents

Abstract

PURPOSE:To provide a staff synchronizing device which generates a staff by detecting phase differences between >=2 pieces of information and frames and then multiplexes and transmits whether or not there is the staff as staff control information with the frame on a reception side, and performs destaffing accord ing to the staff control information and extracts and receives the information from the frame on a reception side. CONSTITUTION:This staff synchronizing device is equipped with a transmitter 1 consisting of a staff circuit 4 which detects the phase differences between at least >=2 pieces of information and the frames and generates and multiplexes the staff with the information and a framing circuit 11 which generates the staff control information, and a receiver 3 consisting of a transmission line 2 which transmits the frame, a deframing circuit 14 which separates the information and staff control information from the frame and a destaff circuit 18 which removes the staff from the information according to the staff control information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stuff synchronizer for synchronizing a frame of information and a frame by correcting the phase difference between the frame of the information and the frame using a stuff in a digital signal frame transmission system. It is a thing.

[0002]

2. Description of the Related Art Generally, when the frequency of information and the clock are slightly different from the stuff synchronization method, the phase difference of the information and the clock is corrected by shifting the information backward by one clock when the phase difference exceeds a certain value. This is a method for synchronizing. In addition, in a method of transmitting information by multiplexing the information in bytes on a frame basis, there is a method of synchronizing on a byte basis by multiplexing the phase difference between the frame and the information as a stuff byte in the data part of the frame.

[0003]

SUMMARY OF THE INVENTION A conventional synchronous digital hierarchy (hereinafter referred to as SDH) which is the above-mentioned stuff synchronization method.
And abbreviated. Nippon Telegraph and Telephone Technical Committee (hereinafter abbreviated as TTC)
Standard JT-G707, JT-G708, JT-G709
Refer to) for synchronous transmission module (hereinafter abbreviated as STM)
Although it is possible to multiplex one piece of information into a frame, such as a virtual container (hereinafter abbreviated as VC) frame to a frame using a pointer, it is not possible to multiplex two or more pieces of information into one frame. could not.

The present invention solves the above-mentioned conventional problems by generating a stuff by detecting a transmission speed difference between at least two or more pieces of information and a transmission frame, and determining whether or not each piece of information has a fixed length. An object of the present invention is to provide a stuff synchronizer which is characterized in that it is multiplexed with a frame as stuff control information and transmitted, and on the receiving side, the presence or absence of stuff is judged by the stuff control information and information is extracted from the frame and received.

[0005]

In order to achieve this object, the stuff synchronizer of the present invention inputs at least two or more pieces of information, determines the transmission speed difference between each piece of information and the frame, and determines staff and staff control information. A stuffing circuit that multiplexes information into a frame and a framing circuit that multiplexes information into a frame, a transmission line that transmits a frame output from the transmitter, and a frame that is input from the transmission line and is separated into respective pieces of information. The configuration includes a deframing circuit and a receiver including a destuff circuit that removes stuff based on the result of majority processing of stuff control information from each information and outputs data according to the transmission rate.

[0006]

With this configuration, the stuff synchronizer of the present invention can multiplex a plurality of pieces of information having different frequencies in synchronization with a frame and transmit / receive them with high quality.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram of a stuff synchronizer according to an embodiment of the present invention. The transmitter 1 and the receiver 3 are connected via a transmission line 2. The digital signal transmitted on the transmission line 2 is an STM-16 frame.

Video information and video clock, audio information and audio clock, and auxiliary information are input to the transmitter 1. The switch 12 can switch the clock synchronized with the VC4 frame to the video clock and the audio clock.

The video signal is input to the stuff circuit 4. The video information is written in the 2-port buffer 5 by the stuff circuit 4 by the video clock, and the VC4 frame timing is generated.
It is read at the STM-16 clock output by the output and input to the framing circuit 11. The staff judgment 9 is 2 so that the phase difference between the video information and the VC4 frame is always constant.
The phase difference between the write phase and the read phase of the port buffer 5 is detected by comparing the values of the write counter 6 and the read counter 8 by the phase comparison 7, and it is determined whether the stuff is generated. The stuff control information generation 10 generates the number of stuff bytes added to the VC4 frame as control information based on the result of the stuff judgment 9 and inputs it to the framing circuit 11. The audio information is input to the framing circuit 11 in the same manner as the video information. The auxiliary information is directly input to the framing circuit 11.

In the framing circuit 11, video information, audio information, auxiliary information and stuff control information are multiplexed in the VC4 frame. The arrangement of video information, audio information, and auxiliary information in the VC4 frame will be described later. After that, the framed VC4 frame is multiplexed into the STM-1 frame to the STM-16 frame by a method conforming to the TTC standard and sent to the transmission line 2.

STM-input to the receiver 3 from the transmission line 2
The 16 frames are input to the deframing circuit 14. The deframing circuit 14 uses the STM according to the TTC standard.
-16 frames are separated from STM-1 frames into VC4 frames. The VC4 frame consists of video information, audio information,
It is separated into auxiliary information and video stuff control information and output from the deframing circuit 14.

The video information is input to the destuff circuit 18, is temporarily written in the 2-port buffer 5 by the write counter 6 at the timing generated by the VC4 frame timing generation 13 from the STM-16 clock input from the transmission line, and is received by the receiver 3 It is read by the read counter 8 with the reproduced video clock generated in step. For error correction, the stuff control information is determined by the 9-bit majority decision 15 which has a larger number of 0 bits and 1 bit to determine the presence or absence of the stuff, and when it cannot be determined, it is detected by the abnormality detection 17. The destuff timing 16 notifies the position of destuff based on the results of the 9-bit majority decision 15 and the abnormality detection 17. The write counter 6 controls the counter at the timing output from the destuff timing 16, removes the stuff from the video information, and writes it in the 2-port buffer 5.

The phase comparison 7 compares the values of the read counter 8 and the write counter 6 with the result of clock recovery circuit 19
Output to. The clock recovery circuit 19 is a loop filter 20,
It consists of voltage controlled oscillator 21 and frequency divider 22, and the result of phase comparison 7 is smoothed by loop filter 20. Based on this, voltage controlled oscillator 21 outputs a clock and frequency divider 22 frequency-divides it. Outputs the playback video clock. The read counter 8 reads out video information from the 2-port buffer 5 with the reproduced video clock output from the clock recovery circuit 19 and outputs it. The audio information is output in the same manner as the video information. The auxiliary information is output as it is. The video information, audio information, and auxiliary information output from the receiver 3 are transmitted to their respective processing systems.

As an example, HDTV with STM-16 frame
Signal (Y, Pb, Pr: sampling frequency 74.25)
FIG. 2 shows a configuration example of a VC4 frame when transmitting an audio signal (sampling frequency: 48 kHz, 64 bit quantization) and a 10 MHz quantization). In the VC4 frame, the path overhead (POH) 23, the video buffer control information 24, and the fixed video information 25 and audio / video in a column unit following the video buffer control information 24.
Auxiliary information 28 and fixed staff 29 are assigned. This POH 23 is fixed in this device. In the VC4 frame, the staff control information 24 is one column, the fixed staff 29 is every 13 columns, a total of 20 columns, and the voice / auxiliary information 28 is every 18 columns, a total of 13 columns and the remaining 22 columns in the area excluding the fixed staff.
The video information 25 is arranged in 6 columns.

The video information 25 is an HDTV signal of 74.25M.
10-bit Y signal and P sampled at Hz
Error correction 1 bit is added to the b, Pr multiplex signal, and further 6
The video frame is composed of 28 bits including an unused area of bits. Therefore, the bit rate Rv of the video information 25 is shown in (Equation 1).

Since Rv = 74.25 [MHz] × 28 “bit” = 2079 [Mbps] (Equation 1), the bit rate of the STM-1 frame is 64.
Since it is Kbps, when the required multiple area per VC4 frame is expressed by the number of bytes Nv, as shown in (Equation 2), Nv = Rv / (16 × 0.064 [Mbps]) = 2030.273438 [Byte] (Equation 2) Becomes When the expression is changed, this becomes 9 [rows] x 225 [columns] + 2 [Bytes] + 35/128 [Bytes] (Equation 3), as in (Equation 3), and the video information per frame of VC4 25 It is possible to calculate the area 226 column required to multiplex. (Formula 3)
35/128 [Byte] means that the video information stuff byte 26 of FIG. 2 is stuffed about 93 times in a 128-frame cycle. 1 per this frame
Due to the stuff bytes arranged in bytes, frequency deviation can be multiplexed within the range of -135ppm to + 357ppm, and the horizontal scanning frequency accuracy of HDTV specified by BTA S-001 is ± 10ppm and the frequency of the transmission clock allowed for NT. The accuracy of ± 20 ppm is fully guaranteed. Actually, in the video staff method of this device, 4
-135ppm ~ +1 because I stuff the frame twice
A frequency shift of 11 ppm can be absorbed.

The video normal stuff control information 31 is, as shown in FIG. 3, a bit b in one byte of each row of the stuff control information 24.
Only use 7. Therefore, since one bit is multiplexed in one row, the video positive stuff control information 31 is 9 bits per VC4 frame, and by the receiver performing error correction by majority decision, it is sufficient for the random error and burst error in the transmission path. Performance is obtained.

The image correct stuff control information 31 is error-corrected by making a 9-bit majority decision by the receiver. The error rate Pe and the error period Te after majority decision error correction are as follows.

[0019]

[Equation 1]

Te = 125 × 10 ⁻⁶ / Pe (sec) (Equation 4) FIG. 3 shows the calculation results of the error rate characteristics and the error rate period after the 9-bit majority decision processing. Sufficient characteristics have been obtained for random errors. Also, VC4 for burst error
Since one bit is arranged in each frame row, it is possible to correct an error with a burst length of up to 50 μsec.

The layout of the voice / auxiliary information area is shown in FIG. 4 (a).
Shown in. The audio information 34 can be multiplexed in four channels per VC4 frame as shown in FIG. Also, voice information (ch1, ch2) 39 and voice information (ch3, ch
4) Since 40 is assigned to the same byte, phase shift between four channels does not occur during demultiplexing. Further, the auxiliary information 35 has 1 as an information bit 43 as shown in FIG.
A (8,4) Hamming error correction code is added to the bit and the error protection bit 41.

The voice information consists of a 64-bit voice frame in which 6-bit error correction and 2-bit frame patterns are added to 16-bit 2-channel voice data sampled at 48 kHz, and unused 16 bits are further added. Therefore, audio information per 2 channels
The bit rate Ra of 35 is Ra = 0.048 [kHz] × 64 [bit] = 3.072 [Mbps] (Equation 5) as shown in (Equation 5), so the number of bytes Na required for 4-channel transmission is As shown in (Equation 6), Na = 2 × 3.072 / 0.64 [Mbps] = 96 [Byte] (Equation 6), and the expression is changed to 10 [Column] +6 [Byte] as in (Equation 7). (Equation 7)

When the video information and the audio information are multiplexed in the VC4 frame, (1) the audio information is synchronized with the VC4 frame. (2) The video information is synchronized with the VC4 frame. There are two possible cases. For example, in the case of (1), the audio sampling number wave number deviation is EIAJ standard CP-34.
0 (AES3-1985), the accuracy level of the sampling frequency is within ± 50 ppm. In case (2), the accuracy level of the sampling frequency is ± 1000 ppm, and the transmitter is synchronized with the network. This is the case where the pointer processing of the VC4 frame is not performed.

In the case of (1), since the voice information 35 is in phase with the VC4 frame, no stuffing occurs. Therefore, the bits b4 and b of each row of the stuff control information 24 in FIG.
The voice positive stuff control information 32 and the voice negative stuff control information 33 of 5 are in the undefined bit 30, the positive stuff byte 37 in FIG. 4A is the voice information 35, and the negative stuff byte 38 is the spare or fixed stuff byte 36. Become.

In the case of (2), ± 1% of frequency deviation can be dealt with by setting 1 byte of positive and negative stuff bytes per VC4 frame in the audio information 34. The staff control information 24 is a voice positive staff control signal as shown in FIG.
32 is placed in bit b5 in 1 byte of each row, and voice negative stuff control signal 33 is placed in bit b4 in 1 byte of each row. Whether or not there is stuff and whether it is positive stuff is determined by the receiver by making a 9-bit majority decision. Determine if it is a negative staff.

The configuration of the synchronization system when the stuff synchronizer of the present invention is connected to the network will be described. FIG. 6 is a block diagram of a synchronization system when the video clock is synchronized with the VC4 frame and the transmitter is not synchronized with the network. Transmitter 44 is STM
The transmission clock 46 (hereinafter abbreviated as f _S ) self-oscillates and V
The C4 transmission clock 50 (hereinafter abbreviated as f _C ) is the video clock 4
6 (hereinafter abbreviated as f _V ) to generate in the PLL circuit.
Therefore, the pointer at the AU4 pointer stuff 51 has a fixed value. In the receiver 45, the clock of the network 52 (hereinafter f _N
Since receiving a f _S in synchronism with the abbreviated) and reproduces f _C by destuffing in AU4 pointer destuff 53. The audio clock 47 (hereinafter abbreviated as f _A ) de-stuffs the audio signal from the VC4 frame and reproduces it by the audio positive stuff control signal and the audio negative stuff control signal. f
_V destuffs the video signal by the video normal stuff control signal from the VC4 frame and reproduces it. FIG. 7 is a block diagram of a synchronization system when the video clock is synchronized with the VC4 frame and the transmitter is synchronized with the network. The transmitter 44 receives the network synchronization signal from the network 46 and generates f _S synchronized with the network 46 by the PLL circuit. Also, f _C is locked to f _V. After that, the video signal and the audio signal are multiplexed by using the staff control information and the AU4 pointer. Therefore, in the receiver 45, A
AU4 pointer destuff 50, video destuff 51, audio destuff by U4 pointer and staff control information
Destuff at 52 and play f _A and f _V. FIG. 8 is a block diagram of a synchronous system when the voice clock is synchronized with the VC4 frame and the transmitter is not synchronized with the network. Transmitter 44 is ST
An M clock (hereinafter abbreviated as f _S ) is self-oscillated and a VC clock (hereinafter abbreviated as f _C ) is generated in a PLL circuit using a voice clock (hereinafter abbreviated as f _A ). Therefore, A
The pointer at the U4 pointer staff 49 has a fixed value.
Since the receiver 45 receives f _S synchronized with the clock of the network 46 (hereinafter abbreviated as f _N ), the AU4 pointer destuff 50
F _C is regenerated by destuffing at. f _A is f _C
Is reproduced by a PLL circuit using the reference signal as the reference signal, and f _V reproduces the video signal by destuffing it from the VC4 frame by the video normal stuff control signal.

Since the video information area, the video staff information area, the audio / auxiliary information area, and the fixed staff area are periodically dispersed in the column direction,
It is possible to realize an LSI with a built-in buffer memory by reducing the buffer memory capacity when multiplexing or separating audio information as much as possible, and receiving video information, audio information, and auxiliary information periodically in the POH. It is easy to demultiplex in the vessel.

[0028]

As described above, according to the present invention,
At least two or more pieces of information and the difference in frame transmission speed are detected, the stuff is multiplexed with the information, and the presence or absence of the stuff for each piece of information is multiplexed with the frame as stuff control information of a certain length and transmitted. It is possible to determine the presence or absence of staff based on the staff control information and receive the staff, and the staff synchronization device is compatible with multimedia.

[Brief description of drawings]

[Figure 1] Block diagram of staff synchronization device

[Fig.2] Layout of VC4 frame

[Fig. 3] Layout of staff control information

4A is a layout diagram of byte allocation of voice / auxiliary information, FIG. 4B is a layout diagram of audio information bit allocation, and FIG. 4C is a layout diagram of auxiliary information bit allocation.

FIG. 5 is an error rate characteristic diagram of the stuff control signal.

FIG. 6 is a block diagram of a synchronization system when a video clock is synchronized with a VC4 frame and a transmitter is not synchronized with a network.

FIG. 7 is a block diagram of a synchronization system when a video clock is synchronized with a VC4 frame and a transmitter is synchronized with a network.

FIG. 8 is a block diagram of a synchronous system when the audio clock is synchronized with the VC4 frame and the transmitter is not synchronized with the network.

[Explanation of symbols]

 1 transmitter 2 transmission line 3 receiver 4 stuff circuit 5 2 port buffer 6 write counter 7 phase comparison 8 read counter 9 stuff judgment 10 stuff control information generation 11 framing circuit 12 switch 13 VC4 frame timing generation 14 deframing circuit 159 Bit majority decision 16 Destuff timing 17 Abnormality detection 18 Destuff circuit 19 Video clock recovery circuit 20 Loop filter 21 Voltage controlled oscillator 22 Divider 23 POH 24 Stuff control information 25 Video information 26 Video information stuff byte 27 Video fixed stuff byte 28 Audio / Auxiliary Information 29 Fixed Stuff 30 Undefined Bit 31 Video Positive Stuff Control Signal 32 Audio Positive Stuff Control Signal 33 Audio Negative Stuff Control Signal 34 Audio Information 35 Auxiliary Information 36 Spare or Fixed Stuff Byte 37 Positive Stuff Byte 38 Negative Stuff 38 Negative Stuff by 39 Audio information (ch1, ch2) 40 Audio information (ch3, ch4) 41 Error protection bit 42 Reserved bit 43 Information bit 44 Transmitter 45 Receiver 46 Video clock 47 Audio clock 48 Video stuff 49 Audio stuff 50 VC4 transmission clock 51 AU4 pointer stuff 52 STM transmission clock 53 network 54 AU4 pointer destuff 55 video destuff 56 audio destuff

Claims (3)

[Claims] 1. When the transmitter side position-multiplexes at least two or more pieces of information into a transmission frame, a phase difference between each piece of the information and the transmission frame is detected, and the presence or absence of staff generated from the determination result is detected. A stuff synchronizer characterized by position-multiplexing and transmitting the stuff control information shown in a transmission frame. 2. The stuff synchronizer according to claim 1, wherein at least two pieces of information are arranged in a transmission frame in a distributed manner. 3. The transmission side arranges a plurality of the same stuff control information in a transmission frame in a distributed manner, and the reception side judges the presence or absence of the stuff by majority-deciding the plurality of stuff control information. The staff synchronization device according to claim 1, which is characterized in that.