JPH08307876A - Packet multiplex transmitter - Google Patents

Abstract

PURPOSE: To reduce load fluctuation with respect to a communication line by reading coded data out of each buffer memory at a prescribed time interval and multiplexing the data while dispersing the peak level. CONSTITUTION: N-sets of video coders 311-31N receive a video signal from video cameras 301-30N and start coding of a video image while awaiting an output signal from corresponding comparators 361-36N. Then a transmission section 350 throws a switch of a changeover device 330 to a contact 331 and a switch of a changeover device 340 to a contact 341 to be connected to a buffer memory 321, from which coded data are read and sent to a communication line. A peak of coded data outputted from the coders 311-31N is dispersed timewise to average the data sent to the communication line. Furthermore, when an output signal is received from the buffer memories 321-32N, reading is stopped and the changeover devices 330, 340 are thrown to the contacts 332, 342 and connect to the memory 322.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packet multiplexer, and more particularly, it is applied to a packet multiplexer which encodes images of a plurality of video cameras by a video encoder, multiplexes the encoded data and transmits the packets. And about effective technology.

[0002]

2. Description of the Related Art Generally, when video images from a plurality of video cameras are coded by a video encoder, and the coded data is multiplexed for packet transmission, it is synchronized with a video sync signal output from each video camera. To obtain a coded data stream that has been coded, and then write this coded data stream to each individual buffer memory one by one, and read the coded data one after another from the memory at regular time intervals to obtain a plurality of coded data. Are generated and transmitted in time series.

[0003]

An example of the coding rule in the conventional multiplexing method and the time characteristic of the data will be described.

FIG. 4 is a diagram showing a relationship between a temporal characteristic of coded data output from a video encoder adopting the MPEG coding system and a picture transition.

In FIG. 4, 100 is a sequence of picture transitions, and 101 is a data amount of encoded data output from the video encoder.

In a video encoder adopting an encoding rule standardized by MPEG, intra-frame encoding (I frame)
There are some picture transitions that combine forward predictive coding (P frame) and forward and backward predictive coding (B frame) processing using the interframe difference.

Among these picture transitions, when a picture is encoded using a picture transition (IBBPBBPBBPBBI) having a high compression rate like the picture transition sequence 100 shown in FIG. 4, at this time, as shown in FIG.
Data amount of encoded data output from the video encoder 1
The temporal characteristic of 01 causes a large peak value in the I-frame processing, especially in a video (for example, a human video) where the motion is not intense.

In consideration of multiplexing and transmitting coded data having such characteristics, the coding start operation in each video coder is normally performed independently of each other and temporally. Therefore, encoded data is output from each video encoder mutually and independently of each other in terms of time.

Now, consider the case where the coded data output from the three video encoders are multiplexed.

FIG. 5 is a diagram for explaining the result of multiplexing when the peak values of the data amounts of the coded data output from the three video encoders overlap.

In FIG. 5, reference numerals 201, 202 and 203 denote data amounts of coded data output from the respective video encoders.

As shown in FIG. 5, the encoded data 20 having the same picture transition phase from the two video encoders and the data characteristic having the peak value P at the time T1 is obtained.
1 and the encoded data 202 are output, and the other video encoder outputs the encoded data 203 having the data characteristic that the phase of the picture transition is different and has a peak at the time of T2. And

In this case, the encoded data (201,
(202, 203) are directly multiplexed, as shown in FIG. 5, two peak values P of the I frame output at the time of T1 are added, so that the peak value 2 at the time T1 is 2
Multiplexed encoded data 20 with data characteristics having P
4 is obtained.

Therefore, in the conventional multiplexing system,
As for the communication line speed when sending the encoded data multiplexed into the communication line as a packet, not only is the maximum required to add the number of peak values of the encoded data output from the video encoder, but also There has been a problem that the data amount of encoded data to be transmitted to the communication line varies greatly over time, the load on the communication line varies greatly, and the use of the communication line becomes inefficient.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a packet multiplex transmission apparatus for multiplexing a plurality of encoded data for packet transmission. , The peak value of the data amount of the encoded data output from each video encoder is temporally dispersed, and the data amount of the encoded data sent to the communication line is averaged to reduce the load fluctuation on the communication line. It is to provide a technology that makes it possible.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0017]

Of the inventions disclosed in the present application, a representative one will be briefly described below.
It is as follows.

(1) Video signals output from a plurality of video cameras that are field-synchronized with a common synchronization signal are encoded by corresponding video encoders and output from the plurality of video encoders. In a packet multiplex transmission device that multiplexes a plurality of encoded data and sends out on one communication line, means for shifting an encoding start start time for starting encoding in each video encoder for each video encoder And a FIFO type buffer memory for storing coded data output from each video encoder, and means for reading and multiplexing the coded data from each buffer memory at fixed time intervals. .

[0019]

According to the above means, video signals output from a plurality of video cameras which are field-synchronized with a common sync signal are encoded by corresponding video encoders, and the plurality of encoded data are multiplexed. In a packet multiplex transmission device that converts the data to a single communication line and sends it to one communication line, each video encoder is started and started at different encoding start start times in units of field scanning time.
The encoded data output from each video encoder is FIFO
The coded data is stored in a fixed type buffer memory, and the coded data is read from each buffer memory at fixed time intervals and multiplexed and sent out on the communication line. It is possible to make the time of the peak value different for all video encoders.

As a result, it is possible to suppress the time variation of the data amount of the encoded data sent to the communication line and average the data amount of the encoded data over time, so that the load variation on the communication line can be prevented. It is possible to reduce the number and efficiently use the communication line.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In all the drawings for explaining the embodiments, parts having the same function are designated by the same reference numerals, and the repeated description thereof will be omitted.

FIG. 1 is a block diagram showing a schematic configuration of a packet multiplex transmission apparatus which is an embodiment of the present invention.

In FIG. 1, reference numeral 300 denotes a sync signal generator,
301 to 30N (N is an integer) are N video cameras, 3
60 is a counter, 361 to 36N are N comparators, 31
1 to 31N are N video encoders, and 321 to 32N are N video encoders.
FIFOs (FirstIn First Out)
Type buffer memory, 330, 340 are switches, 3
Reference numeral 50 is a sending unit.

N video cameras (301 to 30N)
Are all synchronized by a single sync signal from sync signal generator 300.

The counter 360 includes the synchronization signal generator 300.
The counter 360 counts the sync signals from the
It is input to the individual comparators (361 to 36N).

N comparators (361 to 36N) respectively
Outputs an output signal to N video encoders (311 to 31N) when the value of the counter 360 reaches a specific value that is individually preset.

Each of N video encoders (311 to 311)
1N) receives the video signal from the video camera (301 to 30N) and waits for the output signal from the corresponding comparator (361 to 36N) to start the video coding operation.

Each of N video encoders (311 to 311)
1N) stores the encoded data output from the buffer memory (321 to 32N) having both functions of data storage operation and data read operation, and stores the number of stored data and the number of read data. An output signal is output when the difference is less than a certain value.

The switch 330 has a buffer memory (3
21-32N) is a switch for switching the reading of the encoded data, and the switch 340 is a switch for switching the output signal from the buffer memory (321-32N), and the switch 330 and the switch 340. Is connected to the output unit 350.

Here, the switches of the switch 330 and the switch 340 work together.

First, the sending section 350 includes a switch 330.
Is switched to the contact 331 and the switch of the switch 340 is switched to the contact 341 to connect to the buffer memory 321, and the encoded data is read from the buffer memory 321 and sent to the communication line side.

When the output signal is received from the buffer memory 321, the reading of the encoded data from the buffer memory 321 is stopped, the switch of the switch 330 is set to the contact 332, and the switch of the switch 340 is set to the contact 3.
It switches to 42 and connects to the buffer memory 322.

Next, the sending section 350 uses the buffer memory 3
21, the encoded data is also read from the buffer memory 322, and the buffer memory 322
After receiving the output signal from, the switch is further switched to connect to the next buffer memory.

Thereafter, similarly, the read operation of the encoded data is performed up to the buffer memory 32N.

The N buffer memories (321 to 32)
By performing the operation of reading / sending the encoded data of (N) at fixed time intervals shorter than a fraction of one feed or one frame period, each video encoder (311 to 311) on the communication line side. 31N), the multiplex transmission that approximates the time characteristic of the encoded data output from the (N) is obtained.

In the packet multiplex transmission apparatus of this embodiment, the switch 330 selects the video encoders (311 to 31N) in a time division manner and connects them to the communication line.

On the other hand, the coded data is always output from the video encoders (311 to 31N), the coded data output when not connected to the communication line is temporarily stored, and the coded data is sent to the communication line. A buffer memory (321 to 32N) is provided for reading and outputting the encoded data when connected.

FIG. 2 is a diagram showing a format of a multiplexed packet transmitted at regular time intervals in the packet multiplex transmission apparatus of this embodiment.

In FIG. 2, 401 is a video encoder 31.
1 is the encoded data, 402 is the encoded data of the video encoder 312, and 40N is the encoded data of the video encoder 31N.

Next, an operation example of the packet multiplex transmission device in the case of N = 3 in the packet multiplex transmission device of the present embodiment shown in FIG. 1 will be described.

In this case, three video encoders (311
In generating the coding start activation signal of
Comparator (361,
The values of (362, 363) are set in advance.

That is, each comparator (361, 362, 36)
As a result of counting the synchronization signals in 3), the activation signal is set to have a time difference of one frame time.

For example, if a vertical synchronizing signal is used as the synchronizing signal, the setting value of the comparator 361 is "2", the setting value of the comparator 362 is "4", and the setting value of the comparator 363 is "6". .

Further, each video encoder (311 to 313)
As for, the encoding rule standardized by MPEG is used.

FIG. 3 shows the temporal characteristics of coded data between the video encoders (311 to 313) when N = 3 in the packet multiplex transmission apparatus of this embodiment shown in FIG. It is a figure which shows the result of having multiplexed.

In FIG. 3, reference numerals 511, 512 and 513 indicate the data amount of the coded data output from the respective video encoders (311 to 313).

Reference numerals 501, 502, and 503 denote time series of times when one frame is processed (encoded) in each video encoder (311 to 313). The peak value of the data amount of the encoded data output from () is dispersed at each of these times.

Therefore, this encoded data is sent to the sending unit 35.
When multiplexed by 0, the time characteristic of the multiplexed coded data (packet) shown by 514 in FIG. 3 is obtained, and the peak value of the packet amount becomes a single video encoder (3
11 to 313), the data amount of the encoded data is suppressed to a value slightly larger than the peak value of the encoded data amount, and the encoded data amount is dispersed in the time direction.

As described above, according to this embodiment,
When a plurality of encoded data are multiplexed and transmitted in packets, for example, a plurality of image encoders (311 to 31N) adopting the MPEG encoding method are used to obtain a plurality of image data such as a person image having a relatively small motion. When transmitting, the encoding start start time of each video encoder (311 to 31N) is set so that the phase of picture transition between each video encoder (311 to 31N) does not overlap in time units of fields or frames. After shifting, each video encoder (311-31
It is possible to temporally disperse the peak value of the data amount of the encoded data output by the N) during the I frame processing.

As a result, when a plurality of encoded data are multiplexed for packet transmission, the amount of packets sent to the communication line can be averaged, load fluctuations on the communication line can be reduced, and the communication line can be used efficiently. It becomes possible to improve.

Further, each video encoder (311 to 31N)
Since the time required to store the coded data from (1) to (3) can be reduced, the memory amount of each buffer memory (321 to 32N) can be reduced.

As described above, the invention made by the present inventor is
Although the present invention has been specifically described based on the above-mentioned embodiments, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the scope of the invention.

[0054]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

(1) According to the present invention, when a plurality of coded data are multiplexed and packet-transmitted, the coding start start times of the respective video encoders are shifted from each other. It becomes possible to temporally disperse the time when the data amount of the encoded data output from the rectifier reaches the peak value.

As a result, when a plurality of coded data are multiplexed and packet-transmitted, the data amount of the coded data sent to the communication line can be averaged, the load fluctuation on the communication line can be reduced, and the communication can be reduced. It is possible to improve the use efficiency of the line.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a packet multiplex transmission apparatus that is an embodiment of the present invention.

FIG. 2 is a diagram showing a format of a multiplexed packet transmitted at regular time intervals in the packet multiplex transmission apparatus of the present embodiment.

FIG. 3 is a diagram showing temporal characteristics of encoded data between video encoders and a result of multiplexing the same when N = 3 in the packet multiplex transmission apparatus of the present embodiment shown in FIG. Is.

FIG. 4 is a diagram showing a relationship between temporal characteristics of coded data output from a video encoder adopting the MPEG encoding method and picture transition.

FIG. 5 is a diagram for explaining a multiplexing result when the peak values of the data amounts of the encoded data output from the three video encoders overlap.

[Explanation of symbols]

300 ... Sync signal generator, 301-30N ... Video camera, 360 ... Counter, 361-36N ... Comparator, 31
1 to 31N ... Video encoder, 321 to 32N ... Buffer memory, 330, 340 ... Switching device, 350 ... Sending unit, 101, 201, 202, 203, 401, 40
2, 40N, 511, 512, 513 ... the amount of encoded data output from the video encoder, 204, 514
... The multiplexed encoded data.

Claims (1)

[Claims] 1. A plurality of video signals output from a plurality of video encoders that are video-outputted from a plurality of video cameras field-synchronized with a common synchronization signal are encoded by corresponding video encoders. In a packet multiplex transmission apparatus for multiplexing the encoded data of and transmitting the encoded data on one communication line, means for shifting the encoding start start time for starting encoding in each video encoder for each video encoder. A packet comprising a FIFO type buffer memory for storing coded data output from each video encoder, and a unit for reading and multiplexing the coded data from each buffer memory at fixed time intervals Multiplexer.