JP2001008205A - Video data transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To switch and reproduce video data suitable to a purpose on the reception side by performing multiple transmission of pieces of video data of plural cameras by successively switching the data for every minimum image reproduction unit (GOP). SOLUTION: When the video data is inputted in a compressor 13 from a camera 1 from among plural cameras 1 to N, 1 GOP is created by through compression processing of it. An ID corresponding to the camera 1 is added to a header of the GOP, after that, a switching signal is transmitted to an input switching circuit 12, the camera is switched to a camera 2, similar processing as in the case of the camera 1 is performed and repeated to a camera N. As a result, pieces of the video data of respective cameras are multiplexed on a transmission line 14, IDs are added to respective GOP headers, the IDs are identified by an ID separation control circuit 15 and stored in a group 17 of memories for video for every ID. A decoder 20 selects which piece of video data is decoded. No piece of data exists among respective GOPs here, however, a video which approximate a continuous image is reproduced by embedding the last video of the preceding GOP as the still image among the GOPs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an MPEG (Moving
The present invention relates to a video compression transmission system using a Picture Experts Group (coding) system.

[0002]

2. Description of the Related Art Heretofore, when several types of video data taken by a plurality of video cameras are multiplexed and transmitted using one video compression device, video data to be input to the video compression device by a switch is used. Switching methods have been implemented. this is,
Using a switcher, several types of video data taken by each camera are switched and sent to the video compression device, which converts the data into a stream based on standards such as the MPEG system and sends it to the receiving side. . On the receiving side, these unidirectionally sent multiplexed stream-like data are decoded by a video decoding device and reproduced as video data. FIG. 2 is a block diagram showing an example of a conventional video data transmission system. In the figure, 21 is a video data input unit, 22 is an input switching circuit, 23 is a compressor, 24 is a transmission line, and 25 is a decoder. The input video data taken by each of the video cameras 1 to N constituting the video data input unit 21 is selectively switched by the switching circuit 22 and sent to the compressor 23. This switching is often performed by a fixed time (from several tens of seconds to several minutes) so that it is easy to see when the video data is decoded on the receiving side. Therefore, in this case, the video data taken by the camera 1 is sent to the compressor 23, and thereafter, after the input is sequentially switched to the video data of another camera, the video data taken by the camera 1 is again
The time required for inputting to the camera becomes longer as the number of cameras increases. For example, assuming that the number of cameras is 10 and the switching interval is 20 seconds, the image data captured by the camera 1 is obtained again after 3 minutes and 20 seconds. Therefore, when the receiving side extracts and reproduces only video data from a certain camera, a time-lapse is conspicuous, and the reproduced image has awkward movement of the subject.

[0003]

In the above prior art, in order to multiplex and transmit several types of video data taken by a plurality of input cameras, video data of each camera input to a compressor is switched at a relatively long time interval. Therefore, if the receiving side tries to extract and decode and reproduce only video data taken by a specific camera on the receiving side, a reproduced video with a low temporal resolution that remains awkward to the movement of the subject will result. Thus, the problem to be solved by the present invention is to switch several types of video data sent from a plurality of cameras (1 to N) at relatively short time intervals without changing the width of the transmission band. The purpose of the present invention is to make it possible to easily switch and reproduce video data which is compressed and transmitted, and which is suitable for a target on the receiving side.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention selectively switches a plurality of video data, and
In a video data transmission system that compresses and transmits using a PEG encoding system, the plurality of video data are sequentially switched and multiplexed for each minimum image reproduction unit (GOP) and transmitted. Also, when performing multiplex transmission, an identification code (ID) for specifying the video data is transmitted to a video data stream compressed and transmitted for each GOP. Further, on the receiving side, the input video data is classified based on the ID added to the video data and stored in the video memory. Further, when reproducing the predetermined video data, the I
The video memory is searched and read based on D, and the predetermined video data is decoded and reproduced by the video decoding device.

In other words, the present invention will be described in an easy-to-understand manner. Several types of video data taken by a plurality of cameras are compressed,
The data formatted into one stream is transmitted from the transmitting side to the receiving side while being sequentially switched for each OP. At this time, the ID of the camera that is the input source of the video data is added to the GOP header of the stream for each GOP unit. On the receiving side, the input camera is identified based on this ID, and the same I
D is sorted and classified for each video data having D. The classified video data is stored in the video memory. At this time, video data in GOP units is stored in each memory. On the receiving side, in order to extract video data from a camera that is intended (reproduced),
Using D, a video memory in which the corresponding video data is stored is selected, and the corresponding video data is read. The read video data is decoded by the video decoding device on a GOP basis and reproduced on a monitor. As described above, it is possible to reproduce a video suitable for the purpose while retrieving several types of videos, and to enable quick resynchronization and reproduction of a video without failure when switching memories. .
This is particularly effective when transmitting monitoring images from a plurality of locations.

Here, means for sending each video data to the compressor while sequentially switching a plurality of input cameras, and the video data multiplexed and transmitted by the video decoding device on the receiving side are identified by the identification code ID. It is necessary to provide a means for storing video data in each memory for each input camera by using. Hereinafter, their solutions will be described. In this compression processing, an MPEG encoding method is used. In order to achieve high image quality and high compression, this encoding method uses an I (Intra) picture that is temporally delayed and a P (Predictive) picture.
Based on the picture, a B (Bi-directionally) picture in between is encoded to compress the data. For this reason, the compressed video data by the MPEG encoding method is
The information is not complete with only one image. The three types of pictures constitute one integrated complete information, that is, a minimum image reproduction unit of the compressed video data. This is generally called a GOP (Group Of Pictures). Hereinafter, a GOP related to the present invention will be specifically described with reference to an MPEG-2 encoded bit stream as an example. The GOP which is the minimum image reproduction unit of the compressed video data starts from the GOP header. The structure is composed of one or more pictures, and the first picture of a GOP is defined as an I picture. This picture is a picture that is independently encoded without using a reference image.
Therefore, by using an I picture, a GOP can be used as a point for performing random access from compressed data. FIG. 3 shows an example of the configuration of a GOP. However, this figure shows a case where one GOP is composed of 15 pictures. GOP with 15 I,
When composed of P and B pictures, a random access point exists every 0.5 seconds in a video of 30 frames / second. That is, if the video data of the input camera is switched in the minimum image reproduction unit, switching can be performed at a very short interval of 0.5 seconds, and video data of a different camera input can be transmitted for each GOP. Means

Therefore, in the present invention, when a plurality of input cameras are switched, switching is performed in GOP units every several seconds of a comma. That is, the video data from each camera is sequentially switched and input in GOP units to the video compression device. In this method, when the number of cameras is n, data can be transmitted only at t / n per time t. However, since normal video data is 30 frames per second, 1 GOP is 15 pictures and 2 cameras are used. If the video data is transmitted from, the video data can be transmitted while switching every 0.5 seconds (however, a moving image every 0.5 seconds). Note that the number of pictures in a GOP is further reduced, for example, GOP
Is three pictures, ten kinds of video data can be transmitted in one stream per second. Also, in order to enable the receiving side to identify from which camera the video data has been sent, an ID indicating which camera has taken the video data from each GOP is added to each GOP header. The receiving side reads the ID added to each GOP header of the received multiplexed video data, and identifies which camera has transmitted the video data. Based on this ID, the identified video data is classified into different memories for each video data,
It accumulates in OP units. Furthermore, a switching circuit is provided between each memory and the video decoding device, and this circuit is switched on the receiving side so that the video data stored in each memory can be selectively passed to the video decoding device and decoded. Become. Since the video data is switched on a GOP basis at a very short interval, even when the video data stored in the memory is reproduced on the receiving side through the video decoding device, a reproduced image with a time lap close to a continuous image can be obtained. As a result, the receiving side searches for the corresponding video data using the desired ID from the several types of video data sent,
It is possible to extract and view video data suitable for the purpose.

[0008]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the figure, 11 is a video data input unit, 12 is an input switching circuit, 13 is a compressor, 14 is a transmission line, 15 is an ID separation control circuit, 16 is a separation circuit, 17 is a video memory group, 18 is a timing circuit, 19 is an output switching circuit, and 20 is a decoder. Next, the operation of the present embodiment will be described. Several types of video data taken by the cameras 1 to N of the video signal input unit 11 are sent to the compressor 13 while being switched by the switching circuit 12. Switching performed by the switching circuit 12 is controlled by a switching signal fed back from the compressor 13. If, for example, the video data of the camera 1 enters the compressor 13, the data is subjected to a compression process to create one GOP. However, for the sake of simplicity, it is assumed that one GOP is composed of 30 / N pictures. In the header of this GOP, I
Add D. Next, a switching signal is sent to the switching circuit 12 to switch to the input of the camera 2. The video data from the camera 2 is also subjected to a compression process in the same manner as the video data from the camera 1 to create one GOP (30 / N picture), and the GOP
An ID corresponding to the camera 2 is added to the header. The above is repeated while shifting the input camera from the camera 1 to the camera N. When the camera becomes the camera N, the input is returned to the image of the camera 1 again. As a result, as shown in FIG. 4, video data taken from different input cameras for each GOP unit is multiplexed in the transmission path 14 as shown in FIG. Is added. Here, focusing on the video data of the camera 1, video data in GOP units is periodically transmitted from the transmission side.

On the receiving side, the ID added to the GOP header is identified by the ID separation control circuit 15 from the received stream, and based on the ID information at this time, the video data is stored in the video memory group. 17 are stored in the same ID memory. Then, the ID is removed from the GOP header through the separation circuit 16 at the next stage, and only the video data from which the ID has been removed is accumulated while being separated into the video memories constituting the video memory group 17. Here, each video memory is made to be able to store data in GOP units, and the receiving side uses the switching circuit 19 and the decoder 20.
Use to select which memory video data to decode. As a result, the video data of the camera 1 described above is distinguished from the video data of other cameras in the memory 17-1, and data (41, 42, and 43 in FIG. 4) in GOP units are periodically stored. Here, GOP41 and GOP42, GOP42 and G
There is no data during OP43, but during this time, if the last one video of GOP41 and GOP42 is filled as still image data using the timing circuit 18 of FIG. Close video can be played. Similar processing is performed between the subsequent GOPs. Note that the cameras 2 to N are the same as the camera 1. As described above, several types of video data can be transmitted in one stream, and video data suitable for the purpose can be reproduced and extracted on the receiving side.

[0010]

As described above, video data taken by a plurality of input cameras is sequentially switched and compressed for each GOP, which is the minimum image reproduction unit, and the header of each GOP is added to the header of each GOP. By adding an ID corresponding to the input camera, when decoding the received data,
, And the video data of each camera can be stored in a different memory for each ID and selectively decoded. Further, at the time of decoding, by embedding the last one piece of data of the immediately preceding GOP as a still image in a period where there is no GOP and data of the GOP, the output video data from the camera angle which is intended for the receiving side is obtained. Can be reproduced while selecting an image, which is effective when transmitting video for monitoring.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a transmission system according to the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional transmission system.

FIG. 3 is a schematic diagram showing a configuration of a GOP.

FIG. 4 is a schematic diagram showing a configuration of a transmission stream according to the present invention.

[Explanation of symbols]

11: video data input unit, 12: input switching circuit, 1
3: compressor, 14: transmission path, 15: ID separation control circuit,
16: separation circuit, 17: video memory group, 18: timing circuit, 19: output switching circuit, 20: decoder

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Claims (4)

[Claims] 1. A video data transmission method for selectively switching a plurality of video data and compressing and transmitting the data using an MPEG (Moving Picture Experts Group) coding method,
The plurality of video data are divided into minimum image reproduction units (GOP: Grou
A video data transmission method characterized by sequentially switching and transmitting multiplexed data for each (p Of Pictures). 2. The video data transmission system according to claim 1, wherein, when performing multiplex transmission, an identification code (ID) for specifying the video data is added to a video data stream compressed and transmitted for each GOP. A video data transmission method characterized by transmission. 3. The video data transmission system according to claim 2, wherein the receiving side classifies each video data based on the ID added to the video data and stores the classified video data in a corresponding video memory. Characteristic video data transmission system. 4. In the video data transmission method according to claim 3, when reproducing predetermined video data, each of the video memories is searched and read based on the ID of the predetermined video data, and the predetermined video data is read. A video data transmission method characterized in that data is decoded and reproduced by a video decoding device.