KR20030005333A - Method of multiplexing a number of video signals with a compressor - Google Patents

Abstract

The present invention relates to a method and apparatus for multiplexing multiple video signals. According to the invention, the video signal is reduced in its information, combined into a single video signal, and then the video signal is compressed by one compressor. This saves the circuit for the compressor.

Description

METHOD OF MULTIPLEXING A NUMBER OF VIDEO SIGNALS WITH A COMPRESSOR

In order to be able to transmit video signals digitally, one standard was defined by ISO / IEC and defined as the MPEG2 standard ISO / IEC 13818 for video compression, audio compression and multimedia multiplexing. Starting from this standard, EP 0 855 840 A1 describes in more detail a system having a digital signal multiplexer and a digital signal demultiplexer. In the multiplexer of this system, the first number of digital video signals is first multiplexed into the multiplexed digital signal, which is transmitted to the demultiplexer of this system. The digital video signal is an entire television signal for a broadcast program. Alternatively, each program is also referred to as a channel. Each digital video signal includes a digital audio signal or a data signal, or both. The digital signal from the video source is coded, packed, multiplexed in a multiplexer, and then passed to the transfer section as a serial data stream. On the other side of the transmitter, the television channel signal is filtered from the serial data stream. However, the multiplexer is not described in detail herein and no compression procedure is specified.

The present invention relates to a method of multiplexing a plurality of video signals through a compressor.

1 is a block diagram of a multiplexer circuit for reducing a television picture produced by four cameras and outputting each television picture as a partial image in a quadrant of a single television picture in a multiplexed format.

2A is a block diagram of a multiplexer circuit having an intermediate memory in which television images produced by four cameras are intermediate-stored, and a compressor for compressing images on a channel-by-channel basis;

FIG. 2B shows a frame having a sequence of television pictures upstream of an intermediate memory; FIG.

2C shows a frame having a sequence of television pictures downstream of an intermediate memory.

FIG. 3A is a block diagram of a multiplexer circuit having a compressor and an intermediate memory in which compressed television pictures and compression settings generated by four cameras are stored;

3b illustrates a frame having a sequence of television images upstream of the compressor.

4 is a block diagram of a multiplexer circuit having an intermediate image compressor connected in series, an intermediate image memory, and a compressor having a motion compressor.

Therefore, it is an object of the present invention to describe a compression method. The multiplexer should have a simple computer structure of memory and control.

This object is achieved by the features of parallel claims 1 to 4.

According to the first embodiment of the present invention, the video signal is reduced with respect to its information, and then combined into a single video signal, and then the video signal is compressed by one compressor. This saves the circuit for the compressor.

According to a second embodiment of the invention, the television picture of the video signal is alternatively stored in a memory, and then the television picture is continuously read block by block from the memory and compressed by a compressor. In order to achieve high video compression, the correlation between successive images needs to be as high as possible. However, this is only possible if only one camera is connected to the compressor. If several cameras are connected via an input switching device, the image after switching to another camera will be completely different from the previous image. In this case, the compression rate is very low, which leads to high data flow. This problem avoids the subsequent storage and subsequent compression of images on a block-by-channel basis.

According to a third embodiment of the invention, the first television picture of a sequence of several video signals is compressed by a compressor each time and stored in memory as an intermediate image, on which the subsequent image sequence is in each case a video signal. Alternately compressed by the compressor according to the intermediate image associated with the. Thus, various video signals or television images of various channels alternately arrive at the compressor, while nevertheless a high compression ratio can be achieved by time-delayed access to the associated intermediate image.

According to a fourth embodiment of the invention, the television picture of the sequence of several video signals from the compressor is stored in memory as a compressed intermediate image, and the successive images are then stored by the second compressor in accordance with the associated intermediate image. Alternately compressed. This process change suggests two-stage compression whereby single-image compression occurs at the first compressor in the first stage, and motion compression is performed in the second stage. 2 occurs in the compressor. This compression is performed alternately by two compressors for several video signals or video channels. In the second compressor, ie the motion compressor, the previous image to be compared with the subsequent image of the channel is read out of the memory with a time delay so that in each case a high compression rate can be achieved for the subsequent image to be compressed.

In a simple embodiment, a multiplexer having a compressor and converting a video signal into a serial digital data stream has circuitry designed to reduce video signal information and additional circuitry designed to combine several video signals into one video signal. It includes a partial image generator. Thus, only one video signal is compressed.

In a further simple embodiment, a memory is arranged between an input switching device and a compressor in a multiplexer for converting a plurality of video signals into a serial digital data stream, which memory alternately records and digitizes the digitized video signal. And means for continuously reading the received video signal block by block. Block compression, whereby high data rates can be achieved by memory.

In a simple embodiment, the memory has two memory sections. While data is written to one memory section, data is read from the second memory section. This process is repeated alternately for the two memory sections.

In a further simple embodiment, the compressor in the multiplexer for converting multiple video signals into one serial digital data stream has a memory for images of several video signals. The compressor stores intermediate results in memory and processes the data several times. This makes it possible to achieve high compression rates.

In a further simple embodiment, a compressor in a multiplexer for converting multiple video signals into one serial digital data stream comprises a first intermediate image compressor designed to produce an intermediate image, a memory for storing the intermediate image, It has a second compressor for motion compression, ie a series arrangement of motion compressors. This achieves high data compression. The memory has a small memory capacity.

In order to better understand the present invention, the embodiments will now be described in more detail with reference to the drawings.

1 shows four television cameras 1-4 connected via signal cables 5-8 to a partial image generator 9 of the multiplexing device 10, also referred to as a multiplexer, hereinafter. Here, the partial image generator 9 has four connections 11 to 14 to the signal cables 5 to 8. Images are obtained via cameras 1-4. The cameras 1 to 4 generate an electrical signal for the picture, which is output via the signal cable 5 to 8 as a video signal to the partial image generator 9. The television cameras 1 to 4 serve as video sources and generate digital video signals that are used as television signals in broadcast programs. Each program is alternatively also referred to as a channel, table, or frame. Each digital video signal includes a digital audio signal or a data signal, or both. The partial image generator 9 comprises a reduction circuit 15 for reducing video signal information and a combination circuit 16 for combining several video signals into one video signal. The signal from the partial image generator 9 is provided to a compressor 17 which compresses the signal. The compressed signal is provided by the compressor 17 via the switch 18 to the transmitter 19, thus the transmitter 20, or the digital video recorder 21 for recording.

The function of the multiplexer 10 is as follows: Four television signals generated by the cameras 1 to 4 are ¼ size in the reduction circuit 15 of the partial image generator 9 by blanking from the information. And then combined into a signal television signal in the combining circuit 16 of the partial image generator 9. Thus, television images obtained by four cameras 1 to 4 can each appear simultaneously on the screen in a quarter of a single television image. The television signal of a single television picture is provided to the compressor 17 by the partial image generator 9 and compressed in the compressor 17 according to MPEG2 compression.

The disadvantage of this process is that, in response to the program, the image is reproduced inconsistently because information is lost when combining four partial images into a single image.

2A shows a multiplexer 30 having an input switching device 31, an intermediate memory 32, and a compressor 33. The input switching device 31 has four connections 34 to 37 for four cameras, and four television signals are transmitted to the input switching device 31. The signals of all four television images are transmitted to the intermediate memory 32, which includes two partial memories 38 and 39 each having a memory space for 4x10 television images. The intermediate memory serves as a buffer shift register. Each ten consecutive television images from all four cameras may be temporarily stored in one of two partial memories 38 and 39.

The function of the multiplexer 30 is as follows: The input switching device 31 synchronizes the incoming television picture and transmits the image to the first partial memory 38, while following the image of one channel. Each time a switch is made, the images are transmitted alternately. When the first partial memory 38 is filled, switching is made between the two partial memories, and the second partial memory 39 is filled with the television picture by the input switching device 31. While the second partial memory 39 is full, the first partial memory is empty. This means that the first partial memory 38 outputs an image, i.e., ten television images of one channel each time in succession, accordingly in a block-by-block manner to the compressor 33. Compressor 33 compresses the image. Since the image for each channel reaches the compressor 33 continuously, a high compression rate can be achieved. Then, every tenth image, i.e., the image number 1, 11, 21, etc., is an intermediate image in which compression can be performed in the forward or reverse direction.

FIG. 2B shows a frame 40 having a sequence of television pictures provided to the partial memories 38 and 39 by the input switching device 31. The images are alternately recorded in the memory 32. The first natural number before the decimal point defines the camera, and the second natural number after the decimal point defines the sequence of images transmitted by the corresponding camera.

2C shows a sequence of television pictures in frame 41, where such television pictures are output to compressor 33 from one of partial memories 38 or 39. Thus, each partial memory 38 and 39 has ten images of the first channel, followed by ten images of the second channel, followed by ten images of the third channel, and finally of the fourth channel. Ten images are continuously output to the compressor 33 for each block.

FIG. 3A shows a multiplexer 50 with an input switching device 51, a compressor 52, and furthermore a memory for reading the first recorded value, ie a first in first out (FIFO) intermediate memory 53. ). The input switching device 51 has four connections 54 to 57 for four cameras, which transmit four television signals to the input switching device 51. The output signal of the compressor 52 is provided to the switch 58. Compressor 52 processes the data and stores the data in memory 53, and then the same stored data is sent back to compressor 52 for later processing.

3B shows a frame 59, with reference to which the function of the multiplexer 50 will be described as follows: The input switching device 51 synchronizes the incoming video signal and converts this video signal into a compressor ( 52). First the first image from the first camera, then the first image from the second camera, then the first image from the third camera, and then the first image from the fourth camera are the compressors 52. Is provided. Then, the second image from the first camera, the second image from the second camera, the second image from the third camera, and the second image from the fourth camera are followed. The compressor 52 compresses the first image from the first camera and passes this compressed image as an output signal to the switch 58 and the memory 53. Then, the first image from the second camera is compressed by the compressor 52, and both are passed through the switch 58 as an output signal, and are simultaneously recorded in the memory 53. The first image from the third camera is also compressed, output to the switch 58 and recorded in the memory 53. The same applies to the first image from the fourth camera. At the beginning of the second cycle, the compressed first image from the first camera is loaded from the memory 53 into the compressor 52 and from the first camera provided to the compressor 52 by the input switching device 51. Is compared with the second image. MPEG2 compression is performed in the compressor 52 based on this image comparison. The corresponding setting is stored in the memory 53 and simultaneously output to the switch 58. The same applies to the second image from the second, third, and fourth cameras. Then, a third cycle is made for the third image from the first, second, third and fourth cameras. After every ten or twelve images from the camera, a new intermediate image is set up, from which compression can be done in the forward or reverse direction.

4 shows a multiplexer 70 having an input switching device 71 and a compressor 72. The input switching device 71 has four connections 73 to 76 for four cameras, which output four television signals to the input switching device 71. As shown in frame 59, signals from all four television images are transmitted to the compressor 77. Compressor 72 has a first intermediate image compressor 77, an incremental memory 78, and a second motion compressor 79, and acts as an MPEG2 compressor, which generally includes all the cameras from the camera. The tenth or twelfth image is simply compressed into a compressed intermediate image, known as an intra-frame or I-frame, ie a JPEG compressed single image. In the MPEG2 process, I-frames are transmitted as intermediate images at regular intervals, preferably after 10 or 12 transmitted images. If the transmitter goes wrong after the last 10th or 12th image, it is possible to use the new intermediate image as the start image by the intermediate image. Also on cross-fading, the new intermediate image is transmitted as the starting image. Only changes to the previous image or previous I-frame are stored to achieve a high data rate on the digital video recorder or transmitter in addition to the JPEG compression method of other intermediate images. In general, changes in the image only occur when the object moves. Thus, the data amount or data rate can be reduced. Between these I-frames, only the data for the shifted image segment is transmitted. Therefore, in the MPEG process, only the data identifying the changed image segment is transmitted. The input switching device 71 constantly supplies all images from all four cameras to the first compressor 72, which occurs after 10 or 12 images or after cross-fading for each camera. I-frames are temporarily stored in the intermediate memory 78 and held in the intermediate memory 78 for a period of ten or twelve images if no cross-fading occurs. Moreover, the compression settings for subsequent images are also temporarily stored. Thus, the memory 78 is sized to store four compressed television pictures for each camera, and compression settings. Assuming that the MPEG2 process has 10 or 12 images, the I-frame is for the 10th or 12th image of the camera, i.e. the sequential image numbers 1, 11, 21, 31, etc., or 1, 13, Will occur for images 25, 37, and so on. The I-frame and compression settings are constantly supplied to the second compressor 79 over a period of ten or twelve images, and at the same time all intermediate images (2 to 10, 12 to 20, 22 to 30, or 2 to 12, 14 to 24, 26 to 36, etc.) are looped through the motion compressor 79. The second compressor 79 compares the new image and the I-frames with respect to the compression settings of the associated cameras, and generates only data that identifies changes in the I-frames for the previous image or the image between the I-frames. I-frames are passed between the switch 80 for each camera every ten or twelve images, and data about other images, including changes to the previous image or image relative to the I-frame.

As mentioned above, the present invention relates to a method of multiplexing a plurality of video signals through a compressor.

Claims (9)

A method of multiplexing multiple video signals, The video signal is reduced in relation to its information, and then combined into one video signal, after which the video signal is compressed by a compressor (17). A method of multiplexing multiple video signals, The television picture of the video signal is alternately stored in the memory 32, and subsequently the television picture of the video signal is successively read block by block from the memory 32 and compressed by the compressor 33. A multiplexing method of a plurality of video signals. A method of multiplexing multiple video signals, The first television picture of the sequence of several video signals is compressed by the compressor 52 and stored in the memory 53 as an intermediate image, and subsequently the successive image sequences are associated with each video signal. Method of multiplexing video signals, characterized in that they are alternately compressed by the compressor (52) according to an intermediate image. A method of multiplexing multiple video signals, The first television picture of the sequence of several video signals is compressed by a compressor 72 and stored in the memory 78 as an intermediate image, and subsequently the successive image sequence is the intermediate image associated with each video signal. Multiple compression by means of a second compressor (79) according to the invention. A multiplexer 10, provided with a compressor 17 for converting a plurality of video signals into a serial digital data stream and for implementing the method described in claim 1, The partial image generator (9) is characterized in that it comprises a circuit (15) for reducing video signal information and an additional circuit (16) for combining several video signals into one video signal. A multiplexer 30, provided with a compressor 33 for converting a plurality of video signals into a serial digital data stream and implementing the method of claim 2, A memory 32 is arranged between an input switching device 31 and the compressor 33, the memory alternately for writing a digitized video signal and alternating reading the digitized video signal successively block by block. And (38, 39). Device according to claim 6, characterized in that the memory (32) comprises two partial memories (38, 39). A multiplexer 50 comprising a compressor 52 for implementing the method of claim 3, wherein the multiplexer 50 converts a plurality of video signals into a serial digital data stream. The compressor (52) is characterized in that it comprises a memory (53) for the image of several video signals. A multiplexer 70 comprising a compressor 72 for implementing the method of claim 4, wherein the multiplexer 70 converts multiple video signals into a serial digital data stream. The compressor 72 comprises a first intermediate image compressor 77 for generating intermediate images, a memory 78 for storing intermediate images of several video signals, and a second motion compressor 79 for motion compression. A multiplexer comprising a serial array of characters.