JP2004521555A - Method for multiplexing a plurality of video signals using a compressor - Google Patents

Abstract

The present invention relates to a method and an apparatus for multiplexing a plurality of video signals. According to the invention, the video signal is reduced with respect to information and combined into one video signal, which is then compressed by a compressor. This saves circuitry for compression.

Description

【Technical field】
[0001]
The present invention relates to a method for multiplexing a plurality of video signals using a compressor.
[0002]
In order to enable video signals to be transmitted in a digital format, standards have been defined by ISO / IEC and MPEG2 standards for video compression, audio compression and multimedia multiplexing have been defined as ISO / IEC13818. Starting from this standard, EP 0 855 840 A1 describes in more detail a system with a digital signal multiplexer and a digital signal demultiplexer. In the multiplexer of the system, the first plurality of digital video signals are multiplexed to form a multiplexed digital signal, which is transmitted to the system demultiplexer. Digital video signals are all television signals for broadcast programs. Each program is alternatively referred to as a channel. Each digital video signal includes a digital audio signal, a data signal, or both. The digital signal coming from the video source is encoded in a multiplexer, packed, multiplexed and transmitted as a serial data stream to the transmission section. On the other side of the transmission section, the television channel signal is filtered from the serial data stream. However, the multiplexer is not described in detail here, and the compression process is not specified.
[0003]
The object of the invention is therefore to specify a method of compression. The multiplexer should have a simple computer structure of memory and control.
[0004]
This problem is solved by the features of claims 1 to 4 listed below. According to a first embodiment of the present invention, the video signal is reduced with respect to the information of this video signal and then combined into one video signal, which is then compressed by a compressor. This saves circuitry for compression.
[0005]
According to a second embodiment of the present invention, the television images of the video signal are alternately stored in a memory, and the television images are read out of the memory serially in blocks and compressed by a compressor. To achieve a high video compression rate, the highest possible correlation between successive images is required. However, this is only possible if only one camera is connected to the compressor. If many cameras are connected via the input switching device, the image after switching to another camera will be completely different from the preceding image. In this case, the compression ratio is very low, resulting in a high data flow. This problem is avoided by storing successive images of one channel in the block, followed by compression.
[0006]
According to a third embodiment of the invention, the first television picture of a sequence of a number of video signals is in each case compressed by a compressor and stored in a memory as an intermediate image, after which the subsequent images of the sequence are Depending on the intermediate image associated with each video signal, it is alternately compressed by the compressor. Thus, different video signals or television images of different channels arrive at the compressor alternately, even though on the one hand a high compression rate can be achieved by time-delayed access to the associated intermediate image.
[0007]
According to a fourth embodiment of the present invention, a television image of a sequence of multiple video signals from a compressor is stored in a memory as a compressed intermediate image, with successive images depending on the associated intermediate image. And compressed alternately by the second compressor. This process modification proposes two-stage compression with one image compression performed in a first compressor in a first stage and motion compression performed in a second compressor in a second stage. This compression is performed on multiple video signals or video channels alternately by two compressors. In the second compressor or 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 is achieved for the subsequent image to be compressed can do.
[0008]
In a simple embodiment, a multiplexer for converting a video signal into a serial digital data stream using a compressor comprises a circuit designed to reduce the video signal information, and multiple video signals into one video signal stream. And a separate circuit designed to couple to the partial image generator. Therefore, only one video signal is compressed.
[0009]
In another simple embodiment, a memory is located between the input switching device and a compressor in a multiplexer for converting a plurality of video signals into one serial digital data stream, the memory being digitized. Means for alternately writing the converted video signals and continuously reading the digitized video signals in blocks. Block compression and thus high data rates can be achieved by using memory.
[0010]
In a simple embodiment, the memory has two memory parts. Data is read from the second memory portion while data is written to the first memory portion. This process is repeated alternately for the two memory parts.
[0011]
In another simple embodiment, a compressor in a multiplexer for converting a plurality of video signals into one serial data stream has a memory for images of the plurality of video signals. The compressor stores the intermediate result in memory and processes the data several times. This allows achieving high compression rates.
[0012]
In another simple embodiment, a compressor in a multiplexer for converting a plurality of video signals into one serial data stream comprises a first intermediate image compressor designed to generate an intermediate image. , A memory for storing the intermediate image and a serial device with a second or motion compressor for motion compression.
[0013]
BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention, embodiments are described in more detail in connection with the drawings. Here, FIG. 1 is a circuit diagram of a multiplexer that reduces television images generated by four cameras and outputs each television image in a multiplexed format as a partial image in one quadrant of one television image. FIG. 2A is a block diagram of a multiplexer circuit including an intermediate memory for temporarily storing television images generated by four cameras and a compressor for compressing an image of each channel, and FIG. Shows a frame with a sequence of television images upstream of the intermediate memory, FIG. 2C shows a frame with a sequence of television images downstream of the intermediate memory, and FIG. 3A shows a frame generated by four cameras. Intermediate memory in which compressed television images and compression settings are stored 3B shows a frame with a sequence of television pictures upstream of the compressor and FIG. 4 shows a frame with an intermediate image compressor, an intermediate image memory and motion compression. FIG. 4 is a block diagram of a multiplexer circuit in which devices are connected in series.
[0014]
FIG. 1 shows four television cameras 1 to 4 which are connected via signal cables 5 to 8 to a partial image generator 9 of a multiplexing device 10, also hereinafter referred to as a multiplexer. Here, the partial image generator 9 has four connections 11 to 14 for the signal cables 5 to 8. Images are taken using cameras 1 to 4. The cameras 1 to 4 generate electric signals for images, which are output as video signals to a partial image generator 9 via signal cables 5 to 8. The television cameras 1 to 4 operate as video sources and form digital video signals used as television signals in broadcast programs. Each program is alternatively referred to as a channel, table or frame. Each digital video signal includes a digital audio signal, a data signal, or both. The partial image generator 9 includes a reducing circuit 15 for reducing video signal information and a combining circuit 16 for combining multiple video signals into one video signal. The signal from the partial image generator 9 is supplied to a compressor 17, which compresses the signal. The compressed signal is supplied by a compressor 17 via a switch 18 to a transmitter 19 and thus to a transmission path 20 or to a digital video recorder 21 for recording.
[0015]
The function of the multiplexer 10 is as follows. The four television signals generated by the cameras 1 to 4 are reduced in size by a factor of 4 by the blanking of information in the reduction circuit 15 of the partial image generator 9, and the combined circuit of the partial image generator 9 is used. At 16 it is combined into one television signal. Therefore, television images taken by the four cameras 1 to 4 can be simultaneously displayed on the screen in one quadrant of each of the television images. A television signal of one television image is supplied from the partial image generator 9 to the compressor 17, where the television signal is compressed in accordance with MPEG2 compression.
[0016]
The disadvantage of this process is that the information is lost when the four partial images are recombined into one image, so that the program is played back in an unclear manner.
[0017]
FIG. 2A shows a multiplexer 30 including 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. All four television pictures are transmitted to the intermediate memory 32, which includes two partial memories 38 and 39, each with memory space for 4 × 10 television pictures. The intermediate memory operates as a buffer shift register. Each of ten consecutive television images from all four cameras can be temporarily stored in one of two partial memories 38 and 39.
[0018]
The function of the multiplexer 30 is as follows. The input switching device 31 synchronizes the incoming television image, transmits the image to the first partial memory 38, and switches each time the image of one channel ends, so that the image is transmitted alternately. When the first partial memory 38 is filled, switching between the two partial memories is performed, and the second partial memory 39 is filled with the television image from the input switching device 31. While the second partial memory 39 is full, the first partial memory is emptied. This means that the first partial memory 38 outputs the images, ten television pictures of one channel, in each case continuously, and thus serially, to the compressor 33 in blocks. The compressor 33 compresses the image. Since the image reaches the compressor 33 serially for each channel, a high compression rate can be achieved. Each tenth image, i.e., image numbers 1, 11, 21, etc., is an intermediate image from which compression can be performed in the forward or reverse direction.
[0019]
FIG. 2B shows a frame 40 with a sequence of television images supplied from the input switching device 31 to the partial memories 38 and 39. The images are written to the memory 32 alternately. The first natural number before the decimal point represents the camera, and the second natural number after the decimal point represents the sequence of images sent by the corresponding camera.
[0020]
FIG. 2C shows a sequence of television images in a frame 41 where television images output from one of the partial memories 38 or 39 to the compressor 33 are present. Thus, each partial memory 38 and 39 serializes 10 images of the first channel, then 10 images of the second channel, then 10 images of the third channel, and finally 10 images of the fourth channel. And outputs the result to the compressor 33 as a block.
[0021]
FIG. 3A shows a multiplexer 50 including an input switching device 51, a compressor 52, and an intermediate memory 53 for reading values written in first-in, first-out, and FIFO. The input switching device 51 has four connections 54 to 57 for the four cameras, and these connections 54 to 57 supply four television signals to the input switching device 51. The output signal of the compressor 52 is supplied to a switch 58. Compressor 52 processes the data and stores the data in memory 53, and the same stored data is again transmitted to compressor 52 for further processing.
[0022]
FIG. 3B shows a frame 59, and the function of the multiplexer 50 will be described with reference to the frame 59. The input switching device 51 synchronizes incoming video signals and supplies these signals to 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, then the first image from the fourth camera. 52. This is followed by a second image from the first camera, a second image from the second camera, a second image from the third camera, and a second image from the fourth camera. The compressor 52 compresses the first image from the first camera, and transmits this compressed image to the switch 58 and the memory 53 as an output signal. Next, the first image from the second camera is compressed in the compressor 53, transmitted to the switch 58 as an output signal, and simultaneously written into the memory 53. The first image from the third camera is also compressed, output to switch 58, and written to memory 53. The same is done for the first image from the fourth camera. At the start of the second cycle, the compressed first image from the first camera is loaded from the memory 53 into the compressor 52 and is supplied from the input switching device 51 to the compressor 52 from the first camera. Compared to the second image. MPEG2 compression is performed in the compressor 52 based on image comparison. The corresponding settings are stored in the memory 53 and output to the switch 58 at the same time. The same is done for the second images from the second, third and fourth cameras. The third cycle is performed on a third image from the first, second, third, and fourth cameras. Each time 10 or 12 images from one camera end, a new intermediate image is set, from which compression can be performed in the forward or reverse direction.
[0023]
FIG. 4 shows a multiplexer 70 including an input switching device 71 and a compressor 72. The input switching device 71 has four connections 73 to 76 for four cameras that output four television signals to the input switching device 71. Signals from all four television images are transmitted to compressor 72, as in frame 59. Compressor 72 has a first intermediate image compressor 77, an intermediate memory 78 and a second motion compressor 79, operating as an MPEG2 compressor, typically each 10th or 12th from one camera. To form a compressed intermediate image, known as an intra-frame or simply an I-frame, ie, a single JPEG-compressed image. In MPEG2 processing, I-frames are transmitted at regular intervals as intermediate images, preferably after 10 or 12 images have been transmitted. By using an intermediate image, it is also possible to use a new intermediate image as the starting image if there is an error in the transmission interval after the last 10th or 12th image. Also in cross-fading, a new intermediate image is transmitted as a starting image. Only the changes with respect to the previous image or previous I-frame are stored in order to achieve a high data rate in the digital video recorder or transmission section, in addition to JPEG compression, another intermediate image method. Changes in one image typically occur only when the object moves. Therefore, the data amount or data rate can be reduced. During these I frames, data is only transmitted for the moved image segments. Therefore, in MPEG processing, only data identifying the modified image segment is transmitted. The input switching device 71 constantly supplies all images from all four cameras to a first compressor 72, which after each 10 or 12 images for each camera or after cross-phasing. Form an I-frame. The I-frames are temporarily stored in the intermediate memory 78 and, if no cross-fading occurs, over the period of 10 or 12 images. In addition, compression settings for subsequent images are also temporarily stored. Therefore, memory 78 is designed to be able to store four compressed television images, one for each camera, and compression settings. Assuming MPEG2 processing using 10 or 12 images, the I frame is the 10th or 12th image of the camera, ie, the sequential image numbers 1, 11, 21, 31 ... or 1, 13,. .. Are formed for 25, 37... Images. The I-frame and compression settings are constantly supplied to the second compressor 79 over a period of 10 or 12 images, while at the same time all intermediate images 2 to 10, 12 to 20, 22 to 30 or 2 from each camera. , Are looped to motion compressor 79. The second compressor 79 compares the I-frame with the new image with respect to the compression setting of the corresponding camera, and forms only data that identifies changes in the image during the I-frame that take into account the previous image or the I-frame. One I-frame is provided to switch 80 for each 10 or 12 images of each camera, and in the meantime, these data relate to another image that contains a change of one image relative to the previous image or I-frame.
[Brief description of the drawings]
[0024]
FIG. 1 is a block diagram of a multiplexer circuit that reduces television images generated by four cameras and outputs each television image in a multiplexed format as a partial image in one quadrant of one television image. It is.
FIG. 2A is a block diagram of a circuit of a multiplexer including an intermediate memory for temporarily storing television images generated by four cameras and a compressor for compressing an image for each channel.
FIG. 2B shows a frame with a sequence of television images upstream of an intermediate memory.
FIG. 2C shows a frame with a sequence of television images downstream of an intermediate memory.
FIG. 3A is a block diagram of a circuit of a multiplexer with an intermediate memory and a compressor storing television images generated and compressed by four cameras and compression settings.
FIG. 3B shows a frame with a sequence of television images upstream of a compressor.
FIG. 4 is a block diagram of a multiplexer circuit in which an intermediate image compressor, an intermediate image memory, and a motion compressor are connected in series.
[Explanation of symbols]
[0025]
1, 2, 3, 4 camera, 5, 6, 7, 8 signal cable, 9 partial image generator, 10, 30, 50, 70 multiplexer, 11, 12, 13, 14, 34, 35, 36, 37, 54, 55, 56, 57, 73, 74, 75, 76 connections, 15 reduction sections, 16 coupling circuits, 17, 33, 52, 72 compressors, 18, 58, 80 switches, 19 transmitters, 20 transmission sections , 21 digital video recorder, 31, 51, 71 input switching device, 32, 53, 78 intermediate memory, 38, 39 partial memory, 40, 41, 59 frames, 77 intermediate image compressor, 79 motion compressor

Claims (9)

In a method of multiplexing a plurality of video signals,
A method for multiplexing a plurality of video signals, characterized in that the video signals are reduced with respect to the information of the video signals, combined into one video signal and the video signals are compressed by a compressor (17). In a method of multiplexing a plurality of video signals,
The television image of the video signal is alternately stored in the memory (32), and the television image of the video signal is subsequently read out from the memory (32) in a serial block and compressed by the compressor (33). To multiplex multiple video signals. A first television image of a sequence of video signals is compressed by a compressor (52) and stored in a memory (53) as an intermediate image, and subsequently successive images of the sequence are associated with an intermediate image associated with each video signal. A method for multiplexing a plurality of video signals, characterized in that the video signals are alternately compressed by the compressor (52) depending on the video signal. A first television image of a sequence of video signals is compressed by a compressor (72) and stored in a memory (78) as intermediate data, and a subsequent image of the sequence is later converted to an intermediate image associated with each video signal. A method for multiplexing a plurality of video signals, characterized in that the plurality of video signals are compressed by a second compressor (79) alternately depending on the video signal. A multiplexer (10) for converting a plurality of video signals into a serial digital data stream, the multiplexer (10) being provided with a compressor (17) implementing the method according to claim 1.
A multiplexer (9), characterized in that the partial image generator (9) comprises a circuit (15) for reducing video signal information and another circuit (16) for combining a plurality of video signals into one video signal. 10). 3. A multiplexer (30) for converting a plurality of video signals into a serial digital data stream, the multiplexer (30) being provided with a compressor (33) implementing the method according to claim 2.
A memory (32) is arranged between the input switching device (31) and the compressor (33), said memory (32) alternately writing the digitized video signal and transmitting the digitized video signal. A multiplexer (30) characterized in that it comprises means (38, 39) for serially reading in blocks. Apparatus according to claim 6, wherein the memory (32) has two partial memories (38, 39). 4. A multiplexer (50) for converting a plurality of video signals into a serial digital data stream, the multiplexer (50) being provided with a compressor (52) implementing the method according to claim 3.
The multiplexer (50), characterized in that the compressor (52) comprises a memory (53) for a plurality of video signal images. A multiplexer (70) for converting a plurality of video signals into a serial digital data stream, the multiplexer (70) being provided with a compressor (72) for implementing the method according to claim 4.
The compressor (72) includes a first intermediate image compressor (77) for generating an intermediate image, a memory (78) for storing intermediate images of a plurality of video signals, and a second motion compressor for motion compression. A multiplexer (70), comprising a series circuit with (79).