TWI493445B - Video processing apparatus and method thereof - Google Patents

Description

Video processing device and processing method thereof

The present invention relates to a video processing method, and more particularly to a method for processing a high-resolution video image using an original video processing device in a monitoring system.

The traditional photographic device adopts an analog transmission architecture. In this analog transmission architecture, the image resolution finally presented on the display will depend on the resolution of the photographic device itself.

However, with the popularization of high-definition displays, users have relatively higher requirements on the resolution of images presented on the display, so they will switch to images captured by high-resolution cameras. However, in order to match a high-resolution photographic device, the subsequent image processing unit must also use a processing unit that can process high-resolution images. Therefore, the original processing unit must be discarded. the costing payment.

Therefore, how to use a high-resolution photographic device to present a high-quality image on a display under the original image processing architecture is an urgent problem to be solved.

In view of the above, the present invention provides a video processing device and a corresponding method thereof, by first dividing a video data captured by a high-resolution imaging device, and then processing the subsequent image processing device to reduce processing of the subsequent image processing device. Resolution requirements.

One aspect of the present invention provides a video processing device having a first photographing device, a first signal conversion unit, a data processing unit, and a second signal conversion unit. The camera device captures a first analog image signal and divides it into a plurality of second analog image signals. The first signal conversion unit converts the second analog image signals into a plurality of second digital image signals, and processes the second digital image signals into an image stream by time division multiplexing. The data processing unit performs a multiplex processing on the image stream to separate the second digital image signals, and simultaneously combines the plurality of second digital image signals belonging to the same image to form a first digital image signal. The second signal conversion unit converts the first digital image signal into an analog image signal and transmits the image to a display device for display.

In an embodiment, the first photographic device further includes an image sensing unit for capturing the first analog image signal, and an image sensing processing unit for reducing noise of the first analog image signal; The image segmentation processing unit is configured to divide the first analog image signal for reducing noise into the second analog image signals.

In an embodiment, the first signal conversion unit further includes: a plurality of analog digital conversion units for receiving the second analog image signals and converting the plurality of second digital image signals; and the plurality of decoders, decoding the And a second multiplexer image signal; and a multiplexer, the second digit image signals are filled with sequence numbers, and the labeled second digital image signals are mixed to form the image stream.

In an embodiment, the data processing unit further includes: a demultiplexer, separating the labeled second digital image signals from the image stream; and a plurality of auxiliary/image data parsers, parsing the plurality of The second digital image signal is labeled to obtain the sequential number of each of the second digital image signals; and an image data synchronizer determines whether the second digital image signals belong to a same image according to the sequential labels; An image data processor combines the second digital image signals having the same sequence number to form the first digital image signal.

In an embodiment, the second signal conversion unit further includes: a digital analog converter for converting the first digital image signal into an analog image signal and transmitting the image to a display device.

In one embodiment, the video processing device further includes: a second imaging device for capturing a third analog image signal and dividing the third analog image signal into a plurality of fourth analog image signals.

In an embodiment, the first signal conversion unit further includes: a plurality of analog digital conversion units, wherein the analog digital conversion unit sequentially receives the second analog image signals and converts the plurality of second digital image signals into another plurality of digital image signals. A class of analog-to-digital conversion unit sequentially receives the fourth analog image signals and converts them into a plurality of fourth digital image signals; a plurality of decoders, wherein one decoder sequentially decodes the second digital image signals, and the other The decoder sequentially decodes the fourth digital image signals; and a multiplexer, And mixing the decoded second digital image signals and the decoded fourth digital image signals to form an image stream.

In an embodiment, the data processing unit further includes: a demultiplexer that receives the image stream to separate the second digital image signals and the fourth digital image signals; and a plurality of image data parsers, wherein An image data parser sequentially receives the second digital image signals, and another image data parser sequentially receives the fourth digital image signals; and an image data processor receives the second digital image signals respectively Combining a first digital image signal and receiving the fourth digital image signals into a third digital image signal.

In an embodiment, the second signal conversion unit further includes: a digital analog converter for converting the first digital image signal and the third digital image signal into an analog image signal and transmitting the image signal to a display device.

Another aspect of the present invention provides a video processing method, including: capturing a first analog image signal; dividing the first analog image signal into a plurality of second analog image signals; Converting the image signal into a plurality of second digital image signals; sequentially assigning the second digital image signals; mixing the sequentially labeled second digital image signals into an image stream; separating from the image stream The second digital image signals having sequential numbers; the second digital image signals are combined according to the sequential number to form a first digital image signal; and the first digital image signals are converted into an analog image signal and transmitted to A display device performs display.

In summary, the video processing apparatus and method of the present invention are first The image data captured by the high-resolution camera is segmented and processed by the subsequent image processing device. Since the image signal processed by each image processing device is a divided image signal, it can be performed using a lower resolution image processing device, thereby reducing the cost.

100‧‧‧Video processing device

101‧‧‧Photographing device

102 and 106‧‧‧first signal conversion unit

103 and 107‧‧‧ Data Processing Unit

104‧‧‧Second signal conversion unit

105‧‧‧Display device

110, 113, 114 and 115‧‧‧ first analog image signals

111,116‧‧‧Video Streaming

112‧‧‧first digital image signal

601~608, 701~705‧‧‧ steps

1101~1104, 1131~1134, 1141~1144 and 1151~1154‧‧‧ second analog image signal

1011‧‧‧Image sensing unit

1012‧‧‧Image sensing processing unit

1013‧‧‧Image segmentation processing unit

1021~1024 and 1061~1064‧‧‧ analog digital conversion unit

1025~1028 and 1065~1068‧‧‧ decoder

1029 and 1069‧‧‧ multiplexers

1031 and 1071‧‧ ‧ multiplexers

1032~1035‧‧‧Auxiliary/Image Data Parser

1036‧‧‧Image data synchronizer

1037 and 1076‧‧·Image data processor

1105, 1106, 1135, 1136, 1145, 1146, 1155 and 1156‧‧‧ second digital image signals

1072~1075‧‧‧Image data parser

FIG. 1 is a schematic diagram of a video processing device according to a preferred embodiment of the present invention.

2 is a schematic view of a photographing apparatus according to a preferred embodiment of the present invention.

FIG. 3 is a schematic diagram of a first signal conversion unit according to a preferred embodiment of the present invention.

4 is a schematic diagram of a data processing unit in accordance with a preferred embodiment of the present invention.

FIG. 5 is a schematic diagram of a second signal conversion unit according to a preferred embodiment of the present invention.

FIG. 6 is a flow chart showing a video processing method according to a preferred embodiment of the present invention.

FIG. 7 is a flow chart showing the combination of the second digital image signals according to the sequence label to form a first digital image signal according to a preferred embodiment of the present invention.

FIG. 8 is a schematic diagram of a first signal conversion unit according to another preferred embodiment of the present invention.

FIG. 9 is a schematic diagram of a data processing unit according to another preferred embodiment of the present invention.

The following description of the preferred embodiments of the invention is in the

Please refer to FIG. 1 , which is a schematic diagram of a video processing device according to a preferred embodiment of the present invention. The video processing device 100 includes at least one camera device 101, a first signal conversion unit 102, a data processing unit 103, a second signal conversion unit 104, and a display device 105. The photographic device 101 is configured to capture a first analog image signal 110, and divide the first analog image signal into a plurality of second analog image signals 1101~1104, and sequentially output the signals to a first signal conversion unit 102. The resolution of the first analog image signal 110 is greater than the resolution of the second analog image 1101~1104. The first signal conversion unit 102 is configured to convert the plurality of second analog image signals 1101~1104 into a plurality of second digital image signals, and then assign the plurality of second digital image signals to the same sequence number, and perform time sharing. The multiplex processing combines the labeled second digital image signals into a video stream 111 and transmits the same to the data processing unit 103 through the same bus. The data processing unit 103 performs demultiplexing processing on the mixed second digital image signals to separate the second digital image signals, and simultaneously analyzes the sequential labels of each of the separated second digital image signals to separate according to the sequential label pairs. Out The second digital image signal is synchronized to combine the plurality of second digital image signals belonging to the same image to form a first digital image signal 112 and transmitted to the second signal conversion unit 104. The second signal conversion unit 104 is configured to convert the first digital image signal 112 into the first analog image signal 110 and transmit it to the display device 105 for display. In this way, the original subsequent image processing unit can be used to match the high-resolution photographic device, thereby greatly reducing the cost. In an embodiment, if the image resolution of the first analog signal conversion unit 102 and the data processing unit 103 is 720*480 pixels, the resolution of the first analog image signal 110 can be captured by the photographing device 101. 1440*960 pixels. Conventionally, the first signal conversion unit 102 and the data processing unit 103 must be used to process an image processing unit having a resolution of 1440*960 pixels, so that the first analog image signal 110 output by the photographing device 101 can be processed. However, in this case, the first analog image signal 110 of 1440*960 pixel resolution is divided into four second analog image signals 1101~1104 of 720*480 pixel resolution, so that the first one can be used. The signal conversion unit 102 and the data processing unit 103 process the four analog image signals 1101 to 1104 having 720*480 pixel resolution without replacing the existing device.

2 is a schematic view of a photographing apparatus according to a preferred embodiment of the present invention. The photographing device 101 further includes an image sensing unit 1011, an image sensing processing unit 1012, and an image segmentation processing unit 1013. The image sensing unit 1011 is a charge-coupled device (CCD) for obtaining the first analog image signal 110. The image sensing processing unit 1012 is configured to reduce the first analog image sensed by the image sensing unit 1011. The noise of the signal 110 is sent to the image segmentation processing unit 1013 for segmentation, and a plurality of second analog image signals 1101 to 1104 are output. In one embodiment, the resolution of the first analog image signal 110 obtained by the image sensing unit 1011 is 1440*960 pixels. After the image sensing processing unit 1012 processes the noise reduction, the image segmentation processing unit 1013 will One type of image signal 110 is divided to form four second analog image signals 1101~1104, and the resolution of each second analog image signal 1101~1104 is 720*480 pixels. It should be noted that in this embodiment, the application of the present invention is illustrated by taking an example of dividing into a minimum of four second analog image signals. However, in other embodiments, the above embodiment may be divided into more than four second analog image signals, for example, into 16 second analog image signals, without being divided into four second analog image signals. The resolution of each second analog image signal is 360*240 pixels. In other words, the resolution of the second analog image signal that is segmented must not exceed the maximum resolution range that can be processed by subsequent image processing units. Accordingly, the method of the present invention can determine the number of partitions of a picture based on the resolution or the number of internal analysis processing elements.

FIG. 3 is a schematic diagram of a first signal conversion unit according to a preferred embodiment of the present invention. The first signal conversion unit 102 includes four analog-to-digital conversion units 1021 to 1024, four decoders 1025 to 1028 coupled to the four analog-to-digital conversion units 1021 to 1024, and a multiplexer 1029 coupled to the four decoders. 1025~1028. The four analog-to-digital conversion units 1021~1024 receive the four second analog image signals 1101~1104, respectively, and convert them into four second digital image signals for output to four decodings. The four decoders 1025~1028 decode the four second digital image signals to obtain the image signals therein, and reduce the noise. In the image signal, ancillary data is enabled, and the second digital image signal is sequentially filled with the same sequence label, and the second digital image signals are transmitted to the multiplexer 1029, and then transmitted to the multiplexer 1029. Time-sharing multiplex processing. The labeled second digital image signals are mixed to form an image stream 111 for transmission to the data processing unit 103 through the same bus. It should be noted that in this embodiment, the second analog image signal to be processed is four. Therefore, the analog digital conversion unit and the decoder used are all four. However, in other embodiments, This is limited.

4 is a schematic diagram of a data processing unit in accordance with a preferred embodiment of the present invention. The data processing unit 103 includes a demultiplexer 1031, four auxiliary/image data parsers 1032~1035 coupled to the demultiplexer 1031, and an image data synchronizer 1036 coupled to the four auxiliary/image data parsers. 1032~1035 and an image data processor 1037 are coupled to the image data synchronizer 1036. The demultiplexer 1031 receives the video stream 111, thereby separating the mixed four labeled second digital image signals for transmission to the four auxiliary/image data parsers 1032-1035, respectively. The four auxiliary/image data parsers 1032~1035 respectively parse the four labeled second digital image signals to parse the sequential labels in the image data and the ancillary data, and transmit them to the image data synchronizer 1036. The image data synchronizer 1036 determines four second digital image signals respectively transmitted by the auxiliary/image data parsers 1032 to 1035 according to the sequence label. Whether it is synchronized, that is, whether the four second digital image signals are image signals split by the same shooting picture. If the image signals are separated by the same shooting picture, the four second digital image signals are parsed and transmitted to the image data processor 1037. The image data processor 1037 combines and compresses the four second digital image signals to form a first digital image signal 112 for transmission to the second signal conversion unit 104.

FIG. 5 is a schematic diagram of a second signal conversion unit according to a preferred embodiment of the present invention. The second signal conversion unit 104, in an embodiment, is a digital analog converter for converting the first digital image signal 112 into a first analog image signal and transmitting it to the display device 105. The display device 105 performs display based on the first analog image signal to reproduce the photographic scene on the display 105.

FIG. 6 is a flow chart showing the process of determining video processing according to a preferred embodiment of the present invention. Please refer to FIG. First, in step 601, a first analog image signal is captured, and in step 602, the first analog image signal is divided into a plurality of second analog image signals, for example, the photographing device 101 is configured to capture a first analog image signal 110. And dividing the first analog image signal into a plurality of second analog image signals 1101~1104. Then, in step 603, the second analog image signals are converted into a plurality of second digital image signals, and in step 604, the second digital image signals are sequentially labeled, and in step 605, the The second digit image signals of the sequential labels are mixed into a video stream. For example, the first signal converting unit 102 converts the plurality of second analog image signals 1101~1104 into a plurality of second digital image signals, and then performs the plurality of image signals. The second digital image signal is given the same sequence mark And performing time division multiplexing processing, mixing the labeled second digital image signals into one video stream 111, and transmitting the same to the data processing unit 103 through the same bus. Then, in step 606, the second digital image signals having the sequential numbers are separated from the image stream, and in step 607, the second digital image signals are combined according to the sequential labels to form a first digital position. The image signal, for example, the data processing unit 103 performs a multiplex processing on the mixed second digital image signal to separate the second digital image signals, and simultaneously analyzes the sequential labels of each of the separated second digital image signals to Synchronizing the separated second digital image signals according to the sequence label to combine the plurality of second digital image signals belonging to the same image to form a first digital image signal 112 and transmitting the signal to the second signal conversion unit 104. Finally, in step 608, the first digital image signal is converted into an analog image signal and then transmitted to a display device for display. For example, the second signal conversion unit 104 is configured to convert the first digital image signal 112 into the first analog image. The signal 110 is then transmitted to the display device 105 for display.

FIG. 7 is a flow chart showing the combination of the second digital image signals according to the sequence label to form a first digital image signal according to a preferred embodiment of the present invention. First, in step 701, it is determined whether the received sequence numbers are the same. That is, the image data synchronizer 1036 determines whether the sequential labels of the received four second digital image signals are synchronized. If the four second digit image signals have the same sequence label, the four second digit image signals belong to the same photographic image. In step 702, the plurality of second image signals are parsed. That is, the image data synchronizer 1036 parses out the four second The digital image signal is transmitted to the image data processor 1037 for subsequent processing. On the other hand, if the sequence numbers of the four second digit image signals are different, then in step 703, it is determined whether the difference between the largest sequence label and the smallest sequence label exceeds a threshold value. For example, if the threshold value is 2, the image data synchronizer 1036 determines that the maximum sequential number and the minimum order number of the four second digital image signals exceed 2, which represents the shooting picture to which the second digital image signal belongs and the current shooting picture. If there are two screens above the difference, there will be a significant difference if these second digital image signals are combined. Therefore, in step 704, the present invention removes all of the second digital image signals, that is, the image data synchronizer 1036 removes all of the second digital image signals. Conversely, if the difference between the largest sequential label and the smallest sequential label does not exceed this threshold. In step 705, the image signal of the largest sequential label is retained, and the image signal of the smallest sequential label is removed to wait for the next image signal. That is, the image data synchronizer 1036 removes the second digital image signal having the smallest sequential number to wait for the next incoming second digital image signal, and performs step 701 again.

It should be noted that in the previous embodiment, the first signal conversion unit 102 and the data processing unit 103 of the video processing device 100 are configured to process the first analog image signal 110 captured by the single imaging device 101. That is to say, the analog digital conversion units 1021~1024 and the decoders 1025~1028 in the first signal conversion unit 102, and the auxiliary/image data parsers 1032~1035 in the data processing unit are respectively processed by the first A plurality of second analog image signals 1101 to 1104 are separated from the image signal 110. However, in another embodiment, the first signal conversion list of the present invention The meta and data processing unit can be used to process a plurality of first analog image signals 110, 113, 114 and 115 captured by the plurality of photographing devices 101.

FIG. 8 is a schematic diagram of a first signal conversion unit according to another preferred embodiment of the present invention. The first signal conversion unit 106 includes four analog-to-digital conversion units 1061 to 1064, and four decoders 1065 to 1068 are coupled to the four analog-to-digital conversion units 1061 to 1064 and a multiplexer 1069. Decoders 1065~1068. The analog digital conversion unit 1061 sequentially receives the four second analog image signals 1101~1104 segmented by the first analog image signal 110, and converts them into four second digital image signals for output to the decoder 1065 for decoding. The analog digital conversion unit 1062 sequentially receives the four second analog image signals 1131 to 1134 segmented by the first analog image signal 113, and converts them into four second digital image signals for output to the decoder 1066 for decoding. The analog digital conversion unit 1063 sequentially receives the four second analog image signals 1141 to 1144 divided by the first analog image signal 114 and converts them into four second digital image signals for output to the decoder 1067 for decoding. The analog digital conversion unit 1064 sequentially receives the four second analog image signals 1151 to 1154 split by the first analog image signal 115 and converts them into four second digital image signals for output to the decoder 1068 for decoding. The decoded second digital image signals are sequentially transmitted to the multiplexer 1069 for time division multiplexing processing to form an image stream 116. In this embodiment, the analog digital conversion units 1061~1064 respectively receive the first analog image signals 110, 113, 114 and 115 captured by different camera devices. Therefore, the decoded image signals mixed by the multiplexer 1069 are also from different photography. The image captured by the device. and also That is, the multiplexer 1069 performs the time division multiplexing processing of the second digital image signals 1105, 1135, 1145, and 1155 converted by the second analog image signals 1101, 1131, 1141, and 1151. The receiver performs sequential time division multiplexing processing of the second digital image signals 1106, 1136, 1146, and 1156 converted by the second analog image signals 1102, 1132, 1142, and 1152 in sequence, and so on. That is to say, the second digital image signals captured by each camera device are sequentially transmitted to the multiplexer 1069 to be mixed with the second digital image signals captured by the other camera devices to form a video stream.

FIG. 9 is a schematic diagram of a data processing unit according to another preferred embodiment of the present invention. The data processing unit 107 includes a demultiplexer 1071, four image data parsers 1072~1075 coupled to the demultiplexer 1071 and an image data processor 1076 coupled to the four auxiliary/image data parsers 1072~ 1075. The demultiplexer 1071 receives the video stream 116, thereby separating the mixed second digital image signals 1105, 1135, 1145, and 1155 for transmission to the four image data parsers 1072-1075, respectively. The four image data parsers 1072-1075 analyze the image data of the four second digital image signals 1105, 1135, 1145, and 1155, and then transmit the image data to the image data processor 1076 for processing. Wherein, the second digital image signals 1105, 1135, 1145 and 1155 are signals taken from different photographic devices. Therefore, the image data processor 1076 first stores the second digital image signals 1105, 1135, 1145, and 1155 in different memories, and waits for subsequent image data belonging to the same picture to be collected, and then performs subsequent compression processing. Finally, the combined digital image signals are transmitted to the second signal conversion unit 104 and converted into one. The analog image signal is then transmitted to a display device 105 to display a different picture.

According to the preferred embodiment of the present invention, the present invention divides the image data captured by the high-resolution imaging device and then processes it by the subsequent image processing device. Since the image signal processed by each image processing device is a divided image signal, it can be performed using a lower resolution image processing device, thereby reducing the cost. Furthermore, the user can determine the method of segmenting the image data according to the processing performance of the original image processing device, which is quite convenient to use.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention can be modified and modified without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

100‧‧‧Video processing device

101‧‧‧Photographing device

102‧‧‧First signal conversion unit

103‧‧‧Data Processing Unit

104‧‧‧Second signal conversion unit

105‧‧‧Display device

110‧‧‧First analog image signal

111‧‧‧Video Streaming

112‧‧‧first digital image signal

1101~1104‧‧‧Second analog image signal

Claims (12)

A video processing device includes: a first photographing device for capturing a first analog image signal, and dividing the first analog image signal into a plurality of second analog image signals; and a first signal conversion unit Converting the second analog image signals into a plurality of second digital image signals, and performing time division multiplexing processing, mixing the second digital image signals into one image stream; a data processing unit, the image Performing a multiplex processing on the stream to separate the second digital image signals, and combining a plurality of second digital image signals belonging to the same image to form a first digital image signal; and a second signal conversion The unit is configured to convert the first digital image signal into an analog image signal and transmit the image to a display device for display. The video processing device of claim 1, wherein the first signal conversion unit further assigns the second digital image signals to the sequential number; and the data processing unit marks the plurality according to the sequence number The two digital image signals are combined again to form the first digital image signal. The video processing device of claim 1, wherein the first camera device further comprises: an image sensing unit for capturing the first analog image signal; An image sensing processing unit for reducing noise of the first analog image signal; and an image segmentation processing unit for dividing the first analog image signal for reducing noise into the second analog images signal. The video processing device of claim 3, wherein the first signal conversion unit further comprises: a plurality of analog digital conversion units for receiving the second analog image signals and converting into a plurality of second digits Image signal; a plurality of decoders for decoding the second digital image signals; and a multiplexer, the second digital image signals are filled with sequence numbers, and the labeled second digital image signals are The image stream is mixed to form. The video processing device of claim 4, wherein the data processing unit further comprises: a demultiplexer that separates the labeled second digital image signals from the image stream; the plurality of auxiliary And an image data parser, parsing the numbered second digital image signals to obtain the sequential label of each of the second digital image signals; and an image data synchronizer determining the second according to the sequence identifiers Whether the digital image signal belongs to a same image; and an image data processor that combines the numbers with the same sequence number The binary digital image signal forms the first digital image signal. The video processing device of claim 5, wherein the second signal conversion unit further comprises: a digital analog converter for converting the first digital image signal into an analog image signal for transmission to a display device. The video processing device of claim 1, further comprising: a second imaging device for capturing a third analog image signal and dividing the third analog image signal into a plurality of fourth analog image signals . The video processing device of claim 7, wherein the first signal conversion unit further comprises: a plurality of analog digital conversion units, wherein the analog digital conversion unit sequentially receives the second analog image signals and converts And forming a plurality of second digital image signals, and another analog digital conversion unit sequentially receives the fourth analog image signals and converts the plurality of fourth digital image signals into a plurality of fourth digital image signals; and the plurality of decoders, wherein one decoder sequentially decodes the image signals a second digital image signal, another decoder sequentially decoding the fourth digital image signals; and a multiplexer mixing the decoded second digital image signals and the decoded fourth digits The image signal forms an image stream. a video processing device according to claim 8 of the patent application, The data processing unit further includes: a demultiplexer, receiving the image stream to separate the second digital image signals and the fourth digital image signals; and a plurality of image data parsers, wherein the image data is parsed Receiving the second digital image signals in sequence, and another image data parser sequentially receiving the fourth digital image signals; and an image data processor respectively receiving the second digital image signals to form a first The digital image signal and the received fourth digital image signals are combined into a third digital image signal. The video processing device of claim 9, wherein the second signal conversion unit further comprises: a digital analog converter for converting the first digital image signal and the third digital image signal into an analog image signal respectively It is then transmitted to a display device. A video processing method includes: capturing a first analog image signal; dividing the first analog image signal into a plurality of second analog image signals; and converting the second analog image signals into a plurality of second digital images a signal; giving the second digital image signal sequence labels; mixing the sequentially labeled second digital image signals into an image stream; Separating the second digital image signals having the sequential numbers from the image stream; combining the second digital image signals according to the sequence label to form a first digital image signal; and the first digital image signal Converted into an analog image signal and transmitted to a display device for display. The video processing method of claim 11, wherein combining the second digital image signals according to the sequence label to form a first digital image signal further comprises: determining a sequence of the second digital image signals And determining whether the second digital image signals are combined when the second digital image signals have the same sequence label Whether the difference between the largest sequential label and the smallest sequential label exceeds a threshold; when the difference between the largest sequential label and the smallest sequential label in the second digital image signal exceeds the threshold, the first a two-digit image signal; and when the difference between the largest sequential label and the smallest sequential label of the second digital image signals does not exceed the threshold, the second digital image signal having the largest sequential label is retained and removed The second digital image signal having the smallest sequential number.