JPH0759083B2 - Image information transmission method - Google Patents

Description

The present invention relates to an image information transmission method, and more particularly to an image information transmission method for continuously transmitting a screen group having temporal correlation.

<Prior art> When transmitting information such as image information, how to reduce the amount of information to be transmitted so that the original information can be faithfully reproduced has always been a theme. Has been proposed in the past.

There is an adaptive variable density sampling method for appropriately changing the sampling density and the information density to be transmitted after the above-mentioned theme. As an example of this method, the time axis conversion band compression method (hereinafter TAT; Time Axis Transfor
m) will be briefly described below.

FIG. 6 is a diagram for explaining the basic concept of TAT. The original signal is divided every predetermined period as shown by a dotted line, and it is determined whether the information contained in each divided block is rough or dense. For blocks that are judged to be dense, all the data obtained by sampling the original signal are transmitted as transmission data, and for blocks that are judged to be coarse, only a part of all the data is used as transmission data, and the others are thinned out. It shall not be transmitted as data.

Based on the above-mentioned concept, the number of data transmitted per unit time is reduced, and the band compression of the transmission signal becomes possible. The data transmitted in this manner is used on the receiving side to form data corresponding to the thinned-out data. That is, the transmitted data is used to calculate the interpolation data that approximates the thinned-out data. Since this interpolated data corresponds to the coarse information, the interpolated data is very similar to the thinned-out data. Therefore, as compared with the case where all data is transmitted, the fidelity of the restored signal corresponding to the original signal is hardly changed, and the transmission band can be significantly compressed. That is, the amount of information to be transmitted can be reduced.

On the other hand, for each block, whether all sampling data or part of the data is to be transmitted is determined by examining the details of the original signal, and this determination information is also transmitted in some form simultaneously as transmission mode information. .

Now, let us consider applying the above concept to the transmission of image information. Since the image information has a two-dimensional spread and has correlation in both horizontal and vertical directions,
If the sampling interval in the vertical direction as well as the sampling interval in the horizontal direction is variable, more effective transmission becomes possible. This concept is hereinafter referred to as two-dimensional TAT, which will be briefly described below. The concept of this two-dimensional TAT has already been disclosed in Japanese Patent Application No. 60-148112 filed by the present applicant.

FIG. 7 is a diagram showing a data transmission pattern in the two-dimensional TAT. In the two-dimensional TAT, one screen is divided into pixel blocks consisting of m × n pixels, and the density of transmission data is changed for each pixel block. 7th
In the figure, it is assumed that the pixel block has 4 × 4 pixels, and two types of transmission modes are shown.

In the figure, ○ indicates a transmission pixel, and × indicates a thinning pixel. E
Shows a pattern for transmitting all pixel data as shown, and C shows a pattern for transmitting only a part of all pixel data. Hereinafter, the transmission modes based on these transmission patterns will be referred to as E mode and C mode, respectively. As is clear from the figure, it is understood that the C mode transmits at 1/4 the information density as compared with the E mode.

For thinned pixels of pixel blocks transmitted in the C mode, interpolation pixel data is formed by using pixel data adjacent to it among the pixel data transmitted on the receiving side, and the original screen is restored.

The configuration for realizing such two-dimensional TAT transmission will be described below. FIG. 8 is a diagram showing a schematic configuration example on the transmission side of a transmission system using two-dimensional TAT. In the example shown in FIG. 8, an analog transmission system is described as an example.

The input video signal is analog digital converter (A /
D) All pixels are sampled at 1 to generate all pixel data. When all the pixel data are supplied to the thinning circuit 2, thinning corresponding to the C mode pattern of FIG. 7 is performed to obtain C mode pixel data. The C-mode pixel data is supplied to the interpolation circuit 3, and the interpolation pixel data corresponding to the thinned pixel data is calculated.

This interpolated pixel data is supplied to the mode discrimination circuit 4 together with all pixel data output from the A / D1, and it is determined whether each pixel block is transmitted in the C mode or the E mode. In the mode discrimination circuit 4, the difference between the pixel data output from the A / D 1 and the interpolated pixel data is calculated, and the sum of this difference (hereinafter referred to as block distortion) is calculated for each pixel block, and this is calculated by one field. Store in memory.

Then, until the next field data is input, the distribution of the block distortion of all pixel blocks is obtained.
Here, the ratio of the number of pixel blocks transmitted in the C mode to the number of pixel blocks transmitted in the E mode and the number of pixel blocks transmitted in the E mode must always be constant. For example, C
If the pixel block transmitted in the mode is set to 2/3 of the whole and the pixel block transmitted in the E mode is set to 1/3 of the whole, the number of data (compression rate) transmitted as a whole is (2/3 × 1/4 + 1) / 3
× 1 =) 1/2. Therefore, based on the block distortion distribution of all pixel blocks, a distortion threshold value for determining how much block distortion is to be used for C-mode and E-mode distribution is obtained.

Then, the block distortion accumulated at the timing when the video signal of the next field is input is sequentially read out and compared with the distortion threshold value to determine the transmission mode. When the read block strain matches the strain threshold, the C ratio is set to the predetermined ratio as described above.
The transmission mode is determined so that the ratio of the pixel block transmitted in the mode and the pixel block transmitted in the E mode match.

The mode discrimination signal obtained as described above is supplied to the switch 7, and pixel data is read out alternatively from the buffer 5 for E mode pixel data and the buffer 6 for C mode pixel data. The output data of the switch 7 is input to the digital analog converter (D / A) 8 as transmission data,
Here, it is converted into an analog video signal again and output to the transmission path. The mode discrimination signal is also output to the transmission line as mode information via the buffer 9.

FIG. 9 is a diagram showing a schematic configuration example on the receiving side of the two-dimensional TAT transmission system. The video signal, which has been subjected to the above-described processing and is input through the transmission line, is converted into a digital signal by the A / D 10. The output of the A / D 10 is supplied to the C mode interpolation circuit 11, and the interpolation data corresponding to the thinned pixel data in the C mode is calculated.

On the other hand, the transmitted mode information controls the switch 12, and when the mode information indicates the E mode, it connects to the E side, and when the mode information indicates the C mode, it connects to the C side. As a result, all the pixel data including the E mode pixel data, the C mode pixel data and the interpolation pixel data are stored in the frame memory 13. For example, all pixel data are read from the frame memory 13 in the order conforming to the television signal and output via the D / A 14.

As described above, in the two-dimensional TAT transmission system, image information can be transmitted extremely effectively.

<Problems to be solved by the invention> By the way, when the television signal as described above is displayed, the resolution is not noticeable in the moving image area on the playback screen, but the deterioration of the resolution is conspicuous in the still area. easy. On the other hand, the still region on the screen has a high correlation in the time axis direction, and a video signal processing method using the correlation in the time axis direction is advancing in recent years.

However, in the above-described two-dimensional TAT transmission system, even when a group of screens having temporal correlation is continuously transmitted, a still area on the screen and a moving image area are not particularly distinguished from each other. It was Therefore, there is a case where the reproduction screen in the still area is not enough. In particular, when the entire screen is a still image, the deterioration of the image quality in the C mode transmission portion is noticeable.

Under such an object, in the image information transmission method of the present invention, each block is divided into a plurality of pixels, and when transmitting in block units, a block for transmitting image information with a small amount of information and a large block Image information of one screen can be transmitted in a transmission mode including a block that transmits image information with a certain amount of information and a block that does not transmit image information of the screen, and each pixel of the corresponding block of another screen With the increase in the number of blocks that do not transmit the image information of the screen, the block of the screen having a small difference is selected as a block that does not transmit the image information of the screen,
Information in which the number of blocks for transmitting image information with the large amount of information is relatively increased with respect to the number of blocks for transmitting image information with the small amount of information, and the information amount of image information for one screen is defined. It is transmitted as a quantity.

<Operation> In the above-mentioned configuration, when the block corresponding to the still area on the screen is a block that does not transmit the image information of the screen, by using the screen data transmitted immediately before, this part Can be reproduced. Moreover, if this block is a block that transmits a large amount of information in the screen transmitted immediately before, the resolution of the reproduced screen will be extremely high.

Example An example of the present invention will be described below.

In the present embodiment, the number of transmitted data is reduced by utilizing the temporal correlation of image information in the above-mentioned two-dimensional TAT transmission system, which is also called three-dimensional TAT. That is, in the three-dimensional TAT transmission system of the present embodiment, it is noted that it is not necessary to update the pixel data on the receiving side in the static area of the screen, and two-dimensional
When the same amount of data is transmitted as in the TAT transmission system, the image quality is further improved.

The basic idea of this embodiment will be described below. If all pixel data is transmitted once for the pixel block in the still area, the pixel data of the screen is not transmitted for this pixel block when transmitting the subsequent screen. The idea is to use the data repeatedly. For the pixel data of the screen that is being transmitted in this way, there is a pixel block that does not transmit,
Only the information indicating that is transmitted. This transmission mode is hereinafter referred to as the p mode, and the transmission modes corresponding to the E mode and the C mode in the two-dimensional TAT are respectively referred to as the e mode and the c mode in order to distinguish them from the two-dimensional TAT.

When it is considered that the same amount of data is transmitted as in the case of two-dimensional TAT, the number of pixel blocks in the p mode increases, and the number of pixel blocks not transmitted in the p mode decreases. Among them, a pixel block having a high information density can be transmitted in the e mode. Therefore, as the stationary area increases, the number of pixel blocks that can obtain high resolution on the receiving side can be increased, and the reproduced image quality is further improved.

FIG. 1 is a diagram showing a schematic configuration of a transmission side of a transmission system as an embodiment of the present invention, and this embodiment also targets an analog transmission system.

The input analog video signal is converted into a digital signal by the A / D 100, and all pixel data is output. This all-pixel data is supplied to the thinning circuit 101 as in the case of the two-dimensional TAT, thinning corresponding to the c-mode pattern is performed, and c
The mode pixel data (basic pixel data) is obtained. The c-mode pixel data is supplied to the interpolation circuit 3, and the interpolation pixel data corresponding to the thinned pixel data is calculated.

Here, a process of determining which of the three modes, e, c, and p, is used to transmit the pixel block will be described. First, as in the case of the two-dimensional TAT, the difference in the reproduced pixel data between the case of transmitting in the e mode and the case of transmitting in the c mode is calculated by using the output of the A / D 100 and the output of the interpolation circuit 102, The sum of these differences (hereinafter referred to as block distortion Dc) is calculated by the block distortion Dc calculation circuit 103 for each pixel block.

On the other hand, the difference between each pixel data in the past screen stored in the frame memory 104 and each pixel data in the current screen is calculated, and similarly, the difference between each pixel block (hereinafter referred to as block distortion Dp) is calculated. ) Is calculated by the block distortion Dp calculation circuit 105. The comparator 106 compares these Dc and Dp.

That is, the comparator 106 outputs e for each pixel block depending on whether the transmission is in the c mode or the p mode.
This means that it is detecting whether the screen can be reproduced faithfully when transmitted in the mode. Therefore, when Dc> Dp, the c-mode does not occur, and when Dc <Dp, the p-mode does not occur.

The comparator 106 supplies data (Dc / Dp) indicating which of Dc and Dp is larger, and supplies the smaller value to the mode determination circuit 107 as a composite block distortion (Dm).

In the mode decision circuit 107, the e-mode is assigned to a predetermined number of pixel blocks in descending order of Dm. The procedure of this assignment is the same as in the case of the above-mentioned two-dimensional TAT. Dm threshold is calculated based on the distribution, and Dm
If e exceeds this threshold, it is set to the e mode, and if Dm is smaller than the threshold, it is set to a mode other than the e mode. When Dm is smaller than the threshold value, it is natural that Dp> Dc, c mode, Dp <D
When c, p mode is split. In accordance with this, the data (e
/) And Dp / Dc are output.

In the transmission system of this embodiment, the mode information is e /
Only transmit. At this time, whether the transmission mode of the pixel block which is not the e mode is the c mode or the p mode is transmitted as pixel data as follows.

That is, with respect to the pixel block transmitted in the p mode, the basic pixel data of the previous screen reproduced on the receiving side is transmitted. All the pixel data of the previous screen reproduced on the receiving side are stored in the frame memory 104, and the thinning circuit 108 thins it out like the thinning circuit 101 to obtain the basic pixel data of the previous screen. The output data of the thinning circuit 108 thus obtained will be referred to as p-mode pixel data hereinafter. As will be described later, if the basic pixel data of the pixel blocks on successive screens is the same on the receiving side, it is determined that the pixel block on the subsequent screen was transmitted in p mode.

The data stored in the frame memory 104 is all pixel data of the previous screen reproduced on the receiving side. That is, rewriting of data in the memory 104 must be prohibited for pixel data of a pixel block whose previous screen is p mode. Further, even if the previous screen is in the c mode for the pixel block, the image quality improving effect cannot be obtained. Therefore, rewriting the data in the frame memory 104 is performed by the mode determination circuit 1
It may be performed only when the mode is determined to be e mode by 07. Therefore, in the present embodiment, e /
Controls the rewriting of the memory 104.

In this way, the p-mode pixel data, the e-mode pixel data, and the c-mode pixel data are obtained from the buffers 109, 110, and 111, respectively, and the switch 113 selectively supplies them to the D / A 114 using e / and Dc / Dp. is doing. Therefore, D / A114 is a three-dimensional TA.
An analog video signal from the T transmission system will be output. Further, e / is also transmitted as mode information via the buffer 112.

The distribution ratio of each mode in the above embodiment will be considered below. FIG. 2 is a diagram showing a mode distribution state with respect to block distortions Dp and Dc, and FIG. 3 is a diagram showing a change in distribution ratio due to temporal correlation of images.

Considering Dc and Dp of a pixel block shown in FIG. 2, the block having a larger movement goes upward on the Dp axis.
In addition, a part with higher definition, that is, a block with a two-dimensionally higher frequency, goes to the right on the Dc axis. Since Dm takes the smaller value of Dc and Dp, Dc, D located at Xc as shown
Dm of the pixel block with p is D when the perpendicular line is drawn on the Dc axis.
The value is on the c-axis. On the other hand, Dm of the pixel block with Dc and Dp located at Xp has a perpendicular line on the Dp axis, and this perpendicular line and the straight line Dc
= It is the value on the Dc axis when a perpendicular line is drawn from the intersection with Dp to the Dc axis.

Now, when the Dm axis is provided in FIG. 2 and the threshold value T ₁ is considered, Dc, D
It is located at T _{2 on} the p-coordinate, and the e-mode area is determined as shown in the figure. That is, in general, a pixel block that moves rapidly and has a high definition is transmitted in the e mode.

FIG. 3 shows the distribution ratio of each mode when the data compression ratio of one screen is fixed to 1/2. Here, the pixel data transmitted in the p mode is 1/4 of the whole, and it is the same as that in the c mode, so the number of pixel blocks that can be transmitted in the e mode is always the whole.
It becomes 1/3.

In Fig. 3, the straight line forming the right side shows the distribution ratio of the two-dimensional TAT. In other words, in a three-dimensional TAT transmission system, if there is no correlation between the front and rear screens, the same processing as the two-dimensional TAT will be performed. On the contrary, when transmitting a completely still screen, the pixel blocks transmitted in the c mode are eliminated, and the reproduced screen has the same resolution as when all the pixel blocks are transmitted in the e mode. The mode distribution ratio for a certain screen is indicated by the length of the line segment of the portion that intersects the e, c, and p regions on the dotted line indicated by A in the figure. The position of the dotted line A depends on the temporal correlation of the image information to be transmitted, as is clear from the above description.

FIG. 4 is a diagram showing a schematic configuration of the receiving side of the transmission system according to this embodiment. The analog video signal transmitted from the transmission side shown in FIG. 1 is returned to digital data in the A / D 200. The switch 205 is controlled by the transmitted mode information, and outputs all pixel data for each pixel block as it is when transmitted in the e mode. When the data is transmitted in the other modes, the switch 205 side outputs the interpolated pixel data formed by the interpolator 204. It goes without saying that this interpolation pixel data corresponds to the thinned pixel data thinned out on the transmitting side. In this way, the switch 205 outputs all pixel data based on the transmitted pixel data.

On the other hand, the switch 209 outputs only the basic pixel data of the pixel block transmitted in the e mode through the thinning circuit 208, and outputs the basic pixel data as it is for the pixel blocks transmitted in the other modes. This switch
209 is also controlled by the transmitted mode information. Accordingly, the basic pixel data is output from the switch 209 and supplied to the basic pixel frame memory 201.

In addition, the difference between the basic pixel data output from the switch 209 and the basic pixel data of the previous screen obtained from the frame memory 201 is calculated, and the sum of this difference (hereinafter referred to as block distortion Db) is calculated for each pixel block. Calculated by the distortion Db calculation circuit. This block distortion Db is supplied to the comparator 203,
If this Db is smaller than the threshold TH, the pixel block is p
It is determined that the data was transmitted in the mode. Mode information (p /) indicating whether p-mode is output or not
Is supplied to the frame memories 201 and 206. As a result, the rewriting of the frame memories 201 and 206 is prohibited for the pixel block transmitted in the p mode, and the data of the previous screen remains as it is. If the remaining data is e-mode pixel data, a good reproduction screen can be obtained.

In this way, the data in the frame memory 206 for all pixels is updated, and the D / A 207 is read to read D / A.
High-resolution analog video signals will be output from the A207.

It will be apparent that in the transmission system of the embodiment as described above, a high resolution analog video signal can be obtained in the still region.

In the transmission system of the above-described embodiment, the mode information indicating the p-mode is not transmitted, but it is also possible to transmit this and not transmit the pixel data of the previous screen. FIG. 5 shows the distribution ratio of each mode when the compression ratio is fixed at 1/2 in this case. As is clear from the figure, even in this case, if there is no correlation between the front and rear screens, the same processing as the two-dimensional TAT is performed. Further, in this case, if the correlation in the time axis direction is high, the number of pixel blocks transmitted in the e mode increases.

<Effects of the Invention> As described above, according to the present invention, it is possible to obtain an image information transmission method capable of improving the reproducibility of an image having a large number of still regions in a state where the information amount of image data is set to a prescribed information amount. is there.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a transmission side of a transmission system as an embodiment of the present invention, and FIG. 2 is a mode distribution state according to the property of each pixel block in the embodiment of FIG. FIG. 3 is a diagram showing a change in mode distribution ratio due to temporal correlation of images in the embodiment of FIG. 1, and FIG. 4 is a diagram showing a schematic configuration of a receiving side of a transmission system according to this embodiment. Fig. 5 is a diagram showing the change of the mode distribution ratio due to temporal correlation of the image when the pixel data of the previous screen is not transmitted, and Fig. 6 is a diagram for explaining the basic concept of TAT. , FIG. 7 is a diagram showing a data transmission pattern in a two-dimensional TAT, FIG. 8 is a diagram showing a schematic configuration example of a transmission side of a transmission system by the two-dimensional TAT, and FIG. 9 is a transmission side of FIG. It is a figure which shows schematic structure of the corresponding receiving side. 101 is a thinning circuit, 102 is an interpolation circuit, 104 is a frame memory,
107 is a mode determination circuit and 113 is a switch.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomohiko Sasaya, 770 Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Canon Inc., Tamagawa Plant (72) Inventor, Katsuji Yoshimura 770, Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Canon Inc. Company Tamagawa Business Office (72) Inventor Hirohisa Takahashi 770 Shimonoge, Takatsu-ku, Kawasaki City, Kanagawa Prefecture Canon Inc.Tamagawa Business Office (72) Inventor Susumu Katsuki, 770, Shimonoge, Takatsu-ku, Kanagawa Prefecture Canon Tamagawa, Inc. On-site (56) References JP-A-60-158787 (JP, A) Technical Report of the Television Society, ICS67-7 (S59-4-5), P.P. 47-54

Claims (1)

[Claims] 1. A method of dividing image information of a screen group having temporal correlations into blocks each of which is composed of a plurality of pixels and transmitting the blocks in units of a small amount of information. Image information of one screen can be transmitted in a transmission form including a block for transmitting image information, a block for transmitting image information with a large amount of information, and a block for not transmitting image information for the screen. A block of the screen having a small difference in each pixel from the corresponding block of the screen is selected as a block in which the image information of the screen is not transmitted, and the number of blocks in which the image information of the screen is not transmitted is increased. Accordingly, the number of blocks transmitting image information with the large amount of information is relatively increased with respect to the number of blocks transmitting image information with the small amount of information, and the information of the image information of one screen is increased. Image information transmission method characterized by transmitting an information amount of the specified.