JPH02100467A - Image information signal transmission system - Google Patents

Abstract

PURPOSE:To suppress image deterioration and to transmit an image information signal with high compressibility by dividing picture elements of one image plane into cross-shaped picture element blocks and assigning one of plural kinds of different transmission modes to the respective blocks. CONSTITUTION:The picture elements of one image plane is divided into the cross-shaped picture element blocks each formed of a specific number of horizontally and vertically adjacent picture elements. A block distortion Dc arithmetic circuit 103, a block distortion Dp arithmetic circuit 105, a comparator 106, and a mode decision circuit 107 decide a mode in which the picture element blocks are to be sent among three modes, i. e., (e) mode wherein all data are transmitted, C mode wherein some of data are sent, and P mode wherein no information is sent, and picture element data in the picture element blocks are sent according to the assigned transmission mode. Consequently, the compressibility is made higher than before, so the number of picture element blocks assigned to the (e) mode is increased and the picture quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image information signal transmission system for transmitting image information signals.

[Prior Art] Conventionally, for example, in an information compression transmission system, a time axis transform band compression method (Ti+*e Axis Transform
a-tion (hereinafter referred to as TAT) has been announced, but when performing band compression of information signals, this TAT method uses the fact that the density of the information signal differs depending on the location to compress and transmit the information signal. This is a method to do so.

The second VA shows the principle of using the TAT method in processing one-dimensional signals.

In FIG. 2, the original signal is first divided into predetermined amounts of information as shown by dotted lines, and it is determined whether the information is coarse or dense for each divided group. Then, in groups that are judged to be dense, all of the data obtained by sampling the original signal is transmitted as transmission data, and in groups that are judged to be dense, only a part of all the data is used as transmission data. , shall not be transmitted as other thinned data. In addition, the data indicated by the Q mark in the figure is the data to be transmitted (transmission data), and the data indicated by the X mark is the data that is not transmitted (transmission data).
(thinned data).

By transmitting only the transmission data indicated by the O symbol at regular intervals, the number of data transmitted per unit time is reduced, and the band of the transmission information signal is compressed.

The data transmitted as described above is approximately restored by using the transmitted data to remove the thinned out data that was not transmitted during decoding to obtain interpolated data (marked with ◆ in the figure). In addition,
This interpolated data corresponds to the coarse part of the information and is restored as data that is very close to the 1-thinned data, so the actual amount of information does not change compared to when all the data is transmitted, and the information signal This means that the transmission band has been significantly compressed.

At this time, it is determined whether all data or part of the data is to be transmitted in each group by examining the details of the original signal, and this determination information is simultaneously transmitted as a transmission mode information signal.

In the case of image information signals, not only the horizontal sampling interval but also the vertical sampling interval can be changed.
By performing two-dimensional processing, the transmission band of image information can be compressed.

When processing a two-dimensional signal such as an image information signal, one screen is divided into groups of mXn pixels, and the density of the image is determined for each group. Then, in the group judged to be dense, data obtained from all pixels is transmitted as transmission data, and in the group judged to be coarse, data obtained from some of the pixels is transmitted as transmission data. However, the data of the remaining pixels will not be transmitted as thinned-out data.

Here, when transmitting data obtained from all pixels, E
If the mode is called C mode, which is a mode in which only data for some pixels are transmitted, the relationship between pixels to which data is transmitted and pixels to which data is not transmitted in each transmission mode is as shown in FIG.

Figure 3 shows E mode and C mode in 4x4 pixel groups.
(a) Shows the pixels to which mode data is transmitted.
shows E mode, and (b) shows C mode.

One screen of image information to be transmitted is divided into 4 x 4 pixel groups from the upper left to the lower right of the screen, and the two transmission modes described above are selected for each group depending on the density of the image. Select and transmit according to the selected transmission mode.

Figure 4 shows that an NTSC TV screen is component-demodulated using the above method, one field of the time-division multiplexed TV screen is divided into 4 x 4 pixel groups, and each group is FIG. 4 is a diagram in which the transmission modes of E mode and C mode shown in FIG. 3 are assigned. In addition, O
The marks are pixels to which data is transmitted, and the x marks are pixels to which data or no data is transmitted.

By transmitting the pixel data transmitted in this manner at regular intervals, the transmission band is compressed and transmitted.

Furthermore, since the data of pixels that are not transmitted is approximately restored using the data of nearby transmitted pixels during decoding, the actual amount of information does not change compared to when all data is transmitted, and the information This means that the signal transmission band has been significantly compressed.

[Problems to be Solved by the Invention] However, when transmitting information using the information compression transmission method as described above, if you try to make the information compression rate constant for each screen, E mode and C mode Therefore, if the entire screen is small, the image quality deteriorates significantly after transmission.

Also, if you increase the number of pixel groups assigned to C mode in order to increase the compression rate of information, the resolution of the C mode is half in both the horizontal and vertical directions, so if the number of groups assigned to C mode increases, As the number increases, the image quality after transmission will deteriorate significantly.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image information signal transmission system that can suppress image quality deterioration and transmit image information signals at a high compression rate.

[Means for solving the problem] The image information signal transmission system of the present invention is a system for transmitting an image information signal in which one screen is composed of a plurality of pixels, and the pixels for one screen are horizontally arranged on the screen. and divided into cross-shaped pixel blocks formed by a predetermined number of pixels adjacent in the vertical direction, and for each of the pixel blocks, one of a plurality of transmission formats different from each other is transmitted.
The pixel data in the pixel block is transmitted based on the assigned transmission format.

[Operation] With the above-described configuration, the image information signal can be compressed and transmitted at a high voltage m rate without deteriorating the image quality.

[Example] Hereinafter, the present invention will be explained based on examples of the present invention.

Here, the present invention will be explained using an image information transmission system to which the present invention is applied as an embodiment of the present invention.

In this image information transmission system, a plurality of blocks obtained by dividing one screen are divided into a first block group transmitted at a first information density and a second block group transmitted at a second information density. The screen is configured to be transmitted in a format including a block group and a third block group in which information on the screen is not transmitted.

In the above-described configuration, when a block corresponding to a static area on the screen is set as the third block group, this portion can be reproduced by using the data of the screen transmitted immediately before. Moreover, if this block is in the first block group in the screen transmitted immediately before, the resolution of the reproduced screen will be extremely high.

This image information transmission system reduces the number of transmitted data by further utilizing the temporal correlation of image information in addition to the above-mentioned two-dimensional TAT transmission system, and should also be called three-dimensional TAT. That is, in the transmission system using three-dimensional TAT of this embodiment, focusing on the fact that there is no need to update pixel data on the receiving side for the static area of the screen, the transmission system using three-dimensional TAT is the same as the transmission system using two-dimensional TAT. The purpose is to further improve the image quality when transmitting data of .

The basic concept of 3D TAT will be explained below. If all pixel data is transmitted for a pixel block in a static area, when transmitting subsequent screens, this pixel block will be transmitted first without transmitting the pixel data of that screen. The idea is to use the data repeatedly. In this way, regarding the pixel data of the screen that is being transmitted, there are pixel blocks that are not transmitted, and only information indicating this fact is transmitted. This transmission mode is hereinafter referred to as p-mode, and the transmission modes corresponding to E mode and C mode in two-dimensional TAT are referred to as C-mode and C-mode, respectively, to distinguish them from the two-dimensional TAT case.

When considering transmitting the same amount of data as in the case of two-dimensional TAT, as the number of p-mode pixel blocks increases, the number of pixel blocks that do not transmit p-mode decreases. Among them, it is possible to transmit the C mode, which is a pixel block with high information density. Therefore, as the static 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 the transmitting side of a transmission system as an example of the configuration of a three-dimensional TAT, and is intended for an analog transmission system.

In FIG. 1, the input analog video signal for one field is sent to a digital-to-analog (A/D) converter 10.
0 into a digital video signal, and as a C-mode digital video signal, the decimation circuit 101
, block distortion Dc calculation circuit 103, frame memory 10
4. Block distortion Dp calculation circuit 105, buffer circuit 11
0.

Here, Figure @5 shows the C mode transmission pattern used in this embodiment.

In FIG. 5, O marks represent pixels to be transmitted,
The thinning circuit 101 samples the pixel data transmitted by the C mode shown in FIG. 5(d) from the digital video signal supplied from the A/D converter 100. Pixel data indicated by O in the figure is output and supplied to the interpolation circuit 102 and the buffer circuit 111.

Furthermore, the interpolation circuit 102 uses the pixel data sampled in the pixel block (marked with O in FIG. 5(b)) by the thinning circuit lot, and uses the unsampled pixel data in the pixel block (marked O in FIG. 5(b)). (X mark in (b))
is interpolated and supplied to the block distortion DC calculation circuit 103.

The process of determining which of the three motes e+C+Pp is used to transmit a pixel block will now be described. First, when transmitting with C-mote,
The difference between the reproduced pixel data and when transmitted using C mode is A/
The calculation is performed by using the output of D 100 and the output of the interpolation circuit 102, and the sum of the differences (hereinafter referred to as block distortion Dc) is calculated for each pixel block in a block distortion DcrA calculation circuit 103.

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

That is, in the comparator 106, for each pixel block.

This means that it is detected whether the screen can be faithfully reproduced when transmitting using C mode or when transmitting using P mode. Therefore, Da
>Dp, the C mode is not set, and when DC<Dp, the P mode is not set.

The comparator 106 outputs data indicating which of Dc and Dp is larger (Dc/Dp), and the mode determination circuit 1 uses the smaller value as composite block distortion (Dl).
Supply on 07.

In the mode determination circuit 107, C mode is assigned to a predetermined number of pixel blocks in descending order of Dl. The procedure for this assignment is the same as in the case of the two-dimensional TAT described above, where a threshold value of Dl is determined based on the distribution of Dm of all pixel blocks, and if Da exceeds this threshold value, C mote, D*ltr : If the value is smaller than 14, a mode other than C mode is selected. When DI is smaller than the threshold, C mode is naturally assigned when Dp>Dc, and P mode is assigned when DP<Dc. Accordingly, the mode determination circuit 107 outputs data (e/e) indicating whether the mode is C mode or other mode, and Dp/
Da is output.

In the transmission system of FIG. 1, only mode information e15 is transmitted. This I+4? e-mote tenare.

Whether the transmission mode of a pixel block is C mode or P mode is transmitted as pixel data as follows.

That is, for pixel blocks transmitted in P mode, the basic pixel data of the previous screen reproduced on the receiving side (Fig. 5 (b)
(O mark)) is transmitted. All pixel data of the previous screen reproduced on the receiving side is stored in the frame memory 104. The basic pixel data of the previous screen can be obtained by thinning out this data using the thinning circuit 108 in the same manner as the thinning circuit lot. The output data of the thinning circuit 108 obtained in this manner will be hereinafter referred to as p-mode pixel data. As will be described later, on the receiving side, if the basic pixel data of a certain pixel block is the same in consecutive screens, it is determined that the pixel block in the subsequent screen has been transmitted in p mode.

Note that the data stored in the frame memory 104 is all pixel data of the previous screen to be reproduced on the receiving side. That is, data rewriting of the memory 104 must be prohibited for pixel data of p-mode pixel blocks on the previous screen. Further, even if the pixel block whose previous screen is in C mode is in p mode, no image quality improvement effect can be obtained. Therefore, data in the frame memory 104 needs to be rewritten only when the mode determination circuit 107 determines that the mode is C mode. Therefore, in FIG. 1, rewriting to the memory 104 is controlled using e/δ obtained from the mote determination circuit 107.

In this way, P mode pixel data, C mode pixel data, and C mode pixel data are obtained from the buffers 109, 110, and 111, respectively, and the switch 113 provides e/d and Dc pixel data.
/Dp is used to selectively supply these to the D/A 114. Therefore, the D/A l 14 outputs an analog video signal using a three-dimensional TAT transmission system.

Further, e/i is also transmitted via the buffer 112 as mode information.

The distribution ratio of each mode in the above embodiment will be discussed below. FIG. 7 is a diagram showing mode distribution with respect to block distortions Dp and Dc, and FIG. 8 is a diagram showing changes in distribution ratio due to temporal correlation of images.

Considering D c and D p of a pixel block in FIG. 7, the larger the movement of the block, the higher it moves upward on the Dp axis. Further, the higher the definition, that is, the block with the higher two-dimensional frequency, the more it moves to the right on the 2Dc axis. D■ is Dc
Therefore, as shown in the figure, Dm of a pixel block with D c and D p placed in Xc is the value on the DC axis when a perpendicular line is drawn to the Da axis. . On the other hand, for Da of a pixel block with D c and D p located at Xp, a perpendicular line is drawn to the Dp axis, and this perpendicular line is
c = Dc is the wheel axis value when a perpendicular line is further drawn down from the intersection with Dp to the Da axis.

When we set the D■ axis in Figure 7 and consider the threshold Tl, Dc
, Dp coordinates are located as T2, and as shown in the figure
The C-mote area is determined. In other words, when fishing on a boat, a pixel block with intense movement and high definition is transmitted using the C mode.

Regarding the distribution ratio of each mode, FIG. 8 shows the case where the data compression rate for one entire screen is fixed at 1/2. Here, it is assumed that the pixel data transmitted in the p mode is 5/16 of the total, which is equal to that in the C mode, so the number of pixel blocks that can be transmitted in the C mode is always 3/8 of the total.

The straight line portion on the right side of FIG. 8 indicates the distribution ratio of the two-dimensional TAT. In other words, a three-dimensional TAT transmission system performs the same processing as a two-dimensional TAT when there is no correlation between the front and rear screens. On the other hand, when transmitting a completely still screen, no pixel blocks are transmitted in C mode, and the reproduced screen has the same resolution as when all pixel blocks are transmitted in C mode. The mode distribution ratio for a certain screen is indicated by the length of the segment on the dotted line indicated by A in the figure, which intersects with each area of e*c+T'. As is clear from the above description, the position of this dotted line A depends on the temporal correlation of the image information to be transmitted.

FIG. 9 is a diagram showing a schematic configuration of a receiving side corresponding to the transmitting system shown in FIG. 1. An analog video signal transmitted from the transmitting side shown in FIG. 1 is converted back into digital data at an A/D 200. The switch 205 is controlled by the transmitted mode information, and for each pixel block, if it is transmitted in C mode, it outputs all pixel data as it is. If the data is being transmitted in any other mode, interpolated pixel data formed by the interpolation circuit 204 connected to the ; side of the switch 205 is output. Needless to say, this interpolated pixel data corresponds to the thinned-out pixel data (marked with an x in FIG. 5(b)) 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 blocks transmitted in the C mode via the thinning circuit 208, and outputs the basic pixel data as is for the pixel blocks transmitted in other modes. This switch 209 is also controlled by the transmitted mode information. Therefore, 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. It is calculated by the distortion Db calculation circuit.

This block distortion Db is supplied to the comparator 203, and this D
If b is smaller than the threshold TH, it is determined that the pixel block has been transmitted in p mode. This outputs mode information (p/p) indicating whether it is p mode or something else.
are supplied to frame memories 201.206. As a result, the judgment of the frame memories 201 and 206 is prohibited for the pixel blocks transmitted by the p mode, and the data from one screen before remains as is. If this remaining data is e-mote pixel data, a good reproduced screen can be obtained.

In this way, data in the frame memory 206 for all pixels is updated, and by reading data to the D/A 207, a high resolution analog video signal is output from the D/A 207.

It will be clear that in a transmission system constructed as described above, a high resolution analog video signal can be obtained in the static region.

In the above-described transmission system, it is also possible to have a configuration in which the mode information indicating the p mode is not transmitted, or it is transmitted, but the pixel data of the entire screen is not transmitted. In this case, the distribution ratio of each mode when the compression ratio is fixed at 1/2 is shown in FIG. 1O. As is clear from the figure, even in this case, if there is no synchronicity between the front and rear screens, the same processing as the two-dimensional TAT is performed.

Furthermore, in this case, if the correlation in the time axis direction is high, the number of pixel blocks transmitted in the C mode increases.

As explained above, in this embodiment, the pixel block configuration is as shown in FIG. 5, so the compression ratio is improved compared to the conventional one, so the number of pixel blocks allocated to C mode is increased, and the You will be able to improve your skills.

[Effects of the Invention] As explained above, according to the present invention, it is possible to provide an image information signal transmission system that can suppress deterioration of image quality and transmit image information signals at a high compression rate. become able to.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a transmitting side of an image information signal transmission system as an embodiment of the present invention. FIG. 2 is an explanatory diagram of the basic concept of TAT. Figure 3 is a diagram showing pixel data transmission patterns in transmission modes in conventional two-dimensional TAT, where (a) is a pixel pattern transmitted in E mode, and (b) is a pixel pattern transmitted in C mode. be. Figure 4 shows how an NTSC television signal is componentized, one field screen of the time-division multiplexed signal is divided into 4 x 4 pixel blocks, and E mode and C mode are assigned to each pixel block. FIG. 6 is a diagram showing a case of allocation. FIG. 5 is a diagram showing pixel data transmission patterns of transmission modes in an image information signal transmission system as an embodiment of the present invention, (a) is a pixel pattern transmitted in C mode, (b) is a diagram showing pixel data transmission patterns in C mode. This is the pixel pattern that is transmitted at the time. FIG. 6 is a diagram showing the distribution on the screen of pixel data sampled by the thinning circuit on the transmitting side of the image information signal transmission system shown in FIG. FIG. 7 is a diagram showing mode assignment to block distortions Dp and Dc. FIG. 8 is a diagram showing changes in the allocation ratio depending on the image state. FIG. 9 is a diagram showing a schematic configuration of the receiving side corresponding to the transmitting side of the image information signal transmission system shown in FIG. 1. FIG. 10 is a diagram showing changes in the allocation ratio of each mode in the case where basic pixel data is not transmitted for the p mode as another embodiment of the present invention. 101...Thinning circuit 102--Correction circuit 107--Mode determination circuit (a)

Claims (1)

[Scope of Claims] A system for transmitting image information signals in which one screen is composed of a plurality of pixels, wherein the pixels for one screen are formed by a predetermined number of pixels adjacent to each other in the horizontal and vertical directions on the screen. Each pixel block is divided into cross-shaped pixel blocks, one of a plurality of transmission formats having different transmission formats is assigned to each of the pixel blocks, and the data within the pixel block is divided based on the assigned transmission format. An image information signal transmission system that transmits pixel data.