JP2840235B2 - Image information transmission device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an image information transmitting apparatus for transmitting image information. 2. Description of the Related Art Conventionally, when transmitting image information such as a video signal, for example, a variable density sampling method has been devised in which a sampling frequency is adaptively changed according to the frequency of the video signal to perform transmission. FIG. 2 is a schematic diagram showing the principle of the variable density sampling method. In FIG. 2, first, an original video signal waveform (a) is sampled at a sampling frequency fsp, and divided at every predetermined number of sampling points (for example, 4 sampling points) as shown by a period T in the figure, and divided. It is determined for each block whether the original video signal waveform is coarse or dense.
In blocks determined to be dense, all of the data obtained by sampling the original video signal are transmitted as transmission data, and in blocks determined to be coarse, only a part of all data is transmitted. The other is not transmitted as thinned data. Note that the data indicated by a circle in the figure is data to be transmitted (transmission data), and the data indicated by a cross is data that is not transmitted (thinned-out data). By transmitting the transmission data indicated by the circles at regular intervals, the number of data transmitted per unit time is reduced, and the transmission band of the transmission video signal is compressed. The data transmitted as described above is obtained by approximately reconstructing the thinned-out data that was not transmitted at the time of restoration using the transmitted transmission data and interpolation data. Get. This interpolation data corresponds to the portion where the original video signal waveform is coarse, and is restored as data that is very similar to the thinned data, so the actual information amount changes compared to the case where all data is transmitted. In other words, the transmission band of the video signal is largely compressed. At this time, whether to transmit all data or partial data in each group is determined by examining the details of the original video signal waveform, and this determination information is transmitted simultaneously as a transmission mode information signal. You. FIG. 3 is a block diagram for realizing the above-mentioned transmission system. Video signal input from the input terminal (for example, NTSC signal)
Are digitized by an analog / digital (A / D) converter 2. At this time, the sampling frequency fsp is set to be at least twice the highest frequency component of the input video signal. The output signal of the A / D converter 2 is supplied to a decoder 3 and supplied to a luminance signal Y.
And two types of chromaticity signals I and Q. The luminance signal Y is supplied to the mode discrimination circuit 16 and also to the matrix circuit 4, and the I and Q signals are also supplied to the matrix circuit 4. In the matrix circuit 4, the input Y, I, Q
From each signal, three primary color signals R, G, B are obtained by calculation. The relationship between R, G, B and Y, I, Q is as follows. Y = 0.30R + 0.5G + 0.11B I = 0.74 (RY) −0.27 (BY) Q = 0.48 (RY) +0.41 (BY) The three primary color signals R, G and B are stored by the matrix circuit 4 as signals having a band of 1/2 fsp in the R, G, and B memories 10, 11, and 12 of the first memory group, respectively, and are also supplied to the prefilter 6. For example, the second
As shown in the figure, one of four sampling points and one block
When performing dimensional variable density sampling, the band is limited by the pre-filter 6 to a further quarter of 1/2 fsp. In the output of the pre-filter 6, the information of the three sampling points other than the first input sampling point is removed from the information of the four sampling points by the thinning circuit 5. The three primary color signals whose bands have been compressed to 1/4 as described above are stored in the R, G, B memories 7, 8, and 9 of the second memory group. Outputs of the first memory group and the second memory group are led to three input terminals of switch circuits 13 and 14, respectively. Further, outputs of the switch circuits 13 and 14 are connected to input terminals E and C of the switch circuit 15, respectively.
Are led to each. The operation of the mode determination circuit 16 will be described with reference to FIGS. FIG. 5A shows a luminance signal sequence sampled at the sampling frequency fsp. The luminance signal at time t _n is y _n , the luminance signal at time t _{n + 1} is y _{n + 1} , and hereafter y _{n + 2} , y
_{n + 3} ... Now, y _n ~y _{n + 3} is to form one unit block. The luminance signal y _n guided to the mode discriminating circuit 16 is supplied to the latch circuit 30 at the leading edge (t _n ) of the clock 1 shown in FIG.
It is spatula. The output of the latch circuit 30 is guided to a latch circuit 31 and an interpolation circuit 32. In the latch circuit 31, the output of the latch circuit 30 is latched at the leading edge (t _{n + 4} ) of the next pulse of the clock 1. Luminance signal y _n of the sampling point which is first input of thus similarly luminance signal units as thinning circuit 5 to the latch circuit 30 and 31 block, y _{n + 4}
Is latched. Each output is guided to the interpolation circuit 32. Interpolation circuit 32 in the two input y _n, by the linear interpolation as shown by the dashed line in FIG. 5, for example, from y _{n + 4} (d), the time t _n
Interpolated luminance signal y _n ~y _{n + 3} to the calculation outputs of ~t _{n + 3.} On the other hand, the luminance signal y _n is also inputted to the shift register 33, the leading edge of clock 2 shown in FIG. 5 _{(c) (t n, t} n + 1,
t _{n + 2} ……)). As described above, at time t _{n + 4} , the luminance signal sequence
As shown in the figure, the data is output by the interpolation circuit 32 and the shift register 33. Each output becomes an input to a subtractor 34, and the difference is led to an adder 36 via an absolute value detector 35. Adder 36
Is an input of a comparator 37 and is compared with a threshold Yth preset at the other input. As described above, the mode discriminating circuit 16 detects, on a block-by-block basis, the difference in the level or power of the luminance signal between the information on the original sampling points and the information on the sampling points by interpolation. If the sum is greater than a certain threshold, the block's transmission mode is transmitted to a code for transmitting information of all sampling points (hereinafter referred to as E mode). If the sum is less than a certain threshold, information of the sampling point obtained by thinning out the mode of the block is transmitted. Mode (hereinafter referred to as C mode), and the mode information generator 42 generates mode information data in accordance with this determination. The transmission mode information data thus generated is temporarily stored in the mode memory 17 shown in FIG. At the time of transmission, the switches 14 and 13 are respectively connected to the R side in the figure. In accordance with the transmission mode information stored in the mode memory 17, the switch circuit 15 is connected to the first memory group in the case of the E mode, and to the second memory group in the case of the C mode. The transmitted R signal is
Is transmitted together with the mode information data. When the transmission of the R signal is completed, the switching circuits 13 and 14 are sequentially switched to the G side and the B side, and the transmission of the G signal and the B signal is transmitted by the transmission unit 43 in the same manner as described above. [Problems to be Solved by the Invention] By the way, in the conventional transmission method as described above, the mode to be transmitted is determined only by the level or the power difference of the luminance signal in the mode determination circuit 16, so When the video signal transmitted by the transmission method is displayed on the display, the visual characteristics of humans are more sensitive to changes in luminance in the low-luminance area than in the high-luminance area. However, the low-luminance block is larger than the high-luminance block, and the transmitted video signal appears to be considerably deteriorated. The present invention has been made in view of such a problem, and has as its object to provide an image information transmission apparatus capable of suppressing deterioration of image information visually with a simple configuration and compressing and transmitting a band. I have. [Means for Solving the Problems] The image information transmission device of the present invention is a unit for dividing input image information into a plurality of blocks each including a predetermined pixel,
A first detector for detecting a difference between an original luminance signal and an interpolated luminance signal of the image information in each of the blocks; a second detector for detecting a luminance level of the image information in each of the blocks; Transmitting means for compressing the image information by changing the compression ratio in accordance with the outputs of the detecting means and the second detecting means and transmitting the compressed image information, wherein the transmitting means converts the image information of the low luminance level to the high luminance level. It is characterized in that it is compressed and transmitted so that the compression ratio is lower than the image information. Examples Hereinafter, the present invention will be described based on examples. FIG. 1 is a diagram showing a schematic configuration of a mode discrimination circuit as one embodiment of the present invention. As in FIG. 3, the luminance signal Y separated from the input video signal in the decoder is supplied to a mode discriminating circuit as shown in FIG. The supplied luminance signal Y is supplied to the latch circuits 30 and 31 and the shift register 33, and the interpolation signal and the original signal interpolated by the interpolation circuit 32 in synchronization with the clock 1 and the clock 2 as in FIG. The level difference is calculated by the subtractor 34 and the absolute value circuit 35, and the sum of the level differences is calculated by the adder 36 and supplied to the comparator 37. On the other hand, each output y _{n to} y _{n + 3} of the shift register 33 is an adder
The sum of the levels of the luminance signal of the unit block is calculated in the adder 40. Then, the threshold value in the unit block is calculated from the sum of the levels of the luminance signals of the unit block calculated as described above. That is, the output of the adder 40 is multiplied by a constant K preset in the multiplier 41, and the result is supplied to the comparator 37 as a threshold value. By the way, various studies have been made on the visual characteristics of humans. For example, as an example, when the luminance signal level is Y and the amount of change by which human eyes can confirm the change in the luminance signal level is ΔY, Has a relationship of ΔY / Y constant. Therefore, ΔY is calculated by appropriately selecting the value of the constant K to be multiplied in the multiplier 41, and the sum of the level differences between the interpolation signal and the original signal calculated by the adder 36 in the comparator 37 is larger than ΔY. Is determined, the transmission mode (E mode) for transmitting all the information of the sampling points in the unit block, and if determined to be smaller than ΔY, a part of the information of the sampling points in the unit block is transmitted. A transmission mode (C mode) for transmission is set, transmission mode information data corresponding to the judgment result of the comparator is generated by the mode information generator, and the generated transmission mode information data is stored in the mode memory as shown in FIG. . Then, the transmission mode information data stored in the mode memory is read out, and the information signal of the sampling point transmitted from the memory group in FIG. 1 and the second memory group is read out in accordance with the transmission mode information data in the same manner as in FIG. Transmit. At this time, the transmission mode information data read from the mode memory is also transmitted. As described above, by changing the threshold used for determining the transmission mode according to the level of the input luminance signal, the image quality at the low luminance signal level is also considered in consideration of the human visual characteristics, and the deterioration of the visual image quality is conspicuous. It is possible to compress the transmission band of the video signal and transmit it. Further, in the present embodiment, the mode information is determined based on the visual characteristics of the luminance signal of the human eye, but the mode information may be determined based on the visual characteristics of the color signal. [Effects of the Invention] As described above, according to the present invention, not only a change in an image but also a luminance level of the image is taken into account and the image is compressed and transmitted. Can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram of a mode determination circuit of an image information transmission device according to the present invention. FIG. 2 is a schematic diagram of the principle of the variable density sampling method. FIG. 3 is a diagram showing a schematic configuration of a conventional image information transmitting apparatus using a variable density sampling method. FIG. 4 is a schematic configuration diagram of the mode determination circuit of FIG. FIG. 5 is an operation timing chart of the mode determination circuit of FIG. 37 Comparator 40 Adder 41 Multiplier 42 Mode information generator

   ────────────────────────────────────────────────── ─── Continuation of front page       (56) References JP-A-50-158220 (JP, A)                 Journal of the Institute of Television Engineers of Japan, 39 [10               ] (1985) p. 934-940

Claims (1)

(57) [Claims] Means for dividing the input image information into a plurality of blocks each comprising a predetermined pixel; first detecting means for detecting a difference between an original luminance signal and an interpolated luminance signal of the image information in each of the blocks; A second detecting means for detecting a luminance level of the image information in the above, and a transmitting means for compressing and transmitting the image information by changing a compression ratio according to the output of the first detecting means and the second detecting means. An image information transmitting apparatus, wherein the transmitting unit compresses the image information of the low luminance level so as to reduce the compression ratio as compared with the image information of the high luminance level and transmits the image information.