SU1177952A1 - Television system with compression of digital picture signals - Google Patents

Description

The invention relates to television technology and can be used in digital systems for processing and transmitting television images. five

The purpose of the invention is to improve the accuracy of transmission of image signals.

Figure 1 shows the block diagram of a television system with compression of digital image signals; Fig.2 image fragments before and after processing.

A television system with a compres- sion of 15 digital image signals contains a transmitting television camera 1, -block 2 controls, an analog-to-digital converter (ADC) 3, a memory block 4 ′, 20 an arithmetic mean value calculator 5, a comparison block 6 in the transmitting particle ^. , adder 7, block 8 delay ¹ , divider 9 and output register 10, transmitting part of the system through line 11 25

communication is connected with the receiving part containing the input register 12, the control unit 13, the memory block 14, the arithmetic mean value calculation unit 15, the comparison unit 16, the digital-to-analog converter (ADC) 17 and the out-of-control unit 18.

A television system with compression of digital image signals works as follows. ₃₅

Analogue Image signal from a transmitting television camera 1, whose operation is synchronized by a signal arriving at its input from the first output of control unit 2, dd is fed to the first input of the ADC 3, where the image signal is time sampled, quantized by level and encoded with six-bit binary code Procedure 45 of the analog-digital conversion is synchronized by a signal arriving at the second input of the A / D converter 3 from the second output of control unit 2, containing a clock generator, frequency dividers and decoders, and generating a set of signals necessary to synchronize the operation of all blocks of the transmitting part of the system.

Samples of the image signal corresponding to its individual elements from the output of the ADC 3 are fed to the first input of memory block 4, containing 52 2

seven consecutively connected groups, each of six triggers (one trigger per group for each digit). According to the signals arriving at the second input of the memory block from the seventh output of the control unit 2, information is successively advanced through all seven groups of triggers.

Thus, in block 4 of the memory simultaneously stored information about the seven adjacent elements of the image. Information about the six neighboring image elements from the first and second outputs of memory 4 is fed to the first inputs of the arithmetic average calculation unit 5 and the comparison unit 6, which are recorded by signals received at the second inputs of these blocks from the eighth and ninth outputs of the control unit 2, respectively and next with a frequency twice as low as the sampling rate of the analog signal.

Consequently, in block 5 of calculating the arithmetic mean values and block 6 of the comparison, the information about the group of image elements with numbers 1-6 is first recorded, then with numbers 3-8, etc. We denote the first element in each group by the Roman numeral I, the second element by the number II, etc., the sixth element by the number VI.

In block 5, the calculation of the arithmetic mean values simultaneously calculates the arithmetic mean values of elements I and II (I average), III and IV (average) and V and VI (III average), and then calculates the average of I and III averages. The arithmetic mean of I and III averages, as well as II average. Arrive at the third input of comparator block 6, which verifies the equality of the arithmetic mean of I and III of the mean and II of the mean, and also I, II and III elements, IV, V and VI elements.

Block 6 comparison generates a signal "Comparison" (CP) when the following conditions are met:

1. The arithmetic mean of I and III of the mean and the value of II of the mean are the same. At the same time, the output of the NAND element, including ³ 1177952 4

In the block 6 comparison, the signal "Log.O" is generated. Note that the fulfillment of this condition is a permission for additional processing of this group of elements in ₃

reception part.

2. Three neighboring elements are not identical at least in one of two groups of three neighboring elements (I, II and III; IV, V and VI). Note that the same values of the corresponding elements in both the first and the second group of three neighboring elements are characteristic of the limits of a sharp difference in brightness 15

(for borders of large parts of the image).

When the following conditions at the output of comparator unit 6 is formed by a signal "CP" which is conserved nitsya ₂ 0 for a time interval equal to the duration of two adjacent elements.

After forming the CP ₂ 5 (or CP) signal from the third output (the seventh group of flip-flops) of memory block 4, element I will be rewritten at the third input to the adder 7, and element II will be overwritten by the clock. At the same time ₃ θ

element 1 and element II in the presence of a CP signal will correspond with an inverted low-order bit (with minimal error), and the low-order bit will be inverted by the signal ³⁵ arriving at the third input of memory 4. In the next cycle, due to the fact that the signal "Incomparison" is already formed at the output of the comparison block 6 (if the marked conditions are not fulfilled simultaneously), the element III in the adder 7 will be overwritten without change. Element IV will also be rewritten, etc.

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Thus, if these conditions are fulfilled in the transmitting part of the system prior to the implementation of the modified Paley (Walsh) linear transformation, i.e. prior to performing the operation of averaging the original image along two adjacent elements of the row, the elements I and II of the corresponding group are pre-corrected, and 55 this correction is performed by inverting the least significant digits of elements I and II, as a result of which

After the modified Paley (Walsh) linear transformation, the corresponding sequence (group) of averaged elements (I average, II average and III average) for the receiving part will no longer be a resolution for additional processing.

Note that if the first of these conditions is not fulfilled, additional processing in the receiving part will not be made, and therefore there is no need for preliminary processing, if the second condition is not fulfilled, the corresponding elements form a group, which is characterized by sharp brightness differences (large details). Such a group of elements after the modified Paley (Walsh) transformation and additional processing in the receiving part is restored completely and therefore it should not be pre-corrected for it.

From the third output of memory block 4, as already noted, six-digit binary numbers corresponding to discrete samples (elements) of the image are successively fed to the third input of the adder 7 and recorded in the corresponding group of its triggers by the signal received on the first input of the adder 7 from the third output of the block 2 controls. In the adder 7, each element with an even number is summed with the element with an odd number, coming from the output of the adder 7 through the block 8 of the delay to the second input of the adder 7.

The control unit 8 of the delay is carried out by the signal received at its second input from the sixth output of the control unit 2. The delay time is equal to the duration of one image element.

The result of the summation (seven-digit binary number) from the output of the adder 7 is fed to the first input of the divider 9, in which the division operation into two is performed.

It is performed by shifting a seven-digit binary number to the right by one digit. Note that in the divider of known systems, depending on the position of the mode selector switch, the division is carried out by two or four

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(if four adjacent elements are added to the adder).

From the output of the divider 9, the processed samples of the image elements arrive at the first input of the output register 10, -a from its output - into communication 11, while the synchronization of the divider 9 and the output register 10 is performed by signals arriving at their second inputs, respectively the fourth and fifth outputs of the control unit 2.

From the output of the communication link 11, the processed pixel counts are buffered and pre-processed in the input register 12 of the receiving part of the system, which contains five groups of triggers, six in each group, and delays the readings of the averaged picture pixels. The synchronization of the input register 12 is carried out by a signal arriving at its second input from the first output of the control unit 13 of the receiving part of the system.

Binary numbers corresponding to three adjacent averaged values from the first output of the input register • 12 are fed to the first input of memory block 14, which is written to the signals received at its second input from the second output of control block 13.

In memory block 14, containing three groups of Triggers (each group has six triggers), three adjacent averaged (1.11 and III average, II, III and IV average, etc.) elements are memorized. From the first output of memory block 14, digital values I and III of medium (II and IV average, etc.) are fed to the first input of block 15 for calculating arithmetic mean values, which are recorded by signals received at its second input from third output of block 13 control (device unit 15 is similar to the device unit 5 of the transmitting part of the system).

From the output of the block 15 for calculating the arithmetic mean values, the processed counts of the image elements are fed to the first input of the block 16 of the comparison, to the third

the input of which. at the same moment of time from the second output of memory block 14, the value II arrives (III,

Iv, etc.) average. In block 16 comparison, the scheme of which is similar to the scheme of block 6 comparison of the transmitting part, compares the arithmetic mean values of I and III (II and IV, III and V, etc.) averages with the value II of the average (III average, IV average and so on. d.) '. If comparison unit 16 determines that

as a result of comparison, the arithmetic mean of I and III of the mean (II and IV of the mean, III and V of the mean, etc.) and the value of II (, IV, etc.) are equal, which is typical for borders with a sharp difference in brightness, then, at the output of the comparator block 16, a CP signal is generated, which is fed to the first enabling input of the D / A converter 17, while the latter will replace the value I (II, III, etc.) in the middle of the first half of II (III, IV, etc.) .) average, and in place of the second half of II (III, IV, etc.) average - the value. III (IV,

V, etc.) _ъ average. Thus, the border with a sharp drop in brightness will be restored. Note that due to pre-processing (adjustment) of the image signal produced in the transmitting part of the system, such a case will take place only in such groups of elements that characterize the boundary of sharp differences in brightness (large image details). If the comparison unit 16 determines that the arithmetic mean of I and III (II and

IV, III and V, etc.) of the means differs from the value II (III, IV, etc.) of the mean, then at the output of this block a signal CP is formed ("Non-comparison"). In this case, all elements from the second output of the input register 12 to the DAC 17 will be rewritten without change, i.e. with the sequence with which they arrived at the input of the input register 12.

The synchronization of the comparison unit 16 and the D / A converter 17 is effected by signals arriving at their third inputs, respectively, from the fourth and fifth outputs of the control unit 13.

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From the output of the DAC 17, the reconstructed analog image signal is fed to the first input of the video monitor unit 18, to the second input of which the sixth output of the control unit 13 receives the synchronizing pulses.

As an example, figure 2a shows a fragment of a single image line in which elements I and II,, III and IV, as well as V and VI, respectively, have the same brightness values. After transformation of the specified fragment by modified linear Paley transformation 15

(Walsh) None of these elements will change their meaning.

Note that in this fragment, the arithmetic mean value I of the average (it is equal to the mean- 20 arithmetic value of the elements I and II) and III mean (it is equal to the average of the elements) V and VI coincides with the value II of the average III and IV. Therefore, as a result of additional processing of this fragment produced in the receiving part of the known system, element III (first element II of the middle) will take the value of element II (second element I of the average), i.e. I mean value, and. element IV (second element II of the center) is the value of element V (first element III of the middle), i.e. value III is average, and therefore the reconstructed fragment will have the form shown in Fig. 2δ. "In _{40 of} this case, as can be seen from Fig. 2a.and £, elements III and IV will be restored with errors, each of which is

half of the total difference in brightness (the maximum possible error for the restoration of these elements).

During preprocessing (adjustment) of the considered fragment produced in the transmitting part of the system based on the considered algorithm, at the output of the transmitting part of the proposed system, elements I and II (I average) will have values, each of which * is less than the true brightness value of these elements (Elements I and II, i.e. I average instead of the six-bit code combination 111111, which corresponds to the maximum brightness value, will be expressed by the six-digit code combination 111110, which is negligible (minimal) error, and it does not lead to a noticeable distortion of these elements.In turn, as a result of this adjustment of the values of elements I and II (I average), additional processing in the receiving part will be excluded (the first of the two conditions indicated ) and thus the possibility of recovering the elements and IV with the maximum error.

Thus, the result of pre-processing (adjustment) of the original sequence of image elements produced in the transmitting part of the proposed system eliminates unnecessary additional processing in separate sections (fragments), which leads to an improvement in the quality of the reproduced image.

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Claims (1)

TELEVISION SYSTEM WITH COMPRESSION OF DIGITAL IMAGES OF THE IMAGE, containing in the transmitting part a transmitting television camera, the input of which is connected to the first output of the control unit, and the output - to the first input of the analog-to-digital converter (ADC), the second input of which is connected to the second output of the control unit, sequentially the connected adder, divider and output register, the first input of the adder and the second inputs of the divide ^ and the output register are connected respectively to the third, fourth and fifth outputs of the control unit, the block back rzhki having a first input connected to the output of the adder, the second input - to a sixth output of the control unit, and an output - to a second input of the adder, the output register output is connected through a communication line with the receiving part containing serially connected input register, memory unit, calculation of arithmetic mean values, comparison unit _g digital-to-analog converter (DAC) and video control unit, the first input of the input register connected to the output of the line elm and the second output to the second the input of the DAC, the second inputs of the input register, the memory unit, the arithmetic average value computing unit and the comparison unit, the third input of the DAC, the second input of the video control unit are connected to the first, second, third, respectively The Fourth, fifth and sixth outputs of the control unit, and a third input of the comparator is connected to a second output of the storage unit, characterized in that _s in order to increase the accuracy of transmission of the signals in the transmit portion introduced memory block, calculating mean values and the comparator unit, with In this case, the first input of the memory unit is connected to the output of the ADC, the second input is connected to the seventh output of the control unit, and the third input is connected to the output of the comparator unit, the first output of the memory unit is connected to the first input of the arithmetic average calculator their values, the second input of which is connected to the eighth output of the control unit, the second output of the memory block is connected to the first input of the comparison unit, the second input of which is connected to the ninth output of the control unit, the third input to the output of the arithmetic mean value calculator, and the third output of the memory block connected to the third input of the adder. "eight (L with 1177952 ¹ . 1177