SU1434563A1 - Device for receiving television differential pulse-code-modulated signal - Google Patents

Abstract

The invention relates to a television technique. The purpose of the invention is to improve noise immunity. The goal is achieved by introducing into the device delay elements (EZ) 19, 20, a reference sample extracting unit 42, a code combination forming unit 43, two decoders 44, 45, and a luminance signal converting unit 46. To reduce extended-.

Description

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These triples of error on the image in the OS loop on the transmitting and receiving sides are identical multipliers. The multiplication factor is chosen to be less than one, and in this case the distortions (error tracks) become attenuated by eliminating this kind of distortion in the digital coding of the difference signals, This is done by using the correlation links that exist between the thickness M and the color difference signals. For this, each line of elements of the color-difference signals is divided into blocks (groups) containing a certain number of image elements. The last element of each group is the control. The location of the control samples varies from time to line and from frame to frame. Using EZ 19 and 20, the necessary temporal shift of the code combinations of the capacitance and color difference signals is carried out. The outputs of block 46 are formed in parallel with the existing code combinations of the difference of the signal signal, which have the required duration and phase. Decoders 44 and 45 decipher the code combinations of the differences of the luminous and color-difference signals and output control signals in the event that the code combinations of the differences of these signals exceed certain predetermined threshold values, which are determined experimentally.

one

The invention relates to a technique of television and can be used in systems with a differential pulse code module (DICM),

The purpose of the invention is to improve noise immunity.

Fig. 1 is an electrical block diagram of the formation of a television signal with a DPCM for a device for receiving a signal with a DPCM; FIG. 2 is a diagram of a device for receiving a television signal with DPCM; FIG. 3 shows timing charts explaining his work; Fig. 4 is an electrical block diagram of a luminance signal conversion unit; Fig, 5 shows the schemes of the first and second decoders; Fig. 6 is a diagram of the first block of detection of distorted picture elements; Fig. 7 is a table of the truth of states of the elements of the first block of detection of distorted picture elements.

The DICM TV signal generator (FIG. 1) contains a subtraction unit 1, a quantizer 2, a code converter 3, a prohibition unit 4, a control pulse generator 5, an adder 6, a delay element 7, a multiplier 8, a switch 9 channels.

The device for receiving a television signal with DIKM (Fig 2) contains a code converter 10, the first prohibition block 11, an adder 12, the first 5 channel switch 13, a multiplier 14, the first delay element 15, an error detection unit 16, the first control pulse generator 17, pulse shaper 18

50 switches, the eighth, ninth, second, third, fourth, fifth and sixth delay elements 19-25, the first block 26 of detection of distorted picture elements, the second block 27 of the ban,

 5 error correction block 28, second control pulse driver 29, multiplier block 30, error detector block 31, code converter block 32, element block 33

0 delay, the first driver 34 of the switching pulses, the block 35 adders, the switch block 36, the output switch 37, the second block 38 of the distorted picture elements detection, the second driver 39 of the switching pulses, the seventh delay element 40, the second switch 41 channels, the control section 42 the reference, block 43 forming a code combination, the first and second decoders 44 and 45, block 46

luminance signal conversion.

The luminance signal converting unit 46 (FIG. A) comprises the delay line A7, the first to the eighth trigger 48-55,

The first decoder 44 (Fig. 5a) contains a 56 code converter, a comparison block 57 and a threshold code generator 58. The second decoder 45 (Fig. 5b) acquires the first, second, third and fourth converters 59-62 codes, first, second, third and a fourth comparison block 63-66, threshold code generator 67, element OR 68.

The first block 26 of the detection of distorted image elements (Fig. 6) contains an inverter 69, the first and second elements And 70, 71.

The television signal receiving device with the D11KM operates as follows.

Signal formation with DPCM is performed by applying a signal to the first input of block 1, for example, represented by a parallel eight-bit binary code. In block 1, the delayed feedback loop is subtracted from the input signal (for example, the sampling period). value of the video signal. The difference value of two adjacent samples obtained in block 1 is quantized in a quantizer 2 on a nonlinear scale, which allows, taking into account the properties of vision, to significantly reduce the number of quantization levels. Thus, for example, with 256 levels of quantizing an input video signal, 16 levels are sufficient for nonlinear quantization of a difference signal. The 16-level quantized value of the difference signal in the quantizer 2 is converted to a four-bit Gray code for transmission over a communication channel. To perform arithmetic operations in the feedback loop and the code-3 converter, the Greek code is converted to an eight-bit binary code. In the adder 6, the current difference value and the value of the previous count, obtained after a delay in delay element 7, are added.

In a device for receiving a television signal with a DPCM in a cummator 12, a similar operation takes place. Prien

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The differential signal in the Gra code is converted in the converter 10 of the code into an eight-bit binary code, which is summed up in the adder 12 with the value of the previous reading of the video signal obtained using the delay element 15.

Due to the fact that in a system with differential shtulno-code modulation a difference signal is transmitted over a communication channel, an error in one image element, which occurs

due to interference or distortion, it propagates when the video signal is restored, on the receiving side to the adjacent image elements, forming so-called error tracks on the image.

To reduce the length of these tracks, errors in the feedback loop on the transmitting and receiving sides are entered into identical multipliers 8 and 14, respectively. The multiplication factor is chosen to be less than one, and in this case the distortions (error tracks) become fading. However, in case of large errors, the latter are suppressed. Ineffective elimination of this kind of distortion in the digital coding of the color difference signals of the SECAM system with a single (common) DICM encoder can be accomplished by using strong correlation links existing between the color signals and the color difference signals. For this, each row of elements of the color-HocTHbtx signals Dp and Dg is divided into blocks (groups) containing a certain number of elements of the image, marriage. The last element of each group is the control. The locations of the control samples, therefore, the groups vary from line to line and from frame to frame. The number of samples in a group is chosen such that this number and the number of elements in a line do not have common factors. Then the condition of multiplying the control points is fulfilled, and their phases coincide in terms of the number of frames equal to the number of elements in the group. The number of elements in the group, as well as the law of their multiplication, are determined by selecting the frequency divider coefficient included in the driver 5 and the first driver 17, to the inputs of which pulses with a sampling frequency (sampling frequency) are applied.

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At the control points, the difference value of the video signal is not transmitted, and instead of it, the value of the previous count video signal, represented by the four most significant bits, is sprinkled with the switch 9 channel.

The differential signal in the form of a four-bit parallel Gre code is fed to the input of the error detection unit 16 and through the second delay element 21 to the input of the second block 27 bans also the inputs of the second distorted picture pixel detection unit 38 and the error detecting unit 31, In error detection block 16 the comparison occurs at the moments corresponding to the control (Points of the received video signal restored and delayed in the feedback loop for the sampling period with the video signal represented by the four high They do not make a comparison of these values at other points in time, which is ensured by supplying to the strobe input of the error detection unit 16 pulses of appropriate duration from the first driver 17 of the control pulses. if there are no errors in the transmission of this group of elements, these compared signals are equal and there is no signal at the output of the error detection block 16.

There is also no signal at the output of the first block 26 of distorted picture elements. As a result, in the adder 12 and in all four adders of the block 35 of adders, the correct values of the image elements of this group are formed and the output switch 37 detects the corresponding elements of the corresponding group from the output of one of the adders of block 35, for example, the first adder. The operation of the output tator 37 is controlled by a switching pulse driver 34.

If an error occurs during the transmission of a group of image elements, then it affects all subsequent elements of the block that are located before the reference reading. Therefore, as a result of comparing the incorrect restored value of the video signal obtained at the loop output

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By means of a communication, an error signal appears at the output of the reference reading at the output of the error detection block 16. In this case, in the first and second blocks 26 and 38 of the detection of the distorted elements of the image, the distorted elements of the erroneous groups are detected.

The basis for detecting distorted elements in the first block 26 of detecting distorted image elements is the conditions for the existence of strong correlations between the brightness and color difference signals, which is expressed in the fact that the majority of changes in color, density (color difference signal) are accompanied by a change in brightness (brightness). In this connection, the detection of a distorted picture element in block 26 is performed as follows. The code combinations of the differences (t, e. Changes) of the p-bone and color-difference signals of the respective receivers of the devices are post-coupled to the inputs of the ninth and eighth delay elements 20 and 19, With their help, such a time shift of the code combinations of the differences of the density and color difference signals, so that between the sampling frequency of the arrival of tsykh to the first input of block 46 from the second output of the first shaper 17 code combinations of the difference of the luminous signal (Fig. 3b) and code combinations of the differences of the color difference signals (Fig. Sv) b whether the phase relationship shown in FIG. Here, the difference values of the capacitive signal with sequence numbers 4п-3, 4п-2, 4п-1, 4п correspond to the difference value of the color difference signals with the order number p. Block 47 by means of control pulses from the second output of the first driver (Fig. 3a), sequentially converts the existing code combinations of the difference of the luminous signal (Fig, 3b) into parallel ones and at the same time forms them in phase and duration (Fig. 3g, d, e, g) o

Consider the operation of block 46. Code combinations of the difference of the luminous signal (Fig. 3B) in parallel arrive at the inputs of the first, second ,. the third and fourth triggers 48-31, on the synchronization inputs of which

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synchronization (control) pulses are received from the first, second, third and fourth outputs of the delay line 47, respectively. The control pulses received at the first output of the delay lines 47 are shifted relative to the input signals by a time equal to At, 1 / 2-. c, control pulses obtained at the second output, for a time equal to t ut +, 9, c control impulses, obtained at the third output,

for a time equal to J t 1 / 2f.c - + 2 / f with J a control, the pulses received at the fourth output are for a time equal to 11. .c + + .s.c t, +, c, where f ddc the sampling rate of the luminous signal about

Thus, at the outputs from the first to the fourth flip-flops 48-51, the code combinations of the difference of the luminous signal, corresponding to four consecutive samples, exist in parallel, have the required duration equal to Jt. Cs (where the sampling frequency of the color difference signals) are shifted relative to each other Dp of eliminating this temporal shift (that is, to form code combinations of the difference of the luminous signal in phase), the outputs from the first to the fourth flip-flops 48-51 are connected respectively to the outputs from the fifth fifth th flip-flops 52-55, to clock inputs which come

sync (control) signals from the fifth output of the 47 delay line; At the same time, the control signals,

45

The delayed transducers of the 59–62 codes, which are located on the fifth output line 47, are shifted relative to the input ones, which work in a similar way, equal to ut. а.с 4t - to the recipient of the DPCM system codes rkost- 4tj, where 4t-ji is the average time the distribution of information in the first trigger 48; average propagation delay time in the fifth trigger 52. As a result, the flue signal is formed at the outputs of block 46. Thus, if at least one of the three code combinations of the difference of the luminous signal exceeds the threshold value obtained in the shaper 67, the output of the element OR 68 results in a control

In parallel, the existence of a code combination signal as 1, i.e. on the difference of the signal intensity,

which have the required duration

and phase.

The first and second decoders 44 and

45 decrypt the code combinations of 55 differences of brightness and color difference signals and output them at the outputs

control signals in the event that

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code combinations of the differences of these signals exceed certain predetermined threshold values (it should be noted that these threshold values are determined experimentally and for a brightness signal the threshold can be chosen equal to 1/32 parts of its maximum span, and for color difference signals - 1/8 of them maximum swing).

Let us consider in detail the operation of the first and second descriptors 44 and 45 (Fig. 5a, b). Code combinations of the difference of color difference signals (FIG. 3) from the eighth delay element 19 are fed to the input of the code converter 56. Converter 56 codes works similarly to the Converter 10 code, ie, converts the code combination of the difference of color difference signals presented in the Gray code, in binary code. In block 57 comparison, the code combinations of the difference of color difference signals, represented in binary code, are compared with a threshold value, also represented in binary code. The code combinations corresponding to the threshold are obtained in the driver 58. In the event that the difference of the color difference signals is exceeded, the control signal appears at the output of the block 57 in the form. This corresponds to the appearance of the control signal at the output of the first decoder 44. signal in the form of 1.

The code combinations of the difference between the p-signal from the outputs of block 46 are fed to the inputs from the first to even

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to the receiver of the codes of the system DIKM of the signal signal. Thus, if at least one of the three code combinations of the difference of the luminous signal exceeds the threshold value obtained in the shaper 67, the output of the element OR 68 results in a control

 Yu1 signal is in the form of 1, i.e. At the output of the second decoder 45, a control signal is generated in the form of 1.

If there is a control signal from the first decoder 44, and if there is no such signal from the second decoder 45, in block 26 an error signal is generated, which is output to the output when

from block 16 error detection through

shaper 18 receives a signal about the presence of errors in the group of elements. Consider the operation of block 26 "If there is a control signal from the first decipheror 44 in the form of 1 and

: the absence of such a signal from the second decoder 45 at the output of the first element And 70 forms a control

The signal in the form of 1, which passes through the output of the second element And 71 in the event that from the generator 18 a signal about the presence of an error

in the group of elements in the form of 1, Tabli -, - four streams are formed, in the case of

The truth of the state of the elements of block 26 is shown in FIG. 7, Exit; The signal of the first block 26 of detection of distorted elements of the image is fed to the second information ion input of the second switch 41 channels

In the basis of the detection of distorted elements in the second block 38 is detected; Generation of distorted elements of the image20

no control pulses; these streams do not differ from the original. In the presence of control pulses in each stream, one bit of the distorted code pattern is inverted. The signals from the code of the error correction block 28 are fed to the block 32 of code converters. Block 35 adders contains four identical

It is assumed that the input video player of the 25 adder, in each of which the occurrence has a .determined dynamic

There is an addition of the current difference value and the value of the previous count obtained after the delay in block 33 of the delay elements. Block 30 of multipliers consists of four identical multipliers, the multiplication coefficients of which are equal to the multiplier of multiplier 14, Block 31 about-. error bugs contains four

The range in which the algebraic sum of the predicted signal coming from the first switch of the 13 channels and the difference n signal is received is received from the converter 10 of the code. If the summation result is outside the dynamic range of the input video signal, then the second block 38 of the distorted picture elements detection outputs a control signal about the distortion of this code pattern and the TOTAL signal having a duration of one clock cycle through the seventh delay element 40 to the second information input of the second the switch 41 channels and the input of the second driver 39 switching pulses o With the simultaneous presence of control signals at the output of the second block 38 detection of distorted e of the image elements and at the output of the imaging unit 18 of the duration of the switching pulses the second imaging unit 39 of the pulses

There is an addition of the current difference value and the value of the previous account obtained after delays in block 33 of delay elements B of multipliers consists of four multipliers, the multiplication factor of which is equal to the multiplier of multiplier 14, Block 31. error extenders contains couples

detection schemes, where the comparison of the received video signal of the video signals reconstructed and held in the feedback loop to the sampling period and represented by four high-order bits corresponding to the test chambers takes place. Comparison of these values at the total time points does not occur, which is ensured by the supply of the gate input of the block 31 of the pulse error detectors of the corresponding duration through the third delay element 22.

With the correct detection of the damaged element of the erroneous group

40

45

switching control signal, the output of the block 31 detectors

having a duration equal to the duration of a group of elements. In the presence of a control signal to the code of the second Channel Switch 41, the signal from the code of the seventh delay element 40 is passed. In the absence of a control signal on the second block 38 of the detection of distorted picture elements

and the second pulse shaping unit 39, the output of the second channel switch D1, passes the signals from the first block 26, which are then passed to the second control pulse generator 29, where control pulses are formed with a sampling period of time to the error correction unit 28. The second block 27 of the prohibition excludes the penetration of the reference reading in the block 28 error correction, in which from the input sequence

0

no control pulses; these streams do not differ from the original. In the presence of control pulses in each stream, one bit of the distorted code pattern is inverted. The signals from the code of the error correction block 28 are fed to the block 32 of code converters. Block 35 adders contains four identical

adder, in each of which

There is an addition of the current difference value and the value of the previous count obtained after the delay in block 33 of the delay elements o Block 30 of multipliers consists of four identical multipliers, the multipliers of which are equal to the multiplier of multiplier 14, Block 31 of error detectors contains four

detection schemes where the comparison of the received video signal and video signals recovered and delayed in the feedback loop for the sampling period and represented by the four most significant bits at the moments corresponding to the control points occurs. Comparison of these values at the most time points does not occur, which is ensured by applying to the gate input block 31 of the error detectors of pulses of the corresponding duration through the third delay element 22.

With the correct detection of a distorted element of the erroneous group

at the output of block 31 detectors

errors, a signal appears that, after the switching pulse generator 34 has formed, commits to the output of the output switch 37 the signal of the corresponding controller of the adder block 35.

If the distorted element is not correctly detected, the error detectors block 31 causes the control signal to pass to the output of the adder 12 a signal that arrives at the input of the output switch 37 through the sixth delay element 25.

When the distorted element of the erroneous block is correctly detected, in the feedback loop of the adder 12, the output signal of the first block 11 is represented by four higher bits of the penultimate block element (group) transmitted in the control count, the three lower bits are set to zero, and the next lower bits it is in a single state of

If the distorted element is correctly detected or not detected, the same values are recorded in the feedback loop of the adders of block 35 and adder 12.

The value of the reference reading is made by block 42. At the output of block 43 a code combination is formed

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Cg, C-, C, Cy, 1000 (where 0 (1) is the symbol value in the nth digit), which is fed to the input of the first switch 13 and through the fifth delay element 24 to the input of the switch unit 36.

The error introduced due to the rounding of the four bits to the value of the penultimate element of the group necessary for the prediction does not exceed 8 quantization levels. The second, third, fourth, fifth and seventh elements 21, 22, 23, 24 and 40 delay time equal to the duration of the group of image elements

Claims (1)

Invention Formula A television signal receiving device with differential pulse-code modulation, comprising a serially connected code converter, a first prohibition unit, an adder, a first delay element, a multiplier and an error detection unit sequentially connected a second delay element, the input of which is combined with the code converter input and the second the input of the error detection block, the second prohibition block, the error correction block, the code converter block, the adder block and the output switch, the output of which 7 one ten 15 20  , 25 thirty 35 40 45 50 55 is an output of a television signal receiving device with a differential pulse-code modulation, the first driver of control pulses serially connected, the input of which is the input of control signals of a television signal receiving device with differential pulse-code modulation, and a third delay element first connected to the control input of the second prohibition unit, a fourth delay element connected in series, the input of which is connected to the output of the error detection unit and the switch block, the output of which is connected to the second input of the adder block, the fifth delay element, the output of which is connected to the second input of the switch block, the sixth delay element, the output of which is connected to the second input of the output switch, are connected in series to the delay elements block whose input is connected with the output of the block of adders, the block of multipliers, the block of error detectors and the first driver of the commutation pulses, the first output of which is connected to the control input of the output switch, but the connected first channel switch, the first input of which is connected to the multiplier output, and the second input is connected to the output of the error detection unit, and the second switching pulse generator, the second input of which is connected to the output of the code converter, serially connected switching time generator and switching pulses, the first input of which connected to the output of the error detection block, and the second input is combined with the control input of the first prohibition block, with the third input of the error detection block and connected to the output the first control pulse generator, the first block of distorted picture elements detection, the second channel switch and the second control pulse driver, the second input of which is connected to the second input of the error detecting unit and connected to the output of the third delay element, and the output is connected to the second input of the error correction block , the second block of detection of distorted elements of the image, the first input of which is connected with the output of the switching pulse duration generator, the second input is connected to the output of the second switching pulse forming body, and the output is connected to the second input of the second channel switch, as well as the seventh delay element, the course of which is connected to the output of the second switching pulse generator, and the encoder is connected to the third input of the second channel switch, while the output of the first | Channel switch is connected to the second input of the adder, the output of the first driver controls their pulses connected to the input of the third element : delays, the output of the multiplier block I is connected to the third input of the com-block; mutators, and the output of the second delay element is connected to the third input; the block of error detectors, THAT ;, for the purpose of improving noise immunity, I connected to the eighth element in it delays, the input of which iporo is the input of the wind-difference signals of the TV reception device US.1 o five 0 five a differential signal with a pulse code modulation, a pilot sample extraction unit and a code combination generation unit whose output is connected to the input of the fifth delay element and the third input of the first channel switch, the ninth delay element connected in series, whose input is the input of the luminous signal devices for receiving a television signal with differential pulse-code modulation, and a luminance signal conversion unit, the first decoder, the input of which is combined with the input a code generator and is connected to the output of the eighth delay element, and the output is connected to the second. the input of the first block of detection of distorted pixels, as well as the second decoder, the input of which is connected to the output of the luminance signal converting block, and the output connected to the third input of the first block of detection of distorted pixels. about. Ub  sA-l Jj rt-j f chae 62 S7 f.J agl 9и.г.5 Fia