SU1570028A1 - Device for transmission of television signal - Google Patents

Abstract

The invention relates to communications and can be used in the construction of digital television and video telephone systems. The purpose of the invention is to increase the noise immunity of the television signal transmission. In a system with a differential pulse code modulation using the zone-quantization method, a difference signal is transmitted over a communication channel. An error in one image element, caused by noise or distortion, spreads when the video signal is restored at the receiving side to its neighboring image elements, forming a distortion on the image in the form of so-called error tracks. The goal is achieved by providing a reduction in the intensity of this kind of distortion. This television signal transmission system includes transmitting and receiving sides. 4 il.

Description

The invention relates to communications and can be used in the construction of digital television and video telephone systems.

The aim of the invention is to improve the noise immunity of the television signal transmission.

FIG. Figure 1 shows the electrical structure of the transmitting side of the television signal transmission system; in fig. 2 is a structural electrical circuit of the receiving side of the television signal transmission system; in fig. 3 - quantization scale; in fig. 4 shows the layout of the quantization zones.

The television signal transmission system contains on the transmitting side a subtraction block 1, a block 2 quantum, an encoder 3, a decoder 4,

code generator 5, first adder 6, first delay element 7, quantization zone encoder 8, prohibition block 9, block 10, quantization zone decoder 11, quantization zone limit generator 12, second adder 13, second delay element 14, first 15 and toro # 16 switches, forcing 17 control pulses} third delay element 18, and on receiving side receiver 19, decoder 20, code converter 21, first adder 22, first delay element 23, quantization zone encoder 24, block 25 , shaper 26 limits quantization zone, second ummator 27, the first switch 28, decoder 29 zones, the second delay element 30, a comparison unit 31, the first driver 32 control pulses, the second

ate

s

§

S

31

switch 33, register 34. shift, in the second driver 35 control pulses.

The system works as follows.

The first input of the subtraction unit 1 is supplied with an input video signal, represented, for example, by a parallel eight-bit binary code. In block 1, the predicted value of the video signal, also represented by a parallel eight-bit code, and received from the first delay element 7, is subtracted

20

the dn value is quantized in block 2 on a nonlinear scale. Block 2 provides code combinations of C serial numbers of the quantization levels of difference signals dh in a binary parallel code. FIG. 3 as an example, the quantization scale is presented with the corresponding numbers (N 0 ... 15) of levels, quantization and code combinations 25

- WITH; ST

 cn

it is not necessary that code combinations with | be received from the encoder 8 of the zone into the encoder.

As can be seen from the foregoing, the code combinations received at the output of the encoder 3 and which are to be transmitted do not contain a sign bit (character character).

The output signals of the encoder 3 simultaneously arrive at the inputs of the decoder 4 and the first switch 15.

In the decoder of the signals C, Cn and C y, C are added, coming from the encoder 8 zones. Thus, at the output of the decoder 4, code combinations (with signed symbols) are formed.

Cn Ch + C;

h, SP + C

Cn2 Ch-fC; 0 + C; C;

AT C; Ј Spy C ;;

with C "Cj.

 ct-C; + C- ct npH

In the coder 3, the code combinations of the C code numbers corresponding to the lower Limits 8; quantization zones coming from zone 8 encoder. The width of the quantization zones and their location are determined experimentally. FIG. 4, as an example, is shown a variant of the arrangement of quantization zones with a quanta of a scientific research institute of difference signals according to the scale shown in FIG. 3,

At the output of the encoder 3, depending on the ratio between the values of Ch, CT; and C., where C is the code combination of numbers; corresponding to the upper boundaries of П; quantization zones, signals are generated equal to

four

GHS „- S; at C; С „Ё С; ; at Cn. c |;

K Oh

- with - with

at C

1i presented in parallel binary code.

With a known number of quantization levels of block 2 and the nature of the location of the quantization zones, the value of K is also known. For example, for the quoting scale shown in FIG. 3, and the location of the quantization zones (Fig, 4)

ct K

respectfully

with;

g

l

 const. 7 and

ill

G1 p

, follow- ooo.

0 5

0

five

0

five

Converter 5 code according to the quantization scale (Lig. 3) converts the code combinations C

and

4.1

and C

P2,

corresponding to the numbers of the quantization levels, parallel binary code of the dn, dh, d J values of these levels.

In the first adder 6, the current difference value and the predicted value from the first delay element 7 are added through the second switch 16, as a result of which the true value of the video signal is restored. Encoder 8 of the zone by the signals of the preceding elements coming from the first delay element 7, and according to the previously known widths Z (and the location of the quantization zones produces code combinations C of numbers corresponding to the lower D; quantization zone boundaries. The delay element 7 delays the input information, for example, The sampling period corresponds to one image element.

On the receiving side of the device (Fig. 2), operations are performed that are identical to those described. In particular, the code combinations Cn, Cn, and Cu from receiver 19 are fed to the input of the decoder 20, where C, - is added to them, coming from the zone encoder 24. At the output of the adder 22, combinations are formed (with signed symbols)

The converter 21 of the code is similar to the converter 5 converts the code combinations Cn, SP1, SPG into pa

allelic binary code of a.

4h, d. In the adder 22, the current difference value and the predicted value from the delay element 23 are added through the first switch 28, as a result of which the true values of the video signal are restored.

Due to the fact that in a device with a differential pulse code

modulation using zone method .11

In the course of quantization, a difference signal is transmitted over the communication channel, an error in one pixel caused by noise or distortion propagates when the video signal is restored on the receiving side to its adjacent picture elements, forming so-called tracks on the image mistakes. At the same time, since

such devices through the communication channel pe 30 information to the third input of the first

If a video-modified difference signal is generated (a signal that does not contain a sign bit) and the sign bit (symbol) is restored indirectly at the receiver side of the device, the error power (dispersion) (and therefore the intensity of the error tracks) arising at the receiver side the device, due to distortions of the transmitted code combinations by interference in the communication channel, is less than in the known device. However, on the receiving side of the proposed device, in contrast to the known value, due to the distortion of the transmitted code, the value formed using Forward combinations of interference in the channel 12 of the quantization zone limits can be distorted, and the code combination of the second adder 13. The decoder 11 corresponding to the lower bounds on the control information, incoming quantization zones and used for the quantization zone from the encoder 8, recovering the subsequent difference 0 Gives the value of the lower and upper pre-signals (and, therefore, no, subsequent delov that zone (Z (%, Z-u), wherein

is the penultimate element of the block. FIG. 4 as an example

the truth table of the blocking elements of the image is presented. This leads to the further spread of error tracks.

In order to reduce the intensity of such a 12 (26) for the above-considered type of distortion, on the transmitting quantization scale and the location of the system’s corner, each row is divided into groups (blocks) containing

quantization zones. The obtained average value from the second adder 13 through the second delay element 14 enters

a certain number of elements

ten

700286

images. The last element of each block is a control. The location of the control samples, and hence the blocks, varies from 5 lines and from frame to frame. The number of samples in a block is chosen such that this number and the number of elements in a line do not have common factors. Then the conditions of interchange between checkpoints and their fats coincide through the number of frames equal to the number of elements in the block.

The number of elements in the block, as well as the law of their interplay, are set by selecting the frequency divider coefficient that is included in Shaper 17 control pulses and the second Shaper 35 control pulses, which are fed to the inputs of rectangular pulses at a sampling rate (sampling frequency).

At the control points, the difference value of the video signal is not transmitted, but instead, with the help of the first switch 15, the control information, which is generated by the BS zone decoder 11, is sent via the output signal of the zone encoder 8. Control

15

20

25

five

0

switch 15 is transmitted through delay element 18. The control information is the number of the quantization zone in which the penultimate element of the block of elements is located. The bit of control information is equal to the bit of transmitted information.

On the transmission side of the system, instead of the last element of the group in the first adder 6, the average value of the quantization zone in which the penultimate element of the group is located is presented. Specified average

presents the truth table of block 12 (26) for the above-considered type of quantization scale and location

quantization zones. The obtained average value from the second adder 13 through the second delay element 14 enters

to the third input of the second switch 16. The working switches 15 and 16 control the driver 17, as a result of which the outputs of these switches are control, respectively, the information and the average zone value are passed only during the transmission of the last element of the group. At the same time, the prohibition block 10, using the control pulses received from Shaper 17, prevents the difference signals from the switch 15 from entering the first adder 6. Instead of them, the adder 6 receives a signal equal to 0. Second 14 and third 18 delay elements work similarly to the first delay element 7.

On the receiving side of the device (Lig. 2), in comparison block 31, a comparison occurs at times corresponding to the control points of the received control information (the number of the quantization zone in which the penultimate block element is on the transmitting side and the number of the quantization zone in which is the penultimate block element on the receiving side of the device). Comparison at other times does not occur, which is ensured by supplying to the gate input unit 31 the comparison of pulses of corresponding duration from the second driver 35 of 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 comparison unit 31. In this case, the output of the first shaper 32 of control pulses produces such a control signal, which passes the elements of this block from the second output of shift register 34 to the output of the second switch 33. In this case, the delay of the signal at the second output of the shift register 34 relative to its input is equal to the number of elements in the group of elements. If an error occurs during the transmission of a group of image elements, then it affects all subsequent elements of the block located before the reference reading. Therefore, as a result of comparing the control information with the recovered at the receiving side with the corresponding information, an error signal is generated at the output of the block 31. In this case, the output of the first

five

0

five

0

five

0

five

0

five

A control signal generator 32 produces such a control signal that passes to the output of the second switch 33 elements adjacent to this unit and located on the previous side and coming from the first output of shift register 34. In this case, the delay of the signal at the first output of the shift register 34 relative to its second tap is equal to the number of pixels in a row.

To reduce the length of the error tracks

on the receiving side of the device (as

„V and on the transmitter / instead of the last

the group element in the first switch 22 represents the average value of the quantization zone in which the penultimate element of the group is located. This value is obtained by using the reference reading cf of the body 26 and the adder 27 and is written to the adder 22 by means of blocks 28 and 25.

Block 25 of the prohibition prevents the control information, and more precisely the information obtained at the output of the converter 21 of the code at the time of transmission of the control information, from entering the first 22 adder. For this, the control input of the unit 25 from the second Shaper 35 control pulses receives a signal of the appropriate shape and duration. As a result, the first input of the first adder 22 at the time of transmission of control information from block 25 receives a signal equal to 0.

The former 26, according to the control information received from receiver 19, provides the value of the lower and upper limits of the zone in which the penultimate element of this block is located on the transmitting side.

In the second adder 27, from the values of the lower and upper limits of the zone coming from the former 26, the average value of this zone is formed. The output signals of the adder 27 are fed to the first input of the first switch 28. The operation of the switch 28 is controlled by the former 35. In particular, 35, the control input of the first switch 28 receives a signal of such a shape and duration, which at the time of transmitting the control information (i.e. at the time of the restoration of the last block element) passes the average value of that quantization zone into which the swarm is the penultimate block element on the transmitting side, coming from the adder 27. At the indicated time point, the output of the inhibit block 25 with the same control signal coming from the block 35 produces a signal equal to 0, Since 0 with the average value of the zone is equal to the average the value of the zone, then in the summer 22, as the last element of the block, the average value of the quantization zone in which the penultimate element of the block is on the transmitting side is represented.

At the control points, the difference value is not transmitted, and instead of the last element of the group, on the transmitting and receiving sides, there is a modified last but one element of the group. An excessively small number of elements in a group (subject to the condition of multiplying checkpoints) can lead to a deterioration in the quality of recovered images (although, from the point of view of noise immunity, a small number of elements in the group gives better results), therefore, with a known sampling rate, the number of elements in the group is - is done experimentally. For example, when choosing a sampling frequency of 12.5 kHz, the optimal number of elements in a group is 75. In this case, the condition of multiplying the control points (reference samples)

Claims (1)

Formula of Invention signal containing 40 on the transmitter side in series subtractor whose first input is the input of the transmitting side television transmission devices (TV) signal, quantization unit, quantization gif-d, to the input of which Rator, decoder and converter are connected to the output of the second TV signal receiver, the decoder and the converter. A code recipient connected in series to the first adder, the first delay element and the quantization zone encoder, whose output is connected to the second input of the decoder, characterized in that, in order to improve the noise immunity of the TV signal transmission, they are connected between the output of the code converter and an adder input connected in series to the decanter of the quantization zone, to the sink of which the output of the quantization zone encoder is connected, the driver of the quantization zone limits, the second adder and the second The first delay element, the first and second switches, the third delay element, and the control pulse driver, whose input is the pulse input with the sampling frequency, and the output are connected respectively to the second inputs of the inhibit unit and the code converter and the first inputs of the first and second switches, the second and third inputs of which are connected respectively to the outputs of the first and second delay elements, and the output is connected to the second input of the first adder; to the second and third inputs of the first switch are connected respectively, the output of the Ti4-rator and the output of the decoder of the quantization zone through the third delay element, and the output is connected to the input of the transmitter, while the second output of the quantizing limit generator is connected to the second input of the second adder, and a prohibition block is inserted at the receiving side connected between the output of the converter - one and the first input of the first adder, connected in series to the limit driver code, successively connected adder, first delay element and quantization zone encoder; the output of which is connected to the second inputs of the PGAArator and the decoder, as well as the transmitter, whose output is the output of the transmitting part of the TV signal transmission device, the output of the first delay element connected to the second input of the subtractor, and on the receiving side - serially connected receiver the input of which is the input of the receiving part of the device the receiver's forwarding, sequentially connecting 5 0 5 0 five 0 chi tv signal, decoder and transform -.-. A code recipient connected in series to the first adder, the first delay element and the quantization zone encoder, whose output is connected to the second input of the decoder, characterized in that, in order to improve the noise immunity of the TV signal transmission, they are connected between the output of the code converter and an adder input connected in series to the decanter of the quantization zone, to the sink of which the output of the quantization zone encoder is connected, the driver of the quantization zone limits, the second adder and the second The first delay element, the first and second switches, the third delay element, and the control pulse driver, whose input is the pulse input with the sampling frequency, and the output are connected respectively to the second inputs of the inhibit unit and the code converter and the first inputs of the first and second switches, the second and third inputs of which are connected respectively to the outputs of the first and second delay elements, and the output is connected to the second input of the first adder; to the second and third inputs of the first switch are connected respectively, the output of the Ti4-rator and the output of the decoder of the quantization zone through the third delay element, and the output is connected to the transmitter input, while the second output of the quantizing zone limit generator is connected to the second input of the second adder, and a prohibition block is inserted at the receiving side, connected between - one and the first input of the first adder, connected in series to the limit driver a mat the other input of which is connected to the second output of the quantizer network shaper, and the first switch to the second input of which is connected to the output of the first delay element, and the output is connected to the second input of the first adder, connected in series to the decoder of the quantized zone, quantization zone encoder output., the second delay element and the comparison unit, to the second input of which you are connected. Fi. H Impussapotod OfnCVfffjSf N  5-1 4th 13th and 1c h 3n g 4 o -2551 FTG