FR2478924A1 - METHOD AND APPARATUS FOR REALIZING THE COMPENSATION OF SIGNAL LACKS ON A LINE OF COLOR TELEVISION SIGNALS - Google Patents

Abstract

ACCORDING TO THIS PROCESS AND THIS SIGNAL LACK COMPENSATION DEVICE, THE LUMINANCE AND CHROMINANCE COMPONENTS OF A LACK COMPENSATION SIGNAL ARE TAKEN FROM THE SAME PART OF THE COLOR TV SIGNAL IMMEDIATELY PRECEDING THE LACK OF SIGNAL; A HORIZONTAL LINE OF TV SIGNAL IS PERMANENTLY STORED IN CIRCULATING MEMORY 2, 3, 4; 44 AND, IN THE EVENT OF A LACK, THE LAST LINE OF THE SIGNAL RECEIVED THERE CIRCULATES, WITH COMMANDED APPLICATION OF SIMULTANEOUS DELAYS TO THE COMPONENTS, WHICH ARE THEN RECOMBINATED IN 11 TO PROVIDE A SIGNAL OF COMPENSATION FOR LACK OF SIGNAL. APPLICATION IN PARTICULAR TO COLOR TV SIGNAL LACK COMPENSATORS.

Description

The present invention relates to a method and an apparatus for

  to compensate for missing signal

  in color television signals, according to

  which the luminance component and the chromium component

  nance are substantially delayed by a duration equal to a horizontal line, suitable for use in both analog and digital signal systems. As is well known in the art, the compensators of

  gaps in the television signal are used.

  to replace a missing part of the information signal.

  which has "lost" as a result of a lack of

  unpredictable momentum of the system. For example, when the television signal is recorded and then played back from a recording medium, a lack of signal may occur due to the presence of very small defects in the recording medium. When such signal failures appear in the television signal, they

  disturb the image in an optically visible manner. By con-

  If there are any compensators for signal

  to eliminate the effect of signal failures for the observer.

  An extensive study of the prior art television signal loss compensators is shown in the copending application filed by the Applicant in the United States of America under the Provisional Number 88,719 "Composite Digital Signal Processor".

  digital filter 'used for this purpose' and which describes a

  digital thinker of lack of common television signal

  their. In general, the prior art signallessness compensators use a high frequency envelope level detector, which controls the amplitude level or value of the modulated carrier waveform. of the television signal to detect

  lack of signal in the television signal. A book

  A delay timer is used to continuously delay the incoming television signal. When a signal failure is detected in the initial signal, the delayed signal is sent as a loss compensation signal.

  signal to replace the missing part of the informa-

  the television signal. More specifically, a switch in the color television signal transmission path is controlled to apply the incoming color television signal or the delayed signal.

  compensation, signal, in response to a signal

  control signal from the signal failure detector. The color television signal is delayed by a duration equal to - the period of a horizontal line and the component

  chrominance is set so as to have a phase indi-

  paid in consecutive television lines. For example

  full-phase adjustment of the separate chromium component

  signal loss compensation signal is obtained by delaying the chrominance component of an additional period of a television line or, otherwise, the chrominance separate component is inverted in

  successive lines of television, according to the particular system

  to link the color television signal, as this is biln

known in the art.

  - - However, there is a significant disadvantage in

  the above type of compensation for missing

  general of the prior art, as will be described below. The initial color television signal is subdivided into a luminance component and a chrominance component

  each component is respectively delayed and treated

  in separate signal paths. In-

  subsequently the separately processed signal components are recombined for use as a signal-out compensation signal. When the lack of signal has a duration exceeding the period of a horizontal line, the composite signal previously processed and

  recombinant is again separated and treated, as indicated below.

  above, in a repetitive manner, every two successive lines

  compensating for lack of signal. As a result, line-by-line distortion and deterioration

  progressive signal of compensation of lack of signal.

  Thus, when the man-compensation method is used,

  that signal of the prior art, indicated above, the

  signal obtained from signal loss compensation may be

  unacceptable at the end of a small number of consecutive lines. This is why an object of the present invention is

  to provide a method and apparatus for performing the compensation

  of signal failures of composite television signals.

  color scheme, eliminating the disadvantages

above.

  Another object of the present invention is to provide

  a process and apparatus for performing the compensation

  signal failures appearing in the televi-

  in which successive lines of the signallessness compensating signal are derived from the same part of the initial television information signal.

  colors immediately preceding the lack of signal.

  Another object of the present invention is to provide

  a method and apparatus for compensating for signal failures, wherein the same portion of the composite color television initial signal is stored in a memory, while consecutive lines of a video signal are recorded.

  compensation for lack of signal are drawn from this

  signal, said stored original signal remaining

  changed during the time interval where the compensation of the

no signal is made.

  Another object of the present invention is to provide

  providing a method and apparatus for compensating for color television signal failures, whereby both the luminance component and the chrominance component of the initial signal are delayed by a time interval

  substantially equal to a television line.

  Another object of the present invention is to provide

  to establish a process and apparatus for achieving

  signal failures appearing in the color television signal and which are suitable for use in both analogue and digital

color television signals.

  Another object of the present invention is to provide

  and providing a method and apparatus for compensating for signal failures for composite color television signals suitable for use in known television signal systems such as NTSC, PAL, PAL-M, etc.

  Another object of the present invention is to provide

  providing a method and apparatus for signallessness compensation of composite color television signals suitable for use in embodiments in which the signal is sampled at a frequency equal to an integer multiple of greater than two, frequencies of

subcarrier signal colors.

  The objectives mentioned above as well as other objects of the present invention are implemented using the method according to the invention, according to which the chrominance component or the luminance component of the

  composite color television signal are stored in memory

  within a period of time equal to one period of a line

  horizontal, and the stored information is put into circulation

  in response to a signalless signal. The duration

  the delay of the chrominance component is

  phase of the reference burst so as to provide

  a delayed chrominance component, which is in phase with the reference burst component during

  periods of successive horizontal lines. The duration

  The delay of the chrominance component is controlled to provide a luminance component that is in synchronism with the line synchronization component.

  of the composite color television signal

  during periods of successive horizontal lines. The respectively delayed chrominance and luminance components are combined to form a composite signallessness compensating signal which, in turn, is applied to replace the composite color television signal, upon indication of a lack of signal. The color television signal lack compensator according to the present invention comprises a circulating memory device for delaying both the luminance component and the chrominance component of an incoming composite color television signal, and

  with an offset in time substantially equal to a period

  of a horizontal line, in response to a control signal

  of lack of signal. A first control device,

  which corresponds to the reference burst component, is

  used to control the actual delay of the chro-

  to provide a delayed chrominance component

  which is in phase with the reference salvo component.

  this during periods of consecutive horizontal lines. A second controller, responsive to the horizontal line synchronization component, is used to control the actual delay of the luminance component to provide a delayed luminance component which is in synchronism with the horizontal line synchronization component. . A signal combining device is used to combine the components respectively

  delayed luminance and chrominance so as to

  denoting a composite signal for compensating the signal.

  A switching device responding to the control signal

  signal, selectively delivers the incoming color television signal or the composite signal of

  compensation for lack of signal at an offset output

lack of signal.

  Other goals, features and benefits of the

  present invention will emerge from the detailed description

  given below with reference to the accompanying drawings on the

  which Figures 1a and 1b illustrate a preferred method of making a signalless compensation signal according to the invention; Fig. 2 is a functional block diagram of a preferred embodiment of the invention; Figures 3a and 3b illustrate another preferred method according to the present invention; Figure 4 illustrates the operation of the apparatus of Figure 2; Fig. 5 is a functional block diagram of another preferred embodiment of the invention;

  FIG. 6 shows the operation of the apparatus

Figure 5;

  FIG. 7 is a diagram showing the diagram

  functional block of another preferred embodiment of the invention;

  FIGS. 8a to 8h represent consecutive parts

  of a detailed electrical diagram corresponding to the

block diagram of Figure 7.

  With reference to Figs. 1a and 1b, an example of a preferred method of signallessness compensation according to the present invention will be described below. In FIG. 1a, there is shown a sinusoidal wave W1, which

  represents a subcarrier signal waveform

  their, included in the chrominance component of a composite color television signal, as is well known

  in the art. Waveform W1 contains samples

  consecutive lAs, 2A, 3A, etc., provided at identical sampling time intervals and which may be

  obtained by sampling the initial signal of tele-

  color vision, as is well known in the art.

  In this particular example, the above samples are obtained by sampling an NTSC composite color television signal at a frequency equal to three times the frequency of the color subcarrier signal,

  that is, at a frequency of 3 x 3.58 MHz = 10.74 MHz.

  The samples obtained may be coded in numerical form.

  using an analog / digital encoder, using

  eg pulse code modulation (PCM), se-

  where each individual code, or sample, corresponds to

  to a particular value of amplitude of the analog signal

  than at a particular time of sampling,

  this is well known to me in the art. For exemple,

  the subcarrier waveform W1 is indicated as

  during a particular television line interval

  AI. A well-known feature of the NTSC television signal transmission system is that a subcarrier waveform W2 of an immediately following television line interval BI will have a phase opposite to that of W1, as shown in Figure la. Therefore, if a lack of signal occurs, for example after the initial line

  television was received and was delayed by one

  time equal to a television line in sight

  subsequent use as a compensatory signal

  signal to replace the "lost" line Bi, the delayed line Ai would have a phase shift of

    undesirable compared to BI. As a result,

  1A, 2A, 3A, etc. delay signal Wl shall be shifted by one and a half sampling intervals in order to

  to have the same phase as that of the corresponding samples.

  2B, 3B, etc., of the waveform W2, as shown in FIG. Therefore for example

  Sample IA should be offset from the sample

  corresponding one 2B and, similarly, the sample 2A must be shifted with respect to the sample 3B, etc.,

  and that of an interval and a half of sampling.

  Using the preferred method of the present invention

  vention, we obtain the phase shift indicated above of the signal

  of subcarrier colors in successive lines

  alternatively decreasing the delay of one

  horizontal line of the television signal,

  corresponding to periods of one and a half

  pling. This last characteristic is illustrated in Figure la which shows that the sample 3B of the line BI

  is obtained by delaying sample 2A from the initial line

  Ai television immediately preceding, an interval-

  equal to an increased horizontal line period of one

  period equal to one and a half times the sampling period.

  A dashed CHI line, connecting the corresponding samples 3B and 2A, illustrates this feature. Fig. 1b shows the subcarrier waveform W2 of

  the line Bi, followed by the waveform W3 of an immediate line

  next A2. Fig. 1b shows an example in which the line B1 is the last received television initial line and in which the line A2 is the first signal miss compensation line. As shown

  FIG. 1b, the sample 1A of the waveform W3 of FIG.

  subcarrier signal is obtained by delaying the sample 2B of the waveform W2 by a duration equal to the period of

  horizontal lines, less a time interval cor-

  responding to one and a half sampling period. The

  CH2 line, connecting the corresponding samples

  1A and 2B, indicates this latter characteristic.

  However, when using the compensation procedure

  signal loss, described above, both the chrominance component and the luminance component of the signallessness compensation signal are shifted by + one and a half sampling period with respect to the

  previous initial line of the color television signal.

  As is known in the art, such a phase shift of the chrominance component is not harmful since to obtain a high quality color signal for the compensation of the lack of signal, it is

  essential to maintain the line-to-line phase of the samples

  lons of the chrominance component, as close to

  phase required that this is possible. On the other hand,

  above is completely harmful to the

  luminance, for which it is essential to maintain

  set the horizontal line to line line shift of samples, as small as possible, on the screen reproducing the image

  compared to the initial signal.

  In order not to overburden the description, the expression

  "signallessness compensation" will be abbreviated as "DOC" compensation, while "lack of signal" will sometimes be referred to as "loss of signal".

  "missing DO" in the description that follows.

  In order to eliminate the disadvantage described above, the preferred method of signallessness compensation of the

  present invention provides a line-by-line adjustment of the

  of the luminance component, as described below.

  When the delay in the value of a horizontal line

  The initial signal of the television signal is increased by one and a half sampling period, for the purposes of signal loss compensation, as described above with reference to FIG. 1a, the delay of the luminance component is reduced. a sampling period. Thus, the horizontal offset of the sample of the luminance component from a corresponding sample of a previous initial line of the television signal is reduced from one and a half times of sampling to one half-sampling period. What has just been indicated is illustrated in FIG. 1a by means of the line formed by dashes LI connecting corresponding samples 3B and 3A. Similarly, in order to obtain the reduction indicated above in the offset of the luminance component, in the case where the delay, amounting to a horizontal line, of the initial television signal is reduced by one period and half of sampling, as previously described and illustrated in Figure lb, the delay of the component of

  Luminance is increased by one sampling period. This last

  The case is illustrated in FIG. 1b by means of the dashed line L2 connecting the corresponding samples 1A and 1B. From the figure, it can be seen that the luminance component of the sample 3B of the signal-miss compensation line B 1 is obtained by delaying the sample 3A of the line A1 by one period of a horizontal line, increased by only half a sampling period, as illustrated by the line Li. Similarly, in Figure 1b is represented by the

  line L2, the fact that the luminance component of the sample

  Sample IA is obtained by delaying sample IB of line B1 by a period of a horizontal line, increased by only half a sampling period. However, in

  the two cases, the delay of the respective components of

  minance remains unchanged, that is to say that it is shifted by one and a half sampling period, as is desired

  and as previously described.

  More specifically, the characteristics indicated

  The above preferred method of the present invention is obtained in the following manner. A horizontal line

  of the original color television composite signal is

  laughed continuously in a memory. The delay time of the stored composite signal is controlled in response to the line-to-line phase of the reference burst component of the original color television signal. The resulting delayed composite signal is subdivided into its luminance component and its chrominance component and the delay time of the luminance component is modulated in the opposite direction to the delayed chrominance component by an integer number of periods of time. sampling. In relation to the particular example described above and shown in Figs. 1a and 1b, the composite color television signal is delayed by one period of a horizontal line, this delay being -modulated by ± one and one half sampling, corresponding to half a period of the color subcarrier signal, in successive lines. Apart from this, the delay time of the separate luminance component is line-to-line modulated by + a sampling period, in the opposite direction to the modulation of the delayed composite color television signal, in order to reduce the

  row shift to line of the luminance component.

  In order to illustrate the above, we will describe a

  preferred embodiment of the apparatus according to the present invention.

  the invention, with reference to the functional block diagram of

  Figure 2 of the accompanying drawings. A television signal

  their composite is received on an input terminal 12 and is

  sent to the first input 20 of a bidirectional switch

  1. In this particular example, the television signal is received in a digital form obtained for example by

  coding of the color television signal according to a non-code

  back to 0 well known, as was mentioned previously

  with reference to Figs. 1a and 1b. A control signal

  of indicating the presence of a lack of signal is received by

  a control terminal 23, for example from a detection

  conventional lack of signal (not shown).

  An appropriate detector of lack of signal may be of the type constituted by a conventional control device

  carrier, which delivers a control signal when the

  high-frequency envelope of the modulated television signal shortage is below a predetermined level, as described for example in the AVR-2 video tape recorder, theory of operation, catalog number 1809179-01, published in November 1977 by Ampex Corporation, pages 5-31 to 5-33. The control terminal

  23 is connected to a control input 24 of the first com-

  mutator 1 and, also, at the control input 29 of a se-

  2. The output 25 of the switch 1 is connected to an output terminal 13 of the signal loss compensating circuit, and to the first input 26 of the switch

  2. The output 27 of the switch 2 is coupled, via

  of a controlled delay line 3 and a

  late fixed 4 compensation, to a second entry 28 of the com-

  2. The circuit elements 2, 3 and 4 together form

  a circulating memory circuit 44, as will be described later, in more detail. A control terminal 30 is connected to a control input 31 of the controlled delay line 3. The output 32 of the delay line

  3 is connected to an inlet 33 of a filter 5 and, through the

  of a fixed compensation delay line 6, at a first input 35 of a differentiating circuit 7. The

  compensation delay lines 4 and 6 are used

  to compensate for circuit delays in the transmission channel of color television signals,

  as will be apparent from the description given below.

  An output 34 of the filter 5 is connected to a second input

  36 of the differentiator circuit 7 and a first

  37 of a third bidirectional switch 10 and is

  also coupled via a safety line

  9, at a second input 38 of the switch 10. A control terminal 43 receiving a control signal HS / 2 is

  connected to a control input 44 of the third switching

  10. An output 39 of the switch 10 is connected to a first input 40 of a signal combining circuit 11. An output 45 of the differentiator circuit 7 is connected.

  through a fixed delay line 8 to a second

  input 41 of the circuit 11. An output 42 of the communication circuit

  binary signals 11 is connected to a second input

  21 of the first bidirectional switch 1.

  It should be noted that the preferred embodiment de-

  above, and the forms of reali-

  respectively of Figures 5 and 7, which will be described

  subsequently all represent digital compensators

  in the present invention and in which high speed digital data

  are treated. Therefore the different elements represented

  These functional block diagrams can be designed as conventional digital circuits in which the high speed of the data is precisely synchronized to the sampling frequency, equal to three times the frequency of the color subcarrier signal. at 3 x 3.58 = 10.74 MHz, while the clock signal is locked in frequency and in phase on the color subcarrier component of the television signal

  sampled. Therefore, in the description that goes

  follow, we will refer, in an interchangeable manner, to the

  sampling frequency and at the clock frequency.

  To simplify the representation, the channel or the flow path of the clock signal is not shown in the figures indicated above, but is shown in the detailed electrical diagram of FIGS. 8a to 8h, corresponding to the block diagram of FIG. 7, which detailed diagram

will be described later.

  We will now describe the operation of the preferred embodiment of the invention shown on

  the block diagram of Figure 2. A television signal

  their NTSC digital, present as data dis-

  cretes representing consecutive samples, is continuously received at the input terminal 12 and is sent to the first terminal 20 of the switch 1. When the system is in its normal operation, that is to say when no signal shortage is detected in the signal

* arriving, the switch 1 is in its first posi-

  as shown, and receives the input signal at 20 and applies it through output 25 to the terminal

  signal output compensator 13 and, by way of

  and apply it also through the

  26 and from the output 27 of switch 2 to the re-

  3. The delay line 3 provides a delay of a duration equal to a period of one horizontal line,

  least the delays inherent in the circuit in the transit route.

  the color television signal mission, as will be de-

written below.

  The delayed composite signal from the delay line 3 is sent to the filter 5, which may be, for example, of the type described in the aforementioned patent application or may be designed in the form of a band filter.

  in a well known digital comb. A filter 5 separates the

  the luminance of the composite color television signal

  te, in a manner well known in the art. The composition

  separated luminance energy obtained at the output 34 of the filter is sent to the input 36 of the differentiating circuit 7. The composite color television signal from the

  output 32 of the delay line 3 is applied through

  The differentiating circuit 7 at its input 45 provides a signal formed by the difference of the two received signals at its respective inputs. The delay line

  6 compensates for the circuit delay provided by the filter 5,

  this is well known in the art, in order to eliminate any unwanted relative phase shift in

  transmission of signals subsequently processed in the

cooked differentiator 7.

  In connection with the well-known relationship of the

  the frequency of the subcarrier signal and the frequency

  quence fh of the horizontal line of NTSC signals f = h Sc

  227.5 fh in the case of this particular embodiment

  of the invention, a non-integer number is

  number of samples equal to 3 x 227.5 = 682.5 clock cycles

  period of a horizontal line. In order to keep

  all the clarity of the description and in order to simplify this

  Lastly, compensation for delays in the circuit caused by the delay line will not be considered hereinafter.

  3. However this compensation will be described later.

  In this regard the delayed delay line 3 will be considered

  as providing a delay of a fixed duration equal to one

  Horizontal line period represented by 682.5 cycles

  clock. Loading and unloading of samples

  lons in and from the delay line 3 are controlled by the control signal CB received at the terminal 30, which signal is synchronous with the reference burst component of the color television signal during each horizontal line. This last control signal is sent to the control input 31 of the delay line 3; he is

  from the reference burst synchronization component

  this of the incoming television signal, in a way well

  known in the art. Comfite this was mentioned previously

  in the case of this particular embodiment

  In this case, a cycle of the reference salvo corresponds to three

  sampling periods equal to three clock cycles.

  Therefore, the 1800 line-to-line or line-to-line relative phase shift of the reference burst component represents a delay of plus or minus one and a half times of sampling, i.e. more or less a cycle

  and a half clock. Therefore, the delay line

  3 provides alternate delays of the television signal

  composite colors, equal to 682 2 + 1 2 = 684 clock cycles

  ge and 682 2 - 1 2 = 681 clock cycles in lines

2 2

  successive. This last operation can be described as a modulation of the fixed duration of the delay of the

  Composite color television signal stored in the

  delay 3 during successive periods of lines

  television, by the phase of the salvo component of

  It will be understood that the average delay of the signal during several consecutive lines is equal to about 682 times 1 clock cycle, which number is equal to the initial period.

of a horizontal line.

  From the above description, it appears that the

  FIG. 2 is controlled by a control signal CB, synchronous with the reference burst component, which is received from terminal 30

  to provide a color television signal consisting of

  delayed site, whose color subcarrier component is in phase with the reference burst component during each successive line, as previously described in detail with reference to Figures 1a and 1b. As previously described with reference

  in Figures 1a and 1b, it is desirable that the samples

  lons of the luminance component of the compensation signal

  signal failure according to the present invention are

  in order to reduce the horizontal shift of the respective positions of the samples in successive lines on the television screen. We will now describe below the

  line-to-line adjustment of the luminance component delay

  this provided by the apparatus of Figure 2 to perform the operations indicated above. As described above, in the case of this embodiment

  preferred embodiment of the invention, the luminance component is separated

  in the filter 5, the composite signal having a re-

  late modulated. The duration of the delay of the luminance component

  this separate and delayed is further modulated by + 1 clock cycle in the opposite direction with respect to the modulation described above of the delay of the composite color television signal. For this purpose, the separated and delayed chrominance component present at the output 45 of the circuit

  differentiator 7 is delayed by an additional clock cycle.

  provided by the fixed delay line 8. At the same time, the separated and delayed luminance component present at the output 34 of the filter 5 is delayed by two

  additional clock cycles provided by the re-

  late fixed 9 during alternating periods of television lines, as indicated below. The delayed and separated luminance component from filter 5 is

  applied directly to the first input 37 of a switching

  bidirectional transmitter 10 while also being applied via an additional delay line 9 to the second input 38 of the switch 10. The latter is controlled by the control signal HF / 2 received at the terminal

  43 and having a frequency equal to half the frequency

  this horizontal line. The HS / 2 signal is taken from the

  synchronization of horizontal lines of the incoming color television signal received at the terminal

  12. In the respective embodiments of the present invention,

  of the invention described here, the signals

  HS / 2 control units are locked in frequency and

  phase on the synchronization component of horizontal lines

  tales of the incoming color television signal and also

  on the phase of the color reference burst component.

  During the signallessness compensation, when the composite television signal is not received, the signals

  CB, HS or HS / 2 are produced in syn-

  chronism with the respective synchronizing component of the missing television signal, using a general frequency (not shown) of a steering wheel signal and

  are locked in phase on the television signal

  their, as is known in the art. From the description

  In the foregoing, it will be understood that the delay resulting from the luminance component is modulated by a delay of + one clock cycle with respect to the delay of the chrominance component. It is thanks to this last characteristic that the delay time of the luminance component of the signal of compensation of a lack of signal is set in consecutive horizontal lines in response to the synchronization component of horizontal lines in order to

  reduce the horizontal line-to-line shift of the samples

  during the compensation of the lack of signal.

  The respectively delayed luminance components

  this and chrominance are combined in an adder 11

  and the combined signals present at the output 42 of the addi-

  11 represent the composite compensation signal

  lack of signal applied to the input 21 of the first communi-

  1. The last signal is available on a permanent basis

  to be used for the compensation of the lack of

  signal in response to a compensation command signal C

  signal failure received at the communication terminal

  23, as previously described.

  When receiving a command signal DO in

  23, indicating that a lack of signal appeared in the

  TV channel arriving at input 12, switch 1

  is controlled so as to switch the

  20 is applied to the input 21 and the switch 2 switches from 26 to 28. Therefore, the switch 1 applies to the output terminal 13 the received signal compensation signal at its input 21 which is supplied to the circuit of FIG. 2, as previously described. On the other hand, the switch 2 will close the circulating memory circuit 44 and consequently cause the circulation of the last

  line received from the information of the preceding television signal.

  immediately the lack of signal and which has been memorized

  in the delay lines 3 and 4. Therefore the line

  indicated above for the transmission of the initial signal of tzl1-

  color vision will circulate in the circulating memory 44, until the lack of signal is eliminated and the control signal DO at 23 is interrupted. During the

  compensation for lack of signal, the output signal pre-

  32 and from the circulating memory 44 is processed by the signallessness compensating circuit of Figure 2 as previously described, instead of the incoming color television signal. As mentioned above, the duration of the

  delay caused by the delay line commanded e3 is

  the duration of the delay previously considered, of a

  period of a horizontal line to compensate for delays inherent in the circuit and present in the transmission path of the processed composite signal. Thus, if we denote by A the delay provided by the filter 5 in the transmission path

  of the separate luminance signal and if the

  additional late one clock cycle caused both in the flow path of the separated luminance signal

  and in the flow path of the separated chromium signal

  nance, it appears from the block diagram of Figure 2 that to obtain an overall delay time equal to a period of a horizontal line of the composite compensation signal DO without considering the modulation described above the delay by the respective signals of order, the delay provided by

  the delay line 3 must be reduced by A + S.

  it follows from the description given above that

  to obtain a circulating memory 44 providing a delay

  duration equal to exactly one period of a horizontal line

  zontal, it is necessary to reintroduce

  A + 6, in the form of a fixed delay line 4 as shown between the output 32 and the input 27 of the

delay line 3.

  As can be seen from the above description, a

  An important advantage of the invention lies in the fact that consecutive lines of the signallessness compensation signal are drawn from the same part of the initial color television signal immediately preceding the lack of

signal.

  Another important advantage lies in the fact that the composite signal is stored in the circulating memory

  in its original form and remains unchanged as a result of the

  line-to-line component of the signal by means of the signallessness compensation. Therefore it does not

  produces any alteration of the signal resulting from

  the lack of a signal, of the type that appeared in

  signallessness compensators of the prior art. simul-

  momentarily, each sample of the chrominance component of the signal loss compensation signal is processed from

  to have the same phase as a corresponding sample

  of the initial television signal, from which the

  signal-free compensation signal is formed, tan-

  say that the luminance component of the signallessness compensating signal is processed so as to provide a minimum horizontal shift of the samples in successive lines. Since in the example described above and concerning the operation of the block diagram of FIG. 2, a sampling rate or frequency equal to three times the frequency of the subcarrier signal is encountered.

  colors, there is a line-by-line shift of the sample

  lon of signal of compensation of the lack of signal equal to a period and a half of sampling for the component

  of chrominance and only half a sample period-

  swimming for the luminance component. We will understand

  above description that, as a result of the respective shift

  line to line indicated above samples, one reaches

  objectives described above with a compensation signal

  lack of high quality signal.

  The previously described operation of the apparatus of FIG. 2 is illustrated in FIG. 4 where the line-to-line offset of the samples of the luminance component

  and the chrominance component are represented

  in successive lines of the DOC clearing television signal. A last line Ai received from the initial television signal, immediately preceding the lack of signal, comprises the successive samples 2A, 3A, 4A, 5A, etc. In FIG. 4 it can be seen that samples 2B,

  3B, 4B, etc. the first line Bi of the compensating signal

  DOC as well as all subsequent odd compensation lines DOC B2, B3, etc., are obtained from the initial line Ai as previously described and shown in connection with Figure la. In order to allow a better comparison, corresponding samples in FIGS. 1a and 4 are designated by the same reference numerals. However, it can be seen in FIG. 4 that the samples of the chrominance component of the DOC compensation signal in the second DOC compensation line

  A2 and in all subsequent even-numbered lines of

  DOC A3, A4, etc., are obtained by delaying the

  the chrominance component of the initial line Ai exactly of a duration equal to the period of a horizontal line. Therefore, the respective chrominance components of samples 3A, 4A, etc., in DOC, A2, etc., even compensation lines, are in phase with those of the initial line Ai, but being shifted by one period and half of a sample compared to a line

  Odd Compensation DOC immediately preceding. On au

  the samples of the luminance component of DOC A2, A3, etc. are staggered

  sampling period from the initial line

  tial Ai, but only offset by half a period

  sample against an odd line of compensation.

  immediately preceding DOC. It follows from the process

  described above for lack of signal compensation, illus-

  in Figure 4, that a decommissioning scheme is formed

  line-to-line or line-to-line of sampling components, in which lines CH2, L2; CH3, L3; CH4, L4; etc., connecting corresponding samples

  of the chrominance component and the light component

  neighboring DOC offset lines intersect

  reciprocally. This scheme makes it possible to obtain the vertical shift

  respective cal at a line-by-line or line-to-line of + one and one-half sampling periods of the chrominance component and + one half-sampling period of the

luminance component.

  The preferred method indicated above, compliant

  to the invention, in connection with providing a

  delayed luminance of the compensation signal com-

  posit of lack of signal in successive lines of television, is illustrated in Figures 3a and 3b. In FIG. 3a, a waveform M1 represents a portion of the luminance component of an initial line Ai of the color television signal received at terminal 12 by the signallessness compensation circuit of FIG. 2, just before a lack of signal. Samples IA, 2A, 3A, etc., of the M1 waveform are obtained by sampling the color television signal at an equal frequency.

  three times the frequency of the subcarrier signal

  their, as was described previously. When considering the method described above described in relation to providing a luminance component of the signal-failure compensation signal by means of the apparatus of FIG. 2, the luminance component of the first line Bi of the signallessness compensating signal, which succeeds the initial line Ai on the television screen, is represented as illustrated in M2 in FIG. 3A. It can be seen that the waveform M2 is a replica of the initial waveform M1, except that the

  samples 1B, 2B, 3B, etc., of M2 are shifted by

  half a sampling period in one direction, for example to the right with respect to the samples 1A, 2A, 3A, etc., of the waveform M1. However the waveform

  M3 of the immediately following line A2, which is a repli-

  that of the initial waveform M1, is shifted, with respect to M2 of the line Bi, of a duration equal to half a period

  sampling time, but is shifted from the initial waveform

  of the line lA, of a duration equal to one

  sampling, as can be seen from the locations

  samples 2A, 3A, 4A, etc., on M3 relative to

  to the samples of the preceding lines Bi and Ai respectively

  is lying. This last effect is not harmful for the observer

  since only one shift of half a trading period

  the horizontal direction is seen between

  respective samples on successive lines. The pro-

  given above makes it possible to form a composite signal

  signal loss compensation site whose samples

  of the chrominance component are shifted horizontally

  in one direction, while the luminance component samples are horizontally offset in the opposite direction from a previous line of the

  color television on the screen. This scheme appears in

  ternance in successive lines of compensation of

  lack of signal with a change in the directions

  previously to achieve an overall compensatory effect

  for the observer, as described above

in connection with Figure 4.

  Therefore the signal loss compensation (DOC) line A2 is followed by the compensation line of

  lack of DOC B2 signal, which is formed by means of a decal

  ge samples of the luminance component of the line

  Ai for a period equal to one half of a sampling period

  in the same direction as for line Bi and consequently

  quent is in phase with it. Therefore the

  The above procedure is repeated for all lines of communication

  DOC "odd" thinks Bi, B2, ... BN, whose samples

  lons are shifted horizontally in a direction of a duration equal to half a sampling period in relation to the initial line Ai and alternatively for all lines

  DOC "pairs" A2, A3, ... AN, whose exchange

  are shifted horizontally by a duration equal to one sampling period in relation to the initial line A2 and in the same direction, as shown

  in Figure 3a. It will be understood that the overall effect of

  horizontal line to line of the luminance component of the DOC compensation signal for the observer is + half a sampling period. Thus, thanks to the implementation of the method described above according to the invention, the effect of the horizontal shift of the luminance component

  DOC compensation signal is minimized.

  Figure 3b describes the luminance component of a

  initial line Bi television colors immediately preceding-

  a lack of signal. The waveform Ni comprising the samples 1B, 2B, 3B, etc., is identical to the shape

  waveform Mi concerning line Ai in Figure 3a, with the excep-

  of the. that its samples 1B, 2B, etc., are decommissioned

  half of the sampling period with respect to the waveform Mi. In FIG. 3b, it can be seen that N2 describes

  respective waveforms of all the lines of communication

  DOC "Odd" DOC A2, A3, ... AN following the initial line Bi. Similarly, N3 represents all the

  odd DOC compensation lines B2, B3, ... BN success

  In the initial line Bl.-There is a difference in the formation of the DOC compensation luminance components in successive television lines, as shown in FIG.

  on lines 3a and 3b, because the samples

  lons "odd" lines are offset from the initial line by half a sample and the samples of the "even" lines are shifted by

  referred to the initial line, of a duration equal to one sample

  lon complete in respectively opposite directions.

  Referring to the discussion indicated above, it follows that the present method of line-to-line modulation of both the chrominance component delay and the delay of the luminance component in synchronism with the reference burst phase, and line-to-line modulation of the delay of the luminance component in synchronism with the synchronization component of

  horizontal lines in order to reduce the line-to-line delay

  of the latter, is obtained in a relatively simple manner by applying a control signal relating to the reference burst component and a control signal

  concerning the synchronization component of horizontal lines

  zontal, with the respective lines late. Given that.

  the two control signals CB and HS / 2 are locked in frequency and in phase on the incoming television signal as well as one with respect to the other, the above method can be implemented only by affecting arbitrarily the sample shift direction, or phase, at each signal-out compensation line, to the

  right or left as seen on the TV screen.

  compared to the initial signal. Once the directive

  When the phase is assigned, it is kept identical in alternate DOC compensation lines in response to the HS / 2 signal whose frequency is equal to half of the horizontal line frequency. The HS / 2 signal is also used to modulate the delay of the luminance signal as has been described. As a result of the method described above, a compensation scheme or network of

  lack of signal of the type shown in Figure 4.

  FIG. 5 shows another preferred embodiment of the signal loss compensator.

  according to the present invention, which will now be described

  ing. In FIG. 5, similar circuit elements to those previously described in connection with FIG.

  designated by identical reference numbers. We neglect

  to describe these elements related to

  Figure 5 to avoid unnecessary repetition. In the signallessness compensation circuit of FIG. 5, the filter 5, which separates the luminance component from the composite color television signal, is connected to the output of the first bidirectional switch 1. The separate luminance component present at the output 34 of the filter 5 is sent to the input 36 of the differentiator circuit 7 to the other input 35 of which the color television signal is sent

  from the output 25 of the switch 1, through the intermediary

  re of the fixed delay line 6 compensation. The component

  the resultant separate chrominance present at the output 45 of the differentiator circuit-7 is sent to

a first input 45 of a second bidirectional switch

  The output 50 of the switch 14 is connected via a first chrominance controlled delay line 16, the output of which is connected to a second

  input 49 of the switch 14. The delay line 16 and the com-

  mutator 14 thus constitute a first circulating memory circuit 81 for the separate chrominance component. The delay line 16 is controlled by the previously described control signal designated CB and received at the control terminal 30. The separate luminance component at the output 34 of the filter 5 is further applied.

  at a first input 46 of a third bidirectional switch

  15 and is sent from the switch output 51

  via a second delay line controlling

  The delay line 17 and the switch 15 constitute a second circulating memory circuit 82 for the separate luminance component. The delay line 17 is controlled by a control signal designated HS and received at the control terminal 43. A signal lack control signal D0, received at the control terminal

  of 23, is sent to the respective control inputs 24, and 86 of the switches 1, 15 and 14 respectively; During operation, a signal DO control signal, which indicates the presence of a lack of

  signal in the composite color television signal

  received at terminal 12, operates all three switches 1, 14 and 15. Therefore at the output

  25 of the first switch 1 will be sent a compensation signal

  the absence of a signal, from the input of the

  mutator, which signal is produced by the circuit of FIG. 5. The signal indicated above for signallessness compensation is formed in the following manner. During normal operation of the circuit, when no signal is missing, the filter 5 receives continuously, at the terminal 12, the color television signal

  with a frequency equal to three times the frequency

  color subcarrier signal. The separate luminance component present at the output 34 of the filter 5 is sent via the switch 15 to the luminance delay line 17. The delay line 17 produces a delay of a duration equal to a period of a horizontal line. Therefore a horizontal line of

  the separate luminance component from an immediate part

  formerly received color television signal

  at terminal 12, will be stored in the line at

  late 17 at any time of the normal operation of the circuit. The loading and unloading of the signal stored in the delay line 17 will be controlled by the control signal HS received at the terminal 43. The signal HS is

  from the horizontal synchronization component of the

  color television broadcast received and is synchronous with this

  last. In connection with the characteristic indicated below

  above, a separate luminance component is obtained which is delayed by a duration equal to a horizontal line period and which, at the same time, is coherent with the synchronization component of horizontal lines during

  successive lines of television.

  Similarly, the chrominance delay line 16, which also produces a delay of a duration equal to a horizontal line period, continuously receives the

  separate component of chrominance from the different circuit

  5, through the switch 14. Thus, at any given time of the normal operation of the circuit,

  a horizontal line of the separate component of chrominan-

  it will be stored in the chrominance delay line 16, that portion of the chroma component corresponding to that of the separate luminance component simultaneously stored in the luminance delay line 17. The

  loading and unloading of the chromatin component

  this stored in the delay line 16 is controlled by the control signal CD received at the terminal 30, which signal is drawn from the synchronization component of the reference burst of the color television signal received at the terminal 12 By means of the control of the chrominance delay line 16 by the control signal CD, a separate chrominance component is obtained which is

  delayed by a period equal to a period of one horizontal line

  tale and which, simultaneously, is in phase with the reference burst component during successive television lines.

  As shown in FIG.

  respectively delayed and separated luminance

  and chrominance are combined in the combining circuit.

  signal sound 11 and the combined signal present at the output 42 of the circuit It is sent to the. second entry 21

  of the first switch 1, as described above.

  The signal present at 21 represents the signallessness compensation signal, which is used by the apparatus of FIG. 5 when a signal lack control signal D0

is received.

  When a lack of signal is indicated,

  14 and 15 controlled by the signal DO close the cir-

  respective burns of circulating memory 81, 82. Therefore

  both the separate luminance component and the component

  separated from chrominance circulate in their

  circulating memory levels, in synchronism, being controlled by the aforementioned clock signal at a frequency equal to three times the signal frequency

subcarrier colors.

  It follows from the description given above that the

  circuit of the preferred embodiment of FIG. 5a, with respect to the circuit of FIG. 2, the advantage of

  not require additional modulation of the

  separated and delayed luminance compared to the

  separate delayed chrominance health in order to reduce the

  line-to-line horizontal shift of the samples from the

  luminance fixture. Instead, in the form of

  In Figure 5, two separate circulation delay lines are provided, one for the separate component.

  luminance and the other for the separate chromium component

  respectively. The two delay lines 16, 17 are controlled by separate CB or HS control signals so as to provide signal components-reciprocally

in synchronism. -

  In order to illustrate the description given above,

  the operation of the form of reali-

  FIG. 5, in FIG. 6 where the offsets

  horizontal dimensions between the samples of the

  the luminance and the chrominance component in successive lines of signal

  represented. In order to facilitate comparison with a dialogue

  gram previously described, shown in Figure 4 and

  concerning the circuit of Figure 2, the last line ini-

  received from the color television signal preceding the lack of signal, the successive lines of loss of signal compensation (DOC) as well as consecutive samples

  these respective lines are designated by the same numbers

  Reference chips in the diagrams of FIGS. 4 and 6. In the diagram of FIG. 6 it can be seen that the luminance component of each DOC compensation sample 2B, 3B, 4B, etc., in odd compensation lines DOC

  Bi, B2, etc., is obtained by delaying the light component.

  nance of a corresponding sample 2A, 3A, 4A, etc. of the initial line Al, of a duration equal to a period of one

  horizontal line, increased by half a sample period-

  swimming. Simultaneously the chrominance component of each sample above DOC 3B, 4B compensation, and so on. in odd DOC compensation lines is obtained by delaying the chrominance component of a corresponding sample 2A, 3A of the initial line Ai, of a duration

  equal to a period of horizontal line, increased by one

  half and a half of sampling. On the other hand, the

  the luminance of each DOC compensation sample 3A, 4A, etc. in DOC compensation lines pairs A2, A3, etc. is obtained by delaying both the luminance component and the chrominance component of the corresponding samples 3A, 4A, etc. the initial television signal

  colors, of a duration equal to one period of a horizontal line

  tal. Thus, when operating the form of reali-

  preferred embodiment of the invention of FIG. 5, the relative line-to-line vertical shift of the samples of the signal of

  DOC compensation equals + half a sample period-

  swimming for the luminance component and at + a period and

  half of sampling for the chrominance component.

  However, compared to the method of FIG. 4, an advantage of the preferred method of the invention, illustrated in FIG. 6, lies in the fact that one line on two of compensation

  DOC is in phase with the initial line of the televi-

  as regards, at the same time, the components of

  nance and chrominance, and that no horizontal shift of the samples occurs in these lines, from the point of view of both the luminance component and the component

chrominance.

  From the description of FIG.

  that in this particular embodiment of the

  vention, it is not necessary that the television signal

  colors sampled at a frequency equal to one

  entire tiple of the subcarrier signal frequency

  colors, as was the case in the form of

  FIG. 2. In the embodiment of FIG.

  re 5, we can use a frequency equal to a multiple

  rational of the subcarrier frequency.

  In order to provide a more complete description of

  In the apparatus and method according to the present invention, there is shown in the block diagram of FIG. 7 another embodiment of the present invention. An electrical diagram

  corresponding detail is shown in the following figures

  sives 8a to 8h. The embodiment of Figs. 7 and 8a through 8h has been designed for a specific signal loss compensating apparatus in which a delay of the initial color television signal equal to two horizontal lines is required. We will first describe the block diagram of the

  Figure 7, then the diagram of the corresponding detailed circuit.

  In the embodiment of Figure 7, a color television signal is received on an input terminal

  , in the form of consecutive digital samples

  at a frequency equal to three times the frequency of

  color subcarrier, as has been described previously.

  cédemment. The received signal is applied to an input 91 of a bidirectional switch 52 and via the

  exit 93 from the latter, to a first delay line

  54, making a delay equal to a horizontal line,

  minus the delays inherent to the circuit and designated by t.

  The delayed color television signal V from the

  output 115 from the delay line 54 is applied, through

  a second fixed compensation delay line 56 providing a delay equal to e, to a second input 92 of the switch 52. Thus a circulating memory circuit

  94 is formed by the elements 52, 54 and 56, similarly

  to a previously described description in connection with the embodiments of FIGS. 2 and 5. A control signal CB, which is received at a control terminal 124, is sent to a control input 125 of FIG. the line to

  delay 54. The control signal is similar to that

  previously written in connection with FIGS. 2 and 5. The color television signal V emanating from the delay line 54 is also sent via a third

  fixed time compensation line 113 providing a

  later designated by T, at a first input 101 of a circuit

  differentiator 64, in the form of a delayed signal V '.

  The signal V delivered by the output of the delay line 54 is also sent to the input 104 of a digital filter 160. The latter is designed in the manner of the band filter

29 2478924

  in a digital comb described in the patent application

  previously born. Filter 60 separates the light component

  nance of the color television signal, in a manner

  in this patent application. The luminance separated L component obtained at the output 105 of the filter 60 is applied

  at a first input 107 of a second bidirectional switch

  62 and is also sent via a delay line 67, causing a fixed delay equal to

  two clock cycles, to a second input 108 of the switching

  62. An output 109 of the switch 62 is connected to a first input 98 of a signal combining circuit.

  66. Thus, through switch 62, the

  The separated and delayed luminance L is sent from the filter 60 to the signal combining circuit 66, either

  directly or by being delayed by two additional cycles

  clock, identified by 2 d. The switch 62 is controlled at its control input 112 by a control signal designated HS / 2 and received at a control terminal 111. A component of the signal separated from

  luminance, inverted, L ', obtained at an indistinct output

  the jug 106 of the filter 60, is sent to a second input 102 of the differentiator circuit 64. The latter delivers to its

  output 103 a difference signal C 'representing the component

  a chrominance-separated-chromatic energy obtained as the difference between the delayed composite color television signal V 'and the separated and delayed luminance component, both of which signals are applied to the first and second differentiator circuit inputs, respectively. In this preferred embodiment, the differentiator circuit 64 is constituted in the form of a signal adder and the

  chrominance component C 'is obtained by adding

  the delayed composite signal V 'and the se-

  trimmed and inverted luminance L '.

  The chrominance separate component C 'coming from the output 103 of the differentiator circuit 64 is applied via a delay line 68, providing a delay equal to one clock cycle, to an input 99 of a

  signal adder 66. As mentioned above,

  previously, the separate luminance component L from the

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  second switch 62 is applied to the other input 98 of

  the signal adder 66. The latter combines the

  received chrominance and the received component of

  A multichannel color composite television signal is provided at its output 100 which represents the color television signal missing compensation signal. The signal of

  compensation is sent to a first entry 95 of a third

  second bidirectional switch 58. The television signal

  composite color received at the input terminal 90 is applied to a second input 96 of the switch 58

  through the first switch 52, the first

  commanded delay line 54 and a second line to

  compensation delay 56. A control command signal DO

  thought of missing signal is sent to a com entry

  switch 58 via switchboard

  delay 53 producing a delay of a horizontal line.

  This latter control signal is received at an input terminal 110 when a lack of signal in the color television signal arriving at the terminal 90 is detected, for example by a conventional loss detector.

  signal (not shown), as previously described

  is lying. The signal lack control signal present is also sent to a control input 114 of the first switch. An output 127 of the switch 58 is connected through another delay line

  126, at an output terminal of the compensation circuit

  The delay line 126 provides a delay equal to a horizontal line and is controlled by the signal CB applied to its control input 128, simultaneously with and in the same manner as it has been. previously described in connection with the delay line

ordered 54.

  We will now describe the operation of the

  baked signal-loss compensation of Figure 7.

  When a lack of signal is detected in a composite color television signal, for example by a conventional signal loss detector (not shown), a signal

  Signal failure control command received at the boundary

  ne 110 is applied to the switch 52 and, via

  a delay line 53 providing a delay equal to one

  Fig. 52. The switch 52 closes the circulating memory circuit 94 and, therefore, the last horizontal line received from the color television signal immediately preceding the lack of signal, which has been stored in the delay lines 54 and 54. 56, flows through the input 92 and the output 93 of the switch 52 at a clock signal frequency of 3 x 3.58 MHz = 10.74 MHz. The clock signal, which is

  used to periodically control the

  of the circuit of FIG. 7, is not represented on the schemablock in order to preserve a better clarity at

  drawing, but is shown in the detailed diagrams

  8a to 8h, which will be described later.

  quently. The filter 60 receives the composite signal V, retar-

  essentially equal to two periods of

  horizontal and from the circulating memory 94, and separates the luminance component L 'of this signal from a

  described in the aforementioned patent application

  ously. The separate luminance component is applied

  through switch 62 to the combiner circuit

  signal 66, which is constituted in the form of an ad-

  signal editor, in the preferred embodiment of the invention. In response to the control signal HS / 2, the switch 62 alternately applies the separate component

  of luminance L directly or with a delay of two

  additional clock keys in the delay line 67, by

  via switch 62 to a combiner circuit 66

  sound of signals. The control signal HS / 2 has a frequency

  quence which is equal to half the frequency of lines

  horizontal. This signal is derived from the sync component

  horizontal position of the color television signal received on terminal 90. The phase of the HS / 2 signal is controlled by

  the signal CB received at terminal 124 so as to

  rant that the same phase relationship of these two signals of

  command will be maintained during the entire operation.

  Thus the switch 62 is controlled by the signal HS / 2 of

  alternatively, in the course of hori-

  successive zontals, the signal L 'not delayed and delayed

32 2478924

  two clock cycles 2 d respectively at the input 98 of the adder 66. On the other hand, as previously described, the signal adder 64 receives both the delayed composite signal V 'and the inverted luminance component L 'and delivers a separate chrominance component

  this C 'at its exit 103. In order to compensate for the delay in

  cooked T which intervenes during the processing of the component

  luminance in the filter 60, the signal VI is

  delayed by the duration T in the third fixed delay compensation line 113. The separate chrominance component

  This is delayed by one clock cycle S in the line to be re-

  68 and the delayed component of chrominance C is

  the luminance component L described above in

the signal adder 66.

  It follows from the foregoing description that, when

  that the separate component of the luminance L 'delayed

  two additional clock cycles in the course of

  alternating horizontal lines and the separate component

  delayed chrominance of an additional clock cycle

  during successive periods of horizontal lines

  they are combined together in the adder 66, they represent a composite signal of lack of signal compensation, whose delay of the luminance component is modulated by + a clock cycle with respect to the delay of the chrominance component during successive periods of horizontal lines. So the characteristic mentioned

  previously of the invention, concerning the reduction of

  the luminance component with respect to the delay of the chrominance component of the signal resulting from the lack of signal compensation is obtained in the form of

  preferred embodiment of Figure 7 by means of the combination of

  its described above circuit elements.

  It is clear from the description given

  above the block diagram of Figure 7, that the delay T compensates for

  the delay caused by the circuit of the filter 60 and the delay t compensates the combined delays X and the delay 5 provided by the delay line 68; therefore Y = T + S, considering that circuits 64 and 66 do not provide

no delay.

  In connection with FIG. 7, it is also evident that, in this particular preferred embodiment, the controlled delay line 54 is coupled to the

  main channel for the transmission of

  their composites. Therefore, when no signal-out compensation occurs, the incoming composite signal is received at 124 and continuously delayed in the delay lines 54 and 56 by a duration equal to one period.

  of a television line, which delay is controlled, in sync with

  chronism with the component of the reference burst. Therefore, the initial composite signal present at the output 127 of the switch 58 provides an unwanted phase shift of + 1800 in alternate lines. To compensate for this effect, an extra delay line 126 creating an equal delay

  a horizontal line is connected in the main track.

  the transmission of color television signals. The loading and unloading of the delay line 126 is controlled by the control signal CB described above, received at the control terminal 124 and applied to

  the control input 128 of the delay line 126. Given that

  that the color television signal received by the delay line 126 has been previously delayed by one period of a horizontal line in the delay lines 54 and 56 and that

  the two delay lines 54 and 126 are respectively

  by the same control signal CB, the phase shifts remain

  + 1800 positions in opposite directions are applied to

  respective output signals from these delay lines

  54 and 126. Consequently these opposite phase

  slow and no phase shift is present in the output signal.

  issued by exit 70 of the

missing signal from Figure 7.

  As can be seen from the description given

  above, in the block diagram of FIG.

  thought of lack of signal present at the terminal

  70 is delayed by three horizontal line periods.

  to meet the requirements of the

  such a particular in which this particular embodiment of the invention is used. However, as

  this is apparent from the foregoing description, the actual signal of

34 2478924

* compensation of lack of signal obtained at the level of

  tie 127 of switch 58 is still formed from the

  last initial line received from the pre-existing television signal

  at entrance 124, and essentially of the same

  that it has been described above in relation to the

Figures 2 and 5.

  However, it will be noted that, in the forms of

  2 and 5 respectively, the respective controlled delay lines are connected to the main transmission channel of the composite color television signal and therefore have no undesirable phase shift such as that provided by the embodiment of FIG. 7 during normal operation of the system, when no signal failure compensation

is not performed.

  The detailed diagram of the circuit represented in the successive figures 8a to 8h essentially corresponds to

  simplified block diagram previously described in Figure-7.

  For a better comparison, the individual circuits

  in the detailed diagram and corresponding to

  block diagram are indicated by lines formed of

  dashes and are designated by the same reference numerals.

  Similarly, the connection lines present in

  the circuits in the detailed diagram are designated by reference numerals corresponding to the designations

  input / output of the corresponding blocks of FIG. 7.

  In order to provide a complete description, the components of the

  The integrated circuits shown in the preferred embodiment of Figs. 8a to 8h are designated by their respective part numbers commonly used by the manufacturers.

of these components.

  Specifically, the filter circuit 60, which is used to separate the luminance component of the composite color television signal which is shown in the consecutive figures 8d and 8e is similar to that described

  in the patent application already mentioned above. This-

  while it will be understood that a well-known digital comb band filter can be used in its place. As can be seen in the detailed diagram of the figure circuit

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  8a to 8h, an advantage of the signalless digital compensation circuit according to the present invention resides in the fact that the whole of the signal processing is provided in real time using TTL (transistor-transistor logic) standard logic circuits. The circuit of Figs. 8a to 8h is adapted to perform signallessness compensation in a color television signal recording and reproduction system, in which an NTSC color television signal is digitally encoded by

  sampling at a frequency equal to three times the frequency

  The color sub-carrier of the television signal, i.e., the key-sampling rate of 3 x 3.158 MHz = 10.74 MHz. The sampling signal is locked in phase on

  the reference salvo component of the subcarrier signal

  as it is well designed in the art. The frequency

  sampling frequency is equal to the clock frequency as mentioned above in relation to the

Description of Figure 2

  In general, as regards the func-

  signal-null compensator according to the invention.

  the sampling frequency used to code the

  composite analog signal, for example the television signal

  color, does not need to be the same as the frequency of the clock signal used to synchronize the different

  elements of the signal loss compensation circuit.

  In the latter case, the samples can be received and stored for example at the sampling frequency and subsequently retrieved at the clock frequency, which

  is used for circuit synchronization.

  The present embodiment will now be described.

  of the invention shown in the detailed diagram of the

  Figures 8a to 8h. In Figure 8a, successive samples

  Si, S2, S3, etc., of the digital color television signal

  are received on a signal loss compensator input 90, in the form of data in parallel

  8 bits, by a first input set 91 of two selections

  data transmitters / multiplexers A24 and A34 of the bi-directional switch

  directional 52. These multiplexers also receive data on their second input 92 from

36 2478924

  the output 116 of the delay line 56 shown in FIG.

  Figure 8c. A signal of lack of signal is received at the input 110 by the multiplexers, at 114 via a flip-flop A16, from a conventional circuit of lack signal detection of the signal.

  of the high frequency envelope (not shown), like this

  has been mentioned previously. The flip-flop A16 is used to precisely control the signal DO control signal, as is known.

  in the art. During normal operation, a

  tiplexeur applies the input data 90 through the intermediary

  b A23 flip-flop at output 93. In a way

  of the bistable flip-flops similar to A23 are used

  across the circuit to delay data

  treated, with a delay equal to one clock cycle, for

  to prevent a precise timing of the data. When the signal

  DO 110 present command is received, the multiplexers pas-

  by switching from entry 91 to entry 92. The

  from 93 are sent to the output 70 of the signal-canceling circuit via a

  first controlled delay line 54 shown in FIG.

  8b, a second compensation delay line representing

  8c of the switch 58 shown in FIG.

  FIG. 8g and another controlled delay line 126 represent

  shown in Figure 8g, as will be apparent from the description

given below.

  The delay line 54 of FIG. 8b comprises eight

  identical memories with direct or selective access of 4 x 256 digits

  representatives, of whom six memories designated by B1 have been

  B11, B31, B51, B61 and B81. The two groups comprising

  four memories are used to receive higher weight data and lower weight data. The delayed delay line 54 carries a delay of a duration equal to one

  period of a horizontal line of the conventional television signal

  their minus the compensation delay provided by the fixed delay line 56 of Figure 8c connected to the transmission vane of the delayed color television signal. The

  delay line 56 consists of eight registers of

  four registers A51, A61, A52 and A82. The flip-flop B41 located at the output of the delay line 54 is used to ensure correct synchronization of the output data so as to achieve the delay indicated above. The delayed composite signal present at the output 115 is applied via a fixed compensation delay line 56 to the input 96

of the switch 58 of Figure 8g.

  As shown in Figure 8d, the data

  born Si, S2, S3, etc. from exit 115 of the line

  delay 54 and representing the signal V are also applied.

  to a set of inputs 104 of the filter 60. Like this

  has been described in the aforementioned patent application

  Filter 60 continuously delivers an average value of three successive samples Si, S2 and S3. As shown in FIG. 8c, a sample S1, applied via the delay line 56, is obtained at the output 117 of the latter, where it has been delayed by a period equal to a signal of clock so its timing

  correct, with a view to its addition to a sample

  S2 received a clock signal later. The last exchange

  Delayed delay is sent to a second input set 104 of the filter 60. Samples S1 and S2 are added in 4-digit binary adders A33, A43 of FIG.

  8d and their sum Si + S2 is delayed in the bistable flip-flop

  A53 of a duration equal to a clock signal, in preparation for

  its addition to the sample S3 subsequently received from the output 115 of 54. The last summation is performed by 4-digit binary adders A54, P44 and an output signal of these adders represents the somye S = Si + S2 + S3. The signal S is transmitted by means of a flip-flop A55 so as to be certain of its correct timing for its subsequent processing. In this particular embodiment of the invention, an average value of sampling is obtained by dividing the

  signal S by 3. The division by 3 is applied with a precision

  0.13% according to an approximation algorithm

S S + S

  3j 4 16 -TW MiU For the particular application of the formation of

  the average of the samples in the preferred embodiment

  currently described, the approximation algorithm is implemented in two successive phases as follows:

PS = S + S

4 16

PS + PS

  These two operating phases are performed in the

  remaining parts of the filter circuit diagram 60 represented

  shown in Figure 8e as described below.

  Two binary 4-digit adders A64, A65 of FIG. 8e receive the signal S on two input sets and shift the signal S to provide one of the sets of inputs as known in FIG.

  technical, and deliver a sum (S + S). The output signal

  from these last adders is further de-

  stalled to provide a corresponding output signal

  at (S + -4) / 2 as is known in the art. This last

  deny output signal is double the sum of

  PS defined above. The 2PS signal is sent to a

  A75 flip-flop that sends the 2PS signal to two sets of

  input of two 4-digit bit adders A66 and A76. These last adders shift the 2PS signal

  to get 2PS on a set of input and deli-

16 2PS

  an output signal corresponding to (2PS + 16) / 2, as known in the art. This output signal

  represents the S term of the approximation algorithm

  3 as above. The signal -S obtained corresponds to the signal of

  average value output delivered by the filter 60 according to

  the description given in the patent application

  mentioned above. The output signal of the adders A66, A76 therefore represents the color television signal - the chrominance component, i.e. the separate luminance component as described in the aforementioned patent application, with reference in Figure 7. The signal S- is applied to the flip-flops A66 and A77 which provide both a designated output j

  by the on of output 105 to the input 107 of the switching

  62 of Fig. 8f and an inverted output signal (- S-) designated L ', on the output 106 and applied to a first set of inputs 102 of the adder 64 of

  Figure 8f. The adder 64 consists of two addi-

  Binary Digitizers, A36, A46.

  In this preferred embodiment, the line

  fixed compensation delay 113 shown in the schematic diagram.

  block of Figure 7 and providing a delay T, is

  killed by a portion of the fixed compensation delay line 56 at the output 130 of the latter, as

  is shown in Figure 8c. The television signal

  their composite thus delayed is provided at the output 130 of the delay line 56 and designated by VI is applied to a: second set of inputs 101 of two binary adders

  4-bit A36 and A46 of the adder 64 in FIG. 8f.

  The adder 64 provides, at an output 103, a

  output signal indicated by C 'and which represents the component

  separated from chrominance, as indicated above.

  with reference to FIG. 7. The signal C 'is applied

  that via flip-flops A56 and A5

  presenting the fixed compensation delay line 68 to a first set of inputs 99 of two binary bit adders A84, A85 of the adder 66 in Fig. 8g. The separated and delayed luminance component L is applied

  to the other set of enzears 98 of these adders to

  firing outputs 109 multiplexers A87, A86, constituting the switch 72 in Figure 8f. As described above, the separate luminance component L 'is sent to a set of inputs 107 of the multiplexers A87, A86, from the output 105 of the filter 60, in FIG. 8e. AT

  the other set of inputs 108 of these multiplexers constitute

  By killing switch 62 in FIG. 8f, the luminance component L ', which has been delayed by the delay line 67 constituted by flip-flops A68, A78 shown in FIG. 8f, is applied. The multiplexers A87, A86 of FIG. 8f are controlled at an input 112 by the 7.8 kHz control signal HS / 2, received at 111, which signal has been described with reference to FIG. has previously been described with reference to the block diagram of FIG. 7, the switch 62 applies to the input 98 of

  the signal adder 66 the separate component of lumi-

  nance L, directly from the output 105 of the filter

  or via the delay line 67

  a delay of two clock cycles, alternatively

  in successive horizontal lines, in response to the

  HS / 2 command line. The adder 66 of Figure 8g

  combines the respective components of luminance and chroma

  received at its respective inputs 98, 99 to form a composite color television signal representing the signal miss compensation signal. This last signal

  is applied to a first set of inputs 95 of the switching

  58 in FIG. 8g, which is constituted by the multiple

  A73, A74 plexers, via the bistable flip-flop

  A89, used to achieve correct data timing. An output signal from the delay line 56 of Figure 8c is received at the other set of inputs 96 of the multiplexers A73, A74. The output signal at 127 from the switch 58 is sent to the line at

  delay 126 which is represented as a block.

  This last delay line is used, in the specific embodiment of FIGS. 8a to 8h, to eliminate the unwanted phase shift of 1800, as explained previously with reference to FIG. 7. The delay line 126 provides a delay. equal to a horizontal line and is controlled by the control signal CB, simultaneously

  and in the same manner as the controlled delay line 54.

  The delay line 126 may be designed to use direct access memories similar to those of the delay line 54 in FIG. 8b. The output signal of the delay line 126 therefore represents the signal dc

  previously described output of the compensation circuit of

  signal 8a to 8h, present at the level of the

output terminal 70.

  The switch 58 of FIG. 8g is controlled by the signal miss control signal D0 received at the input terminal 110 in FIG. 8a and applied via the output 112 and the output 55 of the delay line 53 of FIG. 8a so as to control

the input 97 of the switch 58.

  Fig. 8h shows a memory address generator 150 providing output signals in different memory address transmission lines A0 to A7, coupled to control the flow of data via a line. memory bus AB, by means of the respective delay lines 53, 54 shown in FIGS. 8a and 8b respectively. In FIG. 8h, counters A2, A12, A22, B2, B12 and B22 are used to count the respective clock cycles corresponding to the actual delay provided by these delay lines. The diagram of FIG. 8h shows the memory address generator 150 in a sufficiently detailed manner and therefore

  it is useless to give a complementary description.

  -To provide a complete description of the circuit

  in the diagram of the circuit de-

  FIGS. 8a to 8h cut out the respective clock signals designated by 10.7 MHz and the inverted clock signals designated by 10.7 MHz used to drive different circuit elements. The sampling signals are obtained at this frequency of the clock signal, as

  is well known and described for example in the application for

already mentioned.

  In the preceding description, the forms of embodiment

  Preferred embodiments of the invention have been described in

  this to a digital compensation circuit of lack of

  general, wherein an NTSC composite color television signal is sampled at a frequency equal to three times the frequency of the subcarrier signal, f. = 3 x 3.58 MHz sampling = 10.74 MHz. As will be apparent to those skilled in the art, the respective block diagrams of FIGS. 2, 5 and 7 could also be used for other digital systems as well as for others.

  analogue systems for transmitting television signals

  such as NTSC, PAL, PAL-M, etc. For example, if the signallessness compensating apparatus according to the invention is used in an analogue color television signal system, it may be preferable to carry out the controlled delay lines, for example the delay line 3 of FIG. 2, using conventional direct charge coupled (CCD) devices. As known in the art, these devices could be used as delay lines for delaying signals in analog form, while the information to be delayed can be introduced and output clocked in and out of the box. line to

  delay in response to a command signal, in the same manner

  that this has been described in relation to the forms of

  previously described. At the same time, the delay lines, such as 8 and 9 in FIG. 2, can be

  constituted by conventional analog delay lines.

  In the latter case, the delay line 8 would provide a

  desired value of the corresponding analog signal

  the line of the color subcarrier signal and advantageously the delay line 9 would essentially provide a value double the value of the delay so as to obtain a desired delay modulation of the

  luminance component in relation to laoemposan delay

  chrominance, as described above.

  In general, the invention relates to

  Figure 2 can be used in any treatment system.

  of digital television signals, in the-

  which sampling rate is equal to a multiple

  integer of the frequency of the subcarrier signal colors.

  For example if an NTSC color television signal is

  sampled at a frequency equal to four times the frequency

  of the subcarrier signal, then, to obtain a desired signal-out compensation signal, with a line-to-line phase of the chrominance component, for example by means of the embodiment of FIG. samples of the initial chrominance component

  signal should be shifted in TV lines.

  succession of more or less two periods of sampling

  pling. Therefore, in order to reduce the offset of the luminance component in successive lines, the delay line 9 of FIG. 2 should provide a delay of four clock cycles 46, while the delay line

  8 should provide a delay of two cycles 2 6.

  The invention described above is equally applicable

  to the PAL-M signal processing systems, since the respective control signals, such as the

  signals CB, HS and HS / 2, in FIGS. 2, 5 or 7, are

  rusted in frequency and in phase on the television signal

  arriving colors. Specialists in the technical field

  considered that the so-called shift of a quarter cycle corresponding to the phase shift at 90 appearing in the subcarrier component PAL during successive television lines can be compensated by means of the signal loss compensator of the according to the present invention, by applying the control signals indicated above to the respective controlled delay lines of the forms of

  mentioned above, which will be responsible for

  loaded in successive lines in synchronism with the control signals of the particular system used from

signal transmission.

  As will emerge clearly for the special-

  lists, other similar embodiments may be used.

  to the diagrams of the detailed circuits described in the

  res 8a to 8g as well as other circuit elements in

  these forms of realization, with a view to obtaining the

  described in the method according to the present invention. Thus, the differentiator circuit 64 must be constituted in the form of a subtractor circuit to which respective signals L ', V' having the same polarity are applied, as is

  known in the art. Similarly, other

  known circuits in the summing circuit 66 can

  can be used to obtain a combination of the

  chrominance and the luminance component. Alternatively, one can use different means to obtain the delay in the delay lines 54, such as shift registers instead of direct access memories. In a similar way to perform the division by three of the samples in the filter circuit 60, dead memories can be used in place of the described circuit elements implementing the approximation algorithm. The individual circuit elements of all the embodiments described above of the invention may be realized by conventional standard built-in devices. Although the invention has been shown and described

  with particular reference to forms of reali-

  tion and preferred embodiments of the invention, it will be understood that any changes and modifications in form and detail may be made without departing from the

of the present invention.

Claims (5)

  1. Method for compensating for signal failures in   color television signals, according to which an interval   the lack of signal appearing during an input color television signal is replaced by a signal of   compensation for lack of signal from a corresponding interval   previous appearance of the television signal   their input with luminance components (L, C)   this and chrominance, defining horizontal lines   consecutive color television information,   characterized by storing intervals of each horizontal line of the input color television signal without missing a signal, storing intervals of an immediately following horizontal line of the input color television signal in the absence of a signal instead of corresponding stored intervals of each line   horizontal position, to keep memory   corresponding lines of each horizontal line instead   intervals of the horizontal line immediately following   te of the input color television signal when signal failures appear in said immediately following horizontal line, separating the luminance and chrominance components (L, C) of the stored color television signal, setting the storage time of the component   chrominance (C) memory of successive line intervals   between a first duration greater than and a second   less than an interval corresponding to a horizontal line so as to synchronize in phase the component   stored chrominance (C), with the corresponding component   dante included in the input color television signal,   to set the storage duration of the light component   nance (L) stored successive horizontal line intervals between a third time greater than and a fourth time less than an interval corresponding to a horizontal line to reduce the phase difference   between the stored luminance component (L) and the component   corresponding chromaticity and luminance components (C, L) adjusted to form the signallessness compensation signal, and to insert the loss compensation signal signal instead of the input color television signal when a lack of signal appears in said input color television signal. -2. Method according to claim 1, characterized   in that said color television signal from   is a digital signal obtained by sampling the analogue form of the color television signal with a   sampling signal having a frequency equal to a multiple   tier, at least triple, of the frequency of subcarrier colors   unmodulated color television signal, that the first   duration and the second duration are respectively   greater than and equal to said interval corresponding to a horizontal line, of a first quantity less than one cycle of the unmodulated color subcarrier frequency,   and that the third duration and the fourth duration are   above and below the corresponding interval   horizontal line, of a second lower value   re to a cycle of unmodulated color subcarrier frequency. 3. Method according to claim 1, characterized in that the color television signal is sampled   at a frequency equal to three times the frequency of   unmodulated color carrier, that the intervals of a   first horizontal line and subsequent horizontal lines   two in two of the conventional television signal.   their input are stored during a first interval   time corresponding to a horizontal line plus one half   sampling signal cycle before the separation of the chrominance and luminance components (C, L), the intervals of a second horizontal line and the horizontal lines taken from the half of the television signal   input colors are memorized during a second inter-   valle corresponding to a horizontal line minus two cycles   and a half of the sampling signal before separation.   chrominance and luminance components (C, L), that the separate chrominance component (C) of each horizontal line is stored during a third time interval equal to one cycle of the sampling signal, which has the effect of that the memories of the chrominance components (C) of consecutive horizontal lines are set respectively before said first and second durations, and that the separate luminance component (L) of said second line and   horizontal lines taken from two to two is memorized   a fourth time interval equal to two cycles of the sampling signal, whereby the storage of the luminance components (L) of successive horizontal lines   are respectively set at said third and fourth durations.   4. Method according to claim 1, characterized in that the color television signal is sampled   at a frequency equal to three times the frequency of the sub-   unmodulated color carrier, only the television signal   input colors is first separated into   chrominance and luminance (C, L), that the chrominance separate component (C) of a first horizontal line and subsequent horizontal lines taken from two to two   stored during a first period of time cor-   corresponding to a horizontal line plus one and a half cycles of the sampling signal, that the separate component of   chrominance (C) of a second horizontal line and   Later horizontal lines taken from two to two are   during a second time interval corresponding to a horizontal line minus one and a half cycles of the sampling signal, which has the effect that the memorizations of the chrominance components (C) of consecutive horizontal lines are respectively set by said first and second   durations, that the separate luminance component (L) of the first   first horizontal line interval and   two horizontal lines are   during a third time interval plus one half cycle of the sampling signal, and that the separate luminance component (L) of the second interval of horizontal lines 35 and subsequent intervals taken from two of two horizontal lines are stored during a fourth time interval corresponding to an interval of one   horizontal line less than half a cycle of the sample signal   the effect of which is that the memorisations of the   of luminance of consecutive horizontal lines are   by the said third and third durations respectively.   5. Signal Loss Compensator for Signals   color television sets incorporating luminance   and chrominance (L, C) defining consecutive horizontal lines of the color television information and in which a signal-fail detection signal is produced when a signal-out interval occurs in the input color television signal for controlling the replacement of said signal gap by a corresponding interval previously appeared in the color television signal, characterized in that it comprises memory devices (44, 8, 9 16,   17; 94, 54, 67, 68) having an input intended to receive   see the color television signal and having a capacity   a memory location sufficient to store at least one horizontal line of said color television signal, memory control devices (30, 43) operatively associated with memory devices for storing intervals of each received horizontal line   at the input of said memory device instead of inter-   corresponding valles of an immediately preceding horizontal line received at the input of the memory devices, a   first switching device (2, 52) for transmitting   setting the input color television signal to the input of the memory device (44, 8, 9; 16, 17; 94, 54, 67, 68) and responsive to the signal failure detection signal   in order to decouple the color television signal from   the devices for separating the luminance and chrominance components (L, C) from the stored color television signal, the devices (8) for setting the storage time of the chrominance (C) stored intervals   successive horizontal lines, the said memory duration   sation of the chrominance component (C) being adjustable between a first duration and a second duration respectively greater than and less than an interval corresponding to a horizontal line so as to synchronize in phase the chrominance component stored with the component   corresponding part of the television signal   input devices, devices (9) for adjusting the   storage time of the luminance component (L)   repeated intervals of successive horizontal lines, said duration of storage of the luminance component being adjustable between a third duration and a fourth   duration respectively greater and less than an interval   the corresponding to a horizontal line so as to reduce   the phase difference between the stored luminance component and the corresponding component contained in the input color television signal, devices (11) for combining the chrominance and luminance components (C, L) adjusted to form a composite signal for lack of a color television signal, and a second switching device (1) for   selectively connect the television signal   their input and the signal-out compensation signal to an output, which switching device responds to the signal-lack detection signal so as to transmit the signal-out compensation signal to said output and transmitting the signal of color television input to the output in the absence of signal from detection of lack of signal.   6. Loss compensator according to the rec.   5, characterized in that the television signal   input color is a digital signal obtained by   sampling of the analogue form of the television signal   color using a sampling signal   the frequency of the unmodulated subcarrier of the color television signal, the memory device (94:; switching device (52), a second memory (68) having an input connected to receive the separate chrominance component (C ') and a third memory (67) having an input connected to receive the separate luminance component (The), said   second memory (68) performing a first delay (6) less than   sampling cycle and the third memory (67) performing a second delay (26) of two cycles of the sampling signal, said first memory (67) responsive to the memory control devices for   memorize a first horizontal line and the horizontal lines   Subsequent two-way terminals of the input color television signal before sending them to the luminance and chrominance separation device (60) during a first time interval corresponding to a horizontal line plus a half cycle of the sampling signal,   and to memorize a second horizontal line and the li-   subsequent horizontal lines taken one out of two of the input color TV signal before transmitting them   the luminance and chromium separation device (60)   during a second time interval corresponding to a horizontal line minus two and a half cycles of the sampling signal, said compensator further comprising a third switching device (62) having an input connected to the output of the third memory (67). ) and whose second input is connected to receive   the separate luminance component from the   tif (60) of luminance and chrominance separation,   said third switching device (62) responsive to the memory control devices for transmitting to the combination device (66) the luminance component received from the luminance and chrominance separation device (60) during said first line horizontally and the subsequent horizontal lines taken one out of two and to transmit to the combination device (66) the luminance component received from the third memory (67) during the second horizontal line and   subsequent horizontal lines taken one out of two.   7. Loss of signal compensator according to the   5, characterized in that the input color television signal is first connected to the luminance component and the luminance component separation devices (5, 7).   chrominance, and that the memory device (16, 17)   carries a first memory (16) and a second memory (17) each having a storage capacity equal to at least one horizontal line, that the first memory (16) is coupled to receive the separate chrominance component and the second memory (16) is memory (17) is coupled to receive said separate luminance component, the first memory (16) responsive to the memory control devices (CB) for providing said first and   second storage times for the chromium component   nance (C) while the second memory device (17) responds to the memory control devices (HS) for   deliver the third and fourth storage times.