FR2467457A1 - MICROPROCESSOR CONTROLLED VIDEO DRIVE AND METHOD FOR SYNCHRONIZING THE DIGITAL CONTROL SYSTEM ON THE VIDEO SIGNAL - Google Patents

Abstract

The invention relates to a videodisc player controlled by a microprocessor, for reproducing a videodisk in which a video signal comprising a subcarrier signal is recorded, the video signal additionally containing a digital information signal encoded during a line. horizontal. According to the invention, a video signal processing means 18 detects the video signal; and means 19 incorporated in the processing means, references this signal to a predetermined level of luminance to produce a difference signal corresponding to the recorded digital information; a control means 10, responsive to the difference signal, detects the recorded digital information. The invention applies in particular to video discs. (CF DRAWING IN BOPI)

Description

The present invention relates to a means for encoding a signal

  digital video signal, as well as means for detecting the digital signal. The present invention is particularly useful in videodisc systems. A video turntable converts recorded parameters on a disc-shaped recording medium into a standard television signal for application to the antenna terminals of a television set. Before registration,

  in the preferred embodiment of the video-

  decribed here, the video signal is processed according to the

  buried subcarrier technique taught by D.H.

  Pritchard in U.S. Patent No. 3,872,498, entitled COLOR INFORMATIONATION TPRI! SLATION SYSTEMS, March 18, 1975. In the turntable, a video processing circuit detects the intermediate frequency modulated recorded video signal and separates the respective chrominance and luminance. This separation is accomplished by comb filtering as described in US Patent No. 3,996,606 entitled "Comb Filter for Video Processing" of December 7, 1976 to DH Pritchard, so that the chrominance signal is transferred to the spectrum. heterodyning frequencies to a standard color subcarrier frequency and is combined with the luminance signal.The resulting composite video signal is further translated into the frequency spectrum up to a channel frequency suitable for viewing on a single channel.

standard TV.

  In addition to video signal processing, it is

  desirable to give the videodisc

  advanced ticks, such as detection and automatic jump of blocked furrows, automatic detection of the end

  a program and display the duration of the program.

  In this case, the term "blocked groove" indicates a condition where things such as defects in the support or contaminants on the surface of the recording medium force the needle to jump backwards.

in the program material.

  Detection of blocked furrows is particularly

  This is important because these deadlocked slots delay the progress of the program unless the viewer or any mechanism advances the reading device past the blocked channel whenever such a fault is encountered. Even in systems where the reading device or sensor is a needle moving in a driven carriage and the carriage drive possibly forces the needle out of the machine.

  blocked path, interruption of the program is important.

  With a blocked groove detection, a needle jumper can be used to automatically advance the needle past the disk defect.In fact, if the system detects a blocked groove sufficiently, the needle can be quickly moved beyond the defective area without any significant interruption

for the viewer.

  At the end of the program, positive detection of the end of the program is preferable compared to a simple loss of the signal. In this way, the viewer has an immediate response from the turntable to change the videodisk. An indicator, presenting the duration of the program, is useful to the viewer, in particular for

  return to a desired point in the program.

  The above features, as well as other features, are implemented in the preferred embodiment disclosed herein by recording digital information on the video signal. In particular, a numerical number is assigned to each frame of the image (or other location index as each turn of the groove). The duration of the program is calculated by dividing the number of frames by a constant. Basically, a blocked groove is then detected by noting at least two sequential frame numbers. One can refer to the patent application filed concurrently in France entitled "Device for reducing errors of course of the needle in the groove of a videodisc and display device of the position of the program", J. Rustman

and Mr. Mindel.

  Another digital number, referred to here as the tape number, is recorded in addition to the frame number to indicate the type of material of the program. For example, the detection of the end of a program is allowed by the

  d4te-etion of the unique end-of-program band number.

  The nmeric format has spare and unassigned bits to allow further expansion to other

characteris tics.

  Upon reading the description above, one can

  note how desirable it is to develop a system for recording digital numbers in some form, on the video signal. We know, by others

  digital video systems used with the recording of

  videodiscs, that digital information pre-

  recorded may occur during one or more horizontal lines occurring during the vertical erase interval. In previously known systems, vertical and / or horizontal synchronization is used to synchronize the data subsystem

  turntable on the pre-recorded data interval

  Tree. Since a videodisc signal has time base variations during playback, some of these systems use self-ordering waveforms to sample the individual bits. As a typical example of a self-ordering waveform used in a videodisk system according to the prior art, the

  Miller coding. In a Miller format, transitions

  signal at regular intervals indicate the start of a clock period, and transitions (or lack of transitions) between clock transitions

indicate the data bits.

  These systems according to the prior art have a disadvantage because the videodisc player requires a

  special circuit for separating the current of digital bits.

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  For example, if the data is synchronous with synchronization

  vertically, then vertical synchronization is detected. Since vertical synchronization is not normally used in a videodisc, you need a separate detector. The system according to the prior art has another drawback because the flanks of the synchronization pulse are not sufficiently precise as a time reference for sampling a digital data item. The sound of the videodisc tends to look like synchronization signals. By

  Therefore, it is desirable to avoid the use of

  video synchronization signals for synchronization

  the digital subsystem on the video signal. Similarly, self-ordering waveforms require a more complex detector, and generally have a reduced data rate, compared to a non-self-ordering waveform. In the present invention, the video carrier is modulated by a digital data stream in synchronism with the color subcarrier signal during a horizontal line. The data is represented

  like a luminance level. Therefore, in order to

  kill the digital system interface on the video system,

  the video signal is sampled using the oscillator-

  color subcarrier as clock.

  The horizontal line adjacent to the line containing the data is a constant luminance level (black). Such an arrangement allows the use of a signal already available in the videodisc rotator, that is to say the output of the comb filter in relation to the chrominance (hereinafter processed video), as a data signal. The processed video signal is considered data, and is continuously sampled at the clock frequency of the color subcarrier signal. Since the comb filter subtracts a line from an adjacent line, the processed video signal is auto-referenced, eliminating a source of data errors caused by slips.

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  the DC level of the video signal.

  To synchronize the digital system with the registered domain, a start code is used. The digital system continuously samples to find the first start code. Then, the digital system stores the rest of the digital message and stops

  the sampling of data. A micro-control

  processor is used to calculate the approximate

  tif the presence of the following start code. The digital system tries to resample the data received shortly before the expected time of arrival of the data containing the next horizontal line. In this way, the digital system is resynchronized on

  the data received at each frame. At the same time, insensi-

  the digital system to signals received for a long time or no data is expected,

  the insensitivity of the system to noise.

  Accordingly, the present invention relates to a digital video recording and playback system, where the digital video interface is arranged to avoid relying on vertical or horizontal synchronization signals and where readily available signals are used. during video signal processing, to detect

  the digital information recorded.

  According to one aspect of the invention, a method

  Videodisc recording is provided for recording

  to draw a horizontal line of a modulated video signal according to the digital information adjacent to a line

  constant luminance of this video signal.

  According to another aspect of the invention, a videodisk recording method is provided, where individual bits of the digital information are recorded in synchronism with the color subcarrier of the signal.

video.

  According to another aspect of the invention, a method and a videodisk rendering device are provided, wherein the digital information signal is detected by storing a horizontal line of the video signal and subtracting the stored horizontal line from a line

adjacent video signal.

  According to another aspect of the present invention, there is provided a method and a device for videodisk playback where individual bits of the digital information are detected by sampling the signal

  digital information in synchronism with the sub-

color carrier of the video signal.

  According to another aspect of the present invention, there is provided a method and means for synchronizing the digital system to a recorded video signal, the method comprising the steps of: detecting a first digital message by continuously sampling individual bits encoded on the video signal recorded until a first digital message is received; time controlling a trigger time interval approximately equal to an interval of the gate or vidCo frame time after the start of each horizontal line containing a digital message; time monitoring a data window time slot starting before and extending after the end of the trigger time interval; and determine if a subsequent digital message is detected during the interval

of data window time.

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  The invention will be better understood, and other objects, features, details and advantages thereof

  will appear more clearly during the description

  explanatory text which will follow with reference to the accompanying schematic drawings provided solely by way of example illustrating a. Embodiment of the invention and in which: - Figure 1 is a graphical representation of ota television signal with the vertical erase interval between the even and odd tries; Fig. 2 is a graphical representation of the digital data format used in the disclosed recording method; FIG. 3 gives a block diagram of a videodisk encoder;

  FIG. 4 gives a block diagram of a turntable

  videodisc; FIG. 5 is a block diagram showing in more detail the digital data generator of the encoder of FIG. 3; FIG. 6 gives a block diagram showing more detail of the information buffer for the videodisc rotator of FIG. 4; Fig. 7 is a diagram of a means for generating an error check code from the information bits for the encoder of Fig. 5; FIG. 8 is a diagram, partly in the form of a blc, of the information buffer for the videodisc rotor of FIG. 4; - Figure 9 shows an embodiment. a TV control counter for the buffer memory of Fig. 8; Fig. 10 is a state transition diagram of the microprocessor control means of Fig. 4; and FIG. 11 is a flow chart showing a program algorithm for the control means

microprocessor of Figure 4.

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SIGNAL FORMAT

  Particular details of an NTSC type television signal, having a format in accordance with the buried subcarrier technique described in US Patent No. 3,872,498 entitled "Color information translating systems" to D. Pritchard, are shown in Figure 1. A vertical erase interval (A, 42 lines

  maximum) separates even and odd interleaved frames.

  Those skilled in television technology will easily recognize the standard vertical erase interval containing a first balancing pulse interval (B, 3 lines), a vertical synchronization interval (C, 3 lines), a second interval balancing pulses (D, 3 lines) followed by a number of horizontal line intervals at the beginning of each new frame. As can be seen in FIG. 1, the video signal information starts on line 22 'of

  the frame 1 and the line 284 'of the frame 2.

  The digital information representative of the frame number appears on the line 17t of the frame 1 and on the line 280 'of the frame 2. The digital information could

  to be inserted in other lines of the inter-

  vertical erase value. To show the details of the format of the digital signal, in FIG. 2, the time scale is dilated during the horizontal line (E)

  containing the data (line 17 'or line 280').

  The data is represented in terms of the luminance level: the 100 IRE units represent a logical "one" and the 0 IRE (white) units represent a logical "zero". The first bit of data follows the pulse

  horizontal synchronization standard 140 and the

  The frequency of the component 142 is of the order of 1.53 MHz, frequency of the buried subcarrier. Each bit of data is transmitted in synchronism with the subcarrier signal buried at 1.53 MHz. As can be seen in FIG. 2, the digital message comprises a 13-bit start or start code indicated by B (x), a 13-bit redundant error check code indicated by C (x), and 51 information bits indicated by I (x). The beginning of the next horizontal line is indicated by the next horizontal synchronization pulse 140a and the chrominance subcarrier synchronization component 142a. Thus, the individual bits of data are synchronous with the color subcarrier, and the total digital message is synchronous with the vertical sync pulse. It should be noted that the rate

  the pace of the data can be a multiple or a subset

  multiple of any subcarrier frequency. Likewise, other luminance values may be associated with logical one and zero, or more than one bit may be associated

a given luminance level.

  A start code is used in the present system to synchronize the data system on the digital message to thereby avoid the need to detect the sidewall of the horizontal or vertical synchronization. Synchronization errors of a serial digital data system result in misregistration, i.e. the received data is shifted by one or more bits from its good

  position. Previously known systems for recording

  The recording of digital data on a coded videodisc signal showed that the sides of the synchronization signals were unreliable as a time reference and produced framing errors. The codes

  starting point proved to be more reliable.

  The specific start code chosen, 1111100110101 is one of the Barker codes known in radar and sonar technology. Reference can be made to R. H. Barker's "Group Synchronization of Binary Digital Systems," published in 1953 by Academic Press, New York, New York, United States of America. Barker codes are designed so that the autocorrelation function of a signal containing a Barker code offset from itself, ie 2467457 i

  maximum when there is coincidence and minimal otherwise.

  Indeed, if we assign a value of +1 or -1 to each bit in the start code and calculate the sum of the products of the respective bits for each offset position of the start code with respect to itself. similarly, this autocorrelation function will produce a net maximum when there is a coincidence. More particularly, a barker code shifted by any odd number of locations per

  ratio to itself produces an auto-correlation of 0.

  Barker code shifted by any even number of slots

  in relation to itself produces an auto-correlation of -1.

  However, when there is coincidence, auto-correlation

  is N, where N is the number of bits in the Barker code.

  In other words, a barker code shifted by any number of locations relative to itself differs by the maximum number of bit positions. In the presence of noise, this feature reduces the likelihood of false start code detection, in comparison

  to an arbitrary departure code.

  The information bits I (x) include a frame number (F), a band number (G), and spare information bits (A) for future expansion. The frame numbers identify each frame of the video signal

  by a unique 18-bit binary number. At the beginning of the video-

  disk, the first frame of the vid6o program is the "zero" frame. Then, each frame is numbered consecutively in ascending order. The band numbers refer to the video signal recorded in a group of adjacent turns of the enspiral grooves giving a band shape. All the material in such a groove band is identified by a common tape number. As an example of the usefulness of the tape number, the video signal after the end of the video program material is recorded with a "sixty-three" tape number. Video turntable detects the sixty-three band as the end of the program

  and responds by raising the needle away from the disc.

  The error checking code C (x) is

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  11 calculated from I (x) in the videodisc recording device. For this purpose, I (x) is multiplied by a constant, H (x). The resulting product is divided by another constant g (x). After this division, the remainder J (the quotient is unused) is added to a third

  constant M (.-). The result is C (x).

  In the E-sidedodisk, the errors of the message have been dividing the whole message, including the code of departure, and the consistency (x) above. If the remainder is equal to the start code, B (x), then the miessag is considered as ... missing error. The constants H (x) and M (x) are chosen so that the remainder of the entire message is actually the code of d (patt. The constant g (x) is used in the videodisc record and in the videodrive is peeled code-generating polymer A specific g (x) value is selected, which precedes a code having particularly advantageous error detection properties for application to an odd-sized video carrier. In the system described here, the addition, multiplication and division operations indicated are performed according to special rules for

  consider the equipment available to perform them.

  The error coding will be described in more detail below

  referring to the coding and decoding material.

  Figure 3 gives a block diagram of a videodecoder. A composite video signal from the source 30 is linearly combined in the adder 36 with a digital bitstream stream to the conductor 37 from the digital data digger 38. Synchronization means 32 provides color subcarrier pulses and synchronization so that the data bits produced by the generator 38 are in synchronism with the color subcarrier appearing at the terminal 31a and so that the digital message is coded on the correct horizontal line in the vertical erase interval. The bits of information, appearing

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  at the bus bar 39, and representing the frame number

  video and the band number are produced by the

  The use of the frame number and band number information will be described with reference to the microprocessor program (FIGS. 10 and 11). The data

  digital and video signal are combined in the addi-

  Another signal processing means 40 conditions the composite video signal for the recording medium. The composite video signal is of the buried subcarrier type and is recorded using

FM modulation techniques.

  In the videodisc player of FIG. 4, the FM signal is detected using a transducer and pick-up assembly 20 and is converted in the video processing circuit 18 to a standard television signal for viewing on an ordinary television. The circuit 18 comprises a means responsive to the synchronization signal of the chrominance subcarrier for phase locking a 1.53 MHz local oscillator on the color subcarrier. The color oscillator, in addition to its usual use in demodulating the buried subcarrier wave, is also used to produce the digital clock signal that appears to the conductor 72. The video processing circuit 18 further comprises means to demodulate the video carrier and comb filter the restored video signal. The comb filter 19 subtracts two adjacent raster lines, this result appearing to the driver 70 as a processed video signal. Since the line 16 ', which is at the black level, is subtracted from the line 17', which is modulated by the digital data, the processed video signal to the driver 70 is the digital data retrieved. Naturally, the line 16 'can be at any constant level of luminance. Note that if the line 18 'subsequent to the data line 17' is a constant luminance line (also black), the subsequent output of the comb filter during the line 18 'will again be the digital data item restored, but the data will be reversed. By subtracting a line from an adjacent line of constant luminance, the rendered digital signal is self-referenced, thereby eliminating data errors due to slips in the DC level of the video signal. If it is desired to place data on consecutive lines, in comparison with the setting up of the data adjacent to lines with constant brightness, then provision must be made for referencing the video signal on a predefined luminance level. or a dc reference level, to separate the digital video current from the video signal. As can be seen in FIG. 4, the information buffer 16 is responsive to the driver-processed video signal 7o and the 1.53 Irz clock signal to the 7-2 fader to extract the digital data from the video signal. . The buffer memory 16 is co-ed by a digital bitmate signal to the driver 71 from the microprocessor 10. In a binary state, the signal to the driver 71 forces the buffer memory 16 to acquire a penny. In the other binary state, the signal to the driver 71 condits the buffer memory 16 to transfer the received data to the microprocessor 10. In particular, when the control signal to the driver 71 is at a high level, the memory Buffer 16 opens to reflect the data received on the driver 70 of the processed video signal by using the 1.53 MHz signal on the conductor 72 as a clock. After receiving a complete message, the status signal to the driver 75 gives the indication that the message is complete. To transfer the message to the memory of the microprocessor, the control signal to the driver 71 is set low. This ction closes the information buffer 16, restores the internal control circuitry and applies the results of the error code check of the message to the state conductor 75. If the status signal indicates that the message is valid (That is, if the error code check indicates the validity), the microprocessor is programmed to transfer the data in the memory 16 to the microprocessor 10. The microprocessor provides an external clock signal to the driver 73 for transferring the data from the memory 16. For each clock pulse, a data bit to the conductor 74 is extracted from the information buffer and introduced into the microprocessor 10. When all the data is transferred to the microprocessor 10 and the program is ready for another digital message, the control driver 71 is again brought back to a high state and the process is repeated.The microprocessor 10, by the buffer memory 16, controls the extraction of the line 17 '(or line 2801) out of the video signal. The first digital message is obtained by continually searching for a start code in the video signal. Then, the buffer memory 16 is closed. Then, based on the timing of the arrival of the first digital message, the buffer opens about six lines before the time when the next digital message is expected. If no valid message is found, the information buffer 16 is

  closed about six lines after this expected arrival time.-

  If a valid digital message is found, the memory 16 is closed and a new arrival time of the next digital message is calculated based on the time of arrival of the current digital message. In this way, the microprocessor opens a gate or 'data window', about twelve lines wide and centered on the expected data.The time interval between the center of a data window and the next is roughly a time interval of a video frame.The width of the data window is chosen so that in the worst case of the time conditions, the expected data is in the data window. , as will be explained below are the following: limited resolution of the digital timer, rate of slip of the timer, uncertainty of the program to determine the moment of arrival of the present data, and time differences between the even fields and The use of another microprocessor and / or timer can be made possible by adjusting the width of the data window accordingly. The search logic for the data and the cernt-rage of the data window will be described below in

referring to Figures 10 and 11.

  The microprocessor 10 is also responsive to the controls 14 on the turntable panel (charge, pause

  and exploration) to control the mechanism 12 of the rotator

  disc and enter the display 22 of the turntable according to

  a definite program, as will be described below.

  The turntable mechanism is further provided with at least one needle initiator which can be controlled by

  the microprocessor 10. A jumper is a means,

  electric, electromagnetic or otherwise, for moving lmusive Se mean reader or signal sensor to adjacent grooves or tracks on the videodisk support. The use of the jumper to suppress the corregation of blocked furrows will be described below by

  referring to the flow charts of Figures 10 and 11.

CODE DIERPEUR

  As mentioned above, the videodisk recording device uses the I (x) bits to calculate C (x). Due to the large number of potenlelate combinations (Il-) and C (x) together are 64 bits long) and the desire to determine the detection and error correction characteristics of a given code without resorting to the enumeration , error codes are processed mathematically. A general mathematical development of the theory of rings and Galois fields GF (2m), applying to error codes in general, can be found in W. Wesley Peterson's "Error Correcting Codes" published by MIT Press. , Cambridge, Massachusetts, United States of America. In this case, the error coding in the videodisc will be better understood in terms

some simple definitions.

  A digital message, including ones and zeros, can be considered to represent a polynomial

  algebraic including powers of x. The coefficients

  The respective powers of x are the individual bits of the message. For example, the 4-bit message 1011 can be represented by the polynomial P (x), where P (x) = 1.x3 + i0.x2 + l.x + 1.x0 = x3 + x + 1 By applying this starting code notation, 1111100110101 we have B (x) = x12 + x9 + x1O + x95 + x4 +1 The highest power of x is called the degree of the polynomial. In the example above, B (x) is a

polynomial of degree 12.

  Polynomials can be added, subtracted, multiplied and divided using the ordinary rules of algebra except for the expression of coefficients in terms of modulo 2. An abbreviated notation for the remainder of a polynomial after division by another polynomial is indicated by square brackets. Indeed, if

δPg = Q (x) + -

  o the rest, r (x) has a degree lower than the divisor, g (x), we have [P (x) J = r (x)

  In the video recording device

  disk, the total message recorded on the videodisk is represented by a polynomial T (x). In Figure 2 we have T (x) = B (x) x64 + C (x) x51 + I (x) (1) The term x64 shifts B (x) by 64 bits, because B (x) is the beginning of the data format. Similarly, the term x51 shifts C (x) by 51 bits to represent that C (x) is recorded before I (x). According to the device described, the recording device calculates a value for C (x) so that the total message, T (x) has a remainder equal to B (x) after being divided by g (x). Indeed, assuming that C (x) has the form C (x) = fI (x) .H (x) J + M (x), (2) then H (x) and M (x) are polynomials constants chosen so that ET (x) i = B (x) (3) We can show that the equations (1), (2) and (3), when they are solved with respect to the constant polynomials H (x) and M (x), give H (x) = l x1279M (x) = EB (x) x13 + B (x) x127j Figure 7 contains a table listing the values chosen for B (x) and g (x), as well as the derived values for H (x) and M (x). It should be noted that the table of FIG. 7 shows the higher order bits to the right, so that they are in the same order as the latching storage elements appearing in the diagram.

logic of the same figure.

  In the videodisc turntable, the digital message

  recorded is read by the electronic circuit of the

  disk. The data recorded on the videodisk is T (x).

  The data read by the turntable is R (x). If there is no error between the recording and the restitution, we have T (x) = R (x). The errors in the received message, R (x), are checked by dividing R (x) by g (x). If the remainder is equal to B (x), the start code, then the message is considered to be error-free. Moreover, if

  remainder does not equal B (x), so this indicates an error.

  The characteristics of a code produced in the above way depend on the choice of g (x), called the generator polynomial. g (x) particular chosen for the videodisk support is one of the codes produced by the calculator, demonstrated by Tadao Kasami in "IOptimum Shortened Cyclic Codes for Burst Error Correction," published in IEEE Transactions on Information Theory 1963. The chrominance synchronization carrier in a digital system is a type of error where adjacent bits in the digital message are lost Chrominance synchronization subcarrier errors are considered a likely type of transmission error in the As shown by Kasami in the above reference, a code which can correct simple chrominance synchronization subcarrier errors of 6 bits or less, can be implemented using a given generator polynomial. by g (x) = X13 + x 2 + x 1x + X10 + x7 + x6 + x5 + x4 + x2 + 1 Moreover, we can see that for g (x) given above, all the subsystem errors carrier of syn chrominance timing of 13 bits or less will be detected, and that 99.988% of all these errors more

  long as 13 bits will also be detected. The turn

  videodisk, as described here, only uses

  error detection capabilities of the chosen code.

  As a specific example of producing the error code, consider the case where the frame number is 25,000, the band number e "of 17 and the reserve bits are 0. As 25,000 in binary representation is 000 110 000 110 101 000, and that 17 in binary representation is 010 001 (the higher-order bits are on the left), the 51 information bits are 000 000 000 000 000 000 000 000 000 110 000 110 101 000 010 001. The transmission order is as follows: reserve bits first, then frame number and then band number, where the most important bit is transmitted first The error code for I (x) specific here above, calculated as the remainder of I (x) by H (x) plus M (x) is represented by 0111100100010 / The following video frame is 25.001 or 000 110 000 110 101 001 in binary representation. information, 000 000 000 000 000 000 000 000 000 110 000 110 101 001 010 001, the correct error code is 1000101101110. The mess Full numerical age for the 25.001 frame including the starting code is therefore 1111100110101 1000101101110 000 000 000

  000 000 000 000 000 000 110 000 110 101 001 010 001, in-

  The first 13 bits form the starting code, the next 13 bits form the code

  error and the 51 bits of information come last.

  In the videodisc player above, the errors are verified in the above digital message by dividing the received message by g (x). If no error is detected, the rest is 1111100110101, which is exactly the

start code.

EQUIPMENT

  Figure 5 gives a block diagram of a means for producing T (x). Under the control of the control means 50 of the 24-bit information transmitters are introduced by the data bus bar 39, and 27 bits of spare information are introduced by the data bus bar 39a into a 51-bit shift register 44. I (x), which includes these 51 bits, is then shifted into another

  52-bit shift register 52.

  At the same time, during the 51 pulses of

  offset, an encoder 45 calculates C (x) in the following manner.

  A means 46 for dividing and multiplying polynomials is responsive to the serial transmission of the 51 bits of I (x)

  to calculate the remainder of I (x) by H (x) divided by g (x).

  l: (x) is then added in parallel in the polynomial adder 48. The resulting code C (x) is introduced into the 13-bit shift register 54 and B (x), the start code, is introduced by the bus bar 49 in another shift register 47 to 13 bits. Since the start code is a constant numerical value, this introduction is preferably accomplished by fixed connections to the parallel inputs of the shift register 47, to oppose a software implementation. In positive logic notation, the corresponding parallel inputs of the register 47 are connected to the potential of the mass each time the start code has a zero, and a

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  positive potential each time the start code has a one. The control means 50 controls the total message T (x), contained in the three registers 52, 54, 47, so that it is in synchronism with the color subcarrier to the driver 31a. A video synchronization pulse applied to the conductor 33 gives the control means 50 a time reference so that the digital message is

  transmitted at the right time with respect to the video signal.

  Figure 7 gives a specific embodiment of

  than the encoder (45 in Figure 5). Flip-flops or flip-flops

  clock-controlled flops having output terminals Q0 to Q12 form a register of the remainder. The multiplication

  by H (x) and the division by g (x) are performed simultaneously

  in series. Then, the rest is maintained in the outputs Q0 to Q12 of the remainder register. Reference can be made to Chapter 7, pages 107-114 of the above mentioned Peterson reference for general processing of such circuits. To appreciate the simplicity of the circuit of Figure 7 for the multiplication and division of polynomials, it will be noted that the addition and subtraction (coefficients of similar power terms) are accomplished by an exclusive OR gate. The multiplication

  of I (x) by H (x) is accomplished by appropriate connections

  to one or more exclusive OR gates 80 to 91.

  In particular, whenever a coefficient of H (x), but not g (x), is equal to 1 (bit position 1, 3 and 8), the input I (x) is connected to an input an exclusive OR gate 80, 82 and 87, respectively. The division of I (x) by g (x) is accomplished by multiplying the output of Q12 by g (x), and subtracting the resulting product from the contents of the registers QO to Q12. In particular, whenever a coefficient of g (x), but not H (x), equals 1 (bit position 4.7 and 11), the output of Q12 is connected to an input of the gate Exclusive OR 83, 86 and 89, respectively. When H (x) and g (x) are both equal to 1 (bit position 0,2,5,6,10 and 12), the output of the exclusive OR gate 91 is connected to an exclusive OR gate entry 81, 84, 85, 88 and 90, respectively. After clock pulses, one for each bit of I (x), the contents of registers Q0 to Q12 are the remainder of I (x) .H (x)

after division by g (x).

  Note how M (x) is added to the contents of the remainder register. The addition of the coefficients is in arithmetic module 2 accomplished as the exclusive OR function. Whenever M (x) has coefficients of +1, we use the output complement U of the flip-flop C correspnd. mte; whenever M (x) has coefficients of 0, the output Q is used. Figure 6 shows a block diagram of a means for decoding the received message, R (x), and it is a mode of

  realization of the memory 16 of FIG.

  above. The command signal to the driver 71, forming an input, conditions the decoder of the receiver of FIG. 6 either to receive the data of the video signal or

  transfer the data to the microprocessor.

  At the receiving state, each bit is simultaneously

  entered into two separate registers. One of these

  very, 60, is for the data and the other, 62, is for checking the error. Register 62 is a polynomial divider. However, when acquiring new data, the divisor feedback path is inhibited, so it functions as a right shift register. The operation of the register 62 will be described subsequently in more detail with reference to FIG. 8. For the moment, the register 62 is sensitive to the means of controlling the receiver 64 to receive successive bits of R (x) or to divide bits successive of R (x) by g (x). In each case, the contents of the register 62 are available at the bus bar 78 and is applied to the detector

  66 of start code and valid data.

  The receiving operation begins with the register 62 conditioned to function as a shift register. After detection of B (x) by the detector 66, the control means 64 conditions the register 62 to function as a polynomial divider. Thus, the division of the polynomial by g (x) begins with B (x) in the divider 62. The control means of the receiver 64 is further sensitive to the detection of B (x) to trigger a period equal to the remaining bits After the triggering period, divisor 62 contains the remainder of R (x) modulo g (x), which must be B (x) if the message is valid. During the error checking process the register 60 has shifted data bits At the end of the triggering period, the register 60 stores only the last 24 bits, however, since the 24 information bits are placed at the end of the message, the register 60 contains the assigned information bits If you want to use

  the reserve information bits, additional stages

  offset register can be added.

  The interpretation of the output state signal to the driver 75 depends on the state of the control signal to the driver 71. When the driver control signal 71 conditions the receiver to acquire data (reception status), the signal of the driver state to driver 75 is defined as "received message". When the command signal to the driver 71 conditions the receiver to transfer the data (transfer status), the conductor 75 of the status signal indicates "valid data". The driver control signal 71 also restores the control means of the receiver 64 and applies the results of the verification

  the remainder at the status signal to the driver 75.

  The received information is transferred from the shift register 60 in response to external clock signals received by the microprocessor from the driver 73. After extracting the data, the control signal to the driver 71 can be brought back to its state. previous conditioning the receiver-decoder for

  continually search for another start code.

  Figure 8 shows a logic diagram, partially

  FIG. 6. The latches having output terminals Q to Q12 form a register of the remainder. The division of the polynomial by g () is accomplished by multiplying successive terms at the output of Q2 by g (x) and subtracting the product (through the exclusive OR gates 100 to 108) from the contents of the remainder register. A feedback connection of Q42 (through the gate NOION-0U 109) is made to a gate 0U e: clusif to cl-acque times aus g (x) has coefficients of 1, the excer-tionr bit 1i. Since the coefficients of g (x) 1n are 1 for. Bit positions 0.2, 4, 5, 6, 7, 10, 11, 12, an exclusive GU gate is placed at the data input of each flip-flop of the remainder register as illustrated. The NAND gate 118 detects B (x), which is h. both the start code and the valid error checking code. The receiver counter 117 of the receiver is counted in response to a start signal of the AND gate 12Ci, it has 63 clock periods and applies a stop signal used by the NAND gate 111 to stop the clock. to all other flip-flops of FIGURE 9 shows an embodiment of the receiver control controller 117 comprising 7 flip-flops at 136% The sequence of operations for data reception is as follows. In this case, the data element 71 is in the high state, the data is applied to the divider 62 by the AND gate 110. The flip-flop 119 has been

  previously established, which inhibits counter signals.

  The controller 62 then operates as a shift register, while the output of the gate NG1-ET 118 changes to the state of the B (x) dstectioi. bottom and the Q output of the basula 119 goes to the low state a clock period later. Therefore, the feedback is validated for the division of the polymome by the output of the AND gate 120 by means of the NOR gate 109 when B (x) is detected in the remainder register. After 63 clock periods, the counter 117 stops and the status signal to the driver

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  goes high, indicating "received message". The shift register 60 holds the last 24 bits of I (x). To transfer the data, the control signal to the driver 71 goes low. The inverted output of the NAND gate 118, which is low if the remainder after division is B (x), is connected to the state signal at the conductor 75. External clock pulses at the lead 73 cause successive offsets of given in the register 60 to the output data signal to the driver 74. The external clock pulses also empty the register of the remainder by introduction

of zeros.

  The above arrangement shows a register of

  remains beginner and ending with the same constant

  nothing. However, it will be understood that other arrangements are possible. For example, after detecting B (x), the remainder register can be set to a first arbitrary constant. So after division, the register

  the rest is checked for a second appropriate constant.

  The first constant, or the second constant, can be

  zero; the two constants may not be zero.

  The simplified material resulting from the error code format described here will be observed. Ending with the start code, B (x), as remaining valid, the start code detector (NAND gate 118) also serves as a valid code detector. By starting the division by the start code in the divisor, a control step is eliminated since one does not have to empty the register

rest.

  Typically, error codes are placed at the end of a message. However, by placing the error code before the information bits, the receiver controller is further simplified because it does not have to distinguish the bit information bits from the error code in that

  which relates to the data storage register 60.

  Moreover, the receiver controller, as can be seen in FIG. 8, is a simple counter 117, having a

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  starting point, a bollard and producing a

  trigger for a single time interval.

IMPLEMENTATION OF THE MICROPROCESSOR

  The digital information, including the band number and the frame number, is recorded on the video signal and is used by the turntable for

  obtain a wide variety of features. The infor-

  tape is used for the turntable

  to detect the end of the refund (sixty-six

* three). The information of the frame number in ascending order

  is used to calculate and display the

  If the program length of the program material is known, the information of the trans number can be used to calculate the remaining restitution time of the program on the light emitting diode 22 in FIG. program. For NTSC type signals, the elapsed time of the program in minutes can be obtained by calculating the frame number divided by 3,600. If desired, the duration of the remaining program can be derived from the previous calculation. This feature is useful for the viewer when he or she searches for a desired point in the program. A particularly useful feature, derived from the information of the frame number or the number of frames, and the correction of the blocked groove which will be described hereinafter with reference to the more general case, the

  error correction of course of the needle.

  The numbers or field numbers represent a real position of the needle. Thus, each time the needle enters a groove again, whether after skipping tracks or after the scanning mechanism has been operated, the actual position of the needle can be determined from the first valid number. frame that is read. Both the run / run error correction system and the program play time display means use the number or frame number data and therefore share the decoding portion of the video data system of the video disc. The particular path error correction system described hereinafter uses the number data or number of frames (needle position) to hold the needle on or ahead of its expected position assuming a predetermined relative speed needle. /disk. The display of the playback time of the program uses the data of the number or

  frame number for an indication of the restitution time

  tion, which is actually another representation of the

position of the needle.

  The microprocessor controller has several internal modes. Fig. 10 is a state transition diagram indicating the mode logic accomplished by the microprocessor program. Each of the circles represents a mode of the machine: load, spinning

  acquisition, restitution, pause, pause locked and end.

  For each mode, the needle position and display status are indicated within each respective circle. The arrows between the modes indicate the logical combination of the signals, applied by the controls (load, pause, scan) of the panel, which cause a transition from one mode to another. The charge signal indicates that the turntable is in a condition to receive a videodisc, the pause signal is derived from a corresponding switch on the control panel, and the cue signal indicates

  the operation of the exploration mechanism.

  After turning on the power, the system goes into CHARGE mode. A videodisc can be placed or loaded on the deck in this mode. After loading, the turntable enters TOURNAMENT mode for several seconds, which allows the turntable to be brought to its full speed of 450 rpm. At the end of the mode

  of TOURNAMENT, is introduced the mode of ACQUISITION.

  In the ACQUISITION mode, the digital subsystem lowers the needle and continually searches for a reading. "In ACQUISITION mode, a" good reading "is defined as a valid start code and a valid check remainder. error. After finding a "good reading", the system enters RE.STITUTUALh mode. In the RESET mode, the microprocessor sets in the memory a next expected number or p isi "the frame, the expected number of The frame is expanded or re-tuned at each frame, and for all subsequent stages the microprocessor uses the programmed number to perform two additional checks to further improve the integrity of the frame.

the data.

  The first additional check is a sector check. The video disc in the playback mode contains eight frames each turn, dividing the disc into eight sectors. As the relative physical position of the sectors is fixed, the sectors follow a recurring periodic order while the disc rotates, a meu if the needle jumps on a certain number of grooves. Although the digital information can not be read during one or more frames while the needle jumps to a new path, the microprocessor maintains the time and increments the expected number of frames in increments. When the needle settles in a new path and picks up a new% message, the new frame number is checked in comparison with the preview number. If the seeter is false, the data is considered as one. The frame number is represented by An 18-bit number The sector information can be ob- tended from the frame number by finding the remainder after dividing the frame number by 8 S. However, it should be noted that the 5 least significant bits of a binary number are in modulo eight. Therefore, the 3 least significant bits of each new frame number must be

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  equal to the 3 least significant bits of the frame number

  scheduled to pass the sector audit.

  A second verification of the integrity of the data is the verification of extent, testing the maximum extent of movement of the needle along the radius of the disc. You can not expect more than 63 furrows to be skipped when you encounter the worst conditions in any mode. The numbers or fillet numbers are represented by the 15 most significant bits of the frame number. The microprocessor subtracts the current channel number from the expected number. If the difference is greater than the acceptable range of 63 furrows, then the

  present is considered as "bad lecturen.

  All other readings are considered good readings and are used to refocus the expected number of the frame. After fifteen consecutive bad reads, the system resumes the ACQUISITION mode. The presence of an exploration signal in certain modes, as illustrated in FIG. 10, also causes a transition for the ACQUISITION mode. When switching from ACQUISITION mode to RESTITUTION mode, the microprocessor sets the count of bad readings to thirteen. This means that when changing from ACQUISITION mode to RESTITUTION mode, one of the following two frames should give a good reading or the count of bad readings will reach

  fifteen, causing a return to the ACQUISITION mode.

  If the pause button is pressed during

  RESTITUTION mode, the system enters PAUSE mode.

  In this mode, the needle is off the disk and is held at its then radial position on the disk.

  When the pause button is released, the LOCKED BREAK mode is entered and held. Pressing the pause button again releases the LOCKED PAUSE mode, causing a transition to the ACQUISITION mode. END mode is introduced from the mode

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  RESTITUTION when the sixty-six band

  three. Figure 11 shows a flowchart of the program

  executed by the microprocessor. The material of the micro-

  processor includes an interrupt line and a

  programmable timer. A commercial microprocessor

  for the present system is the Fairchild model

Semiconductor F8.

  The microprocessor uses the timer to control the window during the time when the information buffer searches for the data. This "data window" has about twelve horizontal lines wide and is centered on the expected data. When no data

  is found, the timer maintains synchronization

  internal program at a time interval of

the frame.

  The interruption of the microprocessor is applied to the state signal to the conductor 75 (FIG. 4). The

  interrupts are validated only in ACQUISI-

  TIONi, when the system continually looks for data. The program is interrupted when a digital message is received. The interrupt service routine (not shown) establishes an interrupt flag signal

  if checking the error code indicates the validity.

  Then, in RESTITUTION mode, the programmable timer is used to indicate the estimated time of

  the arrival of the next digital message.

  The switching inputs (charge, scan, and pause) are conditioned to prevent rebound of the switch from causing unwanted response of the turntable. The microprocessor program includes a logic circuit to suppress bounce or to stabilize the switching inputs. Stable switching values are stored in the memory. An account

  separation is maintained for each switching

  tor. To verify the stabilization 154, the switches are sampled and compared to the stored switching value. If the sampled state and the stored state are the same, the stabilization count for this switch is set to zero. Switch states are sampled as often as possible. Each frame (every 16 milliseconds for NTSC), all stabilization counts are incremented

  unconditionally. If the resulting account of

  If the value is greater than or equal to 2, the memorized state is reset to the new (stabilized) value. We act

  then on the new state of the switch.

  The first programmed step (FIG. 11) after application of the current is the initialization or initiation 150 of all the parameters of the program. The timer is set to trigger a video frame. Mode is established

at CHARGE.

  The next step 152 is a program to perform the state transition logic shown in Fig. 10. The stabilization counts are normally incrementally increased at this time, and examined to determine if a new switch state

is totally stabilized.

  After the mode selection logic 152, the program enters a tight loop 153 to (1) sample the switch adjustment stabilization counts to zero, if necessary, at 154 and (2) verify that the timer is closed to trigger

  in 155, and (3) check whether the flag signal of interrup-

was established in 156.

  If the interrupt flag signal is set to 156, the program transfers the data, 157a, from the information buffer and sets the timer,

  157b, to trigger a new image interval.

  When the interrupt service routine sets the interrupt flag signal, the contents of the timer are stored. The program then uses the previously stored contents of the timer to set the timer, 157b, with a corrected value predicting

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  the approximate time of the presence of the next digital message. As previously noted, even if the data represents the first good reading in ACQUISITION mode, the count of bad readings is set at 157c to thirteen. If the interrupt flag signal is not set, the program branches out because the timer is triggered to start at 155. If the machine is not in RITUTIN mode at 159, then timer O10 is set. triggering another frame interval, at 158. If the machine is in RESTITUTION mode, at 159, then a number of critical tasks 160 are performed. The data window is open, 160a (setting the control signal to the driver 71 of Figs. 1 and 8 to a logical one) about six horizontal lines before the data reached. The received data is read and verified as previously described. After receiving the data, or if no data is received, the data window 6 is closed. The timer content, which represents the current time of arrival of the digital message, is used as a correction factor to reset the timer, 160b. The timer is therefore set to center the window for the expected time of arrival of the digital message based on the current time of the arrival of the present message. The expected frame number is reset, in 16Oc, the band number is checked in search of the departure (band 0) and the end of restitution (band 3 sixty-three), 160d and the count of bad readers is increased by Increment, in 160O, for a bad one reading. For valid frame data in the program display material, time is calculated and displayed, 160f. If the valid frame data indicates that the needle has jumped backward, the needle hopper means is activated, 160th, and the ACQUISITION mode is entered. Similarly, if the count of bad readings reaches 15, the mode of ACQUISITION is directly introduced, 160h. During all the time used for the critical tasks 160, the switch stabilization check routine is periodically repeated so that the switches are checked as well.

  as often as possible. The program returns unconditionally

  by the mode selection logic 152 to the close loop 153 and expects the timer 155 or interrupt check 156 to indicate

  the arrival of the next digital message.

  The timer can be set by loading it directly with programmed instructions. However, rather than using a sequence of instructions, it is better to "set" the timer by setting a location in the memory (a mark) that corresponds to a trigger condition of the timer. The timer is then autonomous. Triggering, or closing for triggering, is detected by comparing the contents of the timer with the mark set in the memory. The next desired trigger condition is established by adding the interval of

  next desired time to the previous content of the temporisa-

  and memorizing the result in the memory. The timer is thus "set" whenever valid data is received, or if no data is received in the data window, establishing a new mark in the memory, corresponding to the condition

following trigger.

  The programmable timer in the micro-

  processor used in the arrangement described, is condi-

  program to divide the entrance cycles

  1.53 MHz clock by a factor of 200. The temporisa-

  For example, it counts once for 200 clock cycles at 1.53 MHz. A vertical frame (1/60 second for the NTSC standard) then represents about 128 timer counts. Alternatively, a timer with a multiple other than 1.53 MHz or a timer using a timing source can be used.

independent of the video signal.

  The data window is large enough to

  allow multiple sources of timing errors.

  The uncertainty of the timer due to the limited resolution of this timer is equal to one least significant bit, which corresponds to two horizontal lines. An accumulated slip error, because the 128 timer counts do not exactly represent a vertical frame, is somewhat less than a line after

  16 frames where there is no valid message.

  Note that since the 1.53 MHz color subcarrier clock is an odd multiple of half the line frequency, a timer that has a multiple 15. of the color subcarrier clock

  will have a sliding slid zero. In the particular arrangement

  Link described here, the uncertainty of the program to determine the time of arrival of the data, is of the order of 97 microseconds, or about 1, 5 lines. Finally, since the frames are interleaved by one out of two, the time of a next digital message is either 262 lines or 263 lines, depending on whether the current frame is even or odd. Although the program can keep track of odd and even fields, it is easier to simply expand the data window of an additional line. By combining the above factors, it can be seen that a data window spanning three timer counts (approximately 6 rows) both before and after the start of the expected data is appropriate to allow the worst conditions of delay.

ERROR CORRECTION FROM

ROUTE NEEDLE OR TRACK

  As mentioned previously, the frame number information can be used to detect blocked furrows. If the new frame number (after verification of the sector and the range) is less than the expected frame number, then the needle has jumped backwards and repeats the course of one or more previously restored turns, that is, to say that a blocked path has been encountered. If the new frame number is greater than the expected frame number, the needle has jumped

  forward, that is towards the center of the disc.

  In this application, skipped furrows are ignored; if the new frame number is higher (but still passes the sector and span check) then,

  the expected frame is reset to the new frame.

  In some other applications, for example when the video disc is used to record digital information on several horizontal lines, it may be necessary to detect and correct the skipped furrows as well. However, in this case, a blocked groove is corrected by operating a needle "jumper"

  until the needle is returned to the desired track.

  Possibly, the needle will be advanced beyond the

blocked groove fault.

  In a more general sense, the use of the frame number information according to the present invention provides a precise means for detecting general route errors. In any video disc system with spiral or circular tracks, with optical systems and without grooves, errors of course due to defects and contaminants are always possible. The present system provides a means for detecting and correcting such errors in a video player. For a positive path, bidirectional jumper means is provided to move the reader backwards or forwards in the program material. So, when a path error is detected, whether it is a skipped track or a blocked track, the drive is moved in such a direction

  that it corrects the error of course. Although the assertion

  If the reader or sensor can be used for purposes of error correction, a separate jumper or means of replacing the reader is preferable. Regular servoing is generally adapted to a stable course of the spiral track of the signal, and may not have the characteristic features to respond to abrupt course errors. A

  separated jumper, on the other hand, may be more

  adapted to a quick response needed to correct errors in the course. A more specific example of a jumper suitable for use with the disclosed device may be found in US Patent Application Serial No. 039 358 entitled "TP.CK SKIPPER APPAFRAJS FOR VIDEO DISC PLAER" II.

  by E. Simshauser filed on May 15, 1979.

  Several control or control algorithms are possible. The reading device can be returned directly to the correct track by producing a movement of the needle proportional to the magnitude of the detected error of course. If a jumper can be commanded in response to a series of pulses, the number of pulses is proportional to the magnitude of the error of travel. The styler is moved on a given number of tracks per pulse until the needle is returned to the desired track. For some applications (for example, restoring a piece of data memorized on the vidodisque support), it may be necessary to return the player to the point of departure and to read a second reading, rather than to bring the reader back to the track. expected. In any case, it can be seen that by using a jumper and a consistent logic of coommade a successful route can be obtained even if the video contains defects or contaminants that might otherwise cause errors.

unacceptable course.

  In the digital path error correction system, security against undetected data errors and particularly important to prevent noisy signals from unnecessarily advancing or delaying the drive. The data system according to the invention reduces the probability of an undetected error of reading at

a negligible level.

  For a rough approximation, we can estimate

  the probability that a statistical numeric entry

  raises the data system as a valid message containing a non-sequential frame number, thereby to actuate the needle jumper. The probability

  statistics of a good start code is 1 in 213.

  The statistical probability of a good error code is also 1 in 213. The statistical probability of a good frame number is calculated as follows. The frame numbers contain 18 bits. Since there are 8 sectors on the disk of the considered system, the 3 least significant bits of each frame number indicate the sector number, which must correspond to the expected sector number. The remaining 15 bits, which represent the groove number, can vary over the permissible range (63 furrows). Therefore, only 126 of the 218 frame rate numbers will pass the sector and span checks. By combining all the security features, the probability of an undetected error is 126 out of 244.

  The above estimate is based on the assumption

  of a truly statistical entry, without

  account of several factors further reducing the probability of

an undetected error.

  For example, on a video disc track, the noise of the chrominance-synchronization subcarrier where the erroneous bits are adjacent to each other is more likely than other types of noises. As previously noted, the particular error code chosen detects all chrominance subcarrier synchronization component errors up to 13 bits, and also a high percentage of all subcarrier synchronization components. of

  longer chrominance. Likewise, as we have

  As explained above, choosing a non-zero remainder for the error checking code further reduces the probability of an undetected error. In addition, the particular departure code chosen, a Barker code, reduces the probability that a noise may cause the detection of a false start code. The revealed data system, applied to the videodisc system, results in a relatively low undetected error rate and the false alarms, otherwise causing unnecessary needle movement, are considerably reduced. The data security obtained by the revealed system improves the stability of many functions of the turntable, such as the display of the program playback time, which depend on the digital data recorded for a given time.

good ov6ration.

  Of course, the invention is not limited to the embodiment described and shown which has been given by way of example. In particular, it includes all the means constituting technical equivalents of the means described and their combinations if they are executed according to its spirit and implemented in

  the framework of protection as claimed.

Claims (8)

R E V E N D I C A T I 0 N S   1. A microprocessor-controlled video-disc player for reproducing a videodisk in which a video signal comprising a subcarrier signal is recorded, said video signal also containing a digital information signal encoded during a horizontal line, characterized by: a means video signal processing (18) for detecting said video signal; means (19) incorporated in said video signal processing means, referencing said video signal to a predetermined level of luminance to produce   a difference signal corresponding to the information signal   registered digital and control means (10) responsive to said difference signal, for detecting said information signal recorded digital.   - 2.- Turn-vifodisqoe se2ola claim 1 of the type o the digital information signal iscodé in a horizontal line adjacent to a line of luminance * 20 constant, characterized in that the generating means of   said difference signals comprises memory means   providing a horizontal line of said video signal in delay memory means; and means subtracting, from a horizontal line present in said video signal, said previously stored horizontal line to produce a difference signal corresponding to the signal digital information.   3.- Turntable-videodisk controlled by micro-   processor for the restitution of a videodisk o is   recorded a video signal containing a sub-signal   carrier, said video signal further comprising a digital information signal encoded during a horizontal line adjacent to a horizontal line of constant luminance, characterized by video signal processing means (18) for detecting said video signal; comb filter means (19) responsive to said detected video signal, said comb filter means having a processed video output representing the difference between the horizontal line containing the digital information signal and the horizontal luminous constant line; and r-L r: control means (10) responsive to said video signal. to detect the information signal digital saves.   4.- video-video source according to any one of   claims I or 3, characterized in that the means   aforementioned video signal processing further comprises a means responsive to the detected video signal for separating the subcarrier signal and that the control means   aforementioned means comprises a means responsive to said sub-signal   carrier for sampling said sub-video signal   processed in synchronism with the subcarrier signal.   5.- Video record player according to any one   claims 1 or 3, of the type where the signal of   The aforesaid digital recording contains a start code, characterized in that said control means further comprises synchronization means (32), with means responsive to the detected digital information for detecting the start code and a sensitive means detecting the start code to synchronize said control means with said stored digital information on said video signal.   6- video tape recorder according to claim 5, caraoterized in that the aforementioned synchronizing means is of a type for detecting a start code represented in digital form by 1111100110101.   7.- Method for synchronizing a system of   digital control on a video signal in a turntable   vid6odisque for restoring a video disc where a video signal modulated according to a data word containing a video is recorded -2467457   starting code, said data word being coded on the same horizontal line of each frame with respect to the vertical synchronization interval and said video disc having a receiving means responsive to said recorded video signal, for detecting the individual bits a word received from data, and further comprising a digital control system for controlling said videodisc, characterized by the steps of: detecting a first start code by storing a predetermined number of bits of the received data word up to said first start code is detected; storing a portion of said received data word following said detected start code; delaying a trigger time interval from the start fudit detected start code, said interval being approximately equal to a time interval   a video frame from the beginning of the horizontal line   tale o is encoded the data word; and detecting a subsequent start code after the end of the trip time interval by storing a predetermined number of bits of the received data word   until the subsequent start code is detected.   8. A method according to claim 7 for synchronizing a numerical control system on a   video signal, said digital control system   both means counter, characterized in that it further comprises the steps of delaying a time interval of a data window starting before and extending after the end of the aforementioned trigger time interval, said time interval the data window is less than said trigger time interval; determining if a subsequent start code is detected in said data window time slot; setting said counter means to a given count if said subsequent start code is detected during said data window time interval, and returning to the aforesaid step of storing a portion of the received data word; incrementally increasing said counter means if said subsequent start code is not detected during the time interval of the data window; determining whether the content of said counter means is greater than a predetermined amount and returning to the step of detecting a first start code if the contents of said counter means are greater than said predetermined amount; and delaying another trigger time interval approximately equal to a time slot of a video frame from the end of the previous trigger time interval if the content of said counter means is not greater than said predetermined quantity, and return to the detection step of a subsequent starting code.