FR2637757A1 - METHOD AND DEVICE FOR RECALIBRATING CHROMINANCE SALVES OF A COLOR TELEVISION VIDEO SIGNAL - Google Patents

Abstract

This method consists in sampling the video signal, in storing the samples in two memory planes operating in parallel, one for writing, the other for reading and exchanging their roles at the end of a time interval corresponding to the duration of a video line, and in reconstituting the signal over a period of transient time straddling the theoretical start of the chrominance bursts, for the part preceding said theoretical start by replaying immediately preceding samples and for the part following said Theoretical start by re-reading one or more groups of samples chosen from the chrominance burst at the end of a sequence of samples connecting in phase with that following the transient time period. The figure illustrates a memory plane with its random access memory 301 and its prepositionable address counter 305 equipped with a prepositioning loop containing a ROM 306 for starting decoding of address jumps, a ROM 307 for decoding. conditions authorizing address jumps and a read only memory 308 for decoding the destination addresses of the address jumps.

Description

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  : eung; c sep uo; oelnpomgp ep aunse; od-cnoc eun c.nodeo? a SeT suip as; Tuoaqouc unod eul: Tl p qnqep enbeqo l, a?; Tl: fn I ;; SOuBU: = OJao Op 0L eATe eoqeo -eoueu'moaqo and oP Teul :; THEREFORE, we have been able to make the most of our experience in the past. IT O. AB 'TeuSTMOOA Ep and.e' Ip and Tsp: osnuT; s TeuST; a su3TT sp uoT; sa-ddn; op as; Tld np me.np iT -, uepusd 'sug; T uo; qou <s Sp uoT; TndmT anbeqo Op.aTe.; aa.T Y; ezaodmoo Tnb aT; odmoo opapT * TeuT; a 'ss9WET; aT seasemcuiq anod uss; TTn.; YDS no' IV, ansenoo uOT; 9, TeZ Sp eemX.s. The following are examples of how to select a non-delayed version of the composite video signal at the onset of each time. synchronization pulse line and switch at the end of the chrominance burst, before the start of the useful video part, on a version having the desired delay and it results from these manipulations an extension of the burst of

  chrominance of the delay time with a phase jump at the switching

  responsible for the fringes moving on the left edge

from the screen to the rhythm of the coding.

  The present invention aims to eliminate these disadvantages by restoring both the position of chrominance bursts with respect to the beginning of the line synchronization pulse and

their spectral purity.

  It relates to a method for recalibrating chrominance bursts of a color television video signal comprising: - sampling the video signal; - storing the video signal samples in two random addressing memory planes operating in parallel with each other; to writing the other to reading, their roles exchanging after a time interval corresponding to the duration of a line and - to read the samples in each memory plane according to their chronological order of registration with the exception of those appearing over a transient period of time straddling the theoretical beginning of the chrominance burst which are replaced, for the part preceding the theoretical beginning of the chrominance burst, by a replay of immediately earlier samples and , for the part following the theoretical beginning of the chrominance burst, by a replay of one or more groups of samples following each other in chronological order registration logic, groups which are selected in the burst, after the transient period of time, on the end of a sequence of samples covering the integer number of periods of the sinuoldal signal of the burst and connecting in phase with the beginning of the sequence of salvage samples succeeding the

transition period.

  It also relates to a method of the aforementioned kind used zd e e. jom u aTomem ajze'maad el op ceauuo p 8p e.anoT op TuUuT: Sú * t aud SToJ VT es aacsepu ZuBIO g Uipuip elneu sap xzuzcu; ojnv suoT:,; puoo sap a9e2pooep el, ueanmscu a.zom Oz; omm eme : xnap eun NaecaUpup anqedmoo eT ad eeuss.pu luameaoe.Tp, ueqe the euaseaapup anue caap elmdpp sep a9epoop al 4utancou eqjou eaziom eaemad aun ose.o9 $ a ep seq sap aud ageuuoT ': oueqopap eouapuo UT ans os Zueml TpnpTaTpuT seTuoqouz. ao, uos aozou op xnmeu9Tu ca, uop cezaom ca; omgm uToaq luemern "9equeve siaodmoo aiTomESE ap uurd enbuqo ap aensapuip anadmoo np ouameuuoT:, coda-d ap * Tonoq el az: o; usum.zc sdme; op apoad o qo e8 cznTzqsod, e sarl,; aque suoTi: ueqofp senz.oUe'i eeiuTmoJqo eeop oo eeop efu: .ooaq4 5z qnqpp el -ne TeAtio g aTts: u'.z udmeo ep apo; zad 't suIp teuuTc aT an2mTjuooeaz anod aion, aoapapapo. aodu and e a.ueaptp senes sap e .. ot 1t e., oa; ej "p, u.Za, .uwad Tn'.ueamuuoT, ': cod% .zd op aTonoq aunp, adTnba 4o e. sanb !: amnu cuol -'tuqoe cal anb; 2oTuu au * o unoe, ueame.zJ OTojos Up Wno.ZTD a l9 OppT. to: TT eunlp eanp and V 4uepuodbaLoo admea op a'TT'a.ou: unp rnoq ne 4uSu.2 oae 89T0lJ úJnOT 'aejnaào? & T ye * aaneaT UJnflOU 5L IT 8 uniT * Us uuuuoç; oỏj; 4 s1a u &, p ;; noa; o OT p p pp pp pp,,,,,,, U U U U U U U U U U U U U U U U U U U U U U U U U,,,,,,,,,,,,,,,,,, uu.ansre aa; zu qçno * p;. o, ueoodmoo seo, oazd sapoo.d sap s.zanoo us MTBE op J'z,; codu; pa; uamauePS suJaouoo 'TTa OL Às2upooep elT No. e3upoo aT aznod azino saw pVsIaJ np aaMPp uT luupuodua.a-oo CuO'lUuaqoeap eAqiou unlp JAT0o -; uuuaq spolaid OITpIT UOT; % nTITUOO.J u e O u t o u t o u t o u t u t u t o u t o u t o u t o u t o u t o u t o u t o u t o u t o u t o u t o u t o u t o u t o u t o u t o u t o u t o u t o u t o o u t o u t o u t o o u t o u t o u t o o o t t o o t t o o t o o t o o o t o o o t , or, in the case of a. zeStnoTJud epoo unp aS nu '; uueoTdgp caxcj czanOTve ap spau; ea sep aid gqdA.zo uce; nb 49 a *' 1n To.zud UT eynbenr eSuoloJd socououul: oq4o Up eAT "u ul juop ae,: odmoo oe p: You are not unaware of this issue.

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  4 - synchronization signals coming from the input circuit and delivering a control signal for prepositioning the address counter, and a third read-only memory decoding the destination addresses of the hops, being addressed in the same way as the second ROM and delivering prepositioning addresses

to the address counter.

  Other features and advantages of the invention disclosed

  of the following description of a given mode of implementation

  as an example. This description will be made next to the drawing

  in which: FIG. 1 represents the block diagram of a digital coding circuit adapted to the implementation of the recalibration method according to the invention and to the encryption of a color television video signal; FIG. Synoptic diagram of a decoding circuit which is adapted to the coding circuit of Figure 1 and also implements the recalibration method according to the invention, - Figure 3 details the constitution of memory planes used in the coding circuits and decoding of Figures 1 and 2,

  Figures 4, 5 and 6 are flowcharts detailing the function of

  the memory plans shown in Figure 3,

  and Figures 7, 8, 9, 10, 11 and 12 are illustrative flow diagrams.

  the transformations undergone by the lines of the video signal in application of the recalibration process and possibly

coding and decoding.

  The implementation of the method according to the invention will be described in the context of an encrypted transmission system of a 625 lines color television video signal employing scrambling consisting of shifts of the useful part of each line with respect to the synchronization pulse line, a value of 0, R or 2R depending on a pseudo-random coding whose keys are known on transmission as on reception Figure 1 illustrates the block diagram of a circuit of digital coding making it possible to obtain the scrambled composite video signal used during transmission There are: u; mazna * :, 9dn; a.mT; úo0., uamaAnooel: .u tSq-aeud e.zo * l; j aI 00oo '05Ze aTomem p; ueTd xnap Sap a. mOJn, e UT no uo;: d; $ ouuT i e.puUmmoo ep lnOJ'To unip qa 901. OAIB Op ans'noo ap uooap ep o, 3no.z; o un1p 'i Ou2Tl ap qnq9p ap T112TU one, nb; cu; w au Aouanb.; UT an1.aPlUeo 0euuo''l:, uuqop aouenbpa; j UT quuccuuno; 0oSL Osiqd Op s "eMiTnoc.sZO sp eionoq y DE

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  that is, a number of people in the same age;

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  At 6 MHz the frequency band occupied by the input video signal and prevents the energy in the frequency band above 6 MHz being superimposed on it by the phenomenon of aliasing of the spectrum

  frequency occurring during subsequent sampling.

  The feedback circuit of the DC component operates, in known manner, by realignment on the black suppression stage immediately following the line synchronization pulse, thanks to a clamp pulse centered on this bearing which is supplied.

  by the synchronization extraction circuit 104.

  The synchronization extraction circuit 104 carries out the separation of the video modulation and the synchronization signals, sorts the SyL line synchronization pulses, SyT pair frame, SyM odd frame and produces the clamp pulses as in any television receiver. Its structure will not be detailed

  because it is conventional and does not form part of the invention.

  The phase locked loop oscillator 105 comprises a voltage controlled crystal oscillator 110 provided with a phase locked loop formed of a low pass filter 111, a phase comparator 112 driving through of the low-pass filter 111 the phase and frequency control input of the oscillator 110, two frequency dividers 113, 114 placed successively between the output of the oscillator 110 and one of the inputs of the comparator of phase 112 and a third divider 115 connecting

  the other input of the phase comparator 112 to the synchronization output

  line of the synchronization extraction circuit 104.

  The voltage-controlled oscillator 110 synchronized with the synchronization signal SyL line of the extraction circuit of

  synchronization 104 delivers to the analog converter-

  digital 101 and memory planes 250, 300, a point H clock signal at the sampling frequency of 17.734 MHz greater than twice the highest frequency of the video signal (6MHz), and

  equal to the 1135th harmonic of the line frequency (15625 Hz).

  The frequency divider 113 divides the frequency of the oscilla-

  110 through 1135 to bring it back to the SyL synchronization signal. The two frequency dividers 114 -7- and 115 are divisors by two making it possible to attack the comparator 112 with symmetrical rectangular signals. The signal delivered by the divider by 1135 is a very stable signal, at the frequency

  line, devoid of the jitter that can affect the synchronization signal.

  However, it can not be used as such in place of the latter since it has a residual phase shift imposed by the phase comparator with respect thereto when the Phase lock loop is at its point of balance. This residual phase shift is corrected by a digital recalibration circuit 116 consisting of a pre-settable counter divisible by 1135, which is repositioned by the rising edges of the output signal of the frequency divider 113 and whose overflow impulses constitute a signal of beginning of line PL synchronous with the average position of the rising edges of the pulses

  the SyL line synchronization signal.

  The burst color extraction circuit 106 comprises a passband filter 120 which is connected at the output of the clamp circuit 102 and centered on the 4.406 MHz frequency of the subcarrier of the red color component of the SECAM system available in the state. unmodulated during the chrominance burst corresponding to this

  component. This bandpass filter 120 is followed by two samples.

  The first sampler 121 is triggered by the clamp pulse occurring during the black suppression step within the chrominance burst and outputs a binary value indicating whether the bandpass filter 120 isolated or

  no the frequency of the subcarrier of the red color component.

  The second sample-and-hold device 122 is triggered by the line start signal PL and stores, over the duration of one line of the video signal, the value delivered by the first sample-and-hold device 121 which constitutes a binary signal Dr representative of the structure of

  the color component of the line of the video signal being

  by reading one of the memory planes 250, 300.

  The code generator 200 will not be detailed because it is not part of the invention. It essentially comprises a manxaldTnm op tiet friendJuoa to the Tnb 00 # a; aou op,; noiTo el ade SE oZZ eaeau) apoo ap anSea9u92 a and goeTdmoa that Tnb apoo op Jneluiup9S have dememettaTuesse eajj ;; p ue TI -amd a, p cefgoejju aeouai; ag cemam cSl aid faidai aq q uo Tnb eSapoo op $ Tnoi7o np S4uemSU9 xneaqmou op puasda agepoopp ep 1noi $ o el -ea; $ opp op jue $ A uo, enb enblamnu.epoo op qnoa; o ne qdep enb , uh, uh, uh, u, u, u, u, u, u, u, u, u, u, u, u, u, u, u,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, * p qnqPp ap TM2 ;; e aird.ouuo; o oSEu erqe; cq eTno; eq eunp * Fzos UT eV? qoeuuoo LSE anSe uF unp caujoq mu e ;; ad ceazTe SZ -uaemrdmoo M & A sanouel eanxFJ; oop eiapio cap 'zD' LD eaepoo op; aeieu; q suo $; = ao; u ;; and w za sxrue op aneTnoo op teu; c and "a * uS3, T ep nq op pluS st 'H od eolaoqp souenba ^; eaqno 'iuoa; obea ú ean2; he 4aemeA,; 4vTa uSmSan.; 9, tn sglT; ei; pp quozes Tnb sonbSTIup; S csanqonJw oP oou -S oSz e.aompm op mUid cml OZ úOlt anse! lodaqu,; cuq-ACCED OAJ; J o ZOH onb; 2oTue-enbTaamnu enm; aeuoo a 'oo00Z * p po ananieaueS np.t; aug sun e.aznÉ & T e Oor' OSZ * JtOmm Op grinds cap a.nlosT;.. aos it '91.OunT uboSuuuoo 9OTTTud vSqJiue xm p, y 9qTo9ad Loh anSxTldT $ TNM aT eaodmoo OO # * # 9Toc op Tnoi $ o el SL ZZ9 Olu OeMi4 uoTcsaiddn ap; op to OT OT ja.adea ap S uP z 4amiad Tnt Ks'; S amia. 14S su2; T uo; ZBcTuoa4ouu; ap xnEu2cc; aT uoPu; uoJuUS p Uo; IOBiqxep ITnoJTp np IToea, tI * a92pOOT aSmacTaSdns opquqslmaesd OLZ TIUTOpm Oa SAie SS21a99a m aunp uoT95 el U aOO OLOCO ap ndnoa $ o np.Ta $ d Zu * cB; J LOt anxasTdTdTnm unp ueúom ni 00ú OSZ OJTamOm * p 8uutd cap ncsT 09PTA Tîu2; c np zg qs oLú mma op uo; ccsaddns * p 8suBTT cOT sUBp eBiPoo np calo op uoTTonpoJa, uT $ l - 'c.a $ oIT, opnacd; qsouu; q caouenbac ep aneS4iauu $ np xmeTqU $ s; uamaS2I4o; aT qusans ;; znocsaooidoaoçmz y SJITTTxnf; TnozTo a ao ao ao opo op opto ao oo tt oo t op tio nt oo eo ao eovo oo 'o oo oo oo nt ooN ooNuTuNiNg ZD' LD.sa; uFuq suo $ - umJoJuT xn p '00ou & 09Z aT; omm ap muTd cap uo $ IoulnSap ie * a $ os uS eA9T9ad uo juop 9aJTO'GTv-opnesd aSTeuTq * ouanbac * p mneqvaupS -9

become useless.

  The inverse code generator 220 delivers, to the memory planes 250 ', 300', decoding bit information C'1, C'2 representing the difference with respect to 2R of the value 0, R, 2R of the coding delay, which difference it is necessary to add to the delay affecting the useful part of the video line being read in the memory planes 2501, 300 'so that the useful parts of all the video lines have the same value delay 2E and recompose a plaintext image . It will not be more detailed than the reverse code generator 200 because it does not form part of the invention. he

  essentially comprises a generator of pseudo-binary sequences

  of the same type as that of the code generator 200, on which the information C1, C2 is taken which is transformed into

  information C'1, C'2 for example by simple inversion if the informa-

  C1, C2 code the value of the delay in natural binary, and a microprocessor auxiliary circuit ensuring the initial loads of the pseudo-random bit sequence generator using local information received via a keyboard 230, and coding keys inscribed in the frame deletion lines 310 and 622 which it isolates in the analog video signal arriving from the input circuit 100 'by means of SyL and SyT frame synchronization signals, SyM delivered

  by this same input circuit 100 '.

  The memory planes 250, 300, 250 'and 300' comprise a fast memory capable of storing the 1135 digital samples of a video line supplied to it at a frequency of 17.735 MHz by the analog-digital converter of the input circuit and an addressing circuit allowing a reading in an order different from that of writing by possible address jumps

repeated.

  Figure 3 details the structure of one of these memory planes. It distinguishes a fast memory 301 input and output separated by eight parallel bits, interposed between two banks of synchronous registers 302, 303 clocked by the signal

  H point clock and a unidirectional amplifier circuit board.

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- OL -

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  of the synchronization register bank 309.

  The pulse of the line start signal PL addresses in the second read-only memory 307 a registered data field of prepositioning commands of the address counter 305 and in the third read-only memory 308 a data field of zero value so that the address counter 305 is reset at each start

video line.

  The registration control signal W or its complement W for the dual memory array, when they are in the high state, put the memory 301 in writing and the bank of bus amplification circuits 304 in the state high impedance output while addressing in the second read-only memory 307 a data field devoid of prepositioning order so that the address counter 305 is incremented regularly without performing address jumps at

  this memory write operations 301.

  In the low state, the inscription control signal W or its complement W for the dual memory array, 301 memory closes and bus amplifier circuit bank 304 in the state of low impedance output. In addition, they address in the second and third read-only memories 307, 308 data fields registered with prepositioning commands and jump destination addresses making it possible to implement the flowcharts of FIGS. 4 and 5 in the case of a SECAM system and that of Figure 6 in the case of a PAL system, these flow charts allowing, as will be seen below, to reconstruct the beginning of the chrominance burst without showing phase discontinuity with the rest of the salvo and also, in the SECAM system, to take advantage of this reconstruction to introduce in the video line the necessary delay

coding or decoding.

  The reconstruction of the beginning of chrominance burst is done

  neglecting the digital samples of the video line appear-

  over a period of transient time straddling the theoretical beginning of the chrominance burst and replacing them for the part preceding the theoretical beginning of the chrominance burst by immediately read earlier samples through

- 12 -

  to address jumps backwards, and for the next part the

  theoretical beginning of the chrominance burst, by a group of samples

  following in chronological order, selected in the chrominance burst after the transient period, at the end of a sequence of samples of the sinusoidal signal of the burst connecting in phase with the beginning of the sequence of samples the sinusoidal signal of the burst appearing after the transitional period, the choice of the group of samples being made by

  forward addressing jumps and connection at the end of the transitional period

  by a back address jump.

  Figure 7 illustrates the process of reconstructing the portion of the transient time period preceding the theoretical beginning of the burst. The curve at 7 represents the beginning of a video line

  SECAM or PAL system with the front edge of the synchronization pulse

  OH line used as the origin of time. The beginning of the black suppression stage appears after 4, 7 Ms and the chrominance burst after 5, 58 As. The cross line b 7 represents, with respect to the chosen time scale, the moments

  sampling of the video signal by the analog-to-digital converter

  of the input circuit, these being numbered, starting from zero, in their chronological order since the origin of the OH times, order which is the one of inscription of the digital samples in the memory 301. The line of crosses c ? represents the reading order of the samples in the memory 301, at an interval video line, that is to say 64As later. This order is the same as the order of inscription Until the beginning of the transitional period which has been fixed at the 95th sample, that is to say at the sample 94, at 30 Bos of the origin of the OH time that is to say 0, 28 is the theoretical beginning of a burst of chrominance SECAM or PAL. The 95th to 99th samples entered in the memory 301, that is to say the samples 94 to 98, theoretically appeared before the start of the chrominance burst are discarded and replaced on reading

  by two successive re-readings of samples 91, 92 and 93.

  As the order of registration of the samples in the memory 301 also corresponds to the addresses delivered by the counter 305

- 13 -

  since this is reset at the origin of the times OH it is done, on reading the memory 301, causing twice a jump from the address 93 to the address 91. Given the delay of three samples between an address loading command and the effective loading thereof in the address counter 305,

  delay imposed by the two successive stages of synchronization registers

  the signals in the prepositioning loop, this is obtained, as indicated in the flow charts of FIGS. 4, 5 and 6, by decoding the address 91 followed by a command to load the address 91 which is executed only when the counter 305 reaches the address 94, this command being repeated once by a looping of which one leaves as soon as the variable x of

hop count reaches 2.

  The reconstruction of the part of the transient period of time following the theoretical beginning of the burst requires the determination of a sequence of successive samples of the sinusoidal signal of the salvo that can be looped on itself without showing up

  phase jump from the last sample to the first. The length of this sequence of samples depends of course

  of the frequency of this sinusoidal signal.

  SECAM has 4.25 MHz chrominance bursts for the blue color component and 4.406 MHz chrominance bursts for the red color component while the PAL system has bursts of

  chrominance at the single frequency of 4.433 MHz.

  A period of one FOB frequency signal of 4.25 MHz sampling

  frequency at 17.734 MHz gives a sequence of four samples, the last of which is taken at 9.7 ns from the end of the signal period at the FOB frequency, which represents, in the case of loopback of the sequence, a phase jump of 15. To reduce this phase jump, we adopt a multiple of this sequence plus a sample, the multiple being chosen so that the residual time is very close to the sampling period and Justifies the additional sample. Since the sampling period is about 5.8 times the residual time interval of 9.7 ns,

- 14 -

  the sixth multiple is chosen, which leads to a sequence of 25 samples during 1.409, while six periods of the signal at the frequency FOB last 1.411 / As. The residual time difference of 2 ns represents, in case of loopback, a phase jump of practically negligible.

  A period of a signal at FOR frequency of 4,406 MHz samples

  The frequency at 17.734 MHz gives a sequence of four samples with a residual time difference of 1.4 ns which represents a negligible phase jump of 2.2 in the case of loopback. It is not

  therefore no need to search for a longer sequence.

  A period of a signal at the frequency of 4.433 MHz samples

  The frequency at 17.734 MHz gives a sequence of four samples with a residual time difference of 1.1 ns which represents a negligible phase jump of 1.70 in the case of rewiring. As in the previous case, it is not necessary to search for a

longer sequence.

  As the length of the sampling sequences at the base of the burst start reconstruction is fixed, it is necessary to determine

  the number of samples actually used of these sequences.

  This number depends on the length of the burst start included in the transient period and also in the case of the SECAM system whose bursts extend without interruption until the useful part of the video line, the delay O, R, 2R to be introduced. for coding or decoding. Different cases arise depending on whether one is in PAL or SECAM system and that in the SECAM system the video line is a line of blue or red color component whose

  useful part must be delayed by O, R or 2R.

  FIG. 8 illustrates the burst start reconstruction method in the case of a blue color component video line of a SECAM system in which there is no need to delay

the video part useful.

  Curve a8 represents the beginning of a video line of the SECAM system with the line synchronization pulse whose front edge OH serves as the origin of the times, the beginning of the recalibrated salvo being placed 5.58 44as further. The cross line b8 represents, by

- 15 -

  ratio to the chosen time scale, the sampling times

  chrominance burst numbered in chronological order

  The line of cross c8 represents the reading order of the samples in the memory 301 at one line.

interval video.

  In practice, it suffices to reconstitute the beginning of the burst over a duration of the order of 1.4.Os, that is to say the segment between the samples 99 and 123 inclusive. Here we proceed to a slightly larger reconstruction for the segment included

  between samples 99 and 130 inclusive.

  The next 25 samples, i.e. samples 131-155, are chosen as the reconstruction sequence. The segment to reconstitute extending over 32 samples, a single reading

  samples of the reconstruction sequence do not suffice.

  It is completed by the reading of the samples 124 to 130 which, although located in the segment to be reconstructed, are more than one microsecond distant from the theoretical beginning of the burst. The reconstruction of the segment between the samples 99 and 130 then amounts to replacing the samples 99 to 130 by the samples 124 to 155. This is obtained, as represented in the flowchart of FIG. 4, by two address jumps in FIG. reading of the memory 301: a first forward address hop enabling the transition from the chronological position 98 with respect to the beginning of the line OH to that of 124 followed by a second address jump backwards, making it possible to go from the address 155 at address 131. As shown in the flowchart of FIG. 4, the first hop is controlled as soon as the address counter reaches 93 at the output of the first loop, which corresponds chronologically to position 96 with respect to FIG. beginning of the line OH, and causes three samples later, at the chronological position 99 the loading of the counter 305 at the address 124. The second jump is commanded as soon as the address counter reaches a first time 153, c e which corresponds chronologically to position 128 relative to the beginning of line OH, and is made three samples

2637.757

- 16 -

  later for the chronological position 131 o the address counter

is repositioned to 131.

  FIG. 9 illustrates the method for reconstructing the burst start in the case of a blue color component video line of a SECAM system when it is necessary to delay the useful video portion by a delay R equal to 902 ns corresponding to a segment

of 16 samples.

  Curve a9 represents the beginning of a video line of the SECAM system with the leading edge OH of the line synchronization impulse serving as the origin of the times and the beginning of the burst of ohromance appearing 5, 58 4s later. The cross line b9 represents,

  compared to the time scale chosen, the sampling times

  chrominance burst start numbered in chronological order from the origin of the OH times, which is the addressing order of the memory 301. The cross line C9 represents the reading order of the samples in the memory 301,

to an interval video line.

  The reconstitution is of interest as above for the segment comprised between the samples 99 and 130 inclusive and is made with the aid of the following 25 samples, that is to say, samples 131

  to 155 chosen as a reconstruction sequence.

  The segment to be reconstructed begins at the position of the sample 99 and contains the 32 positions of the deleted samples plus 16 sample positions representing the delay R which must affect the useful part of the video signal. Its rear part, samples 122 to 146, is elaborated by a complete re-reading of the 25 samples of the reconstruction sequence whereas its front part, samples 99 to 121, is elaborated by a replay of the last 23

  samples of the reconstruction sequence.

  This is obtained, as represented in the flowchart of FIG. 4 by three successive address jumps in reading the

memory 301.

  The first address jump is a leap forward to move from timeline 98 to the beginning

from line OH to that of 133.

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  MT JapezOaJ eJZTUeao9u, s; TT &nb; Jol HD.S emae; c unp 5L * ne9q. ZnaTnno a-4ue; odmoo ap o0PtaA had been eunp ueo SI cuep asTI; Op znq.p np uolonauooS4 Sp ap9ooad sT 9c; NTT: sI eanmJ OL z, c uTeSe;, nmc Sp asedmoo ep x fTqDTeA AND anb cap aoc * uo * uop as pTonoq ama.'xnp a aed er.a * u: .z ama'xnop Uoti np * ADGA its eun..es; asapu * p, nm ema'c;: oz el OL L: apuTeseu e ', eo asu9ep enb; AOT JT: oSJJee.u * AOp es SL, u; eze p 0 s cae.ape1p ansqdmoo * T enb cap fqouOToPp 1ea TI 'LEL esseapel e S ;; EssapT Op aesid ep luviamied ejaZaaze us onev a qua ss; eiapup, nu; emoxnap el -Ul euuo; To, odiid $ o, e SOu ssassapep ansqdmoo ST to lumoum spaue enid p uotTTluurloc; coaI

  JTzoaSJSa lUa * ap the HO au2 $ T ap, nqp aoddj.z sd 96 uo ', sod T e.

  luamanbT9SouoOJqo puodsa.aoo Tnb eo sTonoq azi; ma.d uT EOP * tiou us Z6, uT. a0, 9oS aesaeapeip aneodmoo al snb seap aqouaToap o; has IT

- 1.L -

- 18 -

  138 to 162 inclusive, and its middle part, samples 113 to 137 inclusive, are each developed by a complete replay of the 25 samples of the reconstruction sequence while its front part, samples 99 to 112 inclusive is developed by a reading of the Last 14 samples of the reconstruction sequence. This is obtained, as shown in the flowchart of FIG. 4, by four successive address jumps in reading.

of the memory 301.

  The first address jump is a leap forward to move from the chronological position 98 relative to the beginning of line OH to that of 142. It is always triggered as soon as the address counter 305 reaches 93 at the exit of the first loop, which corresponds chronologically to the position 96 relative to the beginning of line OH and becomes effective three samples later, when the address counter 305 is prepositioned to 142. The second address jump is a backward jump allowing pass from the address 155 to the address 131. It is triggered as soon as the address counter 305 reaches 153 and becomes effective

  when it reaches 156.

  The third and fourth address jumps are repetitions of the second carried out by a second looping of which one leaves

  that the hop count x reaches 3.

  FIG. 11 illustrates the method of reconstructing the burst start of PAL system video lines or a video line of FIG.

  SECAM system with a red color component when it is not necessary

to delay the useful part.

  The all curve represents the beginning of a SECAM or PAL system video line, the end of the burst appearing in the case of the PAL system 7.85As after the rising edge OH of the line synchronization pulse, beyond the section representing * ed. The cross line bll represents, with respect to the time scale, the chrominance burst start sampling times numbered in chronological order from the origin of the OH times, order

  which is that of addressing the registration of the memory 301.

- 19 -

  The cross line cil represents the reading order in the memory 301,

  at an interval video line, burst start samples.

  With the frequency of 4.43 MHz of PAL system bursts, as with the 4.406 MHz frequency of SECAM red component bursts, the reconstruction sequence can be as

  as previously mentioned, limited to four consecutive samples.

  We choose to reconstitute the beginning segment of the salvo

  between samples 99 and 113 inclusive using

  sequence of reconstruction the following four samples,

  ie samples 114, 115, 116 and 117. The reconstruction of this segment is obtained, as represented by elaborating its rear part going from the samples 102 to 113 inclusive by a triple replay of the reconstruction sequence and by elaborating its part before formed samples 99, 100 and 101 by a replay

  of the last three samples of the reconstruction sequence.

  This is achieved as shown in the flowcharts of FIGS.

  and 6 by five successive address jumps in reading of the memory 301.

  The first address jump is a forward hop that allows you to

  to move from chronological position 98 to the beginning of -

  OH line to that of 115. It is still triggered as soon as the address counter 305 reaches 93 at the output of the first loop, which corresponds chronologically to the position 96 relative to the start of line OH and becomes effective three samples later, moment

  the address counter 305 is prepositioned at 115.

  The second address jump is a backward jump from address 117 to address 114. It is triggered as soon as the address counter reaches 115 and becomes effective three.

  samples later while the latter will reach 118.

  The third, fourth and fifth address jumps are repetitions of the second performed by a second loopback

  from which we exit as soon as the variable x of count of jumps reaches 4.

  In cases where it is necessary to delay the useful part of a video line of red color components of the SECAM system by a delay R of 16 samples or 2R of 32 samples, it is sufficient to modify the number of repetitions of the second loop and of

- 20 -

  pass it, as shown in the flowchart of Figure 5 is 3 to 7 in the case of a delay R, the loopback output being effected when the variable x jump count reaches 8, or 3 to 11 in the case of a delay 2R, the loopback output being effected when the hop count variable reaches 12. Indeed each additional repetition of the second looping allows to lengthen the chrominance burst with a duration of four

  samples without causing a disruptive phase jump.

  FIG. 12 illustrates the method of introducing a delay R of 16 samples into the useful part of a video line of the PAL system. The curve at 12 represents the beginning of a video line with the front edge OH of the line synchronization pulse serving as the origin of the times, the chrominance burst appearing 5.58 JJs later over a duration of 2, 25 As and the beginning of the useful video 10.5Ms after. The cross line b12 represents, with respect to the time scale chosen, the sampling times of the black suppression step after the end of the chrominance burst numbered in their chronological order since the origin of the OH times. which is the address addressing the memory 301. The cross line c12 represents the reading order of the memory 301,

  interval video line, samples of the incremental

  black at the end of the chrominance burst.

  The introduction of the delay R between the useful video and the line synchronization pulse is simply done by a repetition of a segment of 16 samples located on the black suppression stage at the end of the chrominance burst between the samples 159 and 174 included. This is achieved, as shown in the flowchart of FIG. 6, using a read address jump of the

  memory 301 to go from address 174 to address 159.

  It is triggered when the 305 address counter reaches 172

  and becomes effective when it reaches 175.

  The introduction of a delay 2R, double of the previous one, is done, as represented on the flowchart of FIG. 6, by repeating the jump of addresses provided for the introduction of the delay R thanks to a third looping of which one leaves as soon as the variable x of counting at the same time is used in a given form, then it is not possible to use it in the same way as it is possible to use it. 91aued ut Op úOaTeInoToTo s92euTop caP.xed eTdmexe jed 'ummmoIJj ;; p se po no sapoo uou.nOTnoo uoT; s, & pTp op oppTa xnmu2; v cap g 4uamemapp ueTq anbTTddeu, Zçzopp aSa.p read $ to Tnb eouwuTmoaqo Op aTAUS ap 4nq9p ep e82aqrTloe9 ap ppooid arq oz

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- 22 -

Claims (4)

  1 / Method for recalibrating chrominance bursts of a signal   color television video in which the video signal is sampling   and their stored samples in two random address memory planes (250, 300) operating in parallel with each other at the write and one at the reading, their roles exchanging after a corresponding time interval. the duration of a line, characterized in that the samples are read in each memory plane (250, 300), according to their chronological order of registration except for those appearing over a transitory period of time straddling the theoretical beginning of the chrominance burst, which are replaced on reading, for the part preceding the theoretical beginning of the chrominance burst, by immediately preceding samples   and for the part following the theoretical beginning of the chromium burst   one or more groups of samples following in chronological order of inscription, groups that are selected from the chrominance burst, after the transient period of time, at the end of a sequence of samples covering a integer number of periods of the sinusoidal signal of the burst and connecting in phase with the beginning of the sequence of samples   the salvo succeeding the transitional period of time.   2 / A method according to claim 1 employed in the context of the encoding or decoding of a composite video signal whose chrominance burst is continuously extended to the useful part and which is crypt by delays of fixed values moving, at the according to a particular code, the useful part of each video line with respect to the line synchronization pulse, characterized in that it furthermore consists in lengthening, during its reconstitution, said transient period of time, by a number of corresponding samples   the delay time to add for encoding or decoding.   3 / Apparatus for implementing the method according to claim 1 comprising an input circuit (100) ensuring sampling   of the video signal to be recalibrated and the development of synchronization signals.   related to the video signal to be recalibrated, two memory planes (250, - 23 -   300) randomly storing the samples delivered by the input circuit (100) and operating one at writing and the other reading, their roles exchanging after a time interval corresponding to the duration of a video line, and an output circuit (400) resuming in analog form the samples from the reading of the memory planes (250, 300), characterized in that each memory plane (250, 300) comprises a random access memory (301) with a prepositional address counter (305) clocked by the sampling rate of the input circuit (100) and equipped with a prepositioning loop enabling it to perform, on reading the random access memory (301) of the address jumps with respect to the write command to reconfigure the signal in the transient time period straddling the theoretical beginning of the chrominance burst by readings of samples previous and after this transient period of time.   4 / Apparatus according to claim 3, characterized in that said prepositioning loop of the address counter (305) comprises three dead memories (306, 307, 308) whose output signals are resynchronized individually by banks of registers (309). , 310, 311), the first read-only memory (306) decoding the starts of the address jumps and being addressed by the address counter (305), the second read-only memory (307) decoding the conditions of authorization of the address jumps, being addressed by the data read in the first read-only memory (306) and by synchronization signals coming from the input circuit (100), and delivering a pre-positioning control signal of the address counter (305), the third read-only memory (308) decoding the jump destination addresses, being addressed in the same way as the second read-only memory (307) and delivering proposal addresses to the address counter (305)