CA1160739A - Method for recording a color video signal - Google Patents

Abstract

ABSTRACT

A method for recording a color video signal in a plurality of parallel tracks extending obliquely on a magnetic tape includes the steps of sampling the color video signal at a frequency which is at least three times the color sub-carrier frequency of the color video signal, converting the sampled color video signal into digital form, and recording respective pluralities of the digitized samples which are arranged in a predetermined sequence sequentially in the plurality of parallel tracks, the last-mentioned step being performed in a first embodiment by recording respective pluralities of contiguous digitized samples sequentially in the tracks, in which each plurality corresponds to at least one cycle of the color sub-carrier or the last-mentioned step being performed in a second embodiment by alternately separating contiguous ones of the digitized samples into first and second blocks and recording respective pluralities of successive digitized samples of the first and second blocks sequentially in the tracks, the sampling frequency in the second embodiment being equal to four times the color sub-carrier frequency. With this method, the chrominance component of the digital color video signal can be separated during reproduction so as to correct any error in the phase of the color sub-carrier. With the method according to the first embodiment a digital filter having a chrominance characteristic C = (1-Z-2)/2 can be used, and with the method according to the second embodiment, a fourth order digital filter having a chrominance characteristic C = (-1+2Z-2-Z-4)/2 can be used, where Z is a delay transfer characteristic of the respective filters.

Description

so 13 BACK~ROUND OF TM~ INVEMTION
-This invention relat:es generally to a data recording and reproducing system and, more particularly, is directed to a method and apparatus for recording and reproducing a digitized color video signàl on a magnetic tape.
Conventionally, apparatus for recording and reproducing a color video signal have been of the analog, rather than digital, type. The reason for this is that it has previously been believed tha~ the video signal, when digitized, would have an excessively high recording frequency which, in turn, would result in higher magnetic tape consumption However, due to progress in the field of high density digital recording, it has recently proved feasible to limit the tape consumption to less than or equal to the amount used by analog apparatus. Accordingly, there has been a recent turn towards development of digital video tape recorders (VTR). Digital VTRs have a very high picture quality, which enables multiple generation dubbing with virtually no picture impairment. Further, digital VTRs provide adjustment free circuits and self-diagnosis systems which enable easler maintenance and higher reliabili~y.
With digital VTRs, an analog video signal is converted into digital form by al, A/D converter. It should be appreciated that the sampling frequency and the number of quantization levels are the fund mental parameters which determine the quality of the digitized video signal. Further, 1~60739 the digitized signal is coded by an error control encoder so that errors may be corrected and concealed on playback, and further, is coded by a channel erlcoder to achieve high density digital recording. The coded, dlgiti7ed signal is then recorded on a magnetic tape by m(~ans oE a recording a~plifier.
In one digital VTR, it has been proposed to separate the digitized video signal into at least two se~arate channels prior to recording it on a magnetic tape. A magnetic head is associate~ with each channel and all of the magnetic heads are aligned to record the ~espective channels on a magnetic tape in parallel tracks extending obliquely on the tape. In order to separate the digitized video signal into, for example, two channels, an interface is provided which distributes alternate 8-bit samples of the digitized video signal into the respective channels. Generally, a plurality of such samples in each channel, for example, 96 samples, are formed into a sub-block of data and each sub-block is provided -with suitable identifyinz and address information for identifying the sub-block. A plurality of sub-blocks are then recorded in sequence in each of the two channels. During reproduction, the two magnetic heads supply the information from the two channels on the mag~etic tape to another interface which, based on the identificati~n and address information associated with each sub-block, recombines the video signal data from each sub-block to form a continuous digitized video signal.
It is desirable, ho~ever, that the digital VTR, like its analog counterpart, have a high speed search mode in which an operator can view the visual information recorded on the tape at a speed which is substantially higher than normal speed. Because of the high tape speed in the search mode, the magnetic heads do not accurately scan the ~.~6Q739 trac~s whicll have been recorded on the tape at the normal speed but rather, scan a plurality of traclcs during each scan.
Accordingly, an interchanger is rJrovlded in the reproducing section for removing the identif~ing signal from eacll sub-block of the reproduced si~,n~l, and for distributing the signal sub-block by sub-block to the channel to which it belongs. ~owever, by using such interchanger, the reference phase of the color sub-carrier may not be continuously uniform in the high speed search mode. In other words, such reference phase may be inverted between successive sub~blocks. ~lore particularly, in the recording operation, each recorded track preferably includes one field of video information, with each field being comprised of a plurality of lines and each line, in turn, being further divided into, for example, three sub-blocks of video information. ~uring the reproducing operation in the high speed search mode, each head scans a plurality of tracks so as to reproduce signals from different fields. Therefore, if, for example, sub-block signals from an odd frame and an even frame are intermi~ed, the reference phase of the color sub-carrier may differ at the connection point of such sub-block signals. In other words, it is possible that a phase inversion of the coLor sub-carrier occurs between successive sub-blocks of informaLion It is therefore desirable to detect such phase inversion oE the color sub-carrier and correct it immediately by, for e~:ample, comnarison with a reference phase.
Since the phase inversion only occurs in the chrominance portion of the video signal, it is desirable to separate the chrominance portion ~rom the luminance portion of the video si.gn~l prior to corl.~cting such phase inversion, . .

1~60739 without converting the digital si~nal to an analog signal.
It has been found, however, that ~/ith t-he a-Eorementioned distribution of successive di~,iti~ed samples alternately into two channels during the recording operation, a composite picture having proper color balance canno~ be obtained during reproduc-tion in the high speed search mode and separation of the chrominance and luminance portions of the video signal in such high speed search mode can also noc be accomplished.

~BJE~,TS A~ SI~ARY OF THE Ir~ lTIO~

Accordingly, it is ar, object of this invention to provide a method and apparatus :Eor recording a digital color video signal that avoids the above-described difficulties encountered with the prior art.
More particularly, it is an object of this invention to provide a method and apparatus for recording a digital color video signal in which the reference phase o~f the color sub-carrier thereof is continuously ~miform upon reproduction in the high speed search mode.
It is another object of this invention to provide a method and apparatus for recording a digital color video signal in ~hich the chrominclnce portion of the color video signal can be easily separa~-ed during reproduction in the high speed search mode In accordance with an aspect of this invention, a method of recording a color video signal in a plurality of parallel tracks extending oblique~v on a magnetic tape comprises the steps of sampling the color video signal at a frequency which is at least three times the color sub-carrier frequency of the color video signal, convert'ng the sampled color video : 1~60~739 signal into digitized form, and ,ecordin~, respective pluralities of the digitized samples which a~e arranged in a predetermined 5equence sequentially in the pluLality of parallel tracks.
In a first preferred embodiment of the invention, the last-mentioned ste~ includes recording respective pluralities of contip,uous ones of the di~,itized samPles sequentially in the plurality of ~arallel tracks For example, in the case where the sampling frequency is four times the color sub-carrier frequency, the contiguous ones of the digitized sam~les include at least four digitized samples so as to correspond to at least one period of the color sub-carrier. In such case, a separation or filter circuit which can be utilized in the reproducing section for separating the chrominance component of the digital color video signal has a chrominance filter characteristic C = (l-Z 2)/2, where Z is a one sample delay transfer characteristic of the filter circuit.
In another embodiment of this invention, the last-mentioned step includes alternately separatin~, contiguous ones of the digitized samples into first and second blocls, and recordin~, respective pluralities of successive digitized samples of the first and second blocks sequentially in the plurality o parallel tracks. In such case, the sampling frequency is chosen as four times the color sub-carrier frequency.
Each of the first and second blocks is divided into at least one plurality of successive digitized samples with the number of pluralities in each of the fir.,t and second blocks bein~
equal to one-half the number of channels into which the di~itized signal is divided. A SæDaration or filter circuit is utilized in the reproducing section for separating the 1~60739 chrominance portion of the video signal from the luminance portion thereo~ during ~he high speed search mode. Such filter circuit is ~referably a f~-urth order :Eilter having a chrominance filter characteristic C = ~ (-1+2%-2-7~-4), where Z is a one sample delay transfer characteri.stic of the filter circuit.
The above, and other, objects, features and advantages of this invention, will be apparent :Erom the following detailed descri,tion which is to be read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF TH~ DRA~INGS

Fig. 1 is a block diagram illustrating a recording section of a digital video tape recorder (VTR) embodying this invention;
Fig. 2 is a block diagram illustrating a reproducing section of a digital video tape recorder (VTR)-embodying this invention;
Fig. 3 is a schematic illustration of a rotary head assembly included in the di~ital VTR of Figs. 1 and 2;
Fig. 4 is a schematic view of rotary heads included in the assembly of Fi~
Fig. 5 is a schematic plan view of a section of magnetic tape showing tracks in which the signals are recorded by the recording section of Fig. L and illustrating the head trace in the high sPeed search mode;
Figs. 6, 7 and 8 are schematic diagrams to which reference will be made in explaining the digitization and code arrangement of a video signal for use in a digital VTR

1~60739 embodying this i.nvention;
Fig. 9 is a waveEorm (liagram illustratlng the phase relationship of the color su~-carrier between lines of different fields and frames;
Fig. 10 is a schematic diagram il'lustrating the structure of one block of digitized information to be recorded in a track corresponding ~o one channel, according to a first embodiment of this invention;
Fig. 11 is a block diagram of a recording circuit of a digital VTR for recording a ~igital color video signal according to the first embodiment of this invention;
Fig. 12 is a schematic: diagram illustrating the structure of one block of digitized information to be recorded in a track corresponding to one channel, with the apparatus of Fig. 11;
Fig. 13 is a schematic diagram to which reference will be made in ex~laining the digitization and code arrangement of a color video sign~l for use with the apparatus of Fig. 11;
Fig. 14 is a waveform diagram illustrating the position of the sampling points in regard to the color sub-carrier when the sampling frequency'is 4fsc;
Fig. 15 is a block diagram of a chrominance-luminance separation filter which ~an be,used in the reproducing section of a digital ~ITR, according to the first embodiment of this invention;
Figs. 16A and 16B are waveform diagrams illustrating the position of the sampling Points in regard to the color sub-carrier for two t,acks when the sampling frequency is 3fsc;
Fig. 17 is a block di.igram of a phase correction circuit that can bc used for corr~cting the phase o tlle color sub-carrier;
Figs 18A to 18F are schematic diagrams to which reference will be made in il:Lustrating the memory addresses to which the sub-blocks of one frame are assigned and the positional relationship of the sub-blocks of successive frames in regard thereto;
Fig. 19 is a schematic diagram to which reference will be made in explaining the recording of the digital color video signal according to a ,second em~odiment of this invention;
Fig. 20 is a block diagra~ of the recording section of a digital video tape recorder (VTR) for recording a digital color video signal accorcling to tlle second embodirllent of this invention;
Figs. 21-23 are schematic diagrams to which re~erence will be made in explaining the recording of a digital color video signal accor~ling to the second embodiment of this invention, with the apparatus of Fi~. 20; and Fig. 24 is a bloclc diagram of a fourth order digital filter which can be used in the reproducing section of a di~ital VTR according to the second embodiment of this invention.

DESCRIPTION OF THE PR~FF,RP~ED Er~ODIME~TS

In order to facilitate a better understanding of the present invention, there wil] I~irst be described the conditions for digital recording oi: an NTSC color video signal.
The NTSC system color video signal is desirably digitized with the following condil:ions being established:
1. Since one frame collprises 525 lines, the number of lines selected for a firs.: (third) and a second 1~6073~

(fourth) field are 262 and 263 " es~ec~ively. In the first field, a vertical synchronizing pulse and a horizontal synchronizing pulse are in phase with each other, and the field in which they are out of phase is considered the second field.

2. The number of sampled picture elements in each horizontal period (H) varies with the sampling frequency tfs) employed. ~ince the color ~ub-carrier frequency (fsc) is 455/2 times the horizontal frequency (f~), the numbers of sampled picture elements in one horizontal period are as shown in the below Table l in the case of fs = 3fsc and in the case of fs = ~fsc' Table l ~s Even line Odd line ~ _ Odd frame 682 683 sc Even frame 683 682 Odd frame 9lO 910 4fsc Even frame 9lO 910 .
In the case of fs = 3fsc, the number of sampled picture elements in the line in ~hich the horizon~al synchronizing pulse and the color sub-carrier are in phase with each other i5 taken as 652, and the number of sampled picture elements in the line in which the horizontal synchronizing pulse and the color sub-carrier are out of phase is taken as 683. The odd frame starts ~ith the line 1~6~)73~

in which the hori20ntal synchronizing pulse and color subcarrier are out of phase with each other, whereas the even frame starts with the line in which they are in phase with each other. As will be appreciated from Table 1, in the case of fs - 3fsc~ the number of sampled picture elements in adjacent lines which are in the same field but differ by one horizontal period (lH) in time from each other are different, but if data of the line of the previous field which is positioned one line below is used as an interpolation line, the number of sampled picture elements in the erroneous line and in the interpolation line become equal to each other. Further, the color sub-carriers of the respective sampled picture elements in both of such latter lines are also of the same phase. This aspect is described more fully in U.S. Patent No. 4,329,7~8 dated May 11, 1980 and having a common assignee herewith.
$he present invention will hereinafter be described as being applied to a previously proposed digital VTR made up of a recording section (Fig. 1) and a playback or reproducing section (Fig. 2), and which proposed digital VTR
will now be described in greater detail. In the digital VTR, a digital video signal is recorded by a rotary head assembly (Fig. 3) in parallel tracks extending obliquely on a magentic tape T (Fig. 5). Since the transmitting bit rate of the digital video signal is high, two rotary heads HA and HB (Fig. 4) are disposed in close proximity to each other, and the digital video signals of one field are distributed through two channels to such heads and recorded on the magnetic tape in two parallel tracks TA and TB. An audio signal may also be converted to a PCM (pulse code modulated) signal and recorded by a rotary head in a third track (not shown) extending parallel to the video tracks TA and TB.

~6~39 Referring in detai] ~o Fig. 1, i~ will be seen that an NTSC color video si~nal lo be recorded is anp]ied through an input terminal 11 to ~n input processor 12.
The input processor 12 comprises a clamp circuit and a synchronizing and burst signal separator and supplies the effective or video information portion of the color video signal to an A/D converter circuit 13. A synchronizing signal and a burst signal separated from the color video si~nal by processor 12 are applied to a master cloc~ generator 21 which is desirably of PLL (phase lockecl loop) construction. The master clock generator 21 generates clock pulses of the sampling frequency, for example, 3fsc or 4fsc. The clock pulses from generator 21 and the synchronizing signal are applied to a control signal generator 22 which produces various kinds of timing pulses, identifying' signals (ID) for identifying lines, fields, frames and tracks, and a control signal, such as, a train of samp'Ling pulses. --The A/D converter circuit 13 generally comprises a sample and hold circuit and an ~/D converter for converting each sampled output to an 8-bit code which is supPlied, in parallel form, to an interface 14. The duration or neriod of one line (lH~ of the MTSC color video signal is 63.5~s and a blankin~ period therein is ll.l~s. Accordingly, the period of the effective video region or portion is 52.4~u s.
~hen the sampling frequency is 31sc = ~ - fH, the nu of samples in one horizontal period is 682.5. Further, the number of samples in the effectiv~ video re~ion or portion is 52.4~4s/Ts = 562.7 samples, where Ts is the sampling period equal to ~.~931217~Us. In consicl~ration of the division of the video information to be re~orded into two channels, the number of effective video sa~l3)1es is selected to be 576 ~60739 per line or horizontal period wil:h 2~ s~mples being assigned to each channel. As shown in Fig. 6, two horizontal periods (1365 samples) are considered as one unit, with the total number of samples in the line in which a horizontal synchronizing pulse HD and the color suh-carrier are in phase with each other being selected to be 682 and the total number of samples in the line in which they are ou~ of phase being selected to be 683.
The number of lines forming one field is 262.5H, with a vertical synchronizing period and an equalizing pulse period accounting for 10.5H. Since test signals VIT and VIP~
are inserted in the vertical blanking period, they are also regarded as effective video signals. Finally, the number of effective video lines in one fie:ld period is selected to be 252.
The digitized effective video region of the color video signal is divided by interface 14 of t.he proposed digital VTR
into two channels. Of the 57~ samples:in eachline, data corres~onding to the odd-numbered samples are assigned to one of the channels and data corresponding to the even-numbered samples are assi~ned to the other channel. The data of the two channels are processed in the same manner. The data in one of the channels is derived as a record signal for head ~A after being applied, in sequence, to a time base compression circuit 15A, an error control encoder 16A, a recording processor 17A and a recording amplifier 18A.
The data in the other channel is also processed by the same arrangement, that is, by a time Base compression circuit 15B, an error control encoder 16B, a recording processor 17B
and a recording amplifier 18R, t~) provide a record signal for head HB. The recording amplifiers l~A and l~B are connected by way of a rotary transformer (not shown) to the rotary heads ~6t~739 HA and l~B disposed in close proxi.mity to each other.
The code arrangemenL of each of the record signals respectively provided at heads HA and H~ will now be described with reference to F'lg. 8. As there shown, a sub-block of the coded di~P,ital signal is composed oE
105 samples (8hO bits) in which a block synchronizing signal (SYNC) of three samples (24 bits), an identifying (ID) and address (AD) signal of two samples (16 bits), information data of 96 samples (768 bits) and CRC (Cyclic Redundancy Check) code of four sarnples (32 bits) are arranged one after another. The data of one line or horizontal period of the color video signal comprises 288 samples per channel, as previously mentioned, and these sarnples are divided into three sub-blocks, that is, there are three sub-blocks for each line, with 96 samples for each sub-block. The bloclc synchronizing signal is used for identifying the beginning of a sub-block, whereupon the identifying and address signals, the information data and/or CRC c.ode can be extracted. The identifying signals I~ indicate ~he channel (traclc), the frame, the field and the line to r~hich the information data of the sub-block belongs, and the address signal AD represents the address of the respective sub-bloclc. The CRC code is used for the detection of an error in the information data of the respective sub-block.
Fig. 7 shows the code arrangement for one field in one channel. In Fig. 7, each reference character SBi (i - l~v858) indicates one sub-block, with three sub-blocks making up one block or line. Since the effective video region of one field is comprised of 252 Lines, as mentioned previously, i~L60739 the data of 252 blocks (756 sub-'~locks) exist in one flelcl.
The video information data o~ a l,ar~icular Eield are sequentially arranged in a 21 x 12 matrix form. Parity data are also nrovided in connec~ion with the hori ontal and vertical directions, respectively, of the video inEorma-tion data in the matrix. More pclrticu].arly, on Fip,. 7, the parity data for the horizontll direction is shown positioned in the thirteenth col-umn of blocks, and the parity data for the vertical direction is positioned in the twenty-second row at the bottom. In the thirteenth column of blocks at the twenty-second row is disposed the horizontal parity data for the vertical parity data. The parity data for the horizontal direction is rormed in three ways by 12 sub-blocks respectively taken out of the 12 blocks forming one row of the matrix. In the first row, for example, parity data SB37 is formed by the modulo 2 addition:
[SBl] ~9 rSB4] 0 [SB7] 6~.... ~ [SB34] = [SB37]
In the above, [SBi] means only the data in the respective sub-block SBi. In this case, samples belonging to respective ones of the 12 sub-blocks are each calculated in a parallel, ~-bit form. Similarly, by the modulo 2 additions:
[SB2] ~9 [SBs] ~ [S~g] ~ [SB35] = [S~3~]

[SB3] ~ [SB6] ~ [SBg] ~ ..... ~ [SB36J = [SB39]
parity data [SB38] and [SB39] are formed. The parity data is similarly formed for each of the second to twenty-second rows in the horizontal direction. Enh~mcement of the error correcting ability results from the fact that parity data is not formed merely by the data of the 36 sub-blocks included ~6~)~3~

in a row, but is ~ormed by the data of 12 sub-bl.ocks positioned at intervals of two sub-blocks ill the row.
The parity data for the vertical direction is formed by the data of 21 sub-blo~-~ks in each of the first to twelve columns of blocks. In the first column, parity data ~SB820] is formed by the modulo 2 addition:

[S~l] ~ [SB40] ~ [SB79] ~ ....[SB7~1] = [S~32~]
In this case, samples belonging to each one of the 21 sub-blocks are calculated in a parallel 8-bit form.
Accordingly, these parity data comprise 96 samples as is also the.case with the vid~o data of each sub-block.
In the case of transmitting the digital signal of one field of the above matrix arrangement (22 x 13) as a series of first, second, third, ... twenty-second rows in sequence, since 13 bloc~.s correspond to the length o.E 12H, a period of 12 x 22 =
264H is needed for transmitting the digital signal of one field.
Incidentally, if the VTR is of the C-format type, and thus employs an auxiliary head for recording and reproducing one part of the vertical blanking period in one field, then a duration of only about 2~0H can be recorded with a video head. In accordance ~.~ith the present invention, a duration of 246H, leaving a margin of several H's, has to be recorded in each track, that is, ~he period of 264H of data to be transmitted is time-base-colllpressed (with a compression ratio Rt of 41/44) to a period a duration of 24611. Further, a pre-amble signal and a post-ambi.e signal, each having the transmitting bit frequency, are i-lserted at the beginning and the terminating end of the record signal of onè field having ~6C~739 the period of 264H.
The time base compression circuit 15 in Fig. 1 compresses the video data with the above-noted compression ratio 41/44 and provides a data blanking period in which the block synchronizing signal, the identifying and address signals and the CRC code are inserted for each sub-block of video data of 96 samples, and at the same time, sets up data blanking periods in which the blocks of the parity data are inserted. The parity data for the horizontal and vertical directions and the CRC code of each sub-block are generated by the error control encoder 16. The block synchronizing signal and the identifying and address signals are added to the video data in the recording processor 17. The address signal AD
represents the previously noted number (i) of ~he sub-block.
Further, in the recording processor 17 there are provided an encoder of the block coding type which converts the number of bits of one sample from 8 to 10, and a parallel-to-serial converter for serializing the parallel 10-bit code. The block coding is such that 28 codes where DC levels are close to zero are selected from ~10 codes of 10-bit and arranged to have one-to-one correspondence to the original 8-bit codes.
By means of the foregoing, the DC level of the record signal is made as close to zero as possible, that is, "O" and "1"
alternate with each other as much as possible. Such block coding is employed for preventing degradation of the trans-mitting waveform on the playback side by substantial DC free transmission. It is also possible to achieve the same results by employing a scramble system utilizing the so-called M-sequence which is substantially random in place of the block coding.

~60739 In the case where each sample colllprises 8 bits, the transmitting bit rate per channel is as follows:

sc) ~ x -2- x ~ = 46.097 ~lb/sec.
After converting the above 3-bit code to the lO-bit code, the recording bit rate is as folLows:
46.097 x ~ = 57.62 Mb/sec.
In the reproducing or playback operation of the digital VTR accor~ing to this in~ention, the two channels of reproduced signals are derived from the h~ads HA and ~B
which scan tracks TA and TB, resl)ectively, corresponding thereto, and are applied through playback amplifiers 31A and 31B to respective waveform shaping circuits (not shown~.
Each of the waveform shaping circuits includes a playback equalizer for increasing the high-frequency component of the reproduced signal and shapes the reproduced signal to a clear pulse signal. Further, each waveform shaping circuit extracts a reproducing bit clock synchronized with the pre-amble signal and supplies the reproducing bit clock to a respective playback processor 32A or 32~ together with the data. In each of the playback processors 32A and 32B, the serial data is converted to parallel form, the block sync~ronizing signal is extracted, the data is separated from the b]ock synchronizing signal and from the ID, AD and CRC codes or signals, and further, block decoding or lO-bit to 8-bit conversion is performed. The resulting data is applied to a r~spective time base corrector 33A or 33B in which any time bas2 error is removed from the data. Each of the time base correctors 33A or 33~ is provided ~16~)~39 with, for example, four memories, in which reproduced data are sequentially written by clock pu.lses synchronized with the reproduced data, and the data ar~. sequentially read out from the memories, by reference clocl; pu'lses. When the reading operation is likely to g~t ahead of the writing operation, the memory from whicll the data has just been read is read again.
The data of each channel is provided from the respective one of the time base correctors 33A and 33B to one of the other of error correc~-ing decoders 34A and 34B
by way of a common interchanger '~1. In an ordinary playback operation in which the rotary heads faithfully scan the recording tracks on the magnetic tape or in slow motion or still picture playback in which lhe rotary heads are controlled in position so that they faithfu''lly follow the recording tracks respectively, signals are reproduced only from the tracks TA and TB corresponding to the two rotary heads HA and HB. However, durinp, high speed Leproducing, in which the running speed of the magnetic tape is as high as several tens of times its ordinary speed, each of the rotary heads scans a plurality of recording tracks, as shown by line HSM (high speed mode) in Fig. 5. As a result, signals reproduced from the tracks TA and TB are mixed together. In such a case, the interchanger 41 identifies the correct channels of the reproduced signals, using track identifying signals, and supplies the reproduced signals ~o the error correcting decoder 34A or 34B for the respective ch~nnel.
Each error correcting decoder 34A or 34B includes error detecting and correcting ci.rcuits using CRC, horizontal l~6n~3s and vertical par.ities, a field memory and so on. Ilowever, durin~
high speed reproducing, no error detection and correction are carried out and the field memory is used instead for converting the intermittently received reproduced data of each channel into a continuous f;,rm, The data from each error correcting decoder 34A or 34B is applied to a respec-tive time base expander circuit 35A or 35R! respectively, which returns the data to the original transmi~ting rate and then applies the data to a common interface 36. The interface 36 serves to return the reproduced data of the two channels into a single channel which includes a D/A converter circuit 37 for conversion of the data into analog form. From the interface 36 there may also be provided a digital video output (not shown).
Since a digital video input and a digital video output may be provided in the recording and reproducing sections of Figs.
1 and 2, editing and dubbing can be carried out with digital signals, that is, without conversion from and/or to analog for~.
The output from the D/A converter circuit 37 is applied to an output processor 33, from which a reproduced color video signal is provided at an output terminal 39. An external reference signal may be supplied to a master clock generator (not shown), from which clock pulses and a reference synchronizing signal are provided to a control signal generator (not shown). The control signal generator provides control signals synchronized with the ex~ernal reference siP,nal, such as, various timing pulses, ident]fying signals for the line, field and frame, and sample clock pulses. In the reproducing section, the processing of the sLgnals from heads HA and HB
to the input sides of time base ~orrectors 33A and 33B is ~L~60739 timed by the clock pulse extracte(~ from the reproduced data, whereas the processing of the signals from the output sides of the time base correctors 33A and 3~B to the outpu~ terminal 39 is timed by the clocl~ pulse frcm the master cloclc generator.
As previously discussed, interchanger 41 (Fig, 2), in the reproducing section, supplies the correct signals to error correcting decoders 34A and 34~ during reproduction in the high speed search mode. In other words, interchanger 41 removes the identifying signal ID from each sub-blocl~ S~ in the rer)roduced digital signal and distributes the signal sub-block by sub-block to the correct channel to which it belongs.
However, interchanger 41 does not take into account any error in the phase of the color sub-carrier, as will now more fully be described.
In the NTSC system, as previously discussed, each frame comprises 525 lines which are divided into two fields such that the first field contains 262 lines and the secohd field contains 263 lines of data. It should be appreciated that, since the second field in each frame includes an additional line, the first line in the seconc~ field will be positioned one line above the first line in the fi.rst field. With a digital video tape recorder (VTP), an effective frame is selected and may be arranged, for example, so that the first field thereof includes video information in lin~s 12-263 and the second field includes video information in linQ~ 274-525. In this manner, each of the first and second fields of each frame includes 25 field lines of video information.
~ eferring now to Fig. 9, which illustrates the phase relationship or waveforms oi the color sub-carrier of the color video signal for scan lines of a picture in first (odd) and second (even) frames, lines in the first field of each frame are ~6073~

indicated by solid l;ines while lines in ~he second field are indicated by broken lines, with t~e pllase of the sub-carrier beihg shown superimposed thereon. In the waveform diagram of Fig. 9, the first or odd frame is comprised of a first field composed of lines Ll 1~ L~ . Ll 2~2 and is represented by solid lines. The second field in the odd frame is composed lines L2-1~ L2-2~ - L2_263, ~his latter line corresponding to line 525 in the odd frame. In like manner, the second or even frame is comprised of a first field composed of lines Ll 1 Ll 2' -- Ll 262 and the second fleld of the even frame is composed of lines L2_1, L2_2, - L2-263 Eac, lines is preferably comprised of three sub-blocks SBi to SBi+2, with lines of both frames with the same numerical suffix being comprised of identically-numbered sub-blocks. For example, each of lines L2 1 and Ll 1 in the odd frame and lines L2 1 and Ll 1 in the even frame is comprised of sub-blocks which are numbered SBl to SB3. Thus, lines in the odd and even frames ~7ith the same numerical suffixes are stored in the same addresses in a respective field memory. In other words, each of lines L2 1 and L~ 1 in the odd and even frames have the same address signal AD associated with the three sub-b].ocks SBl to SB3 of which they are co~prised.
During reproduction in the high speed search mode, reproducing heads HA and HB each helically scan both tracl~.s TA
and T~. In this manner, the reproduced digital signal fro~ head HA includes signals from both channel A and channel B and head HB
also reproduces the digital signal from both channel A and channel B. Because of such arrangement in the hiP,h speed search mode, error control decoders 34A ~nd 34B do not perform an error correction operation. Instead, the reproduced signals from heads HA and H3 are merely stored in respective addresses of a field memory in correspondence with the addresses of the reproduced sub-blocks thereof. It should further be appreciclted that, ~ 61)~3~
during reproduction in the high s~eed search mocle, each of heads HA and ~B scans at least one sub-bloclc :Eor each tracl~ scanned so that at least one address signal A~ can be used for storing the data corresponding to the reproduced sub-block in its respective address of the field mel,lory.
~ owever, during reprc,~luction in the high speed search mode, the signals of the od;l and even fields and odd and even frames are intermixed and some signals correspondlng to a particular address may not even be reproduced. Thus, for example, if the signal of line Ll 1 in the odd frame is written in the field memory at the address corres~onding to the first line of the field memory and the signal of line L2 2 of the same odd frame is next written in the field memory at the address corresponding to the second line of the field memory, the phase relationshi? therebetween remains tlle sa~e. In other words, referring to Fig. ~, it is seen that the Phase of the sub-carrier at the end of line Ll ~ of the odd frame is in proper phase relation with the phase of the sub-carrier at the beginning of line L2 2 thereo so that a uniform phase relationship exists.
In comparison, if, for example, the signal of line L2 1 of the odd frame is written in the field memory at the address corresponding to the first line of the field memory and the signal of line Ll 2 of the even frame is written in the field memory at the address of the second line thereof, the phase of the color sub-carrier is inverted when the sig,nal read from the memory changes from line L2 1 of the odd frame to line Ll 2 of the even frame. In other words the phase of the color sub-carrier at the end of line L2 l of the odd frame is out of phase with the phase of the color sub-carrier at t'ne beginning of line Ll 2 of the even frame so t:hat a uniorm phase 1~610739 ' relationship does not exist. Thus, the phase of the sub-carrier is inverted when these two lines are read continuously from the memory. It should be appreci~lted, however, that although such phase inversion has been indicated as existing between entire lines of the recorded signal, such inversion of the phase of the color sub-carrier most probably occurs between res~ective sub-blocks of each stored line. In any event, the phase of the color sub-carrier is not uniform during reproduction in the high speed search mode.
Therefore, during reproduction in the high speed search mode, any phase inversion of the color sub-carrier between successive reproduced sub-blocks rnust be detected and corrected immediately. It should be appreci~ted, however, that it is only the chrominance portion of the video signal which contains the color sub-carrier. It is therefore only necessary to correct the chrominance portion of the digital video signal, rather than the entire video signal. Accordingly, it is desirable to, ~
separate the chrominance portion of the video signal from the luminance portion thereof, to correct the phase inversion of the separated chrominance portion, and then to recombine the separated chrominance and luminance portions. Unfortunately, this cannot be accomplished in the previously-proposed system in which successive samples of the digital signal are alternately separated into two channels and recorded in two separate tracks TA and TB corresponding to such channels A and ~, respectively.
In other words, known digital filters cannot satisfactorily separate the chrominance portion from the lu~inance portion of the color video signal in the reproducing section when the digital color video signal is recorded with this Tnethod.
Accordingly, a method -md apparatus for recording 1~6~739 a digital color video signal accolding to one embodiment of this invention will now be described. Generally, with such method, the effective video region of the color video signal in each horiæontal scan line is dividecl into N bloclcs, as shown in Fig. 10, in which N is e~ al to the number of channels in which the signal is distributed and is greater than or equal to two. Thus, the signals in bloc!cs A to ~l are recorded in respective tracks TA to TN which correspond to channels A to ~l, respectively. Each block is further comprised oE ~ sub-blocks where each sub-block contains a si~al corresponding to L cycles of the color sub-carrier, L and M being positive integers. Each sub-block further includes a block synchronizing signal (SYN~), an identifying (ID) and address (An) signal and a CRC codel as previously discussed. Further, in accordance with the method of this invention, the sampling frequency fs is selected as KfSc, where K is an integer greater than or equal to three.
It should therefore be appreciated that signals corresponding to at least one cycle of the color sub-carrier are recorded in each track. For example, if fs = 4fsc~ L = 1, and ~l = 1, four contiguous samples are successively recorded in each traclc. A specific example of this method is shown in Fips. 11-13 in wl~ich ~ = 3, ~I = 2, L = 32 and ~ . The code arrangement of each of the record signals respectively provided to heads HA, HB and HC is shown in Figs, 12 an~ 13. As there sho~7n, the data of one line or horizontal period of the color video signal comprises 256 samples Per channel, which is divided into two sub-blocks for each channel with l,~ samples of data for each sub-block. Each sub-block of the ~oded digital signal may be composed of 137 samples (1096 bits) in ~Jhich a block synchronizing signal (SYNC) of three samples (24 bits), an identifying (I~) and address si~nal of two samples (16 bits), the information data of 12~ samples (1,024 bits) alld CRC code oE four sam~les (32 bits) are arranged one after ano~.her as previously discussed ~6~739 in regard to Fig. 8. Fig. 13 shows the code arrangement for one field in one channel. In Fig. 13, each reference charac-ter SBi(i = 1-~572) indicates one sub-block, with two sub-blocks making up one block or line per channel. Since the effective video region of one field is comprised of 252 lines, as mentioned previously, the data of 252 blocks (504 sub-blocks) exist in one field. The video information data of a particular field are sequentially arranged in a 21 x 12 matrix form with parity data also being provided in connection with the horizontal and vertical directions, respectively, of the video information data in the matrix, as previously discussed in regard to Fig. 8. With this lat-ter arrangement, the first block of the first line is recorded in track TA, the second block is recorded in track TB and the third block is recorded in track Tc. The first block of the next line is then recorded in track TA following the first block of the first line, the second block in track TB following the second block of the first line, the third block in track TC following the third block of the first line, as so on. It should therefore be appreciated that 256 digitized contiguous or consecutive samples are recorded successively in each block in each track. For example, the digitized samples which are recDrded in tracks TA, TB
and TC are arranged as follows:

TA Sl-S256;S769-S1,024;S1,537 TB S257 S512;S1 025---Sl 280'Sl 793 ~C S513-S768;S1,281-S1,536;S2,049--A more simplified example of the method according ~:~6073~

to this invention will now he described for explaining how the chrominance portion of the co]..r video si~,nal. can be easily separated therefrom. Thus, in the case where the digital signal is separated into o,~ly two channels A and B, a first plurality of contiguous di.gitized samples is recorded in a first track TA, a second plurality of contiguous digitized samples which is contigu~us with the first plurality is recorded in a second track TB, a third plurality of contiguous digitized samples which is contiguous with the second plurality is next recorded successively.in the first track TA, and so on, whereby each plurality of contiguous digitized samples contains signals which correspond to at least one cycle of the color sub-carrier. For exanple, in the case where the sampling frequency is equal to 4fsc, four samples correspond to one cycle of the color sub-carrier. Thus, in the case where the digital signal is separated into t~ chc~nels and L~
the first plurality of contiguous digitized samples includes samples Sl,S2,S3 and S4, wl~ich are recorded in track TA. The next successive or sequential plurality of contiguous digi.tized samples includes samples S5,S6,S7 and S8, which are recorded in track TB. The third plurality of ~ontiguous digitized samples includes samples S9,SlO,Sll and S12, which are recorded in track TA following the first plurality o~ contiguous samples Sl,S2,S3 and S4 Thus, the digitized samples which are recorded in tracks TA and TB are arranged as follows:

TA Sl S2 S3 S4 S9 Sln Sll S12 Sl.~ S18 Sl9 20 25 T S5 S6 S7 S~ S13 S14 S15 S16 S21 S2? S23 24 ~9 :1~60739 With the above metho~l o recordin~, the chrominance portion of the video signal can be easily separated in the reproducing section by a suitable chrominance filter, as will now be shown for the case whe-l^e the sampling frequency fs = 4fsc~ If the sa~pling frequellcy is se]ectecl as 4fsc, as shown in Fig. 14, the signal levels of the sampling points of the color sub-carrier signal at 0, 90, 180 and 270 are Sl,S2,S3 and S4, respectively. Since the signal level Sk of a color video signal in the NTSC system is defined as follows-Sk = YN + I~T~ (R - Y) cos ~ct + 1 (B - Y) sin oJct = YN + DRN cos ~ct + DBN sin ~ct ... (1), where:
4~c 2 ~fc~ . ...... (2) DRN = T~r~ (R - Y) .... (3) DBN = ~ (B - Y) .... (4), then the following equations for Sl,S2,S3 and S4 can be ohtained:

Sl = Yl + DRl S2 = Y2 + DB2 .... (6) S3 = Y3 - DR3 ---(7) S4 = Y4 - DB4 .... (8), corresponding to sampling points of 0, 90, 1~0 and 27~, respectively. It should therefore ~e appreciated that the odd -2~-0~739 samples include only the red color component of the color video signal while the even samples inci~de only the blue color component of the color video signcll.
It will be appreciate<l that the bandwidth o~ the color difference signals (R - Y) flnd (B - Y) is a~out 5~0Hz which is much smaller than the sampling frequency 4fsc, the latter being approximately equal to 14.3~Ez. Accordingly, the period of the color difference signals (R-Y) and (B-Y) is much larger than the sampling period and any change in level of the color difference signal between successive, or even alternate,samples is negligible. Therefore, since the signal level does not change very quickly between such samples, the following approximations can be made:

DP~ DR3 DB v~ D~
for the samples in the first plurality of contiguous digitized samples Sl,S~,S3 and S~. In like manner, the signal level between successive, or even alternate, levels of the luminance portion of the video signal cannot change very quickly because of the same reasons. Therefore, luminance components Yl,Y2,Y3 and Y~ can be equated with one another. Thus, upon comblning equations (5) and (7), the following equation is obtained:

~ ----+ 21 (DRl - DR3) Yl 3 In like manner, equations (6) and (~) can be combined as fo^llows:

2 4 = 2 4 + 2 (D~2 ~ DB4) Y, 4 .... (10) ~ , ' ' ~ A

3~

Util-i ing equations (9) and (l~), it ~ill now be shown how the chrominance and luminance portions of the color video signal can be separated. In particular, from equations (5) and (9), the following equatiol~ can be obtained:
Sl+S3 Sl-S,j DRl = Sl-Yl Sl 2 = -2 J- .... (11) .

In like manner, from equations (6)-(10), the :Eollowing equations can also be obtained:
S2+5~ S2-S~ .... (12) Sl+S3 S - S
DR3 =-S3~Y3 =-S3+ 2 = --~-- .... (13) S2+S4 52-54 .~.. (14).

It should therefore be appreciated that the red and blue color difference sip~nals can be obtained from the input digitized samples Sl-S4. Therefore, if at least one cycle of the sampled digitized signal is recorded in a track, the luminance and chrominance portions of the video signal can be separated according to the above method. In comparison, in the previously proposed system ~here successive digitized samples are alternately separated into two channels, each sub-block of data is comprised of only odd or even-numbered digitized samples as follows:

TA:Sl S3 Ss S7 Sg -TB:S2 S4 S6 S3 S10 Thus, during reproduction in the hlgh speed search mode, the . -3~-6073$~

samples Sl S3 S5 ~S7 ... in track '!'j~ may be reproduced while the corresponding samples S2 S4 S6 S~ ...in track TB may not be reproduced. It sllould be appreciated that, if the ahove-described method of separating the chrominance portion o~ the video signal is used only with the odd-numbered samples Sl S3 S5 S7 ... from track TA, only the ~ed color component of the video signal will be reproduced. In like manner, if only the even-numbered samples S2 S4 S6 S8 ... from ~rack TB are reproduced, only the blue color component of the video signal will be reproduced. Thus, a composite color signal cannot be separated from the video signal during reproduction in the high speed search mode if the digitized samples are recorded in accordance with the previously-proposed system.
It should be appreciated, however, that each sub-block of information preferably includes a plurality of continuous cycles of the sampled digitized signal so that, in actuality, the contiguous digitized sanples in each ~lurality is gre-ater than four. For example, as previously discussed in regard to the example of Figs. 11-13, each sub-~lock may include 32 continuous cycles of the sampled digitized signal so that, in the case of a sampling frequency of 4fsc, 256 conti~uous sam~les are recorded in each plurality on each tracl~. In such case, a filter circuit 100, as shown in Fig. 15, which is positioned between the output of interface 36 and the input of D/A converter 37 of the reproducinp, section of Fig. 2 can be used for separating the chroninance and luminance portions of the digital color video signal, with filter circuit lOn having a luminal~ce filter characteristic Y = -~--- and a chrominance-filter characteristic C = ~
where Z is a one sample delay char;lcteristic of the filter circuit.

1~60~39 In particular, the di~itized samp]es of tl-e color video signal are applied through two one sample delay circuits 102 and 1~4 to the positive inputsof first and second adding circuits 106 and 108. The digitized samnles are also supplied directl.y to the positive input of adding circuit 1~6 and to the negative input of adding circuit 108. The outPut signal from adding circuit 106 is supplied through a divide-by-two circuit 110 for producing the separated luminance portion of the color video -signal and the output from adding circuit 1~8 is supplied throu~'n a divide-by-two circuit 11~ to produce the separated chrominance portion of the video-signal. Thus, when the heads }IA and H~
repro~uce a signal corresponding t~ only a single sub-block from one of the tracks, the chrominance portion of the signal can be easily separated and contains both the red and blue color components thereof.
In comparison, with the previously-described proposed method of recording successive digitized samples alternately in the two tracks TA and TB, filter 10~ cannot be utilized to satisfactorily separat~ the chrominance portion of the video signal from the luminance portion thereof. In such case, to ensure the same relationship of equations (9) and (10), only one one sample delay circuit :1.02 or 1~ would be utilized since, for example, tracl; TA contains alternate di~itized samPles Sl,S3,S5,...Sr~. By utilizing such a modified filter circuit, when the di~itized samples from track TA which contain the odd-numbered samples are supplied to the modified filter, only the red color component would be produ~:ed. When the even-numbered di~itized samples from track TB are supplied to such modi~ied filter, only the blue color compon-nt would be produced. In .

~L160739 this manner, no composite color si~,nal could be separated in the filter, and therefore, the p'nclse of the color signa] coukl not be corrected.
In like manner, if the sampling frequency is selected as 3fsc~ as shown in Fig. 16, so that the sampled points correspond to no, 120 and 2~0, the followln,~ equations for Sl,S2 and S3 can be obtained f-rom equation (1):

Sl Yl+~Rl (~ = 0) ....(15) S2 Y2 - 2 DR.2 + ~ DB2 (~c = 12~ ) ,..,(1~) S3 = Y3 ~ 2 DR3 ~ DB3 (~c = 240 ) ....(17).

By utilizin~, the same analysis which was previously used in re~ard to the samplin~ frequency of 4fsc~ the following equations can be obtained:
y v~Sl+S2+S3 ....(18) DR ~ S Y .(19) DB - (S2 S3)/ ~ .,,.(2~).

It should therefore be appreciatecl that the chrominance and luminance signals can be easily sel~arated as a result of recordin~
the digitized samples according to the above embodiment of this invention. A similar analysis can be done for a sam~ling frequency ~reater than 4fsc.
Thus, the separated chrominance Portion of the ~ L~60739 video signal can have its phase colrected for each sub-block thereof, for example, by comp~xisont~th a desired reference ~hase.
For examPle, a phase correction circuit 2no shown in Fig. 2 disposed between the output of inter~ace 36 and the inpu~. of D/A
converter 37 may be provided for correcting the phase of the color sub-carrier. As shown more particularly in Fig. 17, phase correction circuit 200 includes chrominance-luminance separation filter 100 which se arates the chrominance and luminance components of the color video signal from interface 36. The chrominance component is supplied to a phase com~ensator 2~2 for adjusting the phase thereof in response to a signal from a phase comparator 204. This latter circuit receives the chrominance component from filter 100 and a reference phase signal from a reference phase circuit ~06 and supplies an output to phase conpensator 202 in response to such phase comparison. In this manner, phase compensator 202 adjusts the phase of the color sub-color in those sub-blocks which contain an error so as to produce a color si~nal having a color sub-carrier ~ith a uniform phase relation.
~n adding circuit 208 is supplied with the chrominance component from phase compensator 2~2 and the luminance component from filter 100 and combines these components to form a composite color video signal which is sup~lied to n/A converter 37. In this manner, during reproduction in the hi~h speed search mode, when the heads HA and ~1~ only scan an area of each track slightly greater than one sub-block, the chrominance portion of the color video signal from each sub-block irldividually can be separated and the phase thereof can be corrected if it is in error.
It should be apprecia~ed that although the a~ove-described method according to this invention has been im~lemented to provide a uniform ~hase of the color sub-carrier durin~
reproduction in the high speed search mode, the method of recordin~

,~, _ )739 may be utilized in the normal reploducing mode in which an error concealing method is used. In the normal re?roducing mode, decoders 34A and 34B generally co~rect any errors in the reproduced signal by ~eans of a c~slic redundancy code (CRC) and by means of horizontal and velt-ical parity data. However, if too many errors exist in the signal, the erroneous sub-block wl~ich contains these errors is replaced by another sub-block to conceal these errors. It is generally necessary in such error concealing method that the substitu~e sub-block have a strong vertical correlation with the replaced block,that is, that it should be in close vertical proximity to the replaced sub-block and that the phase of the color sub-carrier of the substitute sub-block should match that of the erroneous replaced sub-block. In this manner, the corresponding sub-block from a line positi.oned one line below the erroneous line and in the ield immediately preceding the field of the erroneous line is substituted so as to satisfy s~lch conditions. Such concealment method will now be described more particularly with respect to Figs. 18A-18F;
In particular, Fig. 18A represents a field memory in an error correcting decoder 34 in one channel and which contains 572 sub-blocks of data assigned to addresses ADl-AD572. Figs. lSB-18D illustrate the manner in which reproduced data is written into the field memory in the normal reproducing mode. It is seen that the position or address at which the first line of each field is written is shifted down one line in each successive frame. If an error occurs in one of the sub-blocks which is not corrected by the CP~C code and the horizontal and vertical parit~ da~a, the erroneoui~ sub-block is not written in -35 ..

` ~60739 the respective address in the field memory, but rather, the sub-block which belongs to the previous field and is posi-tioned one line below the line of the erroneous sub-block is substituted therefor. For example, as shown in Fig. 16E, erroneous sub-block SBl in the odd field of frame (I+l) is replaced by sub-block SB3 of the even field in frame I. As a further example, an erroneous sub-block SBl of the even field in frame (I+l) is replaced by sub-block SBl of the odd field in the same frame. In this manner, any error in the erroneous sub-block can be concealed by a signal which is correlated thereto. Further, with such concealment method, the phase of the color sub-carrier remains uniform in the normal reproducing mode. See the aforementioned Patent No.

4,329,708.
In accordance with another embodiment of this invention, the phase of the color sub-carrier of the color video signal, which is sampled at a frequency f 4fsc~ can easily be made uniform. In such embodiment, successive digi-tized samples of the color video signal are alternately separated into first and second blocks, as shown in Fig. 19, so that digitized samples having odd numbers Dl to D(2n 1) are included in the first block and digitized samples having even numbers D2 to D2n are included in the second block.
Further, each block is divided into N/2 pluralities of successive ones of the digitized samples in each block, in which N is an even integer which is greater than or equal to 2~N - 2). The number N corresponds to the number of channels into which the digital video signal is separated.
For example, a first plurality in the first block includes samples Dl to D(2i_l) and a first plurality in the second block includes samples D2 to D2i.

,, . ,, . _.

l~6n73s As an example, in th~ case where the digitiæed video signal is separated into four channels, as shown in Figs. 20-23, each of the first and second blocks is divided i.nto two pluralities (~ = t~) o:E sllccessive digiti~ed samrles of the respective blocl;s. In such c.,se, if the total number of samples in the two bloct-.s is equal to the number of sam~les of the effective video si~nal in one horizontal line, 2n = 76~.
Accordinglv, the first plurality of odd-numbered successive digitized samples ~l-D3~3 in the first block is distributed to the first channel A by interface 14 so that 19~ di~itized samples are distributed to channel A from che first hori~ontal line.
In like manner, odd-numbered digi~ized samples D385-~767 form the second plurality of successive digitized samples of the first block distributed to the second channel B. In the second block, even-numbered digiti3ed samples D2-D3~4 are distributed to the third channel (. and even-numbered digitized samples D386-n768 are distributed to the last channel D.
Each of the pluralities is therefGre comprised of the two sub-blocks (Fig. 23), each sub-block containin~ in order, a synchronizing signal (SYNC), identifying (In) and address (AD) signals, effective video data, an-l a CRC, code, as previously discussed.
I~hen the digitiæed sarnples are recorded on tracks TA-TD which correspond to channels A-D, respectively, the chrominance and luminance portions of the composite digital video si~nal can be separated by a fourth order di~l-ital filter circuit so that any erroneous phase of the color ~ub-carrier during reproduction in the high speed search mode can i)e corrected, as previously discussed. One embodiment of such fourth order digital filter circuit 300 is shown in Fig. 2~ and has a luminance filter characteristic Y = ~ (1+2Z 2+7, 4) Ind a chromlnance filter ~6~73~

characteristic C l (-1+27,-2-7.-4~ wllere 7~ i.s a on samp]e delay transfer characteristic of ~-he one samnle ~lelay circuits of the filter circuit. In partic~Lar, digital. filter 300 includes a series combination of four one sample delay circuits 3~2,304,3n6 and 308 supplied with the di~,itize~i samPles. An addin~, circuit 310 receives the four sample delayed signal from delay circuit 30~ at a negative input thereof, tlle two sample delayed sig,nal from delay circuit 304 applied through a multiply-by-two circuit 312 at a positive input thereof, and the input sample at another negative input thereof. Adding circuit 31~ sums these signals and supplies the added signal to & divide-by-four circuit 314 which produces the separated chrominance component. In like manner, an adding circuit 316 rece~ves the four sample delayed signal from delay circuit 308 at fl positive input thereof, the two sample delayed signal from delay circuit 304 applied through multiply-by-two circuit 31~ at another positive input thereof, and the input sample at still anotller positive innut thereof.
Adding circuit 316 sums these si~nals and suPplies the adcled signal to a divide-by-four circuit 318 which produces the separated luminance component. As was previously described in regard to Fig, 17 and the first embodiment, ~he chrominance component then has any phase errors in its color sub-carrier corrected.
It should be noted that, in the previously proposed digital VTR, a sampling frec~uency of 3fsc has only been used In other words, no known di~ital VTr.~s have used samnling frequencies of 4fsc. However, the fourth order digital filter circuit 30 used with the second embodiment of the invention can only be utilized with a sampling frequency of 4fsc and does not operate properly when the sampling frequen(~y is 3~sc -3~-~f)73~

Further, as in the f:i~st embodiment, durin~, the normal reproducing mode, the conce~lment method illustrated in Fi~s. 18A-18F can also be utili~ed when the digiti3ed samples are recorded in the manner according to the second embodiment of this invention.
. Having described specLfic preferred embodiments of the invention with reference to the accomPanyin~, drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes an~
modifications may be effected therein by one s~illed in the art without departing from the scope or spirit of the invention as defined in the appended claims.

-3~-

Claims (12)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of recording a color video signal in a plurality of parallel tracks extending obliquely on a magnetic tape, said method comprising the steps of:
sampling said color video signal at a frequency which is at least three times the color sub-carrier frequency of the color video signal;
converting the sampled color video signal into digitized form; and recording a plurality of groupings of consecutive ones of the digitized samples sequentially in each parallel track, with adjacent samples of adjacent groupings being non-consecutive.

2. The method according to claim 1, further comprising the steps of, prior to said step of recording, distributing said groupings of digitized samples sequentially to at least two channels, time compressing said digitized samples supplied to each channel; generating error control data from said time compressed digitized samples in each channel; adding said respective error control data to said time compressed digitized samples in each channel; and adding synchronizing, identifying and address signals to said color video signal in each channel comprised of said time compressed digitized samples and said error control data.

3. The method of claim 1, in which each of said groupings of consecutive digitized samples corresponds to at least one cycle of the color sub-carrier of said color video signal.

4. A method of recording and reproducing a color video signal in a plurality of parallel tracks extending obliquely on a magnetic tape, said color video signal including a chrominance component and a luminance component, said method comprising the steps of:

recording said color video signal in said plurality of parallel tracks, including the steps of:
sampling said color video signal at a frequency which is at least three times the color sub-carrier frequency of the color video signal;
converting the sampled color video signal into digitized form; and recording respective pluralities of contiguous ones of the digitized samples which are arranged in a predetermined sequence sequentially in said plurality of parallel tracks, with each plurality of contiguous ones of the digitized samples corresponding to at least one cycle of the color sub-carrier of said color video signal;
reproducing said color video signal from said plurality of parallel tracks, including the step of:
separating the chrominance component of the reproducing sampled digitized signal in each track by filter means having a chrominance filter characteristic C =(1-Z-2)/2, where Z is a delay transfer characteristic of the filter means.

5. The method according to claim 4; in which the step of reproducing said color video signal includes the step of correcting any error in the phase of the color sub-carrier of the reproduced color video signal.

6. The method according to claim 5; in which said step of correcting any error includes the steps of comparing the phrase of the color sub-carrier of the separated chrominance component with a reference phase and producing an output in response to such comparison, and correcting any error in the phase of the color sub-carrier of the separated chrominance component in response to said output.

7. Apparatus for recording a color video signal in a plurality of parallel tracks extending obliquely on a magnetic tape, comprising:

means for sampling said color video signal at a frequency which is at least three times the color sub-carrier frequency of the color video signal and for converting the sampled color video signal into digitized form; and means for recording a plurality of groupings of consecutive ones of the digitized samples sequentially in each parallel track, with adjacent samples of adjacent groupings being non-consecutive.

8. Apparatus according to claim 7; in which each grouping of consecutive digitized samples corresponds to at least one cycle of the color sub-carrier of said color video signal.

9. Apparatus for recording and reproducing a color video signal in a plurality of parallel tracks extending obliquely on a magnetic tape, said color video signal including a chrominance component and a luminance component, said apparatus comprising:
a recording section for recording said color video signal in said plurality of parallel tracks, including:
means for sampling said color video signal at a frequency which is at least three times the color sub-carrier frequency of the color video signal and for converting the sampled color video signal into digital form; and means for recording respective pluralities of the digitized samples which are arranged in a predetermined sequence sequentially in said plurality of parallel tracks, in which said digitized samples in each plurality of digitized samples are arranged in a contiguous manner, with each plurality of contiguous digitized samples corresponding to at least one cycle of the color sub-carrier of said color video signal; and a reproducing section for reproducing said color video signal from said plurality of parallel tracks, including:
filter means for separating the chrominance component of the reproduced sample digital signal in each track and having a delay transfer characteristic; in which said filter means has a chrominance filter characteristic C = (1-Z-2)/2, where Z is the delay transfer characteristic of the filter means.

10. Apparatus according to Claim 9; in which said filter means includes an input-receiving said contiguous digitized samples of each plurality from said plurality of tracks; sample delay means for delaying the contiguous samples from said input by a period of two samples; means for subtracting the contiguous samples at the input from said delayed contiguous samples from the sample delay means and producing an output therefrom; and dividing means for dividing said output by two so as to produce the separated chrominance component.

11. Apparatus according to Claim 9; in which said reproducing section further includes phase correcting means for correcting any error in the phase of the color sub-carrier of the separated chrominance component.

12. Apparatus according to Claim 11; in which said phase correcting means includes phase comparator means for comparing the phase of the color sub-carrier of the separated chrominance component with a reference phase and for producing an output in response thereto, and phase compensating means for correcting any error in the phase of the color sub-carrier of the separated chrominance component in response to the output from said phase comparator means.