Apparatus and method for recording and reproducing of digital video and audio signals

Abstract: Methods and apparatus are provided for recording and reproducing digital information signals including image and audio portions in successive tracks on a magnetic tape. An ID signal is produced (112) for one of an image portion and an audio portion of a corresponding digital information signal to be recorded. The ID signal indicates whether the portion is to be after-recorded in a respective track. The ID signal is combined (14) with the portion to form a recording signal. Previously recorded digital information signals are reproduced (13A, 13B, 21A, 21B, 22, 23) from the track and an ID signal thereof is obtained. The recording of the portion in the track is controlled (51, 52, 53, 54, 55) based on the reproduced ID signal.

Description: The present invention relates to methods and apparatus for recording and reproducing digital information signals. Digital video tape recorders (VTRs) for digitizing and recording colour video signals on magnetic tape are in commercial use. These digital VTRs may be categorized as so-called "D1" format component VTRs and so-called "D2" format composite digital VTRs, both of which types are commonly employed in broadcasting stations. In the first-developed D1 format component VTR, a luminance signal and first and second colour difference signals are converted to digital form from analogue form using sampling frequencies of 13.5MHz and 6.75MHz, respectively. After these signals have been appropriately processed, they are recorded on a magnetic tape. Since the ratio of the component sampling frequencies is (4 : 2 : 2), the D1 format is also referred to as a (4 : 2 : 2) system. In the later-developed D2 format digital VTR, composite colour video signals are converted to digital form from analogue form with a sampling frequency of four times the frequency (fsc) of the colour subcarrier signal. After these signals have been appropriately processed, they are recorded on magnetic tape. Since the D1 and D2 digital VTRs are designed principally for use in broadcasting stations, the quality of the pictures produced thereby is accorded the highest priority. Accordingly, the digital colour video signal, digitized at eight bits per sample, is not substantially compressed before being recorded on the magnetic tape. The consequently large amount of data per field is not easily accommodated in a single track, as the influence of improper linearity in the tracks can substantially degrade the system operation. Accordingly, the D1 format digital VTR employs a segmenting technique wherein ten tracks are employed to record each field of a National Television Standards Committee (NTSC) type signal, while twelve tracks are employed to record each field of a phase alternating line (PAL) type signal. This consequently shortens the length of each track and thus reduces the influence of improper linearity, even where the track pitch is narrow. Digital VTRs record digital audio signals as well as tracking pilot signals in the tracks, in addition to the digital image signal. The D1 format digital VTR records audio data in the centre of each track, while recording time code and tracking control signals in the longitudinal direction of the tape. The D2 format VTR records audio data at opposite ends of each track and, like the D1 device, records time code and tracking control signals in the longitudinal direction of the tape. In both the recording and reproducing modes of these devices, data errors sometimes occur. Thus, the digital image signal, as well as the digital audio signal and a subcode signal recorded therewith, are encoded to provide error correction codes. To do so, the data are arranged in matrix format and product codes are formed therefrom, such that line codes are formed using the rows of the matrix and column codes are formed using the columns thereof. It will be seen, therefore, that each data symbol is included in two error correction code sequences when the product code is thus formed. Thus, a highly effective error correction capability can be achieved. EP-A-0 449 276 discloses a recording position compensation circuit for use in a digital recording-reproduction apparatus. The circuit has a microprocessor for generating an offset signal indicating a deviation between standard signal processing time, and inter-head travelling time required for the recording medium to travel a distance from a fixed advanced reproduction head to a fixed recording head. The offset signal indicates the deviation which is required for a process wherein digital medium information already recorded on the recording medium is reproduced through the advanced reproduction head and re-recorded on the recording medium through the recording head. A first counter generates a reference symbol pointer indicating a reference of a sequence whereby digital information stored in a memory is read out so that a part of the digital information is rewritten. A second counter generates a compensated symbol pointer having a phase difference corresponding to the deviation with respect to the reference symbol pointer. Digital information is read out from the memory so that the signal processing time from reproduction to re-recording may coincide with the inter-head travelling time. Thus a correct recording position on the recording medium at which rewriting is performed is selected. In conventional digital VTRs, fixed heads are utilized for recording and reproducing the tracking and time code signals. Consequently, the tape transport mechanism is fairly complex, thus tending to degrade the reliability of the tape path. It is, therefore, preferable to record the tracking and additional control data in the tracks, so that the need for fixed heads may be eliminated. In each track, respective recording sections are provided for the digital image and audio signals, as well as for the subcode. Accordingly, after-recording requires precise control to ensure that the data are recorded in the desired section of each track. One control technique employs a detection signal synchronized with the phase of the rotary head drum to define the after-recording area. However, this technique requires greater mechanical accuracy of the magnetic or optical detectors employed than may be achieved. Consequently, the use of this control technique can result in the erasure of the previously recorded data. In accordance with one aspect of the present invention there is provided, an apparatus for recording digital information signals including image portions and audio portions in successive track sections on a magnetic tape, and for reproducing the digital information signals from the tape the apparatus comprising: digital signal processing means for generating said digital information signals; means for generating ID signals each indicating whether a corresponding digital information signal portion is to be recorded in an after-recording mode in a corresponding one of the successive track sections of said magnetic tape; combining means for combining said ID signal with the corresponding digital information signal portion to form a recording signal; means for recording the recording signal in the successive track sections; reproducing means for reproducing signals recorded in the successive track sections; means for obtaining a reproduced ID signal from the reproduced signals; and control means for controlling the after-recording of a digital information signal on a selectable one of the track sections. the control means comprising means responsive to ID signals reproduced from the tape for detecting track sections which are not after-recorded; means responsive to the detecting means for defining the position of a selected track section referenced to the nearest preceding track section which is not after-recorded and means responsive to the position defining means for producing a control signal enabling after-recording in the selected track section. Since the recording section is defined based on the reproduced ID signal, it is possible to determine whether the previously recorded digital information signals from the respective track are after-recorded signals. Since after-recorded signals are often recorded in imprecisely defined regions, steps may be taken to ensure that the newly after-recorded signals are positioned based on originally recorded signals of the track which are positioned far more precisely. According to a second aspect of the invention, there is provided a method of recording digital information signals including image portions and audio portions in successive track sections on a magnetic tape, and for reproducing the digital information signals from the tape, the method comprising the steps of: generating said digital information signals; generating ID signals each indicating whether a corresponding digital information signal portion is to be recorded in an after-recording mode in a corresponding one of the successive track sections of said magnetic tape; combining said ID signal with the corresponding digital information signal portion to form a recording signal; recording said recording signal in the successive tracks; reproducing signals recorded in the successive tracks; obtaining a reproduced ID signal from the reproduced signals; and controlling the after-recording of a digital information signal on a selectable one of the track sections by the steps of responding to ID signals reproduced from the tape to detect track sections which are not after-recorded, defining the position of a selected track section with reference to the nearest preceding track section which is not after-recorded, and producing a control signal enabling after-recording in the selected track section in dependence upon the defined position of the selected section. In an embodiment of the invention the position of said selected track section is based on reference data wherein said position defining means is operable to define the position of said selected track section based on reference position data stored within said preceding track section and indicating a reference position within said preceding track section. The position of the selected section may be defined based on a scanning distance from said reference position to said selected section. Block synchronisation signals may be reproduced from the successive track sections and the scanning distance of the selected section from the preceding section is based on the block synchronisation signals from the preceding section if the preceding section has not been after-recorded. Data-type signals may be reproduced from the preceding section indicates the type of data recorded therein and the position of the selected section may be determined based on the data-type signal. At least a preferred embodiment of the invention, to be described below, provides methods and apparatus for reproducing and after-recording digital video signals on magnetic tape which alleviate the above-described shortcomings and problems inherent in the prior art, and which can define an after-recording area on a magnetic tape with improved precision. The invention will now be described by way of example with reference to the accompanying drawings, throughout which like parts are referred to by like references. and in which: Figure 1 is a block diagram of a recording signal processing system of a digital VTR in accordance with an embodiment of the present invention; Figure 2 schematically illustrates an (8 x 8) luminance signal block for encoding as a unit; Figure 3 schematically illustrates a technique for sub-sampling and sub-line selection for reducing the sampling frequency of colour difference signals; Figure 4 is a block diagram of a reproduction processing system of the embodiment of Figure 1; Figure 5 is a block diagram of a channel encoder of the recording signal processing system of Figure 1; Figure 6 is a block diagram of a channel decoder of the reproduction processing system of Figure 4; Figures 7A and 7B schematically illustrate alternative rotary recording/reproducing head arrangements which may be employed in the disclosed embodiment of the present invention; Figure 8 illustrates the azimuth angles of respective recording/reproducing heads as illustrated in Figures 7A and 7B; Figure 9 schematically illustrates recording patterns formed in successively arranged slant recording tracks on a magnetic tape as formed by the recording/reproducing heads of Figures 7A and 7B. Figure 10 is a diagram illustrating the arrangement of the component sections of an exemplary recording track formed on a magnetic tape by the embodiment of Figure 1; Figures 11A to 11C are diagrams for illustrating product code compositions for video data, audio data and subcode data, respectively, as formed by the embodiment of Figure 1; Figure 12 schematically illustrates the track format for recording NTSC signals with the use of the disclosed embodiment; Figure 13 is an analogue representation of one channel of a pulse code modulation (PCM) audio signal corresponding with one frame of an NTSC signal; Figures 14A and 14B illustrate interleaving techniques for PCM audio signals corresponding with an NTSC video signal for use in a soft tape mode and a user recording mode, respectively; Figure 15 illustrates a further interleaving technique for PCM audio signals corresponding with an NTSC video signal in the user recording mode; Figure 16 schematically illustrates the track format for recording PAL signals with the use of the disclosed embodiment; Figure 17 is an analogue representation of one channel of a PCM audio signal corresponding with one frame of a PAL video signal; Figures 18A and 18B illustrate interleaving techniques for PCM audio signals corresponding with a PAL video signal for use in a soft tape mode and a user recording mode, respectively; Figures 19A and 19B provide examples of data errors which may occur in a magnetic tape; Figures 20A and 20B provide further examples of data errors which may occur in the magnetic tape; Figure 21 is an example of data loss occurring when one of the pair of magnetic heads employed in the disclosed digital VTR embodiment becomes clogged; Figure 22 schematically illustrates the format of an ID signal included in each sync block for both video and audio data as well as for the subcode, as formed by the embodiment of Figure 1; and Figure 23 is a block diagram of a control subsystem of the disclosed embodiment for use in generating a control signal to define an after-recording section in a track formed in a magnetic tape. An embodiment of a digital VTR in accordance with the invention will now be described in detail in the following topical order: 1. Overall Description 2. Channel Encoder and Channel Decoder 3. Head and Tape System 4. Track Format 5. Data Arrangement 6. Interleaving and Error Correction of Audio Signals 7. Composition of ID Data and Definition of After-Recording Area 1. Overall Description Figure 1 illustrates in block format a recording signal processing system of a digital VTR in accordance with an embodiment of the invention. A digital luminance signal Y and digital colour difference signals U and V, which are formed from three primary colour signals red, green and blue (R, G and B), are received at input terminals 1Y, 1U and 1V, respectively. The three primary colour signals R, G and B are provided, for example, by a colour video camera. In this case, the clock rates of the luminance and colour difference signals are the same as those of the corresponding signals utilized in the above-described D1 VTR, so that the Y signal has a sampling frequency of 13.5 MHz, and that of the U and V signals, is, in each case, 6.75MHz, while each sample is provided as an eight bit word. A valid information extraction circuit 2 reduces the amount of data within the signals Y, U and V by removing blanking interval data therefrom while retaining the data therein from the effective picture area. The luminance signal Y, after removal of the blanking interval data therefrom, is supplied from an output of the valid information extraction circuit 2 to an input of a frequency conversion circuit 3. The frequency conversion circuit 3 serves to reduce the sampling frequency of the luminance signal from 13.5 MHz to a frequency of three-quarters thereof, and provides the thus-converted luminance signal to the input of a block segmentation circuit 5. The block segmentation circuit 5 converts the luminance signal received in line sequential format into a series of blocks for subsequent block encoding, and supplies the thus-converted luminance signal to a combining circuit 7. Figure 2 schematically illustrates the arrangement of an (8 x 8) element luminance signal block to be encoded as a unit by one or more of discrete cosine transformation (DCT), adaptive dynamic range coding (ADRC), and the like. In Figure 2, each picture element (pixel) is illustrated as a circle, and the solid and broken lines represent odd and even field lines, respectively. After removal of blanking interval information therefrom by the valid information extraction circuit 2, the two colour difference signals U and V are supplied to respective inputs of a sampling and subline circuit 4. The sampling and subline circuit 4 serves to reduce the sampling frequency of each of the two colour difference signals from 6.75MHz to one half thereof and then selects alternate pairs of colour difference signal lines to be assembled into a single channel of data which it then outputs as a line sequential digital colour difference signal. The output signal from the sampling and subline circuit 4 is illustrated schematically in Figure 3 wherein circles represent remaining picture elements of the first colour difference signal U, triangular symbols represent remaining picture elements of the second colour difference signal V, and the cross symbols represent positions of picture elements which have been removed from the two colour difference signals by the sampling and subline circuit 4. The line sequential colour difference signals output by the sampling and subline circuit 4 are provided thereby to a block segmentation circuit 6 which, like the first-mentioned block segmentation circuit 5, converts the line sequential colour difference data into a sequence of data blocks. Like the block segmentation circuit 5, the block segmentation circuit 6 converts the colour difference data into (8 x 8) blocks which it then supplies to the combining circuit 7. The combining circuit 7 serves to combine the luminance signal and the colour difference signal supplied in block-sequential form from the block segmentation circuits 5 and 6, respectively, into a one-channel combined signal which the combining circuit 7 supplies to a block encoding circuit 8. The block encoding circuit 8 carries out one or more encoding techniques such as adaptive dynamic range coding, discrete cosine transformation, or the like. The signal as encoded by the block encoding circuit 8 is output thereby to a frame segmentation circuit 9 which converts the received signal into data frames, converting the data from a picture system clock to a recording system clock. A pulse code modulated (PCM) audio signal is received at an input terminal 1A and supplied therefrom to an audio encoding circuit 15 which serves to compress the audio data by means of differential pulse code modulation (DPCM). As will be described in greater detail hereinbelow, the audio encoding circuit 15 interleaves the audio data in response to a mode signal received at an input terminal 15a thereof designating one of a user recording mode and a soft tape mode, described in greater detail hereinbelow. After encoding, the audio data are output by the circuit 15 to a parity generating circuit 16 which encodes the audio data in the form of a product code, to provide an error correction capability. The audio data and resulting parities are supplied by the parity generating circuit 16 to a first input of a mixing circuit 14. As will be explained in greater detail hereinbelow, audio data are recorded in two separate sections of each track, designated audio 1 and audio 2, respectively. The audio encoding circuit 15, together with the parity generating circuit 16, produce the audio data for recording in the audio 1 and audio 2 sections. In a user recording mode of the digital VTR, all data may be recorded in a selected one of the audio 1 and 2 sections, while after-recording is disabled in an anti-theft mode of the digital VTR. As an alternative to the arrangement illustrated in Figure 1, the output of the audio encoding circuit 15 may be supplied instead to the frame segmentation circuit 9, so that the audio data are recorded with the image data. A parity generating circuit 10 receives the data output by the frame segmentation circuit 9 to produce error correction codes therefor, thus adding parities to the received data. The error correction encoded data are supplied by the parity generating circuit 10 to a respective input of the mixing circuit 14, to be combined with audio and subcode data for recording on magnetic tape. The subcode data are produced by a subcode generating circuit 111 and are combined with identification (ID) data produced by an ID generating circuit 112 together with synchronization signals produced by a sync generating circuit 113. The circuits 112 and 113 also serve to produce ID signals and sync signals for the audio and video sync blocks. Appropriate timing signals for the circuits 111, 112 and 113 are produced by a timing generating circuit 114. The subcode can represent certain control signals generated, for example, in response to key operations by a user. The subcode, ID data and synchronization signals are supplied to a parity generator circuit 17 via an input terminal 1S, for generating appropriate error correction codes, thus adding corresponding parities to the received data. The thus-encoded subcode and ID data and synchronization signals are supplied by the parity generator 17 to a respective input of the mixer circuit 14 to be combined with the audio and image data for recording, as mentioned above. The mixing circuit 14 combines the image, audio and subcode data for recording in respective sections of the sequential tracks on the tape as described in greater detail hereinbelow. The data thus mixed by the mixing circuit 14 are provided to a channel encoder 11 which serves to attenuate a low band of the data prior to recording. The data as processed by the encoder 11 are supplied thereby to a respective input of a further mixing circuit 18 which receives a pilot signai at a second respective input 19 to enable automatic track following. The pilot signal is a low frequency signal which may be separated from the recorded data when it is reproduced. The data as mixed by the mixing circuit 18 are provided thereby to magnetic heads 13A and 13B through respective recording amplifiers 12A and 12B and appropriate rotary transformers (not shown for purposes of simplicity and clarity of the figure), so that the data may be recorded on magnetic tape. Referring now to Figure 4, the reproduction signal processor system of the disclosed digital VTR receives data reproduced from a magnetic tape by the heads 13A and 13B which supply the reproduced data to respective reproducing amplifiers 21A and 21B. The data, as thus amplified, are supplied to a channel decoder 22 and an automatic track following (ATF) circuit 34. The channel decoder 22 serves to demodulate the reproduced data and provide the demodulated data to a time base compensation (TBC) circuit 23. The TBC circuit 23 removes time base fluctuating components present in the reproduced signal. The ATF circuit 34 produces a tracking error signal based on a beat component present in the reproduced pilot signal, so that the tracking error signal may be provided to a capstan servo system of the digital VTR (not shown for purposes of simplicity and clarity of the figure), which carries out automatic track following in essentially the same manner as a conventional 8-mm VTR. The time base compensated data from the TBC circuit 23 is provided to three error correction circuits (ECC) 24, 37 and 39 which serve to correct and modify errors present in the reproduced data with the use of the error correction codes accompanying the data as reproduced. More specifically, the ECC 24 corrects and modifies errors within the reproduced image data, while the ECC's 37 and 39 perform the same function for the audio data and subcode, respectively, reproduced from respective track sections dedicated thereto. The error corrected audio data are supplied by the error correction circuit 37 to an audio decoding circuit 38 for decoding the audio signal which was compressed and encoded prior to recording. The reproduced subcode, after error correction by the error correction circuit 39 is provided at an output terminal 33S for supply to a system controller (not shown for purposes of simplicity and clarity of the Figure) for controlling the overall operation of the digital VTR. The image data, as error corrected, are supplied by the error correction circuit 24 to a frame desegmentation circuit 25. The frame desegmentation circuit 25 serves to separate each component within the block-encoded image data, while exchanging the recording system clock thereof with a picture system clock. The various data separated by the frame desegmentation circuit 25 are provided thereby to a block decoding circuit 26 which decodes the block encoded data to retrieve the original data therefrom. The compressed encoded audio signal is decoded by the audio decoding circuit 38 and, as decoded, is supplied thereby to a composition circuit 36 to reproduce separate channels of audio data contained therein. The composition circuit 36 operates either in a soft tape mode or a user recording mode, under the control of a mode ID signal separated from the reproduced data by the frame desegmentation circuit 25 or by the audio decoding circuit 38. In the soft tape mode, the composition circuit 36 provides two channels of audio data by constructing each channel from data contained in both the audio 1 and audio 2 sections of the scanned tracks. In the user recording mode, both channels of audio signals are separately recorded in the audio 1 and 2 sections, and are likewise supplied as separate channels of audio data by the composition circuit 36. The image data decoded by the block decoding circuit 26 are supplied thereby to a separation circuit 27 which separates the luminance and colour difference signals from the decoded data. The luminance and colour difference signals thus supplied by the separation circuit 27 are provided thereby to respective block desegmentation circuits 28 and 29. The block desegmentation circuits 28 and 29 convert the received signals in block sequential form into signals in raster scanning sequence, so that the operations of the block desegmentation circuits 28 and 29 complement those of the block segmentation circuits 5 and 6 of the recording signal processing system illustrated in Figure 1. The luminance signal output by the block desegmentation circuit 28 is provided thereby to an interpolation filter 30 which converts the sampling rate of the received luminance signal from 3fs to 4fs, where 4fs is equal to 13.5 MHz. As thus converted, the luminance signal is supplied by the interpolation filter 30 to an output terminal 33Y. The digital colour difference signals output by the block desegmentation circuit 29 are provided thereby to a separation circuit 31 which separates the received signals U and V therefrom. The separated signals U and V are supplied by the separation circuit 31 to an interpolation circuit 32 which utilizes the received data to reconstruct the lines and individual picture element data that were thinned out prior to recording. The interpolation circuit 32 outputs digital colour difference signals U and V having a sampling rate of 4fs at respective output terminals 33U and 33V, respectively. 2. Channel Encoder and Channel Decoder The channel encoder 11 of the recording signal processing system illustrated in Figure 1, and the channel decoder 22 of the reproduction signal processing system of Figure 4, are illustrated in greater detail in Figures 5 and 6, respectively. Further details of the channel encoder 11 and the channel decoder 22 are provided in the Japanese Patent Application HEI 1-143491, filed by the present applicants. Referring now to Figure 5, the channel encoder 11 includes an adaptive scrambling circuit 41 which receives the output of the mixing circuit 14. The adaptive scrambling circuit 41 includes M system scrambling circuits where M > 1. The output of one of the M system scrambling circuits is selected in operation wherein both the high frequency component and a DC component therein have the smallest values relative to the signal input to the adaptive scrambling circuit 41. The output selected by the adaptive scrambling circuit 41 is supplied to a partial response class 4 detection-type precoder 42. The precoder 42 carries out a calculation of 1/(1 - D 2 ), where D represents a unit delay. After processing by the precoder 42, the data are supplied to the magnetic heads 13A and 13B via the recording amplifiers 12A and 12B, respectively. In the reproduction mode of the digital VTR, the heads 13A and 13B reproduce the recorded signals and supply the same to the reproduction amplifiers 21A and 21B of Figure 4, as described hereinabove. The thus-amplified signals are received by the channel decoder 22, illustrated in greater detail in Figure 6. Referring to Figure 6, the channel decoder 22 includes a partial response class 4 processing circuit 43 provided with the outputs of the amplifiers 21A and 21B which carries out a calculation of (1 + D) for the received data. As thus processed by the processing circuit 43, the data are supplied thereby to a Viterbi decoding circuit 44 which carries out a correlation and probability-based calculation in a known manner to supply decoded data having a high noise resistance. The data as thus processed by the Viterbi decoding circuit 44 are provided thereby to a descrambling circuit 45 which restores the data to their original form as supplied to the channel encoder 11 of Figure 5. The use of the Viterbi decoding circuit 44 serves to improve the C/N ratio by 3 dB over that provided in decoding bit-by-bit. 3. Head and Tape System Figure 7A illustrates an exemplary arrangement of the magnetic heads 13A and 13B in diametrically opposed positions on a rotational drum 46. In an alternative, as illustrated in Figure 7B, the magnetic heads 13A and 13B may be mounted on the drum 46 in a closely-spaced arrangement. In operation, a magnetic tape (not shown for purposes of simplicity and clarity of the figure) is wound obliquely about the peripheral surface of the drum 46 to an angular extent of approximately 180°. It will be seen that, in the use of the head arrangement as illustrated in Figure 7A, the heads 13A and 13B alternately engage the magnetic tape, while in the case of the arrangement of Figure 7B, both heads scan the magnetic tape simultaneously. The angular dispositions of the gaps formed in the magnetic heads 13A and 13B, which define their respective azimuth angles, differ, as illustrated in the example of Figure 8. As shown in Figure 8, the azimuth angles α and β of the heads 13A and 13B, respectively, are fixed, for example at ±20°. Due to the difference in the azimuth angles of the two heads, a recording pattern as illustrated schematically in Figure 9 is formed on the magnetic tape. As shown in Figure 9, adjacent tracks TA and TB formed by the magnetic heads 13A and 13B, respectively, have differing azimuth angles. Accordingly, when the signals recorded in the respective tracks of the magnetic tape are reproduced, the consequent azimuth loss advantageously reduces the cross-talk from adjacent tracks. 4. Track Format Referring now to Figure 10, an exemplary track as formed by the heads 13A and 13B is illustrated schematically therein. As seen in Figure 10, the exemplary track is divided into a plurality of sections disposed at respective locations along the scanning direction thereof. The track is formed by a respective one of the heads scanning from the left to the right as illustrated in Figure 10. The margins of the tape and the inter-block gaps (IBGs) are shown as hatched areas in Figure 10 and no data are recorded therein. The track preamble (T-amble) section, as well as the preamble and postamble sections as illustrated in Figure 10 disposed at corresponding ends of each data recording section, record pulse signals having a bit frequency equal to that of the recorded data, so that a phase locked loop (PLL) of the reproduction system (not shown for purpose of simplicity and clarity of Figure 4) may lock its frequency to that of the signals reproduced from these sections of the track in order to extract a bit clock of the proper frequency. As noted above, corresponding margins are disposed at either end of each track. Pilot signal recording sections ATF1 and ATF2 adjoin each of the margins at the scan commencement and scan termination ends of the tracks, respectively. The sections ATF1 and ATF2 record pilot signals for use in automatic track following. The pilot section ATF1 is followed, in turn, along the scanning direction of the track, by a first audio signal recording section, audio 1, then by a video signal recording section, a second audio signal recording section, audio 2, followed by a subcode recording section and finally, the pilot signal recording section ATF2. As indicated in Figure 10, the valid area of the track is 16,041 bytes long. The pilot signal recording sections ATF1 and ATF2 are recorded at the ends of the track since the head does not contact the tape stably at these locations. In the high-speed reproduction mode, the tape transport speed is significantly faster than in the recording mode and the head contacts the tape more stably at the scan termination side than at the scan commencement side. Consequently, the subcode recording section is disposed at the scan termination side of the track to improve the quality of the reproduced subcode in the high-speed reproduction mode. The data are recorded on the tape in a large number of sync blocks, each of which is composed of a sync block synchronization signal, a block ID representing the position of the block on the screen, data, and error correction parities, in that order. The length of each sync block varies depending upon the type of data is contains, whether video, audio or subcode, since the amount of information therein differs. In this example, the length of each recording and non-recording section of each track, with the exception of the ATF pilot signal recording sections ATF 1 and 2, are measured in units corresponding with the length of an audio sync block and each is an integer number of audio sync blocks long. As illustrated in Figure 10, the length of each audio section, designated as audio 1 and audio 2, is 14 audio sync block long. The length of the video section is 288 audio sync blocks long, while the length of the subcode section is 4 audio sync blocks long. The lengths of the track preamble, section preamble and postamble sections are as shown in Figure 10. Since each of the track sections is an integer number of audio sync blocks long, the design of the timing control circuitry for defining each section in the recording and reproducing modes is simplified. 5. Data Arrangement Figure 11A illustrates the arrangement of the video data as recorded. As shown, each video sync block is 90 bytes long, and includes a 2-byte block synchronization signal at the beginning thereof, followed by 4 bytes of ID data, 76 bytes of video data and 8 parity bytes. An error correction code for the video data is produced by arranging the data in a (76 bytes x 35 bytes) matrix and generating product codes therefor. In other words, 76 bytes of data in each row of the matrix are used to produce inner codes, thus yielding an 8 byte parity, referred to as a "C1" parity. Each column of the matrix, including 45 bytes, is used to produce outer codes, thus yielding a 3 byte parity referred to as a "C2" parity. Reed-Solomon coding can be employed, for example, for generating the error correction codes. Each data matrix, as illustrated in Figure 11A, comprises one-third of the data in a given track, so that three groups of codes are recorded in a video section thereof. Referring to Figure 11B, the arrangement of the audio data as recorded is illustrated schematically therein. Each audio sync block is 45 bytes long, beginning with a 2-byte block synchronization signal, followed by 4 bytes of ID data, 33 bytes of audio data, and a 6 byte parity. Like the video data, the audio data are encoded in the form of product codes to provide an error correction capability. That is, the audio data are arranged in respective matrices each comprising 33 bytes per row and 10 bytes per column. The rows of each matrix are each used to produce an inner code, thus yielding a parity "C1" having 6 bytes, while the audio data in each column of the matrix are used to produce an outer code, thus forming a parity "C2" having 4 bytes. The product code format as illustrated in Figure 11B is employed both for data recorded in the audio section 1 and for that recorded in the audio section 2, as well as for each audio channel. In the user recording mode, each sample comprises 8 bits. In the soft tape mode, each sample comprises 16 bits. As will be described in greater detail hereinbelow, in the soft tape mode, the audio sections 1 and 2 each record a respective one of the left (L) and right (R) audio channels. The respective channel data contained in each section are formed into corresponding product codes in the form as illustrated in Figure 11B. In the user recording mode, audio data from both of the L and R channels are recorded in each section. Accordingly, in the user recording mode, data from both channels are used to produce each of the product codes. In the user recording mode, the data of one respective channel are recorded in the first half of a given audio section, while the data of the other channel are recorded in the second half thereof. Figure 11C schematically illustrates the arrangement of data as recorded in the subcode section of each track. Each subcode sync block is 30 bytes long, commencing with a 2-byte block synchronization signal, followed by 4 bytes of ID data, 20 bytes of subcode data, and a 4 byte parity, in that order. In the case of the subcode, the 40 bytes of data contained in pairs of adjacent lines are used to form an inner code to provide an error correction capability but an outer code is not produced using the subcode data. More specifically, as shown in Figure 11C, the 40 bytes of data contained in two adjacent rows of a (20 byte x 6 byte) data matrix are encoded to form a respective inner code, thus to yield an 8-byte "C1" parity. 4 bytes of the 8 byte parity thus produced are appended to each line to record the "C1" parity. Since the inner code parity formed when encoding the subcode is 8 bytes long, it can be arranged in the same form as the inner code of the video data. This permits the use of a single encoding circuit to form the inner code for each of the different types of data. Shorter sync blocks are more likely to be reproduced as valid data in the high-speed reproduction mode than are longer sync blocks. Accordingly, the amount of data in each subcode sync block is selected as 20 bytes, rather than 40, to shorten its length so that a greater amount of the subcode data is reproduced in the high-speed reproduction mode, to reliably permit detection of the tape's position from the subcode. It will thus be seen that the respective sizes of each sync block of video data, audio data and subcode form a ratio of integers of (90 : 45 : 30 = 6 : 3 : 2). Accordingly, even though sync blocks of different lengths are contained in each track, the necessary timing control circuitry is advantageously simplified. Moreover, the lengths of the block synchronization signals are the same in each of the various types of sync blocks, as are the lengths of each of the ID signals. Also, the data format of the ID signals is commonly shared among the various types of sync blocks. Consequently, the circuitry used to generate and process such data can be commonly employed. 6. Interleaving and Error Correction of Audio Signals In the NTSC system, having 525 scanning lines per frame and 60 fields per second, the data of each frame are recorded in 10 tracks, designated T0-T9, as illustrated in Figure 12. As described above, the disclosed embodiment of the invention records audio data in separate sections, audio 1 and audio 2, in each track separated by a video data section thereof. For example, PCM signals including two channels of audio corresponding with each video frame interval, having a sampling frequency of 48KHz and linearly quantized with 16 bits per sample, are recorded in the audio 1 and 2 sections of the corresponding 10 tracks of that frame. Figure 13 provides an analogue representation of the left channel of a PCM audio signal coinciding with one frame period of a corresponding NTSC video signal. In the NTSC signal, the PCM audio signal sequence of each frame period is divided into five (N = 5) contiguous intervals each including sequential samples of audio data, so that the audio data spanning one frame period are recorded over 2N tracks. Even-numbered samples of the first PCM audio intervals are assembled as a group represented as L0 for recording in a predetermined section of a respective track. A sequence L1 which contains the odd numbered samples of the first PCM audio signal interval is likewise assembled as a group for recording in a predetermined track section. In like manner, sequences which contain even numbered samples of the second, third, fourth and fifth intervals of each PCM audio signal sequence corresponding with each frame, represented as L2, L4, L6 and L8, respectively, are assembled for recording in the same fashion. In addition, groups of odd numbered samples from the second, third, fourth and fifth intervals of the PCM audio signal sequence of each frame, represented as L3, L5, L7 and L9, respectively, are likewise assembled. The PCM audio signals of the right (R) channel within the same frame interval are divided in the same manner into five intervals each including two groups of which each includes a respective one of the odd and even numbered samples of its interval. The groups are designated R0 to R9, wherein correspondingly numbered groups of the left and right channels comprise samples corresponding in time. These PCM audio signal groups are interleaved and encoded to provide error correction codes, and are recorded in this form in the predetermined track sections. As mentioned above, both a soft tape mode and user recording mode are provided for recording the PCM audio signals. The soft tape mode, for example, is used by movie production companies to create soft tapes while the user recording mode is employed, for example, by an individual to record data of personal interest. In the soft tape mode, each sample of the PCM audio signal comprises 16 bits. On the other hand, in the user recording mode, each sample comprises 8 bits. Thus, the amount of PCM data representing the audio signal produced in the user recording mode is half that produced in the soft tape mode. In addition, it is possible to use different sample frequencies for the two modes so that the ratio of their respective amounts is the same. Figure 14A illustrates a technique for interleaving the grouped PCM audio signals corresponding with an NTSC video signal in the soft tape mode. The groups L1, L3, L5, L7 and L9 are recorded in the audio 2 sections of the tracks T0-T4 recording each frame, while the groups R0, R2, R4, R6 and R8 are recorded in the audio 1 sections of the same tracks. The groups R1, R3, R5, R7 and R9 are recorded in the audio 2 sections of tracks T5-T9 of each frame, while the groups L0, L2, L4, L6 and L8 are recorded in the audio 1 sections of these tracks. Figure 14B illustrates a technique for interleaving the grouped PCM audio signals corresponding with an NTSC video signal in the user recording mode. In this mode, as noted above, the amount of data is half that in the soft tape mode for the same time interval. Thus, the same PCM audio signal can be recorded in both audio sections of each track in the same format as in the soft tape mode. As an example, audio data groups L1 and R0 are recorded in the audio 1 section of track T0, and in tracks T1-T9, the groups L3 and R2, L5 and R4, L7 and R6, L9 and R8, R1 and R0, R3 and L2, R5 and L4, R7 and L6, and R9 and L8 are recorded respectively, in both audio sections thereof. In this example, the audio 1 section of each track is divided into first and second half portions such that, in the first half portion, the data recorded in the audio 2 section in the soft tape mode, that is, L1, L3, ..., and R9 as illustrated in Figure 14B, are recorded, while in the second half portion, the data recorded in the audio 1 section during the soft tape mode, that is, R0, R2, ..., and L8, are recorded. Figure 15 provides a further example of an interleaving technique for use in the user recording mode. In the example of Figure 15, the recording positions of audio data groups L2, R2, L6 and R6, as illustrated in Figure 14B, are exchanged with those of groups L3, R3, L7 and R7, respectively. The interleaving technique of Figure 15 can be similarly applied for use in the soft tape mode. In the interleaving technique as shown in Figure 15, the PCM audio signal of each frame is divided into N intervals. These intervals are allocated between the first and second groups of 2N tracks recording each frame and separately recorded therein. In the PAL system which employs 625 scanning lines and 50 frames per second, the data of each frame is divided into tracks T0 to T11 (so that 2N = 12), as illustrated in Figure 16. Thus, the PCM audio signal of each frame period is divided into six (N = 6) intervals over 12 tracks. The PCM audio signal is interleaved from section to section in the various tracks. Figure 17 provides an analogue representation of the left (L) channel of a PCM audio signal spanning one frame interval of a PAL video signal. The PCM audio signal of each frame interval is divided into six contiguous intervals. The PCM audio signal sequence contained in each interval is divided into respective sequences or groups each having either even numbered samples, that is, groups L0, L2 ..., and L10, or odd numbered samples, that is, groups L1, L3, ..., and L11. In like manner, the right (R) channel PCM audio signal of each PAL frame interval is divided into groups of odd and even numbered samples from respective audio intervals and designated R0 to R11. As illustrated in Figure 18A, in the soft tape mode different groups of audio data are recorded in the two audio sections of each track, such that even and odd numbered sequences within respective groups of each audio channel are interleaved as distributed among the tracks T0-T11. Like the example of Figure 14A, the even/odd group interleaving sequence is different in tracks T6-T11 as compared with the sequence in tracks T0-T5. In the user recording mode, as illustrated in Figure 18B, the interleaving technique allocates the same samples to the audio 1 and 2 sections of each track, such that within each section the signals are interleaved between first and second half portions thereof in the same manner as between the audio 1 and audio 2 sections of each track in the soft tape mode. When an error occurs in the reproduced data due to a scratch in the tape, to dust or to fingerprints thereon, the magnitude of the error may exceed the capability of the system to correct in its entirety, so that correction is carried out to the extent possible and the data which has been lost must be reconstructed from validity reproduced data. The above-described interleaving process provides a superior error reconstruction capability. The error reconstruction capability available in the soft tape mode will now be described with reference to Figures 19A and 19B. In this example, as illustrated in Figure 19A, a data error extends both in the lateral and longitudinal directions of a tape, represented therein as a hatched area. Accordingly, in this case, audio data can be reproduced only from the audio 2 section. Referring again to Figure 14A, odd numbered samples of the left channel in groups L1, L3, L5, L7 and L9 and the odd numbered samples of the right channel, R1, R3, R5, R7 and R9, are nevertheless obtained as valid data despite the assumed error. By using these odd-numbered samples, the missing even numbered samples can be reconstructed. As an example, the average values of samples both following and preceding an erroneous sample may be used to produce an average value to be substituted therefor. As a further example, it is assumed that data within the hatched area of Figure 19B have been lost due to an error, so that the data in both of the audio 1 and audio 2 sections of tracks T0-T4 are affected. It will be seen from Figure 14B that the valid data obtained from groups R1, R3, R5, R7 and R9 together with groups L0, L2, L4, L6 and L8 may be employed to reconstruct the lost data of each channel through interpolation. In the user recording mode, a similarly effective error correcting capability is provided. Since the user recording mode records the same data in both audio sections of each track, it may be thought that the loss of data from a given section may be compensated by substituting data from the other. However, since the audio data can also be after-recorded, it is not certain in all instances that the data will be the same in both sections. In this case, errors are corrected or compensated separately in each section. With reference to Figure 20A, an example of a longitudinal defect in a magnetic tape caused, for example, by a scratch resulting from a defect in the tape transport system, has rendered the data reproduced from a first half of the audio 1 section erroneous. Consequently, the PCM audio signal groups in this half of the audio 1 section, that is, R0, R2, ... L6 and L8 as illustrated in Figure 14B have been lost. On the other hand, the data in the upper half of the section, that is, groups L1, L3 ..., R7, and R9, are valid. In this case, the lost data can be reconstructed through average value interpolation. Figure 20B provides an example of data lost from tracks T0-T4 where it is assumed that the data were recorded in the user recording mode. It will be seen that, by using the valid data from the remaining tracks T5 to T9, the erroneous data can be reconstructed. When data are recorded with the use of a pair of heads, as in this embodiment, one head sometimes becomes clogged. When this occurs, valid data can be reproduced from only every other track. In the example of Figure 21, it is assumed that the data in tracks T0, T2, T4, T6 and T8 cannot be reproduced because one of the heads has become clogged. When this occurs, in the case of data recorded in either the soft tape mode or the user recording mode, the odd numbered data of the left channel and even numbered data of the right channel becomes invalid. These data can, nevertheless, be reconstructed with the use of the data reproduced from tracks T1, T3, T5, T7 and T9. 7. Composition of the ID Data and Definition of After-Recording Area Figure 22 illustrates an exemplary format of an ID signal inserted into each sync block. The ID signal format is common to the video and audio data, as well as to the subcode. The ID signal includes four bytes of data labelled in sequence as ID0, ID1, ID2 and ID3. ID0 includes a one-bit frame ID (FR-ID), a two bit data ID, a two-bit broadcasting system-type ID, a two-bit after-recording ID and a one-bit mode ID. The frame ID is inverted with each new frame. The data ID is used to distinguish the type of data within its sync block, whether video, audio 1, audio 2 or subcode. The broadcasting system-type ID includes one bit which is used to distinguish the NTSC (525/60) and PAL (625/50) signals and another bit which is used to distinguish HD (high resolution) and SD (standard resolution) video signals. The after-recording ID is used to distinguish after-recorded data from non-after-recorded data. The non-after-recording mode includes both recording on a blank tape as well as overwriting an entire track. In the non-after-recording mode, the tracking control pilot signals at both ends of the track are always rewritten. The mode ID is used to distinguish the soft tape mode and the user recording mode. The after-recording mode can be employed for after-recording of all video, audio and subcode data. ID1 comprises six bits representing the track in which the data are recorded and a spare two-bit recording area. The track number data represents the track number assigned to each of the 2N tracks of each frame. Since it is anticipated that in the future image signals such as an HD signal having a large amount of information will be recorded with the use of the present embodiment, a relatively large number of bits are assigned for recording the track number data. In addition, the spare area is provided for recording any further ID which may be required in the future. ID2 is a block number comprising eight bits. A sync block number is assigned to each sync block of each track. ID3 is a parity value, generated to enable detection and correction of errors in the ID0, ID1 and ID2 bytes. In the after-recording mode, the recording area should be precisely defined. Should the recording area deviate from that desired, previously recorded data not intended to be changed will be erased. If the non-recording areas such as the IBG's are widened to alleviate this problem, the recording density is disadvantageously reduced. Figure 23 illustrates a subsystem for generating a control pulse for defining the after-recording area by using the above-mentioned after-recording ID. In general, the after-recording area is defined by the subsystem of Figure 23 in the following manner. First, the terminal position of the preceding recording section is detected. A position spaced apart from such terminal position on the tape by predetermined number of sync blocks is selected as the start position of the after-recording area. The terminal position of the after-recording area is defined in accordance with the type of after-recorded data. For example, when video data is after-recorded, the terminal position of the audio 1 section, more specifically, the last position of the following postamble, is detected. Thereafter, the number of sync blocks is counted using the pulses of the reproduced block synchronization signal to define the start position of the video section's preamble. Next, a further number of sync blocks is counted to define the terminal position of the video section's postamble. In this example, the video data area and the pre- and post-amble sections constitute the after-recording area. However, if the data of the preceding section have been after-recorded, the position of a following after-recording area determined by counting the number of block synchronization pulses from the preceding after-recorded data section can be inaccurate. Thus, when the after-recording ID is detected in the data section preceding the area to be after-recorded, its block synchronization signal is not used to define the following after-recording section. If all of the data in the tracking preceding the after-recording area have been after-recorded , the pulses detected from the pilot signal recording section ATF1 at the start position of the track are used. Since the pilot signal has a predefined frequency, even though its data format does not correspond with the defined sync block format, it can nevertheless be employed for this purpose. Likewise, when data are to be after-recorded in the audio 1 section, the detection pulses of the pilot signal are used. The subsystem of Figure 23 provides a means of defining the recording area for use in the disclosed embodiment. The subsystem of Figure 23 includes a decoder 51 provided with the reproduced data ID and sync number. The decoder 51 generates preset pulses at the last sync block of the recording section preceding the area to be after-recorded . The data ID is supplied to the decoder 51 since the number of the last sync block within any given data section depends on the type of data recorded therein. The preset pulses are supplied to a counter 52 which serves to determine the start position of the after recording area. A logic circuit 53 receives the after-recording ID, a pilot signal detection pulse Pf and a block synchronization pulse Psy. When the after-recording ID is at a low level representing the non-after-recording mode, the block synchronization pulses Psy are supplied from the logic circuit 53 to the counter 52. The logic circuit 53 defines the start position of the after-recording area in accordance with the block synchronization pulses of the after-recorded data. The count generated by the circuit 52 is supplied to a decoder 54 which is also supplied with a signal representing the type of data to be after-recorded. The decoder 54 produces data representing the start position of the after-recording area based on the type of data to be after-recorded. An output of the decoder 54 is supplied to an after-recording area generating circuit 55 which is also supplied with a signal indicating the type of data to be after-recorded. The after-recording area generating circuit 55 defines the start position of the after-recording area based on the data from the decoder 54 and determines the terminal position of the area based on the start position as well as the type of after-recorded data. The after-recording area generating circuit 55 produces an after-recording area pulse Px having a high state beginning at the after-recording start position and switching to a low state at the terminal position of the after-recording area as determined in accordance with the type of after-recorded data. When the heads read data from the start position of a track, ATF data is first reproduced. At this point, the data ID representing the ATF-type data is input to the decoder 51 so that a corresponding preset value is loaded in the counter 52. The preset value in this case is the number of blocks from the start position of the T-amble to the start position of the audio 2 section, for example, 317 in this embodiment. The counter 52 proceeds to count the number of internally generated block synchronization pulses starting with the loaded value at least until a count representing the next data section is produced. When the heads read an audio section following the ATF section, they detect the after-recording ID for the data therein. At this point, if the after-recording ID indicates that the audio data has been recorded in the after-recording mode, the counter 52 continues to count the block synchronization pulses rather than presetting a new count number. On the other hand, when the after-recording ID indicates that the audio data of the section being scanned has not been recorded in the after-recording mode, a new preset value is loaded from the decoder 51 into the counter 52. The preset value in this example is the number of blocks from the start position of the video section preamble to the start position of the audio 2 section preamble, for example 296. The counter 52 counts the number of pulses of the block synchronization signal Psy starting with the preset value. At this point, the counter 52 is enabled by the block synchronization pulses. When the section being read contains after-recorded data, the block synchronization pulses generated by the logic circuit 53 are input. When the section contains non-after-recorded data, the block synchronization signal Psy input to the logic circuit 53 are instead used as enabling pulses. When data are after-recorded in the audio 2 section, if the data in the preceding video section are not after-recorded, the counter 52 is preset at the last position of the video section's postamble. For example, after two block synchronization pulses are generated following the terminal position of the postamble, a signal representing the start position of the after-recording area is output by the decoder 54. In addition, by using this signal and the data representing the type of data to be after-recorded, the after-recording area generating circuit 55 can detect the terminal position of the after-recording area. When the after-recording ID indicates that the video area has been after-recorded , the terminal position of the preceding audio 1 section is detected. However, when its data have been after-recorded, the detection pulse Pf from the ATF1 section is instead used. The above-mentioned after-recording area pulse Px is supplied as a control signal to the recording amplifiers 12A and 12B of Figure 1. During the high state of the pulse Px, the recording amplifiers 12A and 12B become active. When necessary, the after-recording pulse Px is supplied to the reproducing amplifiers 21A and 21B to render them inactive. It will be seen, therefore, that by recording an after-recording ID signal indicating whether or not accompanying data has been after-recorded , the present embodiment provides the ability to avoid the use of data as a positional reference in the after-recording mode whose position may be inaccurate. Accordingly, a recording system provided with such information is enabled to define an after-recording area with greater accuracy thus to substantially reduce the likelihood that desired data will be erased inadvertently in the after-recording process.

Claims: An apparatus for recording digital information signals including image portions and audio portions in successive track sections on a magnetic tape, and for reproducing the digital information signals from the tape the apparatus comprising: digital signal processing means for generating said digital information signals; means (112) for generating ID signals each indicating whether a corresponding digital information signal portion is to be recorded in an after-recording mode in a corresponding one of the successive track sections of said magnetic tape; combining means (14) for combining said ID signal with the corresponding digital information signal portion to form a recording signal; means (11, 12A, 12B, 13A, 13B) for recording the recording signal in the successive track sections; reproducing means (13A, 13B, 21A, 21B, 22, 23) for reproducing signals recorded in the successive track sections; means (25, 38) for obtaining a reproduced ID signal from the reproduced signals; and control means (51, 55) for controlling the after-recording of a digital information signal on a selectable one of the track sections, the control means comprising means (53) responsive to ID signals reproduced from the tape for detecting track sections which are not after-recorded; means (51, 52, 54) responsive to the detecting means for defining the position of a selected track section referenced to the nearest preceding track section which is not after-recorded and means (55) responsive to the position defining means for producing a control signal (Px) enabling after-recording in the selected track section. Apparatus according to claim 1, wherein said position defining means (51, 52, 54) is operable to define the position of said selected track section based on reference position data stored within said preceding track section and indicating a reference position within said preceding track section. Apparatus according to claim 2, wherein said position defining means (51, 52, 54) is operable to define the position of said selected section based on a scanning distance from said reference position to said selected section. Apparatus according to claim 3, wherein said reproducing means (13A, 138, 21A, 21B, 22, 23) is operable to reproduce block synchronization signal (Psy) from the successive track sections and wherein said position defining means (51, 52, 54) is operable to determine said scanning distance, based on the reproduced block synchronization signals (Psy), from the said preceding section only when the said preceding section has not been after-recorded. Apparatus according to claim 3, wherein said reproducing means (13A, 13B, 21A, 21B, 22, 23) is operable to reproduce a data-type signal from said preceding section indicating the type of data recorded therein and wherein said position defining means (51, 52, 54) is operable to determine said scanning distance based on the data-type signal. Apparatus according to claim 1, wherein said reproducing means (13A, 13B, 21A, 21B, 22, 23) is operable to reproduce a tracking control pilot signal (ATF) from an initial section of said successive track sections and data from a plurality of sections following said initial section and each having a respective ID signal recorded therein, and wherein said position means (51, 52, 54) is operable to define said position of said selected section based on said tracking control pilot signal (ATF) when the ID signals indicate all of said plurality of following sections which also precede the selected section were after-recorded. A method of recording digital information signals including image portions and audio portions in successive track sections on a magnetic tape, and for reproducing the digital information signals from the tape, the method comprising the steps of: generating said digital information signals; generating (112) ID signals each indicating whether a corresponding digital information signal portion is to be recorded in an after-recording mode in a corresponding one of the successive track sections of said magnetic tape; combining (14) said ID signal with the corresponding digital information signal portion to form a recording signal; recording (11, 12A, 12B, 13A, 13B) said recording signal in the successive tracks; reproducing (13a, 13B, 21A, 21B, 22, 23) signals recorded in the successive tracks; obtaining (25, 38) a reproduced ID signal from the reproduced signals; and controlling the after-recording of a digital information signal on a selectable one of the track sections by the steps of responding (53) to ID signals reproduced from the tape to detect track sections which are not after-recorded, defining (51, 52, 54) the position of a selected track section with reference to the nearest preceding track section which is not after-recorded, and producing (55) a control signal (Px) enabling after-recording in the selected track section in dependence upon the defined position of the selected section. A method according to claim 7, wherein the step (51, 52, 54) of defining a position of said at least one section comprises defining the position of said at selected section based on reference position data stored within said preceding track section and indicating a reference position within said preceding track section. A method according to claim 8, wherein the step (51, 52, 54) of defining the position of said selected section comprises defining the position thereof based on a scanning distance from said reference position to said selected section. A method according to claim 9, wherein the step of reproducing (13, 21, 22, 23) signals comprises reproducing block synchronization signals (Psy) from the successive track sections, and wherein the step of defining the position of said selected section comprises determining said scanning distance based on the reproduced block synchronization signal (Psy) from the said preceding section only when said preceding section has not been after-recorded. A method according to claim 9, wherein the step of reproducing (13, 21, 22, 23) signals comprises reproducing a data-type signal from said preceding section indicating the type of data recorded therein and the step of defining the position of said selected section comprises determining said scanning distance based on the data-type signal. A method according to claim 11, wherein the step of reproducing (13, 21, 22, 23) signals comprises reproducing a tracking control pilot (ATF) signal from an initial section of the successive track sections and data from a plurality of sections following said initial section and each having a respective ID signal recorded therein, and wherein the step of defining said position of said selected section comprises defining said position based on said tracking control pilot signal (ATF) when the ID signals indicate all of said following sections which also precede the selected section were after-recorded.

Inventors: INOUE HAJIME, KANOTA KEIJI, KUBOTA YUKIO, INOUE, HAJIME, KANOTA, KEIJI, KUBOTA, YUKIO, INOUE, HAJIME, C/O SONY CORPORATION, KANOTA, KEIJI, C/O SONY CORPORATION, KUBOTA, YUKIO, C/O SONY CORPORATION
Applicants: SONY CORP, SONY CORPORATION
Application year: 1992
Main classification: H04N9
IPC codes: H04N9, G11B27, G11B20