Digital recording and/or reproducing apparatus of video signal

Abstract: In a digital VCR, which carries out bit rate reduction coding of digital video signals for magnetically recording and reproducing the same, a plurality of blocks each including the digital video signal of a plurality of pixels are formed, and the digital video signals are encoded for each block. A code amount is controlled so that the code amount may be constant on the basis of one or more of the plurality of blocks, and encoding is carried out for correcting a possible error, whereby error correction blocks are formed. The error correction blocks are rearranged so that the error correction blocks included in the blocks, which are adjacent to each other in a screen, may be adjacent to each other on a recording medium, and the data for three rectangular regions, which are obtained by trisecting the screen with respect to the horizontal direction, may be recorded in corresponding three tracks. Thereby, mosaic deformation in a reproduced picture can be prevented.

Description: The present invention relates to a digital recording and/or reproducing apparatus of a video signal, and more particularly, to a recording apparatus for carrying out bit rate reduction coding of a video signal and digitally recording the coded video signal on a recording medium, a reproducing apparatus capable of digitally reproducing a video signal at a changeable or extraordinary speed from a recording medium having such video signal recorded thereon, and a recording/reproducing apparatus having such digital recording and reproducing functions. Description of the Background Art In recent years, an apparatus has been developed for recording digitally a video signal on a recording medium and reproducing digitally the same from the recording medium. One such typical apparatus is the so-called digital video cassette recorder (referred to as "digital VCR" hereinafter) which is available for practical use. In such a conventional digital VCR, a digital video signal which is in a bit rate reduction coded (bandwidth compressed) state for the purpose of reducing the enormous amount of information to a level suitable for recording and reproduction is recorded on a magnetic tape and reproduced therefrom using a rotary head. Fig. 1 is a block diagram schematically showing a structure of the conventional digital VCR using the bit rate reduction coding method. Such conventional digital VCR is disclosed in Japanese Patent Laying-Open No. 2-220270, for example. Referring to Fig. 1, at the time of recording, a digital video signal provided from a video signal source not shown is supplied to a block shuffling circuit 101 included in a digital VCR. The block shuffling circuit 101 divides the digital video signal into a plurality of blocks, each of which is formed of a plurality of pixels and has a certain size, to rearrange the video signal data on the basis of such block. Then, the digital video signal rearranged by the block shuffling circuit 101 is applied to a bit rate reduction coding circuit 102 where the bit rate reduction coding of data on the basis of block is carried out to realize an amount of information suitable for recording onto a tape. More specifically, the video signal of each block entered into the bit rate reduction coding circuit 102 is subjected to the well-known orthogonal transform coding, and then subjected to a variable length coding process according to the information amount of each block. As a result, reduction of the data amount, i.e., bit rate reduction coding of the video signal is realized. The video signal is further supplied to an error correction coding circuit 103. The error correction coding circuit 103 adds an error correction code (parity) to the block data thus subjected to bit rate reduction coding, and supplies the same to a synchronizing signal and ID signal applying circuit 104. The synchronizing signal and ID signal applying circuit 104 adds a synchronizing signal and an ID signal to the supplied video signal to provide the same to a modulation circuit 105. The modulation circuit 105 modulates the supplied signal while suppressing the direct current (DC) component thereof to record the same on the above-described block basis on a magnetic tape 107 as a recording medium via a magnetic head 106. At the time of reproduction, recorded data on the tape 107 are reproduced via a magnetic head 108 to be demodulated by a demodulation circuit 109. The demodulated video signal is supplied to a synchronizing signal and ID signal detection circuit 110 where detection of the synchronizing signal and ID signal is carried out. Then, the video signal is applied to an error correction decoding circuit 111. The error correction decoding circuit 111 carries out error correction of the applied video signal. The corrected data is subjected to variable length decoding and inverse orthogonal transform processes for each block by a decoding and concealment circuit 112 to restore the original data of each block. On the other hand, concealment processing of a video signal is carried out for the portion of data where error correction could not be carried out in the error correction decoding circuit 111. The data thus subjected to the error correction and decoding process is supplied to a block de-shuffling circuit 113 where the data is rearranged in a manner opposite to that by the block shuffling circuit 101 of the recording system. As a result, the video signal arranged in the original form, i.e., the same form as that at the time of recording is reproduced. The data signal of the block de-shuffling circuit 113 is output appropriately to be provided to a monitor device and the like not shown. The digital VCR which processes the video signal on the basis of block as described above has the following disadvantage, compared with the digital VCR (e.g., Dl-format digital VCR) which processes the video signal on the basis of pixel. In the case where the video signal is processed on the basis of block, reproduction at an extraordinary speed such as high speed search is usually carried out by displaying image data belonging to a plurality of different fields as one reproduced picture on a screen. More specifically, in the case where the processing of signal is carried out on the basis of pixel and the shuffled pixels are recorded on and reproduced at a high speed from a track, the image data belonging to the plurality of fields are dispersed in the whole picture, so that unnatural discontinuity does not generate in the picture, and thus the picture can have good quality. Meanwhile, in the case where the data are recorded on the basis of block including the plurality of pixels and are reproduced at a high speed, blocks belonging to different fields may be adjacent to each other in the reproduced picture and a boundary between such small blocks is visually recognized. If a large number of small blocks belonging to different fields are reproduced in the minutely mixed manner, such boundaries are also generated minutely, resulting in the reproduced picture which appears as if a mosaic pattern processing has been applied. As a result, the quality of the reproduced picture in the high speed reproduction remarkably decreases. Patent Abstracts of Japan vol. 14, no. 525 (P-1132) & JP-A-2 220 270 discloses a digital video signal recording device having block forming means for forming data blocks. One data block is taken from each area A to F and combined to form a fixed length block. The fixed length blocks are then recorded on a recording medium. The fixed length blocks containing data blocks corresponding to adjacent regions on the screen are recorded adjacent on the recording medium. Similarly, IEEE Transactions on Consumer Electronics, vol. 37, no. 3, pages 261 - 266 discloses combining data blocks (compression blocks) into sync blocks, and recording the sync blocks on a recording medium. Data blocks that are adjacent on the screen are recorded in different sync blocks, but adjacent sync blocks contain data blocks that are adjacent on the screen. EP-A-0 471 118 (prior art under Article 54(3) EPC) discloses a digital video signal recording device where two data blocks from separate regions are combined to form a fixed length block which is recorded on a recording medium. EP-A-0 470 772 (prior art under Article 54(3) EPC) discloses an apparatus where data blocks from N regions of the screen are recorded on N respective tracks. SUMMARY OF THE INVENTION It is desirable to provide a digital recording and/or reproducing apparatus of a video signal, in which quality of a reproduced picture in an extraordinary speed reproduction is improved. It is also desirable to provide a digital recording and/or reproducing apparatus of a video signal, which prevents a mosaic pattern in a picture reproduced by a high speed reproduction. The present invention provides recording apparatus for recording a video signal on a recording medium as set out in claim 1. The invention also provides a reproduction apparatus for reproducing a digital video signal as set out in claim 5. The invention also provides a method of recording a digital video signal as set out in claim 8. As a main advantage, therefore, the present invention can prevent mosaic deformation of a picture reproduced at an extraordinary speed and thereby can achieve a high speed reproduced picture of good visual quality, because data blocks are rearranged so that the data blocks, which are adjacent to each other on the screen, are adjacent to each other on the recording medium and the screen is divided into N (N is a positive integer) rectangular regions which are arranged in horizontal and/or vertical directions and the data for the respective rectangular regions are recorded on the N tracks, respectively. The foregoing and other features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram schematically showing a structure of a conventional digital VCR; Fig. 2 is a block diagram schematically showing a structure of a digital VCR according to an embodiment of the present invention; Fig. 3 schematically shows an arrangement of magnetic heads in a first embodiment of the invention; Fig. 4 schematically shows rectangular regions on a screen in the first embodiment of the invention; Fig. 5 schematically shows a data arrangement in tracks on a tape in a digital VCR according to the first embodiment of the invention; Fig. 6 schematically shows the relation between recording tracks formed on a tape by a digital VCR of the first embodiment of the invention and a trace of a head during a high speed reproduction; Figs. 7A and 8B schematically show the effects of the first embodiment at the relatively low speed reproduction; Figs. 8A and 8B schematically show the effects of the first embodiment at the relatively high speed reproduction; Fig. 9 schematically shows the relation between recording tracks formed on a tape and a trace of a head during a quadruple speed reproduction in the first embodiment of the invention; Fig. 10 is a waveform diagram showing reproduced signals supplied from heads in the first embodiment of the invention; Figs. 11 and 12 each schematically show signals forming respective rectangular regions in a reproduced picture in the first embodiment of the invention, respectively; Fig. 13 schematically shows a reproduced picture obtained by composition of the signals in Fig. 11; Fig. 14 is a block diagram schematically showing a structure of a digital VCR according to a second embodiment of the present invention; Fig. 15 schematically shows an arrangement of magnetic heads in a second embodiment of the invention; Fig. 16 schematically shows rectangular regions in a screen in the second embodiment of the invention; Fig. 17 schematically shows a data arrangement in tracks on a tape in a digital VCR according to the second embodiment of the invention; Figs. 18 and 19 each schematically shows the relation between recording tracks formed on a tape by a digital VCR of the second embodiment of the invention and a trace of a head during a high speed reproduction; Fig. 20 schematically shows a reproduced picture in the high speed reproduction in the second embodiment of the invention; Fig. 21 schematically shows an arrangement of magnetic heads in a third embodiment of the invention; Fig. 22 schematically shows the manner of setting rectangular regions in a screen in the third embodiment of the invention; Fig. 23 schematically shows a data arrangement in tracks on a tape by a digital VCR according to the third embodiment of the invention; Fig. 24 schematically shows the relation between recording tracks formed on a tape by a digital VCR of the third embodiment of the invention and a trace of a head during a high speed reproduction; Fig. 25 schematically shows the relation between recording tracks formed on a tape by a digital VCR in the third embodiment of the invention and a trace of a head during a triple speed reproduction; Fig. 26 is a waveform diagram showing reproduced signals supplied from heads in the third embodiment of the invention; Fig. 27 schematically shows signals forming respective rectangular regions in a reproduced picture in the third embodiment of the invention; Fig. 28 schematically shows a reproduced picture obtained by composition of the signals in Fig. 27; Fig. 29 schematically shows an arrangement of magnetic heads in a fourth embodiment of the invention; Fig. 30 schematically shows the manner of setting rectangular regions in a screen in the fourth embodiment of the invention; Fig. 31 schematically shows a data arrangement in tracks on a tape in a digital VCR according to the fourth embodiment of the invention; Figs. 32 and 33 each schematically shows the relation between recording tracks formed on a tape by a digital VCR of the fourth embodiment of the invention and a trace of a head during a high speed reproduction; and Fig. 34 schematically shows a reproduced picture in the high speed reproduction in the fourth embodiment of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 2 is a block diagram schematically showing a structure of a digital VCR according to an embodiment of the present invention. Referring to Fig. 2, at the time of recording, a digital video signal provided from a video signal source not shown is supplied to a blocking circuit 1 included in a digital VCR. Similarly to the prior art already described with reference to Fig. 1, the blocking circuit 1 combines a plurality of pixels in the horizontal and vertical directions of a digital video signal to form a plurality of rectangular units (blocks of data) not shown. The digital video signal of each block thus rearranged is supplied to an orthogonal transform circuit 2. The orthogonal transform circuit 2 applies an orthogonal transform process to the entered digital video signal of each block using a well known method such as discrete cosine transform, and supplies the same to an encoding circuit 3. The encoding circuit 3 applies an encoding process to the digital video signal according to the amount of entered information of each block. More specifically, the encoding circuit 3 carries out control so that the code length has a fixed value for each block or for each plurality of blocks, whereby a data block of a fixed length is obtained. The video signal provided from the encoding circuit 3 is supplied to an error correction encoding circuit 4 where an error correction code (parity) is added for correcting a possible error to be generated in a reproduction system. More specifically, the error correction encoding process is carried out using the well known Reed-Solomon product codes including outer codes and inner codes, resulting- in a plurality of error correction blocks. In each error correction block, the above-described fixed length blocks are stored in one-to-one correspondence with inner codes. The video signal of each block subjected to the error correction coding process is supplied to a rearranging circuit 5. The rearranging circuit 5 rearranges the blocks of data into an arrangement which will be described later. The blocks of data thus rearranged are modulated by a modulation circuit (not shown), and then are recorded on a magnetic tape 7 through magnetic heads 6 which are symbolized in the figure. Fig. 3 schematically shows an arrangement of the magnetic heads 6 in Fig. 2. In Fig. 3, the magnetic heads 6 include + azimuth head 20a and - azimuth head 20b mounted on a rotary drum 30, and the data for one picture on the screen is recorded on the magnetic tape 7 for every one and half rotation of the rotary drum 30. Thus, the data for one picture is recorded on the magnetic tape 7 while being divided into three tracks. In a first embodiment of the invention, which will be described below, the whole screen is equally divided into three rectangular regions A1, B1 and C1 aligned in the horizontal direction each of which is formed by a plurality of the above described data blocks as shown in Fig. 4, and the video signal for each rectangular region is recorded in the corresponding track on the magnetic tape 7 by the corresponding magnetic head in accordance with the recording sequence indicated by an arrow, as shown in Fig. 5. For example, the data of blocks for the left rectangular region A1 in Fig. 4 is recorded in a left track 1 among three tracks, which are used for recording the data for one picture and are defined between adjacent two solid lines in Fig. 5, by the magnetic head 20a during an initial half rotation of the rotary drum 30. The data of blocks for the middle rectangular region B1 in Fig. 4 is recorded in a middle track 2 in Fig. 5 by the magnetic head 20b during the next half rotation of the rotary drum 30. Thereafter, the data of blocks for the right rectangular region C1 in Fig. 4 is recorded in a right track 3 in Fig. 5 by the magnetic head 20a during the next half rotation of the rotary drum 30. As described above, the data of blocks which are adjacent to each other in the screen are recorded adjacently in each track. At the time of reproduction, the recorded data on the tape 7 shown in Fig. 5 is reproduced via a magnetic head 8, and is demodulated by a demodulation circuit not shown. The demodulated video signal is supplied to an inverse rearranging circuit 9 where the blocks are rearranged to obtain the original arrangement of the plurality of error correction blocks. The error correction blocks of the video signal which are rearranged by the inverse rearranging circuit 9 are supplied to an error correction decoding circuit 10. The error correction decoding circuit 10 applies error correction to the supplied video signal for correcting an error generated at the time of reproduction, whereby the original fixed length blocks are restored and supplied to a decoding circuit 11. The error correction decoding circuit 10 also applies an error flag to a block that could not be corrected, and provides the same to a concealment circuit 13. The decoding circuit 11 decodes the coded data for each block, and applies the same to an inverse orthogonal transform circuit 12. The inverse orthogonal transform circuit 12 applies an orthogonal transform process, which is opposite to that at the time of recording, to the data for each block to obtain pixel data for each block and applied the same to the concealment circuit 13. If the concealment circuit 13 has received the error flag from the error correction decoding circuit 10, the concealment circuit 13 replaces the pixel data of the block in question by pixel data of the block at the same position in a preceding picture. The pixel data thus obtained for each block is supplied to a block decomposition circuit 14. The block decomposition circuit 14 decomposes the pixel data of each block to restore the arrangement of the digital video signal into the same form as that of the digital video signal supplied to blocking circuit 1 at the time of recording, and applies the same to a monitor device not shown. Thus, display of a reproduced image is possible. Fig. 6 schematically shows the relation between recording tracks formed on the tape by the digital VCR of the above-described embodiment and a trace of the head in the high speed reproduction. At the time of high speed reproduction, the head for reproduction traverses and scans the plurality of record tracks formed on the tape, as shown in Fig. 6. By employing an azimuth recording method, one head can detect a video signal in every other track, as shown by the shaded line in Fig. 6. According to the present embodiment of the invention, data of blocks are recorded successively on each track, as described before, so that a signal can be detected with a certain continuity as such shown in Fig. 6 even at the time of high speed reproduction. According to an embodiment of the present invention, the adjacent blocks in each record track contain the data of blocks located adjacent on a screen, so that the number of the blocks that could be detected successively on the each record track (each of the shaded regions of Fig. 6) at the time of high speed reproduction is equal to the number of the blocks continuous on the screen. As a result, mosaic deformation on the screen at the time of high speed reproduction can be prevented to obtain a picture of good visual picture quality at the time of high speed reproduction. In the operation at the extraordinary reproduction speed of a relatively low value, it is determined whether the reproduction is allowed or not on the basis of blocks of the same number as that of horizontally aligned blocks in each of the rectangular regions A1, B1 and C1 in Fig. 4. When an error is detected, the concealment processing described before is carried out. Thereby, boundaries in the vertical direction between different fields as shown in Fig. 7A are not generated in each rectangular region as shown in Fig. 7B, and mosaic deformation in the reproduced picture can be prevented, and a picture of good visual picture quality is obtained even in case of extraordinary reproduction speed. In the operation at the extraordinary reproduction speed of a relatively high value, the number of blocks which can be successively detected on each track is small. If it is determined whether the reproduction is allowed on the basis of a plurality of blocks as described above in such situation, the ratio of replacement of the picture by the reproduced new data in one field period, that is, update ratio of the picture is reduced. As a result, old data remains in the picture as shown in Figs. 8A and 8B, resulting in the deterioration of the picture quality. Therefore, it is determined whether or not the reproduction is allowed on the basis of each block as encoded in the recording operation described before. When an error is detected, the concealment processing described before is carried out. Thereby, the search at a higher speed is allowed, while increasing the update ratio of the picture and obtaining a picture of good visual picture quality. The relationship between the speed for the extraordinary speed reproduction and the above described unit of data for the concealment processing is preferably changed in accordance with the number of blocks forming one complete picture and the number of tracks wherein data for one picture is recorded. For example, if the reproducing operation at the extraordinary speed may be carried out such that the number of blocks which can be successively detected on each track is less than the double of the number of the horizontally aligned blocks in each rectangular region in Fig. 4, the concealment processing may be carried out based on determination of possibility of the reproduction on the basis of each block as encoded in the recording operation. The embodiment will be further described below in connection with a quadruple speed reproduction by the digital VCR, in which the number of the rectangular regions (A1, B1 and C1 in Fig. 4) is three and is equal to the number of the tracks (1, 2 and 3 in Fig. 5) on the tape as shown in Figs. 4 and 5. Fig. 9 schematically shows the relation between recording tracks and a trace of a head in the quadruple speed reproduction. In Fig. 9, the abscissa represents a rotational phase of the rotary head, and the ordinate represents a series of tracks along a travelling direction of the tape. Shaded portions in Fig. 9 represent regions in the respective tracks wherein signals can be reproduced, for example, the regions in which the level of the reproduced RF signal is 50% or more of the level in the normal reproduction in the present embodiment. The signal recorded in each track on the tape is specified by the combination of two numbers, i.e., the field number at the left of "-" and the track number at the right thereof. For example, "1-1" indicates the signal recorded at the first track of the first field and "3-2" indicates the signal recorded at the second track of the third filed. Fig. 10 represents the levels of the reproduced signals from the heads 20a and 20b in the case shown in Fig. 9. More specifically described with reference to Figs. 9 and 10, during the initial half rotation of the rotary drum 30 (i.e., a period (1) from 0 to π), signals 1-1 and 1-3 are read from the shaded portions in the tracks 1 and 3 of the first field by the head 20a. Then, during the next half rotation of the rotary drum 30 (i.e., a period (2) from π to 2π), the signals 2-3 and 3-2 are read from the shaded portions in the track 3 of the second field and the track 2 of the third field by the head 20b, respectively. Thereafter, during the next half rotation of the rotary drum 30 (i.e., a period (3) from 2π to 3π), signals 3-3 and 4-2 are read from the shaded portions in the track 3 of the third field and the track 2 of the fourth field by the head 20a, respectively. The signals will be read in a similar manner during periods (4), (5), (6), and so on. The reproduced picture of one field in the quadruple speed reproduction is formed of the recorded video signals belonging to four fields. Fig. 11 schematically shows reproduced images of the first field at the quadruple speed in the respective rectangular regions, which are formed by the signals reproduced during the periods (1) - (3) shown in Figs. 9 and 10. In the rectangular region A1 corresponding to the left track 1, an uppermost 1/6 region is formed by the signal 1-1 read by the head 20a during the period (1). In the rectangular region B1 corresponding to the middle track 2, a lower 2/6 region is formed by the signal 4-2 read by the head 20a during the period (3), and a lowermost 1/6 region is formed by the signal 3-2 read by the head 20b during the period (2). In the rectangular region C1 corresponding to the right track 3, an uppermost 1/6 region is formed by the signal 3-3 read by the head 20a during the period (3), an upper 2/6 region is formed by the signal 2-3 read from the head 20b during the period (2), and the lower 2/6 region is formed by the signal 1-3 read by the head 20a during the period (1). Fig. 12 schematically shows reproduced images of the second field at the quadruple speed in the respective rectangular regions, which are formed by the signals reproduced during the periods (4) and (5) shown in Figs. 9 and 10. In the rectangular region A1 corresponding to the left track 1, an upper 2/6 region is formed by the signal 8-1 read by the head 20b during the period (6), a lower 2/6 region is formed by the signal 7-1 read by the head 20a during the period (5), and a lowermost 1/6 region is formed by the signal 6-1 read by the head 20b during the period (4). In the rectangular region B1 corresponding to the middle track 2, an uppermost 1/6 region is formed by the signal 6-2 read by the head 20a during the period (5), and an upper 2/6 region is formed by the signal 5-2 read by the head 20b during the period (4). In the rectangular region C1 corresponding to the right track 3, a lowermost 1/6 region is formed by the signal 8-3 read by the head 20b during the period (6). Fig. 13 is a schematic diagram showing the specific manner in which the picture of the first field obtained by the quadruple speed reproduction, which is formed by composition of the signals read for the respective regions, is constituted by the recorded video signals belonging to four fields F1 - F4. In the first embodiment of the invention, the signals for the three rectangular regions A1, B1 and C1, which are formed by trisection of the screen with respect to the horizontal direction, are recorded on the corresponding tracks 1, 2 and 3, respectively. Therefore, the video signals belonging to the four fields F1 - F4 are mixed as shown in Fig. 13, and horizontal boundaries between the fields are located at the same levels. Therefore, the mosaic deformation of the picture is prevented, and the picture can have excellent quality in the quadruple speed reproduction. On the other hand, a few vertical boundaries between fields may be generated along the boundary of each rectangular region. In case of relatively low speed reproduction, however, such boundaries are prevented from being generated in each rectangular region by determining possibility of reproduction on the basis of a plurality of blocks as described above. Fig. 14 is a block diagram schematically showing a structure of a digital VCR according to a second embodiment of the present invention, and Fig. 15 schematically shows an arrangement of magnetic heads in this embodiment. The structure of the second embodiment shown in Figs. 14 and 15 is basically the same as that of the first embodiment shown in Figs. 2 and 3 except for the following points. More specifically, heads 21a and 21b shown in Fig. 15 are movable heads which can be moved in the track width direction by means of head moving devices 31a and 31b such as moving coils, piezoelectric elements, and a control circuit 32 for controlling positions of the movable heads is provided as shown in Fig. 14. This control circuit 32 carries out dynamic track following (DTF) control for causing each movable head to follow tracks so as to obtain an envelope sufficient for reproduction. Since the present invention is not directed to the mechanism of DTF control itself, the detailed description thereof will be omitted. However, the DTF control of the moving coil type is described in Japanese Patent Publication No. 61-55173 and the DTF control of the piezoelectric element type is described in Japanese Patent Publication No. 62-55204. While the horizontally aligned three rectangular regions A1, B1 and C1 are formed by the trisection of the screen in the foregoing first embodiment, as shown in Fig. 4, the screen in the second embodiment, which will be described below, is trisected into three rectangular regions A2, B2 and C2 with respect to the vertical direction, which are vertically aligned to each other, as shown in Fig. 16. Video signals for the respective regions are recorded by the corresponding magnetic heads in the corresponding tracks 1, 2 and 3 on the magnetic tape in accordance with the recording sequence indicated by an arrow in Fig. 17. For example, data for a plurality of blocks included in the uppermost rectangular region A2 in Fig. 16 is recorded by the magnetic head 21a in the left track 1 among the three tracks for one picture defined between solid lines in Fig. 17 during the initial half rotation of the rotary drum 30. The data of blocks included in the middle rectangular region B2 in Fig. 16 is recorded in the middle track 2 in Fig. 17 by the magnetic head 20b during the next half rotation of the rotary drum 30. The data of blocks included in the lowermost rectangular region C2 in Fig. 16 is recorded in the right track 3 in Fig. 17 by the magnetic head 21a during the next half rotation of the rotary drum 30. As described above, the data of blocks which are adjacent to each other on the screen are recorded adjacently in each track. Now, an operation of the second embodiment for the quadruple speed reproduction will be described below. If it is assumed that there is not any limit in displacements of the movable heads 21a and 21b, it is desirable to control the positions of the movable heads with displacements in three steps, as shown in Fig. 18 for the following reason. More specifically, the triple speed reproduction by the DTF control will be considered in comparison with the quadruple speed reproduction without DTF control, that is, without moving the heads. Since the video signal data corresponding to one picture is recorded in the continuous three tracks such as A2, B2 and C2 in Fig. 18, the data corresponding to one picture belonging to the same field can be reproduced by DTF controlling each head to scan the continuous three tracks A2, B2 and C2 as the triple speed reproduction. Accordingly, the displacement of the head from the condition wherein the head is not moved becomes stepwise as shown in Fig. 18. Thus, in the case shown in Fig. 18, one picture to be reproduced is formed of the data belonging to the same field, so that it is not necessary to define the relationship between the positions of data on the tracks and the positions of data on the screen. For this reason, the above control is desirable. In practice, however, there is a limit in the displacements of the movable heads. Generally, each head may be moved within the range of several 10µm with high accuracy and without any time delay. If it is assumed that such range is 50µm and track width is 104µm, for example, the limit of the head displacement will be 5 tracks. Accordingly, reduction of the head displacement is desirable in view of mechanical loads on the heads. In the second embodiment, therefore, the positions of the movable heads are controlled as shown in Fig. 19. In this case, each of F1, F2, F3 and F4 in Fig. 19 indicates tracks wherein data of one picture is recorded, and more specifically, the data in the upper rectangular region A2 in Fig. 16 is recorded in the track A2 in Fig. 19, the data in the middle rectangular region B2 is recorded in the track B2, and the data in the lower rectangular region C2 is recorded in the track C2. If the heads are DTF controlled to scan the track B2 of F1, the track C2 of F2 and the track A2 of F4 as shown in Fig. 19 in such situation, the data belonging to the three fields F1, F2 and F4 are displayed in the quadruple speed reproduction at vertically aligned three regions, as shown in Fig. 20, resulting in excellent quality of the picture reproduced at the quadruple speed. In Figs. 15 and 16, "DTF" indicates dynamic track following (i.e., dynamic tracking). Fig. 21 schematically shows an arrangement of magnetic heads in a digital VCR of a third embodiment of the invention. Although the first and second embodiments described before relate to the digital VCRs carrying out so-called "multisegment recording", the digital VCR of the third embodiment carries out multichannel recording in addition to multisegment recording of the first and second embodiments. In the following description, it is assumed that, for the sake of simplification, four heads shown in Fig. 21 are used to record digital video signal data for one picture in eight tracks in a divided form. Referring to Fig. 21, heads 22a and 23a are + azimuth heads, and heads 22b and 23b are - azimuth heads. With the pair of heads 22a and 22b and the pair of heads 23a and 23b, the data for one picture is recorded in the eight tracks on the tape using the two pairs, i.e., a total of four heads, by two rotations of the rotary drum 30 in Fig. 21. Figs. 22 and 23 show the manner where data for one picture is recorded in the eight tracks using the four heads. In the third embodiment of the invention, which will be described below, the screen is quartered into rectangular regions A3, B3, C3 and D3 with respect to the horizontal direction, as shown in Fig. 22. The video signal in each region is recorded in the corresponding track pair on the magnetic tape by the corresponding pair of heads in accordance with the recording sequence indicated by an arrow in Fig. 23. For this purpose, the rearranging circuit 5 (Fig. 2) rearranges the data in such manner. More specifically, as shown in Fig. 23, a region defined between thick solid lines is a region wherein the data for one picture is recorded. Four regions quartered and defined by thin solid lines are regions formed by the head pair 22a and 22b and head pair 23a and 23b. Each region defined by dotted lines corresponds to the track formed by the single head. For example, the data of blocks for the left rectangular region A3 in Fig. 22 is recorded in the track pair (tracks 1 and 2) at the left end among the four track pairs for one picture shown in Fig. 23 by the magnetic head pair 22a and 22b during the initial half rotation of the rotary drum 30. The data of blocks for the left rectangular region B3 in Fig. 22 is recorded in the left track pair (tracks 3 and 4) among the four track pairs shown in Fig. 23 by the magnetic head pair 23a and 23b during the next half rotation of the rotary drum 30. Then, the data of blocks for the right rectangular region C3 in Fig. 22 is recorded in the right track pair (tracks 5 and 6) among the four track pairs shown in Fig. 23 by the magnetic head pair 22a and 22b during the next half rotation of the rotary drum 30. Thereafter, the data of blocks for the rectangular region D3 at the right end in Fig. 22 is recorded in the track pair (tracks 7 and 8) at the right end among the four track pairs shown in Fig. 23 by the magnetic head pair 23a and 23b during the next half rotation of the rotary drum 30. In this manner, the data of blocks which are adjacent to each other in the screen are recorded adjacently in each track pairs, and the data for rectangular regions formed by quartering the screen into four are recorded in a divided forms on the corresponding track pairs. Fig. 24 schematically shows the relation between the recording tracks formed on the tape by the digital VCR of the third embodiment of the invention and the trace of the head during the high speed reproduction. At the time of high speed reproduction, the head pair for reproduction traverses and scans the plurality of record track pairs formed on the tape, as shown in Fig. 24. By employing the azimuth recording method, the video signal is detected from the regions shown by the shaded lines in Fig. 24. According to the third embodiment, the substantially same regions in the two tracks forming the pair are scanned by the head pair. Therefore, by rearranging the data so that the blocks which are adjacent to each other on the screen are alternately disposed on the paired tracks, the blocks which are adjacent to each on the screen can be double the number of the blocks which can be successively detected with one head. Thereby, the blocks which are successively reproduced on the screen can be double in number, compared with the case not employing the multichannel recording described before. As a result, mosaic deformation of the picture at the time of high speed reproduction can be prevented more reliably, and thus a picture of high visual picture quality can be obtained at the time of high speed reproduction. Then, an operation of the digital VCR will be described below in connection with a triple speed reproduction, in which the number of the rectangular regions (A3, B3, C3 and D3 in Fig. 22) in the screen is four and is equal to the number of the track pairs (tracks 1 and 2, 3 and 4, 5 and 6, and 7 and 8 in Fig. 20) on the tape, as shown in Figs. 22 and 23. Fig. 25 schematically shows the relation between recording tracks and a trace of the head in the triple speed reproduction. In Fig. 25, the abscissa represents a rotational phase of the rotary head, and the ordinate represents a series of tracks along the travelling direction of the tape. Shaded portions in Fig. 25 represent regions in the respective tracks which can be reproduced, for example, the regions in which the level of the reproduced RF signal is 50% or more of the level in the normal reproduction in the present embodiment. The signal recorded in each track on the tape is specified by the combination of the numbers, i.e., the field number at the left of "-" and the track number at the right thereof. Fig. 26 represents the levels of the signals reproduced through the heads 22a (or 23a) and 22b (or 23b) in Fig. 21. More specifically, as shown in Figs. 25 and 26, during the initial half rotation of the rotary drum 30 (i.e., a period (1) from 0 to π), signals 1-1, 1-2, 1-3, 1-4, 1-5 and 1-6 are read from the shaded portions in the tracks 1 - 6 of the first field by the heads 22a and 22b. Then, during the next half rotation of the rotary drum 30 (i.e., a period (2) from π to 2π), the signals 1-7, 1-8, 2-1, 2-2, 2-3 and 2-4 are read by the heads 22a and 22b from the shaded portions in tracks 7 of the first field through 4 of the second field. Thereafter, during the next half rotation of the rotary drum 30 (i.e., a period (3) from 2π to 3π), signals 2-5, 2-6, 2-7, 2-8, 3-1 and 3-2 are read by the heads 22a and 22b from the shaded portions in tracks 5 of the second field through 2 of the third field. Thereafter, during the next half rotation of the rotary drum 30 (i.e., a period (4) from 3π to 4π), signals 3-3, 3-4, 3-5, 3-6, 3-7 and 3-8 are read by the heads 22a and 22b from the shaded portions in tracks 3-8 of the third field. The reproduced picture of one field in the triple speed reproduction is formed of the recorded video signals belonging to three fields. Fig. 27 schematically shows reproduced pictures of the first field, which are reproduced at the triple speed reproduction and are formed of the signals reproduced during the periods (1) - (4) shown in Figs. 25 and 26. In the rectangular region A1 corresponding to the tracks 1 and 2, the shaded regions are formed by the signals 1-1, 1-2, 2-1, 2-2, 3-1 and 3-2 read by the heads 22a and 22b during the periods (1) -(3). In the rectangular region B3 corresponding to the tracks 3 and 4, the shaded regions are formed by the signals 1-3, 1-4, 2-3, 2-4, 3-3 and 3-4 read by the heads 22a and 22b during the periods (1), (2) and (4). In the rectangular region C3 corresponding to the tracks 5 and 6, the shaded regions are formed by the signals 1-5, 1-6, 2-5, 2-6, 3-5 and 3-6 read by the heads 22a and 22b during the periods (1), (3) and (4). In the rectangular region D3 corresponding to the tracks 7 and 8, the shaded regions are formed by the signals 1-7, 1-8, 2-7, 2-8, 3-7 and 3-8 read by the heads 22a and 22b during the periods (2), (3) and (4). Fig. 28 is a schematic diagram in which the picture of the first field, which is obtained by the triple speed reproduction and is formed by composition of the signals read for the respective regions, as shown in Fig. 27, is formed by the video signals belonging to recorded three fields F1 - F3. In the third embodiment of the invention, the signals for the four rectangular regions, which are formed by quartering the screen with respect to the horizontal direction, are recorded on the corresponding track pairs, respectively. Therefore, the three fields F1 - F3 are mixed as shown in Fig. 28, and horizontal boundaries between the fields are located at the same levels. Therefore, the mosaic deformation of the picture is prevented, and the picture can have an excellent quality in the triple speed reproduction. Fig. 29 schematically shows an arrangement of magnetic heads in a digital VCR of a fourth embodiment of the invention. Heads 24a, 24b, 25a and 25b are movable heads which can be moved in the track width direction by means of head moving devices 31a and 31b. The digital VCR of the fourth embodiment basically has the same structure as that of the second embodiment shown in Fig. 14 and a controlling circuit 32 for controlling positions of the movable heads is provided as shown in Fig. 14. While the four rectangular regions A3, B3, C3 and D3 are formed by quartering the screen with respect to the horizontal direction in the foregoing third embodiment, as shown in Fig. 22, the screen in the fourth embodiment, which will be described below, is quartered into four rectangular regions A4, B4, C4 and D4, with respect to the vertical direction as shown in Fig. 30. Video signals for the respective regions are recorded by the corresponding magnetic head pairs in the corresponding tracks on the magnetic tape in accordance with the recording sequence indicated by an arrow in Fig. 31. For example, data of a plurality of blocks for the uppermost rectangular region A4 in Fig. 30 is recorded by the magnetic head pairs 24a and 24b in the track pair (tracks 1 and 2) at the left end among the four track pairs for one picture defined between thick solid lines in Fig. 31 during the initial half rotation of the rotary drum 30. The data of blocks for the rectangular region B4 at the second position in Fig. 30 is recorded in the track pair (tracks 3 and 4) at the second position from the left in Fig. 31 among the four track pairs by the magnetic head pairs 25a and 25b during the next half rotation of the rotary drum 30. The data of blocks for the rectangular region C4 at the third position in Fig. 30 is recorded in the track pair (tracks 5 and 6) at the third position from the left in Fig. 31 among the four track pairs by the magnetic head pairs 24a and 24b during the next half rotation of the rotary drum 30. The data of blocks for the rectangular region D4 at the lowermost position in Fig. 30 is recorded in the track pair (tracks 7 and 8) at the right end in Fig. 31 among the four track pairs by the magnetic head pairs 25a and 25b during the next half rotation of the rotary drum 30. Now, an operation of the fourth embodiment for the triple speed reproduction will be described below. If it is assumed that there is not any limit in displacements of the movable heads 24a, 24b, 25a and 25b, it is desirable to control the positions of the movable heads with displacement in four steps, as shown in Fig. 32 for the reason already described in connection with the second embodiment with reference to Fig. 18. More specifically, in the case shown in Fig. 32, one picture to be reproduced is formed of the data belonging to the same field, so that it is not necessary to define the relationship between the positions of data on the tracks and the positions of data on the screen. For this reason, the above control is desirable. In practice, however, there is a limit in the displacement of the movable heads as already described, and thus reduction of the displacement is desirable in view of mechanical loads on the heads. In the fourth embodiment, therefore, the positions of the movable heads are controlled as shown in Fig. 34. In this case, each of F1, F2 and F3 in Fig. 33 indicates track pairs wherein data of one picture is recorded and more specifically, the data in the uppermost rectangular region A4 in Fig. 33 is recorded in the track pair A4, the data in the middle rectangular region B4 is recorded in the track pair B4, the data in the third rectangular region C4 is recorded in the track pair C4 and the data in the lowermost rectangular region D4 is recorded in the track pair D4. If the heads are DTF controlled to scan the track pair B4 of F1, the track pair A4 of F2, the track pair D4 of F2 and the track pair C4 of F3 as shown in Fig. 33 in such situation, the data belonging to the three fields F1 - F3 are displayed in the triple speed reproduction at vertically aligned four different regions, as shown in Fig. 34, resulting in excellent quality of the picture reproduced at the triple speed. In the above description, the rectangular regions, for which data are recorded on the corresponding tracks, are formed by the division with respect to only one direction, i.e., the horizontal direction (first and third embodiments) or the vertical direction (second and fourth embodiment). However, the regions may be formed by the division in both the directions, in view of balance of mixed fields in the reproduced picture at the extraordinary speed. Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being limited only by the terms of the appended claims.

Claims: A recording apparatus for recording a video signal on a recording medium comprising: block forming means (1) for forming data blocks each corresponding to a plurality of pixels; means (2, 3) for combining a plurality of data blocks and coding the combined data blocks to form a fixed length block; characterised in that the apparatus further comprises: means (5) for decomposing the fixed length block into recording blocks corresponding to data blocks; and means (5) for rearranging the recording blocks so that blocks corresponding to data blocks for regions adjacent on a screen are recorded adjacent on the recording medium; wherein data for N regions of the screen are recorded on N respective tracks. A recording apparatus as claimed in claim 1 wherein the N regions are obtained by dividing the screen horizontally. A recording apparatus as claimed in any one of claims 1 or claim 2 wherein the N regions are obtained by dividing the screen vertically. A recording apparatus as claimed in any one of claims 1 to 3 wherein the data in the N regions is recorded on NxM tracks with M heads by dividing the data for each of the N regions into M channels. A digital video signal reproduction apparatus for reproducing a digital video signal recorded by an apparatus according to any one of claims 1 to 4 comprising: means (9) for rearranging recorded blocks into fixed length blocks; means (11) for decoding the fixed length blocks and reconstructing data blocks; and means (14) for restoring the original arrangement of the decoded digital video signal. A reproducing apparatus as claimed in claim 5 comprising: concealing means (13) for concealing a reproduced signal for a data block when the signal is not reproduced correctly because of an error. A reproducing apparatus as claimed in claim 6 wherein said concealing means (13) substitutes the incorrectly reproduced signal with a corresponding signal of a previous screen. A method of recording a digital video signal on a recording medium comprising: forming a plurality of data blocks each corresponding to a plurality of pixels; combining a plurality of data blocks and coding the combined data blocks to form a fixed length block; characterised in that the method further comprises: decomposing the fixed length block into recording blocks corresponding to data blocks; and rearranging the blocks so that blocks corresponding to data blocks for regions that are adjacent on a screen are recorded adjacent on the recording medium; wherein data for N regions of the screen are recorded on N respective tracks.

Inventors: TAKAKURA EIICHI, TAKAKURA, EIICHI
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1993
Main classification: H04N5
IPC codes: H04N5, H04N7, G11B20