KR0185387B1 - Method and apparatus for reproducing a digital video signal - Google Patents

Abstract

None.

Description

Video signal playback device

1 is a block diagram showing a first embodiment of the present invention.

2 through 7 are diagrams provided in the description of the first example, respectively.

8 is a plan view showing a conventional rotating head.

9A-9C are diagrams illustrating the D-1 format.

10 is a diagram showing a screen configuration corresponding to the D-1 format.

11 and 12 are diagrams provided in the description of the operation of the eighth example, respectively.

13 is a plan view showing a rotating head of the application.

14 to 17 are diagrams provided for explaining the operation of the FIG. 13 example, respectively.

* Explanation of symbols for main parts of the drawings

2: Video tape in D-1 format 20: Playback head

24,33: Time Base Collector (TBC) 26a, 28a, 35a, 36a: Frame Memory

27 microprocessor (MPU)

The present invention relates to a video signal reproducing apparatus suitable for, for example, a digital videotape recorder (digital VTR).

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal reproducing apparatus suitable for use in, for example, a digital VTR. A plurality of reproducing heads for reproducing, detecting means for detecting the block identification information for each of the reproducing heads, determining means for determining that the block identification information has changed, and a plurality of storing the reproduced video signal. A block unit having a memory and switching means of these plural memories, and determining that all the video signals of the block when the block identification information from all the reproduction heads of the plural channels are in a predetermined combination, for example, When the video signal is reproduced in one field unit, even before the video signal is reproduced by the so-called multihead method. Mistaken for a video signal into a video signal of the next field and de one will prevent the image quality is degraded.

In the case of recording a large amount of information, such as a digital VTR, it is difficult to record a video signal of one field on one track. Therefore, a method of recording the video signal of one field on a plurality of tracks is employed. In this case, since the burden of processing speed of data obtained by alternately tracing these tracks in a pair of recording or reproducing heads provided in the rotating head is excessively large, two magnetic heads of two channels are used in parallel in one trace. To be injected. In addition, even in a digital VTR, noiseless reproduction is performed at a wide speed range, so that a dynamic tracking technique developed for an analog VTR is applied.

FIG. 8 shows a rotating head for a conventional dynamic trackable digital VTR. In this FIG. 8, (1) is a rotating head, (2) is a video tape conveyed in the forward direction (V direction), R (A ) R (D) are the recording heads, P (A)-P (D) are the reproduction heads, respectively, and (3) and (4) are bimorph elements each supporting a pair of reproduction heads. In the following, the reproduction heads are denoted by the symbols A to D, respectively. When the rotary head 1 rotates at the rotational speed W, the pair of regeneration heads P (A), P (B) and a pair of regeneration heads P ( C), is P (D) is freely displaceable within a predetermined range in the direction θ ₁ and θ ₂ each direction.

In addition, as a format of a video tape for a digital VTR, the international standard D-1 format is popular. In this D-1 format, as shown in FIG. 9A, video and audio signals for one field of the NTSC system (525/60 system) are recorded in a curved line in 10 tracks. An audio sector portion 2b containing a timecode located therein and two video sectors 2a and 2c for video signals sandwiched by the audio sector portion 2b. The audio sector portion 2b is arranged in the center because the audio data needs to have a lower error rate than the audio data. In addition, the 10 tracks are divided into five segments (segment number 0 4) by 2 tracks, and each segment 0 to 4 is each composed of four sectors (sector numbers 0 to 3). It is identified by the ID address (identification address) defined similarly. ID address = (sector number, segment number (field number))

Sector number = 0 to 3

Segment number = 0 to 4

Field number = 0 to 3 (2 bits)

However, as the field number, the least significant bit number is used, 0 is the even field, 1 is the odd field, and the second bit of the regular field number is used as the frame number.

Each video sector is composed of a preamble including a sync pattern and an ID pattern, 160 sync blocks, and a postamble (not shown), as shown in FIG. 9B. An ID pattern is added, and the ID pattern includes information of an ID address as shown in FIG. 9C. Further, in the PAL system (625/50 system), for example, video signals for one field are distributed and recorded in 12 tracks, so that the segment numbers are 0 to 5.

Referring to FIG. 11, the operation in the case of reproducing at triple speed using the rotating head of FIG. 8 will be described. In this case, the video tape 2 is conveyed at triple speed in the V ⁺ direction. The tape 2 is stopped and displayed as if the pair of reproducing heads A and B and the pair of reproducing heads C and D move in the V ⁺ direction while tracing the tape. In addition, the trajectory of the playhead when the dynamic tracking is not operating is indicated by a broken line, and the trajectory of the actual playhead caused by the dynamic tracking operation is represented by a solid line. In this case, assuming that the playback heads A and B start tracing from segment 0 of the Nth field, the deviation amount due to dynamic tracking of the Nth field is indicated by arrows 6a to 6e, and the initial state. In this case, the deviation amount of ± 1/2 field can be generated, so the maximum amount of deviation is about 3 fields, and the burden on the mechanical system and the driving system becomes large.

In addition, since the playhead needs to jump along the path 7 from the video sector at the end of the Nth field to the video sector at the start of the (N + 3) th field, it is recorded in the audio sector sections 8a and 8b. There was the inconvenience of not being able to read the time code.

As a method of eliminating the jump at the center of the track, as shown in FIG. 12, the rotational speed of the rotating head drum is increased by 12/10 times, and in FIG. 11, the reproducing head has a tape for one field (10 tracks). Another way is to trace the tape for 12 tracks at the time of tracing. In this case, the data of the tracks 9 and 10 are only discarded after playback. However, in the twelfth example, when the rotational speed of the conventional rotating head is set to 9000 rpm, the rotational speed increases by about 20% in the 525/60 system and about 16% (14 tracks / 12 tracks) in the 625/50 system. In addition to durability issues, increasing the rotational speed only in dynamic tracking mode complicates the system.

Therefore, the digital VTR which improved the 8th example was proposed. In FIG. 13, the recording head is the same as the conventional one, but the number of the reproduction heads supported by the bimorph elements 3 and 4 is four (P (A ₁ ), P (B ₁ ), P (C ₂ ), respectively). , P (D ₂ ) and P (C ₁ ), P (D ₁ ), P (A ₂ ), P (B ₂ )). When these playheads are simply represented by A ₁ to D ₂ and C ₁ to B ₂ , the four play heads A ₁ , B ₂ , C ₂ , and D ₂ simultaneously trace the tape in parallel, and the 180 With four phases delayed, four playback heads C ₁ , D ₁ , A ₂ , and B ₂ synchronously trace the tape.

In the rotating head of FIG. 13, for example, the operation of each of the reproduction heads in the case of performing the triple speed reproduction will be described with reference to FIG. 14. From the segment 0 of the Nth field, the reproduction heads A ₁ and (B) are described. ₁₎ (that is, the reproducing head from the segment 1 C _2, D ₂ a) Assuming that the start of tracing, with the shift amount by the dynamic tracking is indicated by arrow (11a) ~ (11c), ± of the initial state 1 Since the deviation amount of the / 2 field may be generated, the maximum deviation amount is about 1.5 fields, which is about 1/2 of the conventional example.

In addition, since there are eight playback heads in total, the video signal for one field and the video signal for two tracks (total 12 tracks) can be reproduced by 2.5 rotations of the rotating head, and the rotating head is rotated at a normal rotational speed. It is possible to move from the Nth field to the track of the (N + 3) th field without jumping in the audio sector portion of the center of the tape.

As described above, when a dynamic tracking rotary head is used in a multi-head as in FIG. 13, theoretically, noiseless reproduction is possible in a wide range.

However, in the case of the multihead, since a large amount of data is randomly reproduced in parallel, it is inconvenient that it is difficult to reconstruct the video signal without missing every field.

In other words, with reference to FIGS. 15 to 17, the state of the playback data in the case of performing playback at 1x speed using the rotating head of FIG. 13 will be described. As shown in FIG. It is assumed that data is reproduced in the order of field 01, field 00, and field 11 (= 3) from 10) (= 2) in the reverse direction. In addition, the field number is a number of two bits, and strictly as described above, fields 00 to 11 (0 to 3) can be identified. In the present example, the lower 1 bit is used to determine whether the field is an even field or an odd field. It only identifies. In addition, the video tape is conveyed in the reverse direction (V direction). FIG. 15 shows that the playhead is conveyed in the reverse direction of the V-direction in turn by using a tape stop system. An ID address which is a segment number and a field number of 0 or 1 is attached. Again, the data reproduced in the sector having the ID address is identified with the ID address.

In this case, as shown in FIG. 15, the reproduction heads A ₁ , B ₁ , C ₂ , and D ₂ start tracing from sectors 4 (1), 4 (1), 0 (0), 0 (0), respectively. Assuming that the playheads C ₁ , D ₁ , A ₂ , and B _{2 then} trace from two tracks less, and again the play heads A ₁ , B ₁ , C ₂ , and D ₂ also track 2 tracks. Since traces are performed from the positions reduced by, the data reproduced from each reproduction head is parallel to the time axis, as shown in FIG. 16. The data reproduced in the fields 10, 01, and 00 are recorded in the field memories 16, 17, and 18 for each segment, respectively. Further, a method of reproducing one field of data from the end track to the head track during reverse playback is disclosed in Japanese Patent Laid-Open No. 61-150476.

In the reproduction data of FIG. 16, for example, it is a problem to determine whether all the data of the field 10 has been reproduced and written to the field memory 16. However, in the D-1 format, there is an audio sector part in the center, The determination is difficult because there are areas whose numbers change from 01 to 10 (1 to 0 for processing images) or 0 to 01 (0 to 1 for processing images) in the reverse order of the original order. For example, as the determination method, when focusing on a specific reproduction head (for example, A ₁ ) and the data of the segment 2 or the segment 3 in the field is reproduced in the reproduction head A, the previous field may be A determination method that considers that all the data has been reproduced can also be considered. This is a judgment method based on the assumption that since the segment 2 or the segment 3 corresponds to an almost center portion of the display screen, when the data of the center portion is reproduced, all the data of the previous field may be considered to have been reproduced.

According to this determination method, at the time points t ₁ and t ₃ in FIG. The time points t ₁ and t ₅ correspond to positions 12 and 13 of FIG. 15, respectively. Then, at the time t ₁ , writing of the data into the field memory 16 of FIG. 17 is stopped, and the data of the next field number of 0 (00 or 10 in 2 bits) is determined to be the data of the next field 00. As a result, data 0 (0) (data at position 14 in FIG. 15) output from the reproduction heads A ₂ and B ₂ from the time point t ₁ to t ₂ is written into the error field memory 18. FIG. Therefore, the image of the old field is superimposed on the image of the next field and the image quality deteriorates. Similarly, data 4 (0) (data at position 15 in FIG. 15) output from the reproduction heads C and D is also written into the field memory 18, which is written in the regular memory.

The data of the previous field is processed as the data of the next field in this way because there are eight playback heads, and the playback phase is significantly different between the head of the head and the head of the end.

In view of the above, the present invention provides the video of the previous field when the video signal is reproduced in a multihead manner from a video tape in which one field video signal is recorded in blocks in a plurality of tracks as in the D-1 format. It is an object of the present invention to accurately determine that all signals have been reproduced, and to prevent the video signal of the previous field from being mistaken for the video signal of the next field.

The video signal reproducing apparatus according to the present invention is divided into predetermined block units (e.g., one frame unit or one field unit as shown in FIG. 1), and block display information (e.g., field number or And a plurality of channels of the reproduction head 20 for reproducing the signal on the recording medium 2 having the video signal recorded therein, and detection means 24 and 33 for detecting the block identification information for each of the respective reproduction heads. Determining means 27 for determining that the block identification information has changed, a plurality of memories (e.g., a plurality of field memories or a plurality of frame memories) for storing the reproduced video signal, and switching of the plurality of memories. Means 27, and when the block identification information from all the reproduction heads 20 of the plurality of channels is in a predetermined combination (e.g., all field numbers are updated as in the states 34 and 41 of FIG.As the state) to the ever determines that both the video signal of the previous block reproduction.

According to the present invention as described above, when not only the block identification information from a specific reproduction head but also the block identification information from all the reproduction heads 20 are in a predetermined combination, it is determined that all the video signals of the previous block are reproduced. In this case, it is possible to avoid a state in which only one playback head is still reproducing the previous block video signal. Therefore, when the block unit is a field unit, it is possible to reliably determine that all the video signals of the previous field have been reproduced for all the reproduction heads, and the video signal of the previous field is not mistaken for the video signal of the next field.

Hereinafter, the video signal reproducing apparatus according to the present invention is signed with reference to FIGS. In this example, the present invention is applied to a digital VTR using a video tape with the D-1 format. As the rotating head of this example, a dynamic tracking method is used in the multihead of FIG. 13 as it is.

FIG. 1 shows a playback section of the digital VTR of this example. In FIG. 1, 20 is an eight playback heads for playing back video signals recorded on the video tape 2, and these playback heads 20 are shown in FIG. As shown in FIG. 13, the bimorphs 3 and 4 are attached to each of the four corresponding ones. In Fig. 1, reference numeral 21 denotes a master reproducing apparatus which processes reproduction signals from four reproduction heads, each of which corresponds to two corresponding ones in the reproduction head 20, and 22 represents the remaining (4) pieces. A slave reproducing apparatus for processing a reproducing signal from the reproducing head, 23 represents a monitor for reproducing an image corresponding to the finally obtained video signal. In the master reproducing apparatus 21, 24 is a timebase collector (TBC) including a PLL for bit clock reproduction, 25 is an internal code error correction circuit, and 26 and 28 are memory boards, respectively. The TBC 24 extracts the ID address (sector number, segment number, field number, etc.) by the reproduction signal, and passes the extracted ID address and image data through the internal code error correction circuit 25 to the memory board ( The frame memory 26a of the 26 and the frame memory 28a of the memory board 28 are supplied.

In this example, the memory playback boards 35 and 36 are also mounted in the slave reproducing apparatus 22, and the frame memories 35a and 36a are also provided in the memory boards 35 and 36, respectively. Then, the storage capacity of the sum of the frames 26a, 28a, 35a, and 36a can be stored for at least three fields in color video data of a so-called 4: 2: 2 component. Reference numeral 27 denotes a microprocessor (MPU), which supplies an address signal for designating an address for writing and reading to those frame memories 26a and 36a, as will be described later. From these frame memories 26a and 36a, data of an ID address is taken in. The address signal consists of a signal corresponding to a field number for specifying one field in three fields.

The image data read from each frame memory 26a and 28a is supplied to the input ports of one and the other of the multiplexer 29 via the external code error correction circuits 26b and 28b, respectively, and the data selector 30 ) Is supplied to the monitor 23 via the error correction circuit 31 and the digital / analog (D / A) converter 32.

On the other hand, in the slave reproducing apparatus 22, the ID address is extracted from the reproduction signal by the TBC 33, and the extracted ID address and image data are passed through the internal code error correction circuit 34 to the frame memories 35a and 36a. To feed. Then, the image data read out from these frame memories 35a and 36a is supplied to one and the other input ports of the multiplexer 37 via an external code error correction circuit, respectively, and the multiplexer 37 ) Is supplied to the other input port of the data selector 30 of the master reproducing apparatus 21. In this case, the error correction circuit 38 may also be provided in the slave playback device 22.

The operation in the case of performing variable speed reproduction in the search mode in the digital VTR of FIG. 1 will be described. First, a case where reproduction is performed at 1x speed will be considered. At this time, as shown in FIG. ₂ , the initial phases of the reproduction heads A ₁ , B ₁ , C ₂ , and D ₂ have ID addresses of 4 (1), 4 (1), 0 (0), and 0 (0), respectively. Assuming the video sector, the phases of the playback heads C ₁ , D ₁ , A ₂ , and B ₂ in the data stop system have ID addresses of 2 (1), 2 (1), 3 (1), and 3 (1), respectively. Moving in the video sector, the phase of the playhead is similarly moved in the old field direction in turn. Further, by the action of dynamic tracking, each of the reproduction heads A ₁ to D ₂ and C ₁ to B ₂ always traces along the inclined track of the video tape 2.

In FIG. 2, a state in which reproduction data output from each of the reproduction heads A ₁ -D ₂ and C ₁ -B ₂ is arranged along the time axis is shown in FIG. 3, and in FIG. The sign of the reproduction data (4 (1)) indicates that this reproduction data is reproduced in the video sector whose ID address is (4 (1)). In this example, the image data reproduced in the fields 10, 01, 00, 11, ... are sequentially written in the first, second and third field memories, respectively. When all the image data is reproduced, the image data of the first field memory is read and supplied to the monitor 23. When all the image data of a certain field is reproduced, the image data of the corresponding field memory is monitored. To feed. These first and third field memories are logically formed among the frame memories 26a, 28a, 35a, and 36a of the first embodiment.

At this time, it is an object of the present invention to accurately determine whether or not any field of image data has been reproduced. In this example, as in the state 39, the field number of one bit of all reproduction data is set to 1 (i.e., odd field). When the 1-bit field number of the straight line determines that all of the image data of the zero field (i.e., even field) has been reproduced, and the field number of the reproduction data of all the reproduction heads becomes 0 as in the state 41, It is determined that all the image data of the field (i.e., odd field) of field 1 immediately before is reproduced. Further, in the state 39, the field number of the reproduction data in all the reproduction heads becomes 1 between the time point t ₃ and the period y, and even in the state 40 immediately after the state 39, the time period y at the time t ₄ . The field number of the reproduction data in all the reproduction heads is 1, however, this state 40 is ignored. Similarly, in the state 41, the field number of the reproduction data in all the reproduction heads becomes 0 from the time point t ₄ to the period x. Also in the state 42 immediately after the state 41, the time period x at the time t ₇ . The field number of the reproduction data in all the reproduction heads is 0, however, this state 42 is also ignored. In this case, noise is also added in the periods y and x by adding an algorithm that determines that the field numbers in each of the playheads matched as many as N times (N is a positive integer) at predetermined intervals. Can reduce the probability of false judgment.

The positions of the respective playback heads on the videotape 2 corresponding to the states 39 and 41 of FIG. 3 are the positions 39a and 41a of FIG. And as is clear from Fig. 2, when all the reproduction heads are present at the position 39a during the -1.0x speed reproduction, the data in the field 10 is not reproduced from any of the reproduction heads thereafter. Similarly, if all the reproduction heads are present at the position 41a, the data in the field 01 is not reproduced from any of the reproduction heads thereafter. Therefore, when the field number in the ID address from all the reproduction heads changes to the number representing the odd field (or even field) as in this example, it is determined that all the image data of the immediately preceding even field (or odd field) has been reproduced. This has the benefit of accurately determining that all the image data of the previous field has been reproduced.

In this case, since the image data of the previous field is not reproduced thereafter, the image data of the previous field is not mistaken for the image data of the current next field.

In addition, the operation in the case of reproducing at -1.0 times speed from the initial phase different from the second embodiment in this example will be described with reference to FIG. 4. In FIG. 4, the reproduction heads A ₁ , B ₁ , The initial phases of C ₂ and D ₂ assume that the ID addresses are 4 (1), 0 (0), 0 (0), 1 (0), respectively. In this case, arrangement of reproduction data output from the reproduction heads A ₁ to D ₂ and the reproduction heads C ₁ to B ₂ along the time axis is as shown in FIG.

Then, it is determined that the first field number of the output data from all the playhead as the period y overlooked from the 5 degrees of the time t is playing all the image data of the even field of the immediately preceding time is 1, and the period of x as the liver from the time t ₉ When the field number of the output data in all the reproduction heads becomes 0, it is judged that all the image data of the immediately preceding field has been reproduced exactly as shown in FIG. do.

Next, with reference to FIG. 6, the operation in the case of reproducing at + 2.0x speed in the digital VTR of the present example will be described. The initial phases of the reproducing heads A ₁ , B ₁ , C ₂ , and D ₂ are each assigned an ID address. Assume that we are on sectors of 4 (1), 4 (1), 0 (0), 0 (0). In this case, in the tape stop system, the phases of the reproduction heads C ₁ , D ₁ , A ₂ , and B ₂ are each divided into video sectors having ID addresses of 1 (0), 1 (0), 2 (0), and 2 (0). After the rotational head has rotated once, the phases of the playback heads A ₁ , B ₁ , C ₂ and D _{2 have} the ID addresses of 3 (0), 3 (0), 4 (0) and 4 (0), respectively. Transferring to the video sector, the phase of the playhead is likewise moved below the new field in turn. Since the trajectory of each playhead is corrected in the direction of the arrow 45 in the trajectory as shown by the broken line, each playhead A ₁ to D ₂ and C ₁ to B ₂ always show the inclined track of the videotape 2. Therefore, trace is performed.

FIG. 17 shows a state in which reproduction data output from each reproduction head is arranged along the time axis in FIG. Then, similarly to Fig. 3, when the field numbers of the reproduction data obtained from all the reproduction heads are zero in each period x from the time points t ₁₀ and t ₁₃ in Fig. 7, all the image data of the immediately preceding odd field is reproduced. When the field number of the reproduction data obtained from all the reproduction heads becomes 1 in each period y from the time points t ₁₂ and t ₁₅ , it is determined that all the image data of the immediately preceding even field has been reproduced. Also, at the time points t ₁₁ and t ₁₄ immediately after each of the time points t ₁₀ and t ₁₃ , the field numbers of the reproduction data obtained from all the reproduction heads are 0, but these states are ignored.

The positions in FIG. 6 corresponding to the states 43 and 44 including the time points t ₁₀ and t ₁₂ in FIG. 7 are 43a and 44a, respectively. And as is clear from Fig. 6, when all the reproduction heads are at the positions 43a and 44a in the forward reproduction, the image data of the immediately preceding field is not reproduced. Therefore, according to the determination method of this example, even in the case of reproduction at +2.0 times, there is an advantage of accurately determining that all the image data of the previous field has been reproduced.

In general, according to this example, image data of all a series of fields can be reproduced in sequence without noise from -1.0 times to +2.0 times. Further, for example, noiseless reproduction is performed in a wider speed range by skipping image data of a middle field. In addition, conventionally, it was theoretically possible to perform a completely noiseless reproduction from -1.0 times to +2.0 times by applying a dynamic tracking method using eight playback heads in a digital VTR in the D-1 format, but in practice, the ID address is reversed. It is possible to say that the image data of the previous field has been reproduced for all the reproduction heads exactly as in the present example, which was difficult due to the phenomenon, and thus, it can be said that complete noise-free reproduction is possible in a wide speed range in reality.

Further, according to this example, the timing of field switching is performed by simply extracting an ID address from the reproduction data output from all the reproduction heads and supplying this ID address to the microprocessor 27 as the determination circuit, so that the apparatus is simple and inexpensive. In addition, the algorithm also benefits from simplicity.

Further, in the above embodiment, when the field numbers of the reproduction data of all the reproduction heads are switched to the number of the next field, it has been determined that all the video signals of the previous field have been reproduced. Remembering that the number has been changed to the number of the next field, the same result can be obtained even if it is determined that all the video signals of the previous field have been reproduced, with the field number of the reproduction data of all the playback heads finally changed to the number of the next field. . In other words, it is not always necessary to determine the field numbers for all the reproduction heads at the same time.

In the above-described embodiment, the determination is made using only the lower 1 bit in the field number of the ID address. The determination may be made using the 2-bit field number as it is, or the determination is made using only the upper 1 bit in the 2-bit field number. You may also In the latter case, since the upper one bit corresponds to the frame number, in the above-described embodiment, the part processed in one field unit is modified to process in one frame unit each to determine whether all the image data of the previous frame has been reproduced. There is a benefit to be able to judge accurately.

In addition, this invention is not limited to the above-mentioned embodiment, Of course, a various structure can be taken in the range which does not deviate from the summary of this invention.

Advantageous Effects of Invention According to the present invention, when the block unit is used as a field unit, it is possible to accurately determine that all the video signals of the previous field have been reproduced, and there is no mistake in misidentifying the video signal of the previous field as the video signal of the next field. There is this.

In addition, when the multi-head dynamic tracking method is applied to the digital VTR in the D-I format, the present invention has the advantage that noiseless reproduction can be realized in a wide range of reproduction speeds.

Claims (1)

A reproduction channel of a plurality of channels for reproducing the signal by a recording medium on which a video signal is recorded, together with block identification information indicating the block for each block, divided into predetermined blocks, and the block identification for each reproduction head; Detecting means for detecting information, determining means for determining that the block identification information has changed, a plurality of memories for storing the reproduced video signal, and switching means for the plurality of memories, and all of the plurality of channels. And determining that all the video signals of the previous block have been reproduced when the block identification information from the reproduction head is a predetermined combination.

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