JPH03119570A - Digital information signal reproducing device - Google Patents

Abstract

PURPOSE:To perform accurate track control even at the time of variable-speed reproducing by reproducing two kinds of digital audio signal double recorded on two close tracks and selecting them in accordance with the presence or the absence of track jump. CONSTITUTION:One of first and second double recorded digital audio reproduced signal from deshuffling circuits 27A and 27B at the tie of normal-speed reproducing is selected by a selector 51 and is demodulated by an outside code decoder 28A and is outputted through an error correcting circuit 30A. Meanwhile, first and second double recorded digital audio reproduced signals from a certain track and a third track (a second track is jumped) based on deshuffling circuits 27A and 27B are processed in the same manner and are supplied to a cross fader 53 at the time of reproducing at a variable speed like a double speed. A selector 52 is controlled in accordance with detection or non-detection of a track jump detecting circuit 55 to select the output of the circuit 30A or the output of the fader 53 for tracking control, and accurate tracking control is performed even at the time of variable-speed reproducing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital information signal reproducing apparatus applied to processing audio signals of a digital VTR that records/reproduces digital video signals and digital audio signals.

[Summary of the invention]

In this invention, the same first digital audio signal and the same second digital audio signal are applied to each of two adjacent tracks on the tape.
digital audio signals are recorded in duplicate,
In a digital information signal reproducing device that uses a rotary head to reproduce digital information signals from a tape, control is performed so that the scanning position of the rotary head matches the track during variable speed reproduction when the tape is run at a speed different from the normal speed. head position control means for detecting that the rotary head jumps over a plurality of tracks based on a drive signal for the head position control means; and a means for switching between the first digital audio signal and the second digital audio signal, and selecting one of the first digital audio signal and the second digital audio signal depending on the error state outside of a predetermined period, during variable speed playback. , it is possible to prevent the error correction ability of the reproduced digital audio signal from deteriorating.

[Conventional technology]

For example, as one of the digital VTRs that record/play back a composite digital color video signal and a digital audio signal, there is one that records the digital audio signal in duplicate. In such a digital VTR,
The reproduced first audio data (referred to as the first copy) and second audio data (referred to as the second copy) are separately decoded (e.g., erasure corrected) and output, and then the first audio data (referred to as the first copy) and the second audio data (referred to as the second copy) are decoded (e.g., erasure corrected) and output. The second copy is used for decryption. In other words, since the same data is recorded twice as the first copy and the second copy, the error flag obtained by decoding the inner code is referenced to extract non-error data from the first and second copies. A code block of the outer code is selected and the outer code is corrected with respect to this code block. Therefore, error correction ability can be improved.

[Problem to be solved by the invention]

Digital VTRs are capable of variable speed playback where the tape speed is different from the normal tape speed. During variable speed reproduction, the scanning locus of the rotary head and the inclination of the track no longer match. However, when the tape speed is several times the normal tape speed, the rotating head is displaced in the height direction by the piezoelectric element.
The scanning locus of the rotating head is made to coincide with the track.

Such tracking techniques are called dynamic tracking.

During variable speed playback, for example double speed playback, the rotary head uses dynamic tracking to scan the track where the signal for one field has been recorded, and then jumps to the track where the signal for the next one field has been recorded. The track on which the signal for the next one field was recorded is scanned. When this track jump occurs, the audio data in the first copy and the second copy are no longer the same. Therefore, as in normal playback, the first
If the copy and decoding using the second copy are performed, an erroneous correction process will be performed.

To avoid this erroneous correction process, during variable speed playback,
Only the audio data of either the first copy or the second copy was used as a playback output.

As a result, there is a problem in that the error correction ability is lower than that during normal playback.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a digital information signal reproducing apparatus that can prevent the error correction ability from decreasing during variable speed reproduction.

[Means to solve the problem]

In this invention, the same first digital audio signal and second digital audio signal are recorded in duplicate on each of two adjacent tracks on the tape 43, and the digital information signal is transferred from the tape 43 to the rotating head. H
In a digital information signal reproducing apparatus configured to reproduce using A-HD, control is performed so that the scanning position of the rotary head HA-HD coincides with the track during variable speed reproduction in which the tape 43 is run at a speed different from the normal speed. a head position control means 56; a detection means 55 for detecting that the rotary head HA-HD jumps over a plurality of tracks based on a drive signal to the head position control means 56; Means 51. for switching between the digital audio signal and the second digital audio signal, and selecting one of the first digital audio signal and the second digital audio signal depending on the error state outside the predetermined period. 52
．． 53.

[Effect]

During the variable speed playback operation, when the tape speed is relatively close to that during normal playback, track control is performed by the head position control means 56 using, for example, a piezoelectric element. Tracks of multiple fields are jumped depending on the ratio of the tape speed to that during normal playback. As a result, the first copy and the second copy have different time periods. During this period, a switching process such as a cross-fade is performed, and in other periods when the first copy and second copy have the same data, error-free data is transferred from the first copy and second copy as in normal playback. selected. Therefore, during variable speed playback, it is possible to have the same error correction ability as during normal playback.

〔Example〕

Hereinafter, an embodiment in which the present invention is applied to the reproduction of audio data of a digital VTR will be described with reference to the drawings.

This description is given in the following order.

a. Recording circuit and playback circuit of digital VTR; Scanner and track format; C6 variable-speed playback operation; d; Data processing during variable-speed playback; The overall configuration of the recording side of an applicable digital VTR is shown. In FIG. 1, 1 is an analog audio signal input terminal, 2 is a digital audio signal input terminal, and 3 is an analog/digital interface.

A buffer memory 4 is connected to the interface 3, and the buffer memory 4 compresses the time axis of the audio data and converts it into the order of the block structure. 5 indicates an outer code encoder, and 6 indicates a shuffling circuit. The outer code encoder 5 encodes the outer code, which is an error correction code. The shuffling circuit 6 is constituted by a memory and rearranges the order of data.

7 is an input terminal for an analog video signal, 8 is an input terminal for a digital video signal, and 9 is an analog/digital interface. The output signal of the interface 9 is supplied to the channel day multiplexer 10,
Converted to a channel data series. The data series of each channel is supplied to the outer code encoder 11 and subjected to outer code encoding processing. The output data of the encoder 11 is supplied to the intra-sector shuffling circuit 12, which rearranges the order of data within the sector and synchronizes and IDs the audio data from the shuffling circuit 6 and the video data from the intra-sector shuffling circuit 12. Generation circuit 1
The synchronization signal and TD double signal from 3 are supplied to the data multiplexer 14. The output signal of data multiplexer 14 is supplied to inner code encoder 15 . The inner code encoder 15 performs inner code encoding processing.

The output signal of the inner code encoder 15 is supplied to the channel encoder 16 and subjected to mirror square code encoding processing. An output signal from the channel encoder 16 is taken out to an output terminal 18 via a recording amplifier 17.

A rotary head is connected to the output terminal 18. Recorded data is recorded onto the magnetic tape by the rotating head.

Data reproduced from the magnetic tape by the rotary head is supplied to a reproduction amplifier 22 from an input terminal 21 in FIG. The output signal of the reproduction amplifier 22 is supplied to the channel decoder 23, and the Miller square code is decoded.

0 The output signal of the channel decoder 23 is sent to the synchronization detection circuit 24
, and the synchronization signal is detected.

The output signal of the synchronization detection circuit 24 is supplied to the inner code decoder 25, and the inner code is decoded. Inner code decoder 25
The output signal is supplied to the switch circuit 26, and audio data and video data are separated.

The audio data is de-shuffled by the de-shuffling circuit 27 and then supplied to the outer code decoder 28 . The outer code is decoded by the outer code decoder 28 and written into the memory 29.

The decoding of the outer code is, for example, erasure correction with reference to an error flag generated in the decoding of the inner code.

The memory 29 expands the time axis of the data.

The audio data read from the memory 29 is supplied to the error correction circuit 30, and error data is corrected. Output data of the error correction circuit 30 is supplied to an analog/audio interface 31 and an output terminal 32
An analog audio signal is obtained at the output terminal 33, and a digital audio signal is obtained at the output terminal 33.

The video data separated by the switch circuit 26 is written into the buffer memory 34. Video data read from the buffer memory 34 is supplied to an outer code decoder 36 via an intra-sector deshuffling circuit 35. The error-corrected data from the outer code decoder 36 is supplied to the channel multiplexer 37, and the two-channel data is converted into one-channel data. The output signal of the channel multiplexer 37 is sent to the error correction circuit 38.
The error data is corrected.

The output signal of the error correction circuit 38 is provided to an analog/digital interface 39. An analog video signal is obtained at an output terminal 40, and a digital video signal is obtained at an output terminal 41.

b. Scanner and track format FIG. 3 shows an example of a scanner for a digital VTR. Four head chips HA-H are mounted on the drum 42 rotating in the direction of the arrow.
D is attached. Head chips HA and HB are close to each other, head chips HC and HD are close to each other, head chips HA and HC have a facing interval of 180°, and head chips HB and HD have a facing interval of 180°. There is. drum 42
A magnetic tape 43 is obliquely wound around the circumferential surface of the magnetic tape 43 at a winding angle slightly wider than 180°. magnetic tape 43
A pair of head chips HA and HB and a pair of head chips HC and HD alternately slide into contact with each other. The angles of the gaps between the head chips HA and HB are made different, and similarly the angles of the gaps between the head chips HC and HD are made different to perform azimuth recording. A reproduction signal is formed by time-division multiplexing of the reproduction signals of the head chips HA and HC having the same azimuth angle, and a reproduction signal is similarly formed by time-division multiplexing of the reproduction signals of the head chips HB and HD.

Head chips HA and HB are provided at one end of a support plate consisting of two plate-shaped piezoelectric elements, and head chips HC and H
D is provided at one end of a similar support plate. The support plate is
The head chip is displaced in the height direction by an amount corresponding to the driving voltage. For example, (-1 to +3) (the sign is the magnetic tape 43
When playing back at a tape speed set in the tape speed range (where +1 means the tape speed during normal playback), the drive voltage to the piezoelectric element is adjusted by a microcomputer, etc. according to the tape speed. generated. As a result, the head chips HA-HD# (FAQ) correctly scan the tracks formed on the tape 43.

In the case of a video signal with a field frequency of 60 Hz, such as the NTSC system, the field is divided into three segments, and one segment is recorded as two tracks.

In other words, the video signal for field ■ is 3 segments and 6
It is recorded on the magnetic tape 43 as a track.

4B shows the track format formed on the magnetic tape 43. FIG. Figure 4A shows the magnetic tape 4
FIG. 4B shows a track pattern seen from the magnetic surface side of No. 3, and FIG. 4B shows one track in the order of scanning by the head. AOlAl, A2, and A3 each indicate an audio sector, and these 3 4 audio sectors AO to A3 are arranged at the end of the track. A 0 - A 3 is data of the first, second, third and fourth channels. Furthermore, the same content of audio data is recorded twice at different ends of two tracks. That is, audio data having the same content is recorded on the end of the previous track on the head separation side and the end of the current track on the head entry side. The first audio data recorded on the end on the head separation side will be referred to as a first copy, and the second audio data recorded on the head entry side will be referred to as a second copy. The video sector is located in the center of the track. TOlTl is the track number, and SO is the segment number.

Fourth, as shown in FIG. B, editing gaps are provided between audio sectors and between audio and video sectors. The audio sectors AO to A3 each consist of six sync procs, and the video sector is
It consists of 204 sync programs. In FIG. 4B, T indicates a track preamble, E indicates an edit gap preamble, and P indicates a post preamble.

As shown in FIG. 5, each sync block has a length of 190 bytes, and a 2-hide synchronization pattern is added to the beginning. Next, a 2-byte ID pattern is added, and this ID pattern and 85-byte data are encoded with an inner code to form an 8-hide check code. Furthermore, an 8-byte check code is added to the other 85 hide data to form an inner code block.

The inner code is common to audio data and video data. Reed-Solomon codes are used as the inner code and outer code. The number of samples of audio data recorded in each audio sector is 266 or 267 samples. FIG. 6 does not show the block configuration included in one audio sector.

In FIG. 6, numbers 0 to 266 indicate audio sample numbers, P10 to PV3 indicate outer code check codes, and AUXO to AUX3 indicate auxiliary words.

These audio data, check codes and auxiliary words are shuffled. In FIG. 6, illustration of the inner code check code is omitted. The bit length of one sample of audio data is 20 bits,
In the encoding of the inner code, one byte is one symbol.

A plurality of bytes aligned vertically in the array shown in FIG. 6 constitute a block of the outer code. Therefore, 1 sec is 85
It consists of blocks of outer codes.

C0 variable speed regeneration operation The variable speed regeneration operation will be explained with reference to FIG. The track format described above is shown in FIG. 7A. In FIG. 7A, reference numbers A and -D are head chips HA to H.
This means the track D scans. During variable-speed playback, for example, during double-speed playback, dynamic tracking control allows the three segments (in which field F1 is recorded)
6 tracks) are played back by the head chips HA to HD in the same way as during normal playback. When the reproduction of field F1 is completed, the signal of the next field F2 is recorded.
The actual track is skipped over, and the track in which the signal of the next field F3 is recorded is played back. Therefore, the seventh
As shown in Figure B, during double speed playback, field F1
Next, the reproduced data of field F3 is obtained. In FIG. 7B, 5O1S1, S2 are the first and second
, indicating the third segment.

If we pay attention to before and after the track jump, as shown in FIG. 7A, the first copy DAI is recorded at the head separation side end of the track in field F1, and the first copy DAI is recorded at the head entry side end of the track in field F2. Two copies DA1' are recorded. First copy DAI and second copy DAI
' are the same audio data. however,
Since field F2 is not reproduced, the skipped second copy DA2 of field F2 is reproduced as the second copy paired with the first copy DAI, as shown in FIG. 7C. Naturally, the second copy DA2 is different data from the first copy DAI.

Therefore, in this embodiment, cross-fade processing is performed at the joint between fields where the first copy and the second copy have different data, and during the period where the first copy and the second copy have the same data, the normal The same decoding process as during playback is performed.

d. Data processing during variable speed playback FIG. 8 shows an audio data processing circuit that can be applied during variable speed playback. 27A and 27B indicate deshuffling circuits, respectively. One de-shuffling circuit 27A is supplied with reproduction data in which the reproduction outputs of the head chips HA and HC are alternately located, and the other de-shuffling circuit 27B is supplied with reproduction data in which the reproduction outputs of the head chips HB and HD are alternately located. Positioned playback data is provided. Output signals from these deshuffling circuits 27A and 27B are supplied to outer code decoder 28A via selector 51. Furthermore, output signals of deshuffling circuits 27A and 27B are supplied to outer code decoders 28B and 28C, respectively.

The selector 51 refers to the error flag generated in the inner code decoder, selects the non-error data of the first copy and the second copy, and forms a code block of the outer code. Outer code decoder 28A decodes the output data of selector 51.

The decoded output of outer code decoder 28A is supplied to error correction circuit 30A via memory 29A. The output signal of the error correction circuit 30A is supplied to the selector 52.

The data decoded by the decoders 28B and 28C are stored in the memories 29B and 29C and the error correction circuits 30B and 30C.
is supplied to the crossfader 53 via. The output signal of the crossfader 53 is supplied to the selector 52. The signal selected by the selector 52 is supplied to the analog/digital interface 31 (see FIG. 2). A control signal is supplied to the selector 52 and crossfader 53 from a control signal generation circuit 54. Control signal generation circuit 5
A detection pulse Pd is supplied from a detection circuit 55 to 4.

9 0 A drive signal Sd for dynamic tracking is supplied from the controller 57 to the support plate 56 of the head. The detection circuit 55 detects a track jump from this drive signal Sd. FIG. 9 shows the operation of detecting a track jump. During double speed playback shown in FIG. 7, a sawtooth drive signal Sd is supplied to the support plates of the head chips HA and HC. Field F1 is played back, and then a track jump occurs and playback shifts to field F3. During this track and jump, the level of the drive signal Sd changes rapidly, and the detection pulse Pd is formed from this change.

In order to accurately detect track jumps, the drive signal S
The detection pulse Pd is detected only when the change in d is equal to or higher than a predetermined level.
is generated. The start timing of the crossfader is determined from this detection pulse Pd, and the selector 52
A control signal for is formed.

As shown in FIG. 10, error correction circuits 30B and 30
A first copy and a second copy of the reproduced audio data are obtained from C. For simplicity, FIG. 10 shows only the audio data of the first channel (decoded output of audio sector AO), aOlal and C2 are reproduction data of each segment of field F1, and bOlbl and b2 are reproduction data of each segment of field F2. data, co, cl, C
2 is playback data of each segment of field F3, d
O, dl, d2 mean the reproduction data of each segment of field F4.

During double speed playback, field F1 is played back by dynamic tracking, then the track of field F2 is jumped, and field F3 is played back. Audio data a2 of segment s2 of field F1 is obtained as the first copy. However, due to the track jump, the second copy has segment s in field F2.
2 audio data b2. When track jumping from field F3 to F5, the audio data of segment S2 of field F3 becomes data d2 of field F4.

1 = 22 The crossfader 53 operates in different segment periods for the audio data of the first copy and the second copy, and each sample of the audio data of the first copy is multiplied by a gradually decreasing coefficient. Each sample of the two copies of audio data is multiplied by a gradually increasing coefficient.

The selector 52 selects the output of the error correction circuit 30A during a period when the data of the first copy and the second copy are the same, and selects the output of the crossfader 53 during a period when these are different, that is, the operation period of the crossfader 53. do.

e. Modification The processing for switching the period in which a track jump occurs is not limited to cross-fade, but may also include processing for generating an average value of the data of the first copy and second copy, processing for muting the second copy, etc. . However, cross-fade processing has the advantage that the sounds are smoothly connected at the field switching point.

〔Effect of the invention〕

The present invention can prevent erroneous correction processing in which different data is used for decoding during variable speed reproduction.

Further, according to the present invention, when the first copy and the second copy contain the same data, data with no errors is selected from both copies, so that the same error correction ability as in normal reproduction can be obtained.

[Brief explanation of drawings]

Figure 1 shows a digital V to which this invention can be applied.
FIG. 2 is a block diagram of the recording side of an example of a TR, FIG. 2 is a block diagram of the reproduction side of an example of a digital VTR to which the present invention can be applied, and FIG. 3 is a plan view showing the configuration of a scanner.
Figure 4 is a route map showing the format on a digital VTR tape, Figure 5 is a route map showing the configuration of a sync plotter, Figure 6 is a route map showing the block arrangement of audio data, and Figure 7 is a variable speed playback operation. FIG. 8 is a block diagram showing the configuration of the main parts of an embodiment of the present invention, and FIGS. 9 and 10 are route maps used to explain the operation during variable speed reproduction. 3 4 Explanation of main symbols in the drawings 21: Reproduction data input terminal, 27. 27A, 27B: De-shuffling circuit, 28.
28A, 28B, 28c: Outer code decoder, 51.5
2: Selector, 55 Detection circuit for Nidrakku Jump, 56: Support plate for displacing the head.

Claims (1)

[Claims] The same first digital audio signal and second digital audio signal are recorded in duplicate on each of two adjacent tracks on a tape, and the digital information signal is rotated from the tape. In a digital information signal reproducing device configured to reproduce data using a head, head position control is performed to control the scanning position of the rotary head to match the track during variable speed reproduction in which the tape is run at a speed different from the normal speed. means for detecting that the rotary head jumps between a plurality of tracks based on a drive signal for the head position control means; means for performing switching processing with the second digital audio signal, and selecting one of the first digital audio signal and the second digital audio signal according to the error state outside the predetermined period. A digital information signal reproducing device characterized by: