AU620046B2 – Apparatus for reproducing an information signal
– Google Patents
AU620046B2 – Apparatus for reproducing an information signal
– Google Patents
Apparatus for reproducing an information signal
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Publication number
AU620046B2
AU620046B2
AU23951/88A
AU2395188A
AU620046B2
AU 620046 B2
AU620046 B2
AU 620046B2
AU 23951/88 A
AU23951/88 A
AU 23951/88A
AU 2395188 A
AU2395188 A
AU 2395188A
AU 620046 B2
AU620046 B2
AU 620046B2
Authority
AU
Australia
Prior art keywords
audio signal
signal
frequency
quality
video
Prior art date
1987-10-21
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
AU23951/88A
Other versions
AU2395188A
(en
Inventor
Noboru Murabayashi
Kenji Nakano
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sony Corp
Original Assignee
Sony Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1987-10-21
Filing date
1988-10-17
Publication date
1992-02-13
1988-10-17
Application filed by Sony Corp
filed
Critical
Sony Corp
1989-04-27
Publication of AU2395188A
publication
Critical
patent/AU2395188A/en
1992-02-13
Application granted
granted
Critical
1992-02-13
Publication of AU620046B2
publication
Critical
patent/AU620046B2/en
2008-10-17
Anticipated expiration
legal-status
Critical
Status
Ceased
legal-status
Critical
Current
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Classifications
G—PHYSICS
G11—INFORMATION STORAGE
G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
G11B20/10—Digital recording or reproducing
H—ELECTRICITY
H04—ELECTRIC COMMUNICATION TECHNIQUE
H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
H04N5/00—Details of television systems
H04N5/76—Television signal recording
H04N5/91—Television signal processing therefor
H04N5/92—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback
H04N5/928—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback the sound signal being pulse code modulated and recorded in time division multiplex with the modulated video signal
H—ELECTRICITY
H04—ELECTRIC COMMUNICATION TECHNIQUE
H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
H04N9/00—Details of colour television systems
H04N9/79—Processing of colour television signals in connection with recording
H04N9/7921—Processing of colour television signals in connection with recording for more than one processing mode
H—ELECTRICITY
H04—ELECTRIC COMMUNICATION TECHNIQUE
H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
H04N9/00—Details of colour television systems
H04N9/79—Processing of colour television signals in connection with recording
H04N9/80—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback
H04N9/802—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback involving processing of the sound signal
H—ELECTRICITY
H04—ELECTRIC COMMUNICATION TECHNIQUE
H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
H04N9/00—Details of colour television systems
H04N9/79—Processing of colour television signals in connection with recording
H04N9/80—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback
H04N9/82—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback the individual colour picture signal components being recorded simultaneously only
H04N9/8205—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback the individual colour picture signal components being recorded simultaneously only involving the multiplexing of an additional signal and the colour video signal
H04N9/8233—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback the individual colour picture signal components being recorded simultaneously only involving the multiplexing of an additional signal and the colour video signal the additional signal being a character code signal
H—ELECTRICITY
H04—ELECTRIC COMMUNICATION TECHNIQUE
H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
H04N9/00—Details of colour television systems
H04N9/79—Processing of colour television signals in connection with recording
H04N9/80—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback
H04N9/82—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback the individual colour picture signal components being recorded simultaneously only
H04N9/83—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback the individual colour picture signal components being recorded simultaneously only the recorded chrominance signal occupying a frequency band under the frequency band of the recorded brightness signal
H04N9/835—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback the individual colour picture signal components being recorded simultaneously only the recorded chrominance signal occupying a frequency band under the frequency band of the recorded brightness signal involving processing of the sound signal
Abstract
In an apparatus such as an 8-mm format VTR for selectively reproducing video data and digital data, such as PCM audio data, recorded on a magnetic medium (1) with any one of a plurality of recording densities, the recording density of the digital data is detected (16) on the basis of a characteristic of the reproduced digital data, such as a characteristic clock frequency regenerated therefrom, and the processing (21 or 22) to which the reproduced digital data is subjected is selected (23,28) automatically in accordance with the detected recording density thereof, thereby facilitating the use of the apparatus for reproducing digital data recorded with different densities.
Description
J
*if i
AUSTRALIA
PATENTS ACT 1952 COMPLETE SPECIFICATION 620 0.4 6
(ORIGINAL)
FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Related Art: TO BE COMPLETED BY APPLICANT 9# 4 It 4 4 I CI Ir 1 *r II
L
*e I tIC.
IC
I t C t(I CCII C Name of Applicant: Address of Applicant: SONY CORPORATION 7-35 KITASHINAGAWA 6-CHOME
SHINAGAWA-KU
TOKYO
JAPAN
Actual Inventor: Address for Service: GRIFFITH HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.
S;i,
D
Complete Specification for the invention entitled: APPARATUS FOR REPRODUCING AN INFORMATION SIGNAL The following statement is a full description of this invention including the best method of performing it known to me:- BACKGROUND OF THE INVENTION Field Of The Invention This invention relates generally to information reproducing apparatus and, more particularly, is directed to an apparatus suitable for reproducing digital data recorded on a magnetic recording medium.
DESCRIPTION OF THE PRIOR ART It is known to employ an 8-mm format video tape recorder (VTR) as an apparatus for the play back or reproducing of digital data recorded on a magnetic tape. In such 8-mm format VTR, an FM audio signal is interposed between the frequency band of a FM luminance signal and the frequency band of a low-frequency converted chrominance signal, and the resulting combined signal which is o. hereinafter simply referred to as a video signal is recorded oo° in video track portions TRVD constituting the main portions o I of successive slant record tracks TRA and TRB which are S disposed alternately on a magnetic tape 1, as shown on Fig.
7. In order to record and/or reproduce audio signals of 1 higher quality, in the 8-mm format VTR, the audio signals 0 are PCM-encoded, time-base compressed and recorded in so-called overscan or audio track portions TRAD situated at one of the end portions of the slant tracks TRA and TRB. A V0o particular type of modulation used to record the time-compressed, PCM-encoded audio signals is bi-phase-mark dution for example as described in detail in U.S.
modulation, for example, as described in detail in U.S.
-2-
I
II-
7 Patent No, 4,551,771, issued November 5, 1985, and having a common assignee herewith. As shown in Fig. 8A, in bi-phase-mark modulation, frequency signals S 1 and S 2 having frequencies fl, for example, of 2.9 MHz, and f 2 for example, of 5.8 MHz, are recorded as digital data on the magnetic tape while maintaining a phase relationship in which their zero cross points coincide with each other. For example, when a PCM audio signal is at logic the frequency signal S 1 having the low frequency fl is recorded, whereas, when the I’CM audio signal is at logic the frequency signal S 2 having the high frequency f2 is recorded on the magnetic tape.
When an audio signal recorded in an audio track portion TRAD is reproduced or played back, the zero cross points of the picked-up frequency signal S 1 or S2 are detected, as shown in Fig. 8B. In response to such detection, for example, a sampling pulse oscillator with a phase locked loop (PLL) arrangement is made to oscillate and thereby provide output pulses PLL 0 which are phase shifted 450 from the frequency signal S 1 having the low frequency fl’ or phase shifted 900 from the frequency signal S 2 having the high frequency f 2 Those of the output pulses PLL
O
generated at the phase angles of 350, 1350, 2250 and 3150 of the frequency signal S 1 are used as sampling pulses PS (Fig.
8C) for sampling the reproduced data. When every other two of the resulting sampled values are positive, it is 8 00o0 o a 0 P 00 000 0 0 0 0 0 oa a o B o o 1& t r -3determined that the respective reproduced data is at the logic level Further, those of the output pulses PLL
O
generated at the 900 and 2700 phase angles of the frequency signal S 2 are also used as sampling pulses PS for sampling the reproduced data and, when every other of these sampead values are positive, it is determined therefrom that the respective reproduced data is at the logic level The reproducing of bi-phase-mark modulated data is further described in U.S. Patnt Appliation SrialNo 115,045 and in the corresponding EPO laid-opon Publization No. 026422–, which also ha a common assignee herewith.
As shown more specifically in Fig. 9, the video signal SVD recorded in the video track portion TRVD of each of the tracks TRA and TRB is known to include an FM I luminance signal, for example, as indicated at S1VN, a low frequency or down-converted chrominance signal S3V, and an o FM audio signal, for example, as indicated at S 2
VM
interposed between the frequency bands of the signals S1VN and S3V. An automatic track follower (ATF) signal SATF is 8 c ‘ATF superposed on the signal SVD for recording therewith in each video track portion TRVD. The same rotary magnetic head used for recording the signal SVD in each video track i portion TRVD is also used for recording the PCM audio signal SADNR in the audio signal portion TRA of the respective track. The frequency spectrum of the PCM audio signal SADNR
ADNR
is shown on Fig. 9 to have a peak value at a frequency which i 4r substantially coincides with the center frequency of the FM luminance signal S1V N Further, the PCM audio signal SADNR has a frequency characteristic in which the signal level nears zero in the high and low frequency ranges of the signal SVD. By reason of the foregoing, the same degrees of azimuth loss are obtained when one of the rotary magnetic heads reproduces the signal SVD and the PCM audio signal SADNR recorded in respective portions TPvD and TRAD of the same slant track. Therefore, the PCM audio signal SADNR can be recorded without guard bands between adjacent tracks so long as the two rotary magnetic heads provided for recording and reproducing signals in the adjacent tracks TRA and TRB, respectively, have gaps with different azimuth angles for substantially minimizing cross talk between the PCM audio h rr signals recorded in such adjacent tracks.
Depending upon the application thereof, digital data redorded on a magnetic recording’mediur may have Sdifferent sampling frequencies. Therefore, recording media of different types are used for recording digital data having respectively different recording densities. It is St apparent that, if a reproducing or playback apparatus can be I ,adapted for reproducing data from the different types of S tapes having respectively different recording densities, the C uses of such play back apparatus will be accordingly extended. Thus, for example, it is advantageous to provide StVh an 8-mm VTR capable of use with first and second types of f recording media, in which the first type of recording medium records PCM audio data having a standard digital information content sampled at a standard sampling frequency, while the second type of recording medium records PCM audio data having a relatively larger content of high-quality digital data sampled at a frequency that is a predetermined multiple of the standard sampling frequency. If these first and second types of recording media can be reproduced in a common 8-mm VTR, that is, the same apparatus can be used for reproducing a standard-quality audio signal from the first type of recording medium and for reproducing a high-quality audio signal from the second type of recording medium, such 8-mm VTR will have a substantially expanded utility.
However, the reproducing apparatus heretofore w C o available has required the user to determine whether the o recording medium about to be played back or reproduced is recorded with standard- or high-quality. PCM audio or other o digital data, and, after making such determination, to select the appropriate processing circuits. Thus, the known o reproducing apparatus is relatively inconvenient in that it requires the user thereof to adapt the apparatus for the *o°o playback of the type of recording medium in question, and in so doing is susceptible to errors on the part of the user.
OBJECTS AND SUMMARY OF THE INVENTION o tO ac Accordingly, it is an object of this invention to provide an apparatus for selectively reproducing PCM audio a I I -7 .9-4.
4 .9 4′ .4, 0f 0 *0 09 4 0* 0 4 0* 04000* 0 0 00404: or other digital data recorded on a recording medium with a standard-quality or high-quality recording density, and which is less susceptible to the previously mentioned disadvantages of the prior art.
According to the present invention there is provided an apparatus for reproducing an information signal recorded in a plurality of successive parallel tracks on a record medium and comprised of a video signal and at least one audio signal from the group of a frequency-modulated monaural audio signal, frequency-modulated stereo audio signals, a standard digitized audio signal and a high-quality digitized audio signal, with the video signal and the frequency-modulated audio signals being recorded only in a main section of each track and the digitized audio signals being recorded at least int an overscan 15 section of each track, said apparatus comprising: transducer means for scanning said tracks to reproduce said information signal recorded in said successive parallel tracks; separation means for separating a signal reproduced 20 during scanning of the main section of each track by said transducer means and a signal reproduced during scanning of the overscan section of each track by said transducer means; f requency-modulated monaural audio signal processing means connected to said separation means for receiving said 25 signal reproduced during scanning of said main section of each track and having an output; frequency-modulated stereo audio signal processing means connected to said separation means for also receiving said signal reproduced during scanning of said main section of each track and having an output; standard digitized audio signal processing means connected to said separation means for receiving at least said signal reproduced during scanning of said overscan section of each track and having an output; high-quality digitized audio signal processing maeans connected to said separation means for also receiving at least said signal reproduced during scanning of said overscan section of each track and having an output; frequency-modulated audio signal detecting means connected to said separation means for detecting whether said signal reproduced during said scanning of the main section of -8each track includes said frequency-modulated monaural audio signal or said frequency-modulated stereo audio signals; digitized audio signal detecting means for detecting whether said signal reproduced during scanning of said overscan section of each track includes said standard digitized audio signal or said high-quality digitized audio signal, said digitized audio signal detecting means being connected between said separation means and said standard and high-quality digitized audio signal processing means; selecting and controlling means for automatically selecting an audio signal from among said frequency-modulated monaural audio signal, said frequency-modulated stereo audio signal, said standard digitized audio signal and said high- Go 4quality digitized audio signal, in response to said frequencymodulated audio signal detecting means and said digitized audio signal detecting means; rc Caudio output means; and switching means controlled by said selecting and controlling means for selectively connecting said outputs of said frequency-modulated monaural audio signal processing means, said frequency-modulated stereo audio signal processing means, said standard digitized audio signal processing means 4544 r and said high-quality digitized audio signal processing means to said audio output means.
25 The above, and other objects and advantages of the invention, will be apparent in the following detailed description of an illustrative embodiment thereof which is to be read in connection with the accompanying drawings, in which r r corresponding parts or elements are identified by the same reference numerals in the several views.
BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of a recording and reproducing or play back apparatus in accordance with an embodiment of the present invention; Fig. 2 is a block diagram of a circuit included in the apparatus of Fig. 1 for recording and reproducing digital audio signals; Fig. 3 is a block diagram showing a specific circuit arrangement that may be advantageously employed in g -I each of a plurality of digital audio data detection circuits included in Fig. 2; Fig. 4 is a block diagram showing details of a reproduced video signal processing section included in the apparatus of Fig. 1; Fig. 5 is a block diagram showing details of a mode detecting and controlling section included in the apparatus of Fig. 1; Fig. 6 is a flow chart illustrating a mode selection program executed by a controller or the like included in the section of the apparatus shown on Fig. Fig. 7 is a schematic view of a length of magnetic tape on which a pattern of record tracks is illustrated; Figs. 8A, 8B and 8C are waveforms to which reference is made in describing the reproducing of a signal Itt which has been bi-phase-mark modulated; and Fig. 9 is a graph showing the frequency spectra of various components that may be included in a signal to be recorded and/or reproduced by the apparatus embodying this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings in detail, and initially to Fig. 1 thereof, it will be seen that a recording and/or play back or reproducing apparatus 10 according to an embodiment of this invention is thereshown applied to an 8-mm format VTR in which a pair of magnetic heads 12A and -9r. t i 12B (hereinafter referred to as the A and B heads) on a rotary drum 11 helically scan a magnetic tape 1 wrapped about the drum. As has been earlier described with reference to Fig. 7, as the tape 1 is longitudinally advanced in the direction of the arrow a and the heads 12A and 12B are rotated in the direction of the arrow b on Fig.
1, the A and B heads 12A and 12B sequentially and alternately scan slant record tracks TRA .nd TRB, respectively. As shown on Fig. 1, the heads 12A and 12B are substantially diametrically opposed on the drum 11 and the tape 1 is wrapped about the drum 11 over an angular extent exceeding 1800. As earlier mentioned with reference to Fig.
7, each of the tracks TRA and TRB includes a main or video Sc track portion TRVD which corresponds to the scanning of the respective track by the rotary head 12A or 12B while moving .with the drum 11 through an angle of 180′, and an overscan 4o #8 or audio track portion TRAD which is scanned by the respective head 12A or 12B during the remainder of its scanning movement in contact with the magnetic tape 1.
SThe A and B heads 12A and 12B are connected to a PCM audio signal processing section 13, a video signal processing section 14, an ATF signal processing section for automatic track following, and a mode detect/control section 16 through a video/audio switch circuit 26. The apparatus 10 embodying this invention is further shown to generally comprise a system controller 100, for example, a microprocessor or the like which provides various control signals hereinafter described in detail and represented generally at S on Fig. 1.
CONT
In a recording mode of the apparatus 10, a signal S and an ATF signal S from the video signal processing VD ATF section 14 and the ATF signal processing section respectively, are superposed and recorded in the main or video track portion TR of each slant record track TRA or
VD
TRB. A PCM audio signal S output from the PCM audio
AD
signal processing section 13 is recorded in the audio track portion TR of each slant track.
AD
The PCM audio signal processing section 13 is shown on Fig. 2 to include an audio data processing unit 13A and a recording/play back circuit 13B which are controlled by the control signals S from the system controller 100
CONT
Sand by selection signals S supplied from the mode s
SEL
detect/control section 16, as hereinafter described.
l ,The audio data processing unit 13A is shown on Fig. 1 to include a standard-quality audio signal processing circuit 21 and a high-quality audio signal processing circuit 22. In the recording mode, either recording audio data Sl formed by the processing circuit 21 in
REC
correspondence to an analog audio input signal S1i or
IN
recording audio data S2 formed by the processing circuit
REC
22 in correspondence to a second analog audio input signal -11reproduce said information signal recorded in said successive parallel tracks; separation means for separating a signal /2 1 1 r S2IN’ are supplied to a mode/head selector circuit 23 included in the recording/play back circuit 13B. The mode/head selector circuit 23 selects one of the recording I audio data S1 and S2R in accordance with the REC REC establishment of a standard-quality recording mode or a high-quality recording mode, respectively. The selected data S1 or S2 to be recorded in the audio track REC REC portions TRAD of the slant tracks TRA and TRB are supplied
AD
through an A-head recording amplifier circuit 24A and a B-head recording amplifier circuit 24B, respectively, to a recording/play back selector circuit The selector circuit 25 and the video/audio switch circuit 26 cooperate to sequentially supply the digital audio data from the A-head recording amplifier circuit 24A S and the B-head recording amplifier circuit 24B to the A-head 12A and the B-head 12B, respectively, during suitably timed intervals so as to constitute the audio data SAD recorded in the audio track portions TRA of the slant tracks TRA and TRB, respectively (Fig. The video/audio switch circuit 26 similarly cooperates with the video signal processing circuit 14 and is suitably timed so that the rotary heads 12A and 12B record fields or other specified intervals of the video signal SD in the video signal portions TRVD of VD V D Sthe slant tracks TRA and TRB, respectively.
In the play back or reproducing mode, the video/audio switch circuit 26 and the record/play back -12- S I I PATENT 39-0100.2118 selector circuit 25 direct the audio signal S reproduced
AD
by the A and B heads 12A and 12B from the audio track portions TRAD of the tracks TRA ane TRB, respectively, through an A-head play back amplifier 27A and a B-head play back amplifier 27B to a mode/head selector and equalizer circuit 28. The mode/head selector and equalizer circuit 28 selectively fetches the reproduced audio signal from the A-head or B-head play back amplifier 27A or 27B, and performs a predetermined equalizing process thereon in accordance with the established play back mode of the apparatus, that is, whether the apparatus is in its standard-quality play back mode or in its high-quality play back mode. Then, play back audio data Sl or 52 is PB PB selectively supplied from the circuit 28 to the standard-quality audio signal processing circuit 21 or the high-quality audio signal processing circuit 22, L t respectively, once again in’dependence on the established Se play back mode of the apparatus. The operative audio signal /i processing circuit 21 or 22 converts the reproduced audio data Sl or S2 respectively, into an analog signal which PB PB is output from the circuit 21 or 22 as a first or second audio output signal S1 or S2 respectively.
OUT OUT In the embodiment of the invention being here described, the audio signal processing circuit 21 samples the respective input audio signal, S1 at a standard
IN
sampling frequency, for example, a sampling frequency of 2f
H
-13-
M
MHz and a frequency range of 2 to 8 MHZ, and the 1- 7 I 31.5 KHz, for converting the input audio signal S1 into
IN
PCM digital data. A CRCC (cyclic redundancy check code) error code is added to such digital data, and the number of bits of the digital data is compressed by 10-8 bit conversion or compression. The 10-8 bit conversion or compression is preferably effected in a non-linear encoder or compressor which effects non-linear quantization for reducing quantizing noise. The resulting compressed data is subjected to bi-phase-mark modulation at a clock frequency CK NR, for example, of 11.6 MHz, for forming the recording
NR
audio data Sl which is output from the circuit 21 and
REC
which consists of two frequency signals S and S (Fig. 8A) 1 2 having, for example, the frequencies f 2.9 MHz and f 1 2 5.8 MHz, respectively.
*c os In the standard-quality play back mode, the audio d u signal processing circuit 21 bi-phase-mark demodulates the go reproduced audio data S1 and effects error :orrection by
PB
S means of the CRCC error code. The circuit 21 further effects interpolation of the audio data and then performs 10-8 inverse conversion, whereupon the resulting data is D/A converted so as to provide the audio output signal Sl
OUT
It will be appreciated that the standard-quality audio signal processing circuit 21 may be substantially the same as the circuit disclosed for similar purposes in the previously mentioned U.S. Patent 4,551,771.
-14- In the high-quality recording mode of the apparatus 10, the high-quality audio signal processing circuit 22 samples the respective audio input signal S2IN at a high-quality sampling frequency, for example, of 3f 48
H
KHz, which is higher than the standard sampling frequency, so as to obtain 16-bit PCM digital data. Then a CIRC (Cross Interleaved Reed-Solomon Code) error code is added to the digital data, whereupon the digital data and the error code added thereto are compressed. The compressed data is then 8-10 modulated and NRZI (Non-Return to Zero Inverted) converted at a clock frequency CK 14.8 MHz (that is, tie
HI
Nyquist frequency f 7.4 MHz), whereby the data is
NYH
modulated into a data string which is not easily influenced by DC level shift. The converted data string is output from the circuit 22 as the second recording audio data S2
REC
S’ The foregoing 8-10 modulation of the compressed data is a e kind of group coded modulation in which .withN 8 and M the data bits are segmented into N-bit blocks, each N-bit block is converted to an M-bit data string or code, N M and 2 patterns or codes are sel.ected from the converted 2 patterns or codes for reducing the DC and low frequency components in the frequency spectrum of the modulated Ssignal. A modulation system similar to the foregoing 8-10 «modulation is described in detail in the previously mentioned U.S. Patent No. 4,577,180, and in U.S. Patent No.
i j 4 4 4,617,552, issued October 14, 1986, and also having a common assignee herewith.
In the high-quality play back mode of the apparatus 10, the audio signal processing circuit 22 effects NRZI decoding and 8-10 demodulation of the reproduced audio data S2pB supplied thereto. Further, the demodulated data is subjected to error correction by means of the CIRC error code and, thereafter, the corrected data is subjected to interpolation and then converted to the analog audio signal S2 which is output from the circuit 22.
OUT
A sampling circuit having a sampling frequency of 48 KHz and a circuit for processing 16-bit PCM digital data, as described above in respect to the processing circuit 22, are available, for example, such circuits may be of the j no: types presently employed in rotary-head digital audio tape o recorders (R-DAT).
e a SThe recording audio data S1 and S2 obtained REC REC from the audio signal processing circuits 21 and 22, 0 I respectively, are supplied to standard- and high-quality input terminals NR and HI, respectively, of a mode selecting switch circuit 23A included in the mode/head selector 23, as shown in Fig. 2. The mode selecting switch circuit 23A is controlled by a mode designating or establishing signal Cl included in the control signals S provided by the system
CONT
controller 100. When the signal C1 designates the standard-quality recording mode, the mode selecting switch -16circuit 23A engages its input terminal NR, as shown on Fig.
2, so that the audio data SIRE C is supplied through the mode switch circuit 23A to a head switching circuit 23B which is also included in the mode/head selector 23. On the other hand, when the signal C1 designates the high-quality recording mode, the mode switching circuit 23A is made to engage its terminal HI so that the audio data S2REC is supplied through the mode switch circuit 23A to the head switching circuit 23B. The head switching circuit 23B is changed over or controlled so as to alternately engage its output terminals A and B by a head switching signal C2 also included in the control signals SCONT from the system controller 100. Thus, the audio data supplied to the head switching circuit 23B is alternately output from the S terminal A or B thereof as recording data D1 or D2, respectively.
The recording data D1 is amplified by the A-head recording amplifier 24A and supplied therefrom to a terminal t REC of a record/play back switch 25A of the record/play back selector 25. Similarly, the recording data D2 from the terminal B of the head switch circuit 23B is amplified by the B-head recording amplifier 24B and then applied to a terminal REC of a record/play back switch 25B of the selector 25. The record/play back switches 25A and 25B are shown to be controlled by a record/play back control signal C3 included in the control signals SCONT from the system I CONT -17controller 100 so that the switches 25A and 25B engage their respective REC terminals as shown on Fig. 2, when the apparatus 10 is in a recording mode, and so that switch circuits 25A and 25B have their moveable contacts changed-over to engage respective terminals PB when the apparatus is in a reproducing or play back mode.
The moveable contacts of the record/play back switches 25A and 25B are shown to be connected to terminals AD of video/audio change-over switches 26A and 26B which are included in the video/audio selector 26 and have their moveable contacts connected to the A-head 12A and the B-head 12B, respectively. The video/audio change-over switches 26A and 26B are controlled in response to a video/audio switching signal C4 which is also provided among the control signals SONT from the system controller 100.
The video/audio change-over switches 26A and 26B are conditioned by the video/audio switching signal C4 004 So** included in the control signals S from the system
CONT
0 controller 100 so as to engage their respective contacts or terminals AD during the intervals when the heads 12A and 12B are scanning the overscan or audio track portions TR of the tracks TRA and TRB, respectively. On the other hand, O, during scanning of the main or video track portions TRvD of the tracks TRA and TRB by the heads 12A and 12B, V respectively, the video/audio change-over switches 26A and 26B are respectively changed-over to engage their terminals S-18- -18- VD which are connected to the video signal processing section 14, the ATF signal processing section 15 and the mode detect/control section 16.
With the above described arrangement of the apparatus 10, in the standard-quality recording mode, the standard-quality PCM audio signal S which is sampled at
ADNR
the standard sampling frequency in the standard-quality audio signal processing circuit 21 is recorded in the overscan or audio track portion TRAD of each of the tracks TRA and TRB at a standard recording density. In the high-quality PCM recording mode, the high-quality PCM audio signal SADHI which is sampled at a high-quality sampling frequency in the high-quality audio signal processing circuit 22 is similarly recorded, but at a higher recording density than the standard recording density.
So In the play back mode, the A-head 12A and the B-head 12B pick up the PCM audio signal SAD from the
AD
so 40 overscan or audio track portions TRAD of the tracks TRA and TRB, respectively. The reproduced signal SAD is supplied to the A-head play back amplifier 27A and the B-head play back amplifier 27B through the audio terminals AD of the video/audio switch circuits 26A and 26B and the play back terminals PB of the record/play back switch circuits 25A and The resulting reproduced data D3 and D4 from the play back amplifiers 27A and 27B are supplied to mode switch circuits 31A and 31B of a mode selector 31 included in the -19-
A
mode/head selector and equalizer circuit 28. The mode switch circuits 31A and 31B are switched in response to a mode selection signal L1 provided as one of the selection signals S from the mode detect/control section 16. When
SEL
the PCM audio signal S which is being played back or
AD
reproduced is of the standard quality, the mode switch circuits 31A and 31B are conditioned as shown on Fig. 2 so as to engage their respective terminals NR, with the result that the reproduced data D3 and D4 are respectively supplied to standard-quality A-head and B-head equalizer circuits 32 and 33, respectively. On the other hand, when the PCM audio signal S which is being reproduced is of the high-quality,
AD
the mode switch circuits 31A and 31B are changed-over by the signal L1 so as to engage their respective terminals HI and thereby supply the reproduced data D3 and D4 to high-quality A-head ar.d B-head equalizer circuits 34 and respectively.
rl It will be appreciated that, when there is a change from one to the other of the standard- and high-quality modes, or from one to the other of the A and B heads 12A and 12B of the apparatus 10, the audio data S
AD
‘which is recorded in, or reproduced from the audio track portions TR have different response characteristics with
AD
changes in frequency. Thus, the equalizer circuits 32, 33, 34 and 35 are provided to equalize the frequency characteristics of the reproduced data D3 and D4 picked up from the audio track portions TR of the tracks TRA and TRB
AD
I
by the heads 12A and 12B, respectively, in the standard-quality reproducing mode and in the high-quality reproducing mode, respectively. By reason of the foregoing, a desirably low bit error rate can be maintained, that is, the so-called eye pattern opening of the two frequency signals S 1 and S 2 constituting the bi-phase mark can be increased to the greatest extent possible.
As further shown on Fig. 2, the mode/head selector and equalizer circuit 28 includes a head selector circuit 36 made up of head switch circuits 36A and 36B each having input terminals A and B. Output data D5 and D6 from the equalizer circuits 32 and 33 are supplied to the input terminals A and B of the head switch circuit 36A.
Similarly, output data D7 and D8 from the equalizer circuits 34 and 35 are supplied to the input terminals A and B of the head switch circuit 36B. The moveable contacts of the head (tt switch circuits 36A and 36B are suitably changed-over *t CC between the respective input terminals A and B in response C r c to a head selection signal C5 included in the control signals CONT from the system controller 100. The moveable SCONT sse contact or output of the head switch circuit 36A is connected to a standard-quality audio data detecting circuit 37 so that output data D5 or D6 from the equalizer 32 or 33, respectively, is supplied through head switch circuit 36A to the standard-quality audio data detecting circuit 37.
Similarly, the output of the head switch circuit 36B is -21connected to a high-quality audio data detecting circuit 38 so that output data D7 or D8 from the equalizer circuit 34 or 35 is supplied to the high-quality audio data detecting circuit 38 through the head switch circuit 36B.
As shown in Fig. 3, each of the standard- and high-quality audio data detecting circuits 37 and 38 includes a comparator 50 in which input data D
PBIN
(constituted by the data D5 or D6, or the data D7 or D8) supplied to the inverted input of the comparator 50 is compared with a zero cross reference voltage V provided by
R
a variable reference voltage source 51 and applied to a non-inverted input of the comparator 50. A data detection signal D21 is derived from the output of the comparator Such data detection signal D21 is at a logic level when the input data D is raised to a positive value exceeding
PBIN
0, and the signal D21 attains a logic level when the input data falls to a negative value. The data detection signal D21 is supplied to a clock signal regenerating rC SC circuit 52 having a phase locked loop (PLL) arrangement.
The clock signal regenerating circuit 52 provides a detect clock signal CK which is phase-locked with the data
PB
detection signal D21 and is supplied to a clock input Sterminal C of a synchronization circuit 53 to serve the same function as the sampling pulse P which has been described
S
with reference to Fig. 8C. The clock signal CK is also
PB
Si supplied to the system controller i -22- Jg 100 as a system clock, and to the mode detect/control section 16 as a PCM mode detection signal S
MD
The synchronization circuit 53 is shown to be comprised of a D-type flip-flop circuit having the data detection signal D21 applied to its input terminal D. When the detection clock signal CK is supplied to the clock
PB
input terminal C of the flip-flop circuit 53, the latter is set or reset in response to the data detection signal D21 attaining the logic or level. The Q output of the flip-flop circuit 53 provides detection output data D
PBOUT
which, in the case of the standard-quality audio data detecting circuit 37, constitutes the first reproduced audio data S1 and, in the case of the high-quality audio data
PB
detecting circuit 38 constitutes the second reproduced audio data S2
PB
SIn the play back mode, the signal S picked up rc •VD Sfrom the video track portion TR by the A and B heads 12A t iVD V. and 12B is input to the ATF signal processing section 15 and the mode detect/control section 16 (Fig. 1) through the video output terminals VD of the video/audio switch circuits 26A and 26B (Fig. 2) of the video/audio switch circuit 26.
As shown in Fig. 4, the reproducing or playback system of the video signal processing section 14 supplies the input signal S to A-head and B-head input terminals A
VD
and B of a head selector circuit 61 through A-head and B-head play back amplifiers 60A and 60B. The head selector circuit 61 is switched in response to a head selection -23signal C6 supplied as one of the control signals S from
CONT
the system controller 100. The signal S obtained from the
VD
circuit 61 is input to a subsequent video mode selection switch circuit 62. In addition, the FM audio signals S2V
M
and S2V shown on Fig. 9, and together comprising the FM
S
audio signal S on Fig. 4, are extracted from the signal
FM
S through a band-pass filter 63 having for example, a pass
VD
band of 1.4 MHz to 1.8 MHz., and are input to an FM audio selection switch circuit 66.
The video mode selection switch circuit 62 is switched in response to a video mode selection signal L3 supplied as one of the selection signals S from the mode
SEL
detect/control section 16. When the standard-quality mode is selected by the video mode selection signal L3, the signal S is output to a standard-quality video signal
VD
processing circuit 64 through a standard-quality output C# I lift i terminal NR. In contrast to this, when the high-quality i t mode is selected by the signal L3 applied to the switch circuit 62, the signal S is output to a high-quality video
VD
signal processing circuit 65 through a high-quality output terminal HI.
The standard- and high-quality video signal processing circuits 64 and 65 each perform a respective predetermined playback processing of the input signal S,
VD
and output the processed signal as output video data D
VD
(Fig. 4).
The FM audio mode selection switch circuit 66 is switched in response to an FM mode selection signal L4 -24-
L
supplied as one of the selection signals S from the mode
SEL
detect/control section 16. When a monaural FM audio mode is selected, the FM audio signal S2V input to the switch
M
circuit 66 is output to a monaural FM audio signal processing circuit 67 through a monaural FM output terminal MN of the switch circuit 66. When a stereo FM audio mode is selected, the FM audio signals S2V and S2V input to the M S switch circuit 66 are output to a stereo FM audio signal processing circuit 68 through a stereo FM output terminal ST of the switch circuit 66.
The monaural and stereo FM audio signal processing circuits 67 and 68 perform respective predetermined playback processing of the input FM audio signal S2V and of the
M
signals S2V and S2V respectively. The obtained stereo M S and monaural audio output signals SS and SM are output OUT OUT oto input terminals 69C and 69D, respectively, of an audio selector circuit Other terminals 69A and 69B of’ the o° audio selector circuit 69 receive audio output signals S2
OUT
and SL respectively, obtained from the high- and
OUT
standard-quality PCM audio signal processing circuits 22 and 21, respectively. The selector circuit 69 is switched in 0 0 response to an audio selection signal L5 supplied as one of the selection signals S from the mode detect/control
SEL
ao t section 16. At any time, one of the audio output signals o a SlouT and S 2 0UT and the stereo and monaural audio output .o signals SS and SM supplied to the input terminals 69A, 69B, 69C and 69D OUT OUT 69B, 69C and 69D of the selector circuit 69 is selected, and a a is output from the output terminal of the audio selector circuit 69 as output audio data DAD.
As shown on Fig. 1, the mode detect/control section 16 receives the signal SVD picked up by the A and B heads 12A and 12B from the video track portion TRvD of each of the tracks TRA and TRB on the magnetic tape 1 and the PCM mode detection signal SMD obtained from the standard- and high-quality data detect circuits 37 and 38 (Fig. 2) of the mode/head selector and equalizer circuit 28. Based on these signals, SVD and SMD, the mode detect/control section 16 detects the modes of the various audio and video signals recorded on the magnetic tape 1. On the basis of such detection, the mode detect/control section 16 provides the selection signals SEL which, in combination with control
SEL
signals SCONT select and control the playback modes of the PCM audio signal processing section 13 and the video signal •processing section 14.
In the embodiment being described and as shown in Fig.. 9, the standard-quality PCM audio signal SNR is of a
ADNR
first clock frequency CKNR 11.6 MHz) and the alternatively used high-quality PCM audio signal SADHI is of
ADHI
a second clock frequency CKHI 14.8 MHz). Which ever PCM audio signal is used is recorded in the audio track portion TRAD of each record track on the magnetic tape 1. The AD O standard-quality video signal includes a standard-quality FM luminance signal SVN having a first center frequency of -26- -26- I MHz and a frequency range of 2 to 8 MHZ, and the alternatively used high-quality video signal includes a high-quality FM luminance signal SlVH having a second center frequency of 7 MHz and a frequency range of 2 to 12 MIHIz.
Further, in the embodiment being described, a multi-channel recording mode may be employed as a further function of the 8-mm format VTR. In such multi-channel mode, a plurality of channels of PCM audio signals are recorded using the full lengths of the recording tracks TRA and TRB consisting of the audio and video track portions TRAD and TRVD for the recording of such PCM audio signals.
When the standard-quality PCM audio signal SADNR is recorded as the PCM audio signal in the multi-channel recording mode, a first pilot signal P 1 of a first frequency, for example, of 230 kHz, which is higher thani the frequency of the ATF late*: t I signal SATF is superposed thereon. When the high-quality t i t r PCM audio signal SADHI is recorded in the multi-channel
ADHI
recording mode, a second pilot signal P 2 of a second Sfrequency, for example, of 280 kHz, higher than that of the first pilot signal P. is superposed thereon.
1 Further, the monaural FM audio signal S 2V M has a first center frequency, for example, of 1.5 MHz, and is superposed as an FM audio signal on the video signal recorded in the video track portion TRVD of each of the record tracks on the magnetic tape 1. Alternatively, the stereo FM audio signal S 2V uses the first center frequency t C -27-
I
signal, for example, of 1.5 MHz, as a main carrier, and a second center frequency signal, for example, of 1.7 MHz, as a subcarrier and is again superposed on the video signal recorded in each video track portion TRD.
The mode detect/control section 16, is adapted to detect the quality oi the PCM audio signal, the presence or absence of the use of PCM multi-channel recording, the mode of the FM audio signal, and the quality of the video signal.
More specifically, in the mode detect/control section 16 as shown in Fig. 5, the input video signal SVD is supplied to A-head and B-head input terminals A and B of a head selector circuit 41 through A-head and B-head playback amplifiers 40A and 40B. The head selector circuit 41 is switched in response to a head selection signal C7 supplied as one of the control signals SCONT from the system controller 100, and the signal SVD obtained thereby is input to a video mode detect circuit 42, a PCM multi-mode detect circuit 43, and an FM audio mode detect circuit 44.
The video mode detect circuit 42 includes a first band-pass filter 42A having a pass band centered at 5 MHz and a second band-pass filter 42B having a pass band centered at 7 MHz and through which the input signal SVD is Ssupplied to non-inverting and inverting input terminals, respectively, of a comparator 42C constituted by an operational amplifier. Thus, the video mode detect circuit 42 detects if the FM luminance portion of the signal SVD is
VD
S-28- 1 i c recorded on the magnetic tape 1 in the standard- or high-quality mode. When the FM luminance portion of the signal SVD is recorded in the standard-quality mode, that is, with the center frequency of 5.0 MHz, the level of the signal SVD passing through the first band-pass filter 42A is higher than that passing through the second band-pass filter 42B. In this case, the output from the comparator 42C exhibits a positive level. In contrast to this, when the FM luminance portion of the signal SVD is recorded in the high-quality mode, that is, with the outer frequency of MHz, the output from the comparator 42C exhibits a negative level. Thus, a video mode detection signal CVD O is obtained as the output from the comparator 42C and is supplied to a mode select/control circuit 46 which may comprise a microcomputer.
The PCM multi-mode detect circuit 43 includes a first band-pass filter 43A having a pass band centered at the frequency of 230 kHz and a second band-pass filter 43B K having a pass band centered at the frequency of 280 kHz, and through with the input video signal SVD is supplied to non-inverting and inverting input terminals of a comparator 43C. The PCM multi-mode detect circuit 43 determines from the full recording tracks TRA and TRB, that is, from the audio and video track portions TRAD and TRVD, whether or not
