JPH0191389A - Digital audio tape recorder - Google Patents

Abstract

PURPOSE:To obtain an audio signal and an SMPTE code which are synchronized with each other at the time of reading through a simple constitution by converting the time difference between an audio signal and an SMPTE code to digital data, adding the data to a time code, and writing the result. CONSTITUTION:An audio signal is A/D-converted 1 and inputted to a signal processing circuit 2. The circuit 2 stores one-frame-quantity of input signals in a RAM 4. Meanwhile, a time code signal enters a biphase decoder 5 and a clock extracting circuit 6. The decoder 5 converts an input signal to a binary signal. A timing data generation circuit 7 obtains the time difference between a time point when the fetching of an audio signal starts and the time point of the segmenting time code, and outputs thus obtained time difference information as the bit information. This time difference information and a time code outputted from the decoder 5 are added 8 with each other and supplied to a microprocessor 9. A rotary head 11 records an audio signal in the PCM area of a specific track, and records an SMPT code and time difference information in the subcode area of the same respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to the installation of a digital audio tape recorder (so-called DAT) l', and more specifically, the present invention relates to the installation of a digital audio tape recorder (so-called DAT) l', and more specifically, This invention relates to a digital audio recorder capable of reading out time codes.

(Prior art) Digital audio recorder (hereinafter simply referred to as D
An AT device (abbreviated as an AT device) is a device that converts an audio signal into a digital signal, records it on a magnetic tape at high density, and can reproduce it.

Compared to conventional analog recording methods, it has unprecedented characteristics such as no characteristic deterioration due to dubbing and an extremely wide dynamic range from low frequency range to high frequency range, so it will rapidly become popular in the near future. It seems that this is coming.

FIG. 4 is a diagram showing a DAT track format. A tape with a tape width of 3.81 ml is assumed to travel in the direction of the arrow, and the first track 1 is recorded on the diagonal angle of the tape by the rotating head (the angle of inclination is called the track angle and is set to approximately 6.3 degrees). - R1 and a second track TR recorded in the longitudinal direction of the tape by a fixed head;
It consists of 2. Of these, the second track TR2
are provided above and below the tape (ΔUX1 and ΔUX2 in the diagram)
ing. The rotary head used for recording the first track TR1 is composed of a pair of heads with mounting numbers marked on a 30 mm diameter drum at 180° divisions.

TRl-1 in the figure is + azimuth track, TR1-2 is -
It is an azimuth track. The traces of this pair of heads constitute one frame of the digitized audio signal, and signal processing is completed in this one frame. The drum is standardized to rotate at 200Q rpm, so the time required for one rotation is 30 m5ec.
becomes. That is, one frame contains data for 3 Q m5ec. The first track TRI includes an F"0M area where digitized audio signals are stored, an ATF area where auto-tracking signals are stored, and an area where subcode data is stored (SU[31,5UB2
). Of these, the audio signal and subcode signal can be recorded and reproduced independently. Note that there are upper and lower guard bands G1. between the first track TR1 and the second track TR2, respectively. G2 is provided.

When the DAT is used for recording and reproducing audio signals (general consumer use), it is sufficient to use only the first track TRI of the tape shown in FIG. Although DAT was originally developed for such consumer use, demands for commercial use naturally arose. For example, D
, when an AT and a VTR are used in combination. In commercial applications, VTRs and tape recorders have conventionally been operated in synchronization using time codes.

As this type of time code, SMPTE/EBU code, which has been standardized for compatibility, is common. Fifth
The figure shows the structure of S M P T and E code. As shown in the figure, one frame of the SMPTE code consists of 80 pits from pit O to bit 79, and the content of A is the time 0 minutes.

It consists of seconds, frame time information, and user bits. Then, these data are recorded in the bi-phase "a-key system." Figure 6 is a timing diagram for explaining the bi-phase recording system. (b) is the bi-phase modulation recording waveform, and (c) is the synchronous clock.In other words, in the bi-phase recording method, a clock transition occurs at the start point of each bit period, and when the bit value is This is a modulation method that causes a transition at medium heat and does not cause a transition at the center of the cycle for flashes with a bit value of '0'.

The time of one frame of this SMPTE code is the V used.
Since it corresponds to one frame of TR or movie film, it differs depending on the equipment. For example, 33.4 msec (29.97 frames/second) for NTSC color one-way system, 40 m5ec (25 frames/second) for PAL color one-way system, and approximately 41. 7tasec
(24 frames/second). This time code signal is biphase modulated and recorded as described above.

In VTRs and audio tape recorders, this time code is recorded on a time code track along the length of the tape using a fixed head. In this case, during high-speed search, the frequency and output will change in proportion to the speed.
Because of this, it is difficult to read 1B at 30x speed or higher, so the amount of movement of the tape is often read by separately bringing a roller for pulse generation into contact with the tape.

When operating the DAT in synchronization with a VTR, etc., the SM
It is necessary to record the PTE code on the DAT side as well. As a recording method, there are two methods: recording on the longitudinal track TR2 (see FIG. 4) and recording on the subcode area (SLJBl, 5UB2) of the first track TR1.

(Problem to be solved by the invention) In the case of the former recording method, the tape advance speed is 8°15
Since the recording wavelength is extremely slow at mm/sec, it is necessary to make the recording wavelength extremely short. This makes it difficult to record and reproduce time codes. Also, the second track (△UX1~Rack)
Since TR2 is on the tape edge and the track width is narrow, signal dropout (disappearance) due to tape damage.
may occur.

In the case of the latter method, absolute time, running time, program time, etc. can be recorded in the subcode area of the first track TR1 recorded and reproduced by the rotary head on the DAT. In this case, only time information is considered. Also, the DAT frame is SM
P:TE Coco:.

Unlike 3Q, it is 111300, so the SMPTE code cannot be recorded as is. Therefore, it may be possible to adjust the frame by connecting a frame exchanger to the input and output of the DAT subcode, as shown in FIG. In the figure, the SMPTE time code input (NT
30 frames/sec with C8C.

25 frames/sec for PΔL, 24 frames/sec for movies)
enters the first frame exchanger 21 and transfers 33 for DAT.
．． 3 frames per second, DAT22 has 33.3
Recorded in frames/second.

The 33.3 frames/second time code read from the DAT 22 enters the second frame exchanger 23, where it is reconverted to the original m<for example, 30 frames/second on NT8G) and then converted into an SMPTE code. Output.

However, such a system in which a separate frame exchange circuit is provided requires a dedicated circuit, making the device bulky, and furthermore, the user's bits of the SMPTE code must be taken out separately and recorded in another back of the subcode. No. Also, due to the signal processing, the audio signal is 30 m5EC during recording and 3 QS during playback.
Since there is a delay of eO ml 60 m5ec, there is a discrepancy between the time code and real time. In order to correct this problem, it was necessary to perform time adjustment processing on the time code, which had the disadvantage of increasing the hardware size.

The present invention has been made in view of these points, and
The target number is tS continuously during normal playback.
The object of the present invention is to realize a DAT device having a simple configuration that can read SMPTrE codes intermittently in continuous search mode and accurately read SMPTrE codes in both normal reproduction mode and high-speed surge mode.

(Means for Solving the Problems) The present invention, which solves the above-mentioned problems, is a digital audio tape using a rotary head.
In a digital audio tape recorder device that records and plays back MPTE time code, data for one frame or more of the time code, a start point for taking in an audio signal when performing digital signal processing, and a time code break point are provided. The time difference information between
This is characterized in that it is configured to be recorded as bit information in a part of the subcode area.

(Function) The subcode area (5 in Figure 4) in the track recorded and reproduced by the rotating head (first track TR1)
UB1.5LIB2) with SMPTE code &! Along with recording and playing, the normal playback is just like J! ! The time code is handled like a continuous signal, and during high-speed search playback, at least one frame of time code can be played back, and time information is read out.

(Embodiments) Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. The audio signal enters signal processing @282 where it is converted into a digital signal by the A/DI converter W1. tA
@The processing circuit 2 first stores one frame of input signal in the RAM 4. In the next step, the data is read from the RAM 4 and applied to the error flexigine @m3, and the error flexigine circuit 3 adds an error correction code to the input signal and stores it in the RAM 4 again. On the other hand, the time code input signal enters the pie-face decoder 5 and the 0x extraction port 6. The pie-phase decoder 5 converts the pie-phase code into 2i1 of o and i while synchronizing with the output clock provided from the output extraction circuit 6.
Convert to 1 signal (CII tone).

The timing data generation port 1217 receives the clock supplied from the clock extraction circuit 6 and the signal 9 from the audio side.
I! In response to the timing signal given from the 0-path 2, the timing difference between the start point of capturing audio data and the time code break point when performing digital signal processing is measured. Then, the lFl difference information is output as bit information. At this time, the tS difference information and the time code output from the pie-phase decoder 5 are added by the adder 8, and after the 80-pit time code, Time II
It is output in a format with difference information added and given to a microprocessor unit (hereinafter simply abbreviated as MPU) 9. The MPU 9 temporarily stores the input data in the RAM 10.

The 4R month processing circuit 2 applies an error correction 3 to the time code 10:00 B difference information stored in the RAM 10 for error correction.
After adding the hood, it is stored in RAM4. Then, the signal processing 11 circuit 2 sends these audio signal ten o'clock @ difference information to the rotary head 11 at a predetermined timing, and the rotary head 11 specifies the audio signal in the PCM area of the first track TRI by the MPU 9. SMPTE code + confrontation in the subcode area! J difference information is recorded respectively.

The rs2 diagram is a time chart showing the timing of DAT audio data and subcode data. (a) shows the PCM data input (audio signal input) that has been converted into a digital format for digital processing, (b) shows the nap code data input, and (c) shows the tape recording number a. PCM data os e Dz t Da e”
” is in units of 30 asec per frame, and is also taken into RAM4 at the timing of 30 asec (this is called an AT frame). Since it takes 30m5et-1 to write PCM data, the actual When recording on tape, as shown in (c), the signal is processed in such a way that the S1 code is delayed by one frame in the +azimuth, the B and t codes are delayed by one frame in the -7 azimuth, and the A4 is added. After that, &! is recorded. This recording signal is sent to the rotary head 11.
recorded on tape.

The A-day A signal (P
CM Shingetsu) and SMPTE time code Shino (subcode data) are read out from the second head section of the rotary head 11 and entered into the signal processing circuit 12. 1l (A target lI! The circuit 12 extracts only the audio signal from the read signal and sends it to the error correction circuit rB13. The error correction circuit 13 receives the input audio data and checks the error code. , check whether the read signal is correct.If correct, if it is incorrect excluding the error code, correct it if it can be corrected, and if not, check if it is incorrect considering the context. Change to the most appropriate data and store it in RAM14, RAM1
The audio data inputted into 4 is read out in the form shown in FIG.
5, where it is converted into an audio signal and output.

On the other hand, the signal processing circuit 12 also corrects errors in the data in the subcode area and sends it to the MPL 116. The sent data is temporarily stored in the RAM 17 via the MPtJ16. The subcode data stored in RAM17 is MPU1
6 is read out sequentially. Only the SMPTE code is extracted and enters the timing decoder 18 and time code generator 19. On the other hand, the time code generator 19 has 3Q l1lSeC from the signal processing circuit 12.
The timing of is also input.

The timing decoder 18 converts the timing of the compressed data given from the MPtJ 16 to the original timing,
Time code clock - given on evening 19. The time code generator 19 returns the compressed time code to the original length time code, and converts the compressed time code to 30 m5ec.
In response to the timing, the time difference data added to the time code is subtracted and output as a complete SMPTE code.

Next, the interpolation and reading of time difference information between one frame of DAT and one frame of SMPTE code will be explained in detail. FIG. 3 is a diagram showing details of timing during recording and reproduction. As shown in (a), the PCM data is 1
Frame 3 Q is in units of m5ec. In conjunction with this, the time code is recorded as bit information for a minimum of 30IllSOC. At this time, from the time code input shown in (b), (
c) Extract the time code clock as shown in (c). As described above, a time difference Δ occurs between the time code data acquisition timing shown in (a) and the time code clock shown in (c). This time difference Δ is counted by the DAT clock, and the count (direction is represented by 8 pits).Then, the sum of the clock time width B (80 bits of time code) and this time difference is Δ10B. 8
It is stored in the subcode area as 88-bit data of 0+8 as shown in (d).

In the case of normal playback, one frame of DAT (30
m5ec) or higher (73 bits for NTSC color, 60 bits for PAL).

Since 58 bits (58 bits) are recorded on movie film, this is sufficient to restore the time code, and a continuous time code can be obtained. On the other hand, in the case of a 100 times faster search, for example, only one of the 100 time code data can be read out. however,
The read time code itself can reliably read out 80 bits for one frame of the time code.

Please note that the time code data is 84 bits (of which 4 bits are
By setting the bits to be the overlap portion), it is possible to eliminate defects at the joints of time data. Furthermore, if the time code data is increased to 160 bits, which is 62 times 80 bits, a reliable 80-bit time code can always be reproduced. In the above embodiment, the time code break point was set at the data bit (audio data) border, but
It may be placed at the top or approximately in the middle of the frame.

(Effects of the Invention) As described above in detail, according to the present invention, in order to synchronize the audio signal and the SMPTE code, the time difference between the two is added to the time code as digital data and written. With a simple configuration, when reading out, the audio signal and SMP are always the same in frame units.
TIH code can be obtained. A continuous time code can be obtained in the normal reproduction mode, and a time code of at least one frame of 80 bits can be obtained in 114 in the high speed surge mode.

[Brief explanation of the drawing]

Figure 1 shows an embodiment of the present invention. Figure 2 shows the timing of DAT audio data and subcode data. Figure 3 shows the timing during recording and playback. Figure 4 shows the details of DA
Figure 5 shows SMP
FIG. 6 is a diagram showing the structure of a TE code, FIG. 6 is an explanatory diagram of the pi-phase modulation method, and FIG. 7 is an explanatory diagram of frame conversion. 1... A/D converter 2, 12... Signal processing circuit 3, 13... Error correction circuit 4.10.14
．． 17...RAM 5...Biphase decoder 6...Clock output circuit 7...Timing data generation circuit 8...R adder 9.16-=MPV11...
・Rotating head 15...D/△converter 18...Timing decoder 19...Time code generator TR1...First track TR2...Second track 21.22...Frame Converter 23...DAT Patent applicant Fostex Co., Ltd. Agent Patent attorney Knee Ijima 1 non-judicial person

Claims (6)

[Claims] (1) In a digital audio tape recorder device that records and plays back SMPTE time code in the subcode area of a digital audio tape using a rotating head, data of one or more frames of the time code and digital signal processing are performed. A digital audio tape recorder device characterized in that it is configured to record time difference information between a start point for capturing an audio signal and a time code break point as bit information in a part of a subcode area. . (2) The digital audio tape recorder apparatus according to claim 1, wherein the time code data is 80 bits, and a time code break point is a data bit border. (3) The digital audio tape recorder apparatus according to claim 1, wherein the time code data is 84 bits, and a time code break point is a data bit border. (4) The time code data is 160 bits,
2. The digital audio tape recorder device according to claim 1, wherein a time code break point is a data bit break point. (5) The digital audio tape recorder device according to claim 1, wherein the time code data is 80 bits, and the time code break point is set at the beginning or approximately the middle of a frame. . (6) The time code data is recorded on a + or - azimuth track, and the time code data for 30 msec is recorded on an azimuth track opposite to the above. digital audio tape recorder device.