JPH03278369A - Post-recording method for digital audio tape recorder - Google Patents

Abstract

PURPOSE:To obtain the post-recording method for the DAT capable of rewriting a subcode data recorded under a long time mode in a short time and also reproducing a sound data by thinning out and reproducing only PCM sound data stored at a prescribed address. CONSTITUTION:Post-recording is performed under a prescribed standard mode in drum revolving speed and magnetic tape speed, etc., to shorten the post- recording time to approximately 1/2, and at this time, a RAM 20 is adroitly utilized as a buffer memory, and without reading all of the PCM sound data stored in this RAM 20, but only necessary data is thinned out and read out, so that the subcode data is rewritten in a short time, and also the PCM sound data can be reproduced. By this method, the post-recording method for the DAT capable of rewriting the subcode data recorded under the long time mode in a short time during the time when the sound data is reproduced can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an after-recording method for a digital audio tape recorder, and particularly to an after-recording method for rewriting subcode data while reproducing audio data.

[Conventional technology] Due to the rapid progress of digital technology, digital technology has come to be actively used in audio equipment, which until now was an application field of analog technology.In particular, digital technology that can not only playback but also record Audio tape recorders (hereinafter referred to as DATs) are attracting attention.

This DAT not only eliminates problems inherent to analog technology such as wow and flutter, hiss, and modulation noise, but also
It has the advantage of having a wide dynamic range of dB or more and exhibiting flat characteristics over a wide frequency band. Also, unlike conventional analog cassette tape recorders, a large space is reserved for recording sub-codes that carry various information in addition to the area where music is recorded, making it easy to perform high-speed searches and editing. There are features that can be used.

There are two known DAT formats that have these advantages: R-DAT, which uses a rotating head, and 5-DAT, which uses a fixed head. , research and development is being actively carried out in preparation for commercialization.

As shown in FIG. 7(A), this R-DAT records data on a track 12 that is tilted by 6 inches with respect to the traveling direction of the magnetic tape 10. PCM that records audio data (PCM)
In addition to this area, it is made up of a SUB area for recording subcodes including information such as the beginning of the recorded song and song number, and an ATF area for recording an ATF signal for tracking. Of these multiple areas that make up the track 12, the subcode area SUB consists of 8 blocks each consisting of 32 symbols (8 bits as one symbol), 256-bit subcode data, 8-bit ID code data, etc. The PCM area consists of 128 blocks each including 32 symbols of PCM audio data, 8-bit ID code data, etc.

Since the SUB area where subcode data is recorded and the PCM area where PCM audio data is recorded are divided and formed on the track 12, only the subcode data can be rewritten while playing back the PCM audio data.
So-called after-recording is possible.

That is, as shown in FIG. 7(B), this track 1
2, and when it reaches the SUB area where the subcode data is recorded, the magnetic head mode is switched to recording mode and the desired subcode data is rewritten, and the magnetic head writes the PCM audio data. By switching the mote of the magnetic head from the recording mode to the reproduction mode when the recorded PCM area is reached, it is possible to rewrite only the subcode data while reproducing the audio data.

In the standardized format of the R-DAT mentioned above, the same subcode data must be recorded for 300 frames (300 rotations of the drum) for convenience such as high-speed search. Therefore, 1
The after-recording of this subcode data was performed in the standard recording/playback mode with a drum rotation speed of 200 rpm, a magnetic tape speed of 8.15 mm/s, and a sampling frequency of 48 kHz, which are equipped with two magnetic heads arranged 80 degrees opposite each other. It will take about 9 seconds to do this.

[Problem to be Solved by the Invention] As described above, it takes about 9 seconds to perform after-recording of subcode data in the standard recording and playback mode, but in R-DAT, in addition to this standard recording and playback mode, There is also a long-term recording and playback mode that allows you to record for long periods of time.

This long-time recording/playback mode has a tram rotation speed of 1100O.
rp, a magnetic tape speed of 4.075 mm/S, and a sampling frequency of 32 kHz.The number of data to be processed is half that of the standard recording/playback mode, and the recording time is twice as long with the same magnetic tape length. It is now possible to do so.

However, when recording subcode data and audio data in this long-time mode and then performing after-recording in which only the subcode data is rewritten, the drum rotation speed and magnetic tape speed are 1/2 compared to the standard mode.
Therefore, there is a problem in that the time required to rewrite subcode data for 300 frames is twice as long as in the standard mode, that is, about 18 seconds.

Of course, if you perform after-recording with the subcode data and audio data recorded in long-time mode set to a drum rotation speed of 2000 rpm and a magnetic tape speed of 8.15mm/s, the rewriting time of the subcode data will be the same as in standard mode. It may take about 9 seconds to do so, but in this case, there will be an inconvenience that the audio data cannot be played back.

That is, in R-DAT, data is sent intermittently to two magnetic heads, or continuous data is reproduced from intermittent data sent from these two magnetic heads, and the effects of burst errors are In order to suppress this to a minimum, two RAMs each having a capacity of 64 mm are used as buffer memories for temporarily storing data.

When recording, PCM audio data is stored in 64kRAM.
is interleaved and stored at the same time as the other 64kR.
Data is read from the AM and supplied to the magnetic head.

On the other hand, during playback, audio data from the magnetic head is similarly stored in 64kRAM, and at the same time data is read out from another 64kRAM and played back.

Therefore, if PCM audio data recorded in long-time mode is read out at the drum rotation speed and magnetic tape speed in standard mode, twice as much data will be stored from the magnetic head into this RAM within the same amount of time. While data is being read from the 64kRAM, the next data from the magnetic head is written to this RAM, making it impossible to read PCM audio data correctly.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a DA that can rewrite subcode data recorded in long-time mode in a short time and also reproduce audio data.
The purpose of this invention is to provide an after-recording method for T.

[Means for Solving the Problems] In order to achieve the above object, the DAT after-recording method of the present invention includes a process of rewriting subcode data recorded in a long-time recording mode using a standard mode, and a process of rewriting subcode data recorded in a long-time recording mode. A process of reading out PCM audio data recorded in the standard mode, storing the read PCM audio data in a RAM as a buffer memory, and storing the stored PCM audio data in a predetermined atte I/s. It has a process of thinning out and reproducing only audio data by reading it out, and is characterized by rewriting subcode data in approximately the same short time as in the standard mode while reproducing PCM audio data.

[Function] As described above, the DAT after-recording method of the present invention uses a drum rotation speed of 1100 Orp.

After-recording of subcode data recorded in a long-time mode with a magnetic tape speed of 4.075 mm/s and a sampling frequency of 32 kHz was performed at a drum rotation speed of 2000.
After-recording is performed at standard mode speeds of rpm and magnetic tape speed of 8° and 15 mm/s.

At this time, the PCM audio data read by the magnetic head is twice as large as after recording in the normal long-time mode, but this read PCM audio data is stored in RAM as a buffer memory, and then stored. By reading and playing only the PCM audio data stored at a predetermined address instead of reading all of the PCM audio data, the RAM capacity can be reduced even if twice as much PCM audio data is read from two magnetic heads. It becomes possible to reproduce PCM audio data without exceeding the PCM audio data.

In addition, by thinning out the PCM audio data and playing it back, will the playback be different from the normal playback sound?
By setting the thinning amount to about 1/2 and performing double-speed playback, it is possible to obtain reproduced sounds that allow the songs to be identified even when the song number etc. are rewritten in after-recording.

[Embodiments] Hereinafter, preferred embodiments of the DAT after-recording method of the present invention will be described with reference to the drawings.

FIG. 5 is a schematic block diagram of the R-DAT in this embodiment. The L and R two-channel audio signals pass through a low-pass filter and sample-and-hold circuit, and are then sent to the AD
It is converted into a PCM signal by a converter. As mentioned above, in the standard mode, the sampling frequency when converting into a PCM signal by this AD converter is 48 kHz, and the number of quantization bits is 16 bits.

On the other hand, in the long-time mode, the sampling frequency is 32 kHz and the number of quantization bits is 16 bits, but this 16-bit PCM signal is converted into a 12-bit PCM signal by the logarithmic conversion circuit built in the input data conversion circuit 10. converted. Furthermore, the converted LCH and RCH
The 12-bit PCM signal consists of the upper 8 bits and lower 4 bits, respectively.
8-bit symbols L and R1 and
8-bit symbol LR combining the lower 4 bits of each
It is converted into a total of three symbols.

The PCM signal is not recorded as is on the magnetic tape, but instead is stored in an external RAM as a buffer memory.
(64kX2)20.

At this time, in order to minimize burst errors, I:
An interleave method is used to store PCM audio data in a distributed manner.

The interleaving method in this long-time mode will be explained below with reference to FIG. As described above, the RAM 20 is composed of two 64k RAMs, and each 64kRAM is divided into two areas A and B corresponding to two magnetic heads A and B. The input data conversion circuit 10 converts the symbol L into three symbols L, R, and LR every sampling period, but the symbol L is converted into three symbols L, R, and LR by the interleave address control circuit 30 at block address 0 and symbol address 0 in area A of the 64KRAM 20. The symbol R is stored at the address of block address 0 and symbol address 2 (■), and the symbol LR is stored at the address of block address 0 and symbol address 2 (■).
is stored at block address 2 and symbol address 0 (■).

In this way, LCH and RCH are represented by a total of three symbols.
After the PCM signal is stored in area A, the storage address of that PCM signal will be in area B in the next sampling period.
The symbol L (■) is stored in the block address 76 symbol address 0, the symbol R (■) is stored in the block address 76 symbol address 2, and the symbol LR (■) is stored in the block address 68 symbol address O.

Furthermore, in the next sampling period, return to area A again, block address 2 symbols, symbol L (■) at block address 2, symbol R (■) at block address 4 symbol, symbol R (■) at address O, block address 4 symbol, symbol at address 2. LR (■) is stored.

In this way, the left half area La and area B
When the even block addresses in the rows of symbol addresses 0 and 2 in the right half of Rb become full, symbols are then stored in the even block addresses in the rows of symbol addresses 1 and 3.

Further, when the even block address column becomes full, symbols are stored in the odd block address column in the same order as described above. When the area La and the area Rb are filled with symbols, symbols are then alternately stored in the left half area Lb of the area B and the right half area Ra of the area A in the same order.

In this way, based on the symbols stored in areas A and B of the RAM 20, the error correction circuit ECC1 is configured for each area.
4, an error correction code is created and stored in the parity areas Q and P of each area. The symbols stored in area A are then read out in the order of the block addresses, modulated into 10 bits by the 8-10 modulation circuit 16, supplied to the rotating magnetic head A via the rotary transformer, and stored on the magnetic tape. be done. Similarly, the symbols stored in area B are read out in the order of block addresses, and 8
The signal is converted into 10 bits by the -10 modulation circuit 16, supplied to the magnetic disk B via the rotary transformer, and recorded on the magnetic tape.

In addition, data indicating the beginning of the song to be recorded (start I)
D), data indicating the song number (PNO), etc. are generated from the CPU 24, and after predetermined subcode processing is performed, they are sent to the data bus and supplied to the magnetic head. ) is recorded on the magnetic tape 10 at the track format shown in FIG.

At the time of reproduction, tracking servo is applied based on ATF signals for tracking control placed and recorded at both ends of the PCM audio data, and the PCM audio data is reproduced. That is, the PCM audio data read by magnetic heads A and B is passed through a waveform equalization circuit and a data strobe circuit to 8-
The signal is input to the 10 demodulation circuit 26 and demodulated to the original 8 bits. The demodulated 8-bit symbols are then stored in areas A and B of the RAM 20 in the order of the block addresses.
Thereafter, errors are detected and corrected by the error correction circuit ECC14. At this time, as mentioned above, the interleave format for recording PCM audio data in a distributed manner is 2.
track, that is, the PCM audio data read by the two magnetic heads A and B, so these two
After all the PCM audio data for the track is stored in the RAM 20, the stored data is read out from the RAM 20 by the interleave address control circuit 30, and the D
It is reproduced into two channels of audio signals through an A converter, a sample hold circuit, and a low pass filter.

Now, the drum rotation speed is 10,100 Orp, and the magnetic tape speed is 4.
．． Consider a case where subcode data and PCM audio data recorded in a long-time mode at a speed of 0.075 mm/s and a sampling frequency of 32 kHz are to be after-recorded.

Drum rotation speed 11000 rp, magnetic tape speed 4.07
When performing after-recording in the 5 mm/s long-time mode, in the area where subcode data has been recorded, magnetic heads A and B are switched to recording mode by a control signal from the mode decoder 32, and then the PCM
In the PCM area where audio data has been recorded, magnetic heads A and B are switched to playback mode to perform after-recording. At this time, the subcode data is 300
The same data must be rewritten over one frame, that is, over 600 tracks, and the time required for this rewriting is about 18 seconds.

Therefore, in this embodiment, in order to reduce this after-recording time to about 1/2, the drum rotation speed is 200.
Orpm, and after-recording is performed in the standard mode with a magnetic tape speed of 8.15 mm/s. At this time, as already mentioned, the PCM audio data read from magnetic heads A and B is twice as much as in normal long-time mode after recording, and if this continues, the RA
PCM audio data stored in M2O cannot be read and played back.

Therefore, in this embodiment, magnetic head A is used.

By thinning the PCM audio data read from B to 1/2, it is possible to rewrite the subcode data in a required time of about 9 seconds, and the PCM audio data can also be reproduced.

The PCM audio data thinning method of this embodiment will be explained in detail below with reference to FIGS. 1 to 4.

FIG. 1(A) schematically shows the reproduction of PCM audio data by two magnetic heads A and H in a normal after-recording method and the reproduction of PCM audio data by magnetic heads A and B in after-recording of this embodiment. This is a timing chart.

In this embodiment, both the tram rotational speed and the magnetic tape speed are set to double compared to normal after-recording, so in normal after-recording, one rotation of the drum, that is, two magnetic heads A and B, During the time when the PCM audio data is read, a total of four tracks worth of PCSI audio data are read by the two magnetic heads A and B.

The PCM audio data read by magnetic head A is stored in area A of 64kRAM, while the PCM audio data read by magnetic head B is stored in area A of 64kRAM.
The PCM audio data for two tracks, that is, for one frame, is stored in area B of M. Next is magnetic head A.

One frame worth of PCM audio data read by B is stored in the other 64 kRAM of the RAM 20. At this time, the PCM audio data stored in one 64kRAM is read out, but instead of reading out all the stored PCM audio data, the PCM audio data stored in the predetermined address is
Read only the CM audio data, the PCM audio data stored at the address of the left half area La of Sunawachi area A, and the PCM audio data stored at the address of the right half area Rb of area B, and thin out the data amount to 1/2. (See Figure 1 (B)).

When recording PCM audio data, it is recorded using the interleaved format as described above, but in this interleaved format, PCM audio data is stored sequentially from the addresses of the left half area La of area A and the right half area Rb of area B of 64kRAM. There is no need to make any changes to the deinterleave circuit that solves the interleave format when reading it, and it becomes possible to reproduce PCM audio data.

FIG. 2 shows a circuit diagram of an interleave address control circuit 30 that controls the address of the RAM 20 for thinning out PCM audio data, and FIG. 3 shows a timing chart of the same circuit.

The interleave address control circuit 30 of this embodiment includes a decoder section 30a which is internally equipped with a total of 14 counters O to U3 that sequentially count based on a clock signal, and an output from this decoder section 30a as a mode signal from a mode decoder 32. It is composed of a logic gate section 30b controlled by.

For convenience of explanation, S is applied to a total of 14 output control lines output from the decoder section 30a in sequence. -813,
In addition, a total of 14 output control lines outputted from the address circuit 30 are sequentially supplied with A. -A13 is attached.

Of a total of 14 counters from 0 to 13 in the decoder section 0a, a total of 11 counters from 0 to 10 have the function of an 11-bit binary counter, and are connected to the output terminal of each of these counters. Output control line AO = 0 due to AlO
-2047 addresses are specified. And this 0~
A total of 2048 addresses up to 2047 are the 64k mentioned above.
Either the left or right area La of RAM area A1 area B
.

A total of 2048 addresses of Lb, Ra, and Rb are specified, and the specified format is shown in FIG. Further, the output from the output control lines 81□ to S13 of the decoder section 30a has the waveform shown in FIG. 3, and in normal after-recording, the output side i
#MA11 to A13, all addresses in the RAM 20 are designated, and all stored PCM audio data is read out.

However, in this embodiment, the AND gate and EX-
The logic gate section 30b composed of an OR gate etc. controls the output of the output control lines 81□ to S13 of the decoder 30a, and the address and address of the left half area La of the area A among the PCM audio data stored in the RAM 20 are controlled. Only the address of the right half region Rb of area B is designated and data is read out. That is, when the output from the mode decoder 32 is an H level indicating a long-time mode with a sampling frequency of 32 kHz and an H level indicating an after-recording mode, an L signal is output via a NAND gate.
A level signal is input to this logic gate section 3ob.

Then, the output from the output control line A1□ becomes the output control line S
When the output from 11 is L level, it becomes L level,
Further, when the output of the output control IjS1□ is at H level, it becomes H level, and the output control line A1□ and output control line A1
□ indicates the same output waveform (see Figure 3).

On the other hand, the output control line A does not depend on the output level from the output control line S13 (as long as the L level is output from the mode decoder 32, the output from the AND gate is independent of the output level from the output control line S13). output is at L level), and shows the same output waveform as the output control line S1°. The output control lines A1□ to A13 are respectively A11: area A corresponding to magnetic heads A and B;
H left/right switching A12: Area A; H switching A: Specifies switching between 64k RAM of RAM 20, that is, switching between even and odd frames. Then, as shown in the timing chart of FIG. 3, when the output control line A13 is L, the RAM20
64kRAM of even frame is selected, and during this period A
-L, A12-L specifies the address of the left half area La to area I, and A11''
H-A t 2 ” Right half area R of area B by H
The address b is specified and the PCM audio data is read out.

After all seven addresses of La5Rb are specified, the output control line A13 changes to H level, and the RAM20
The odd frame 64kRAM of is selected, A1□ and A1
2 output waveforms are the same, so 64kR for even frames.
Similarly to AM, addresses in the left half of area A and addresses in the right half of area B are alternately designated (see FIG. 4). Therefore, the address of the right half area Ra of area A and the address of the left half area Lb of area B are not specified, and the PCM audio data stored at these addresses will not be read out.

Then, the PCM audio data thinned out to 1/2 in this way is played back by a DA converter, etc., but the normal 1/2
Since the playback is performed in the time of 2, the playback is performed at double speed.

In this way, in this embodiment, the RAM as a buffer memory is skillfully used, and instead of reading out all the PCM audio data stored in this RAM, only the data necessary for playback is thinned out and read out. This makes it possible to rewrite subcode data in a short time and to reproduce PCM audio data.

[Effects of the Invention] As explained above, according to the DAT after-recording method according to the present invention, it is possible to rewrite subcode data recorded in long-time mode in a short time while playing back audio data. Become.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing PCM audio data processing in the DAT after-recording method according to the present invention, Fig. 2 is a circuit diagram of an interleave address control circuit in the same embodiment, and Fig. 3 is an interleave address control in the same embodiment. 4 is an explanatory diagram showing RAM access in the same embodiment; FIG. 5 is an overall configuration block diagram in the same embodiment; FIG. 6 is an explanatory diagram of the interleaving mat in the same embodiment; FIG. 7 is an explanatory diagram showing the points etc. in R-DAT. 10 ... Magnetic tape 12 ... Track 20 ... RAM 24 ... CPU 30 ... Interleaver 32 ... Mode decoder track former address control circuit Bufo

Claims (1)

[Claims] A standard recording and reproducing mode with a drum rotation speed R and a magnetic tape speed V and a long-time recording and reproducing mode with a drum rotation speed R/2 and a magnetic tape speed V/2 are provided. In the after-recording method of a digital audio tape recorder, which rewrites the digital subcode data while reproducing the PCM audio data of the digital subcode data and PCM audio data, the digital subcode data recorded in long-time recording mode is recorded as standard. A process of rewriting the PCM audio data recorded in the long-time recording mode in the standard playback mode, and storing the read PCM audio data in a buffer memory, and rewriting the PCM audio data at a predetermined address within the stored PCM audio data. PCM of
An after-recording method for a digital audio tape recorder, comprising the steps of thinning out and playing back audio data by reading only the audio data, and rewriting digital subcode data in a short time.