JPH054748B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording method for a multi-channel PCM recording/playback device, and more particularly to an improvement in the recording method for overdubbing recording in a fixed head type multi-channel PCM recording/playback device.

FIG. 1 is a diagram showing the recording format of a conventional multi-channel PCM recording/playback device. first,
In FIG. 1, a magnetic tape 1 includes information tracks 11 to 18 on which the information of one audio channel is recorded as a digital signal, and redundant signals for error correction of the audio information data of each information track 11 to 18, for example. Redundant tracks 1a, 1b are provided on which parity check codes are recorded.

FIG. 2 shows redundant tracks 31 and 32 shown in FIG.
It is a figure which shows the method of adding. In FIG. 2, the information signals a1 to a8 are connected to the information track 11.
to 18, and the error correction redundant signal c
1 and c2 are recorded on redundant tracks 1a and 1b, respectively. These information signals a1 to a8 and correction redundant signals c1 and c2 have a bit length of b. In order to create the redundant tracks 1a and 1b, the information tracks 11 and 1 described above are
Information signals a1 to a8 of b bits each are extracted from positions adjacent to each other in the width direction of the tape from 8 to 8, error correction signals c1 and c2 are obtained from the information signals of a total of 8 b bits, and these are sent to redundant tracks 1a,
Record each in 1b.

FIG. 3 is a diagram showing a state in which a large number of data shown in FIG. 2 are arranged in the running direction of the tape, and redundant signals are also added in the tape running direction. In FIG. 3, redundant signal d1 and d10 are information track 1.
1 to 18, 7b for each of 1a and 1b
Bits are added to children and recorded. These redundant signals d1 to d10 are normally generated by a CRC code algorithm, and a synchronization mark S is added for each track to the CRC code (information signal+redundant signal) thus generated. Below, from the synchronization mark S to the redundant signal di (i=1 or
10) will be called a frame. A collection of ten tracks of these frames constitutes one code block 10.

It is known that according to the above recording format, errors in up to two tracks can be corrected in one code block. Therefore, even if the recording state of any one track is poor and code errors occur frequently, they can be sufficiently corrected. In addition, even if one track completely fails and becomes inoperable, it can be corrected even if a dropout occurs in other tracks, so the operation of the recording device is not impaired and stability is greatly increased. can.

FIG. 4 is a schematic block diagram of a conventional multi-channel PCM recording/playback device. Next, the configuration and operation of a conventional multi-channel PCM recording/playback device will be explained with reference to FIG. The multitrack playback head 21 plays back the digital signal recorded on the magnetic tape 1, and the playback signal is given to the time axis correction circuit 22.
Jitters during tape running are absorbed. Thereafter, the reproduced signal is applied to a decoding processing circuit 23 for error correction, and then is converted into an analog signal by a D/A converter 25 via a signal switching circuit 24. This analog signal is outputted from the output terminal 26 as an audio reproduction signal.

The PCM recording and reproducing apparatus shown in FIG. 4 has an overdubbing function (described in detail later). For this purpose, in the channel on which overdubbing is performed, a signal applied from the audio input terminal 27 is converted into a digital signal by the A/D converter 28, and is applied to the encoding circuit 29 via the signal switching circuit 24. . This encoding circuit 29 constitutes the encoding block 10 described in FIG. 3 above. The encoded signal is applied to a delay circuit 30, and adjusted so that the tape running time from the multitrack reproducing head 21 to the multitrack recording head 32, which will be described later, matches the delay time of a series of signal processing. The output signal of the delay circuit 30 is sent to the multitrack recording head 3 via a switch group 31.
2 and recorded on the magnetic tape 1 by overdubbing. Note that the channels to be recorded are controlled by the overdubbing control section 33.

The time axis correction circuit 22 performs an operation of replacing a reproduced signal containing jitter with a jitter-free clock of crystal accuracy. For this purpose, the traveling servo section 3
4 controls the capstan motor 35 so that the reproduction synchronization mark S is phase synchronized with the crystal precision clock.

FIG. 5 is a diagram showing tracks that are rewritten during overdubbing. In FIG. 5, it is assumed that the magnetic tape moves from right to left in the drawing. Therefore, the position of the recording head will move from left to right relative to the magnetic tape. In addition, Fig. 6, Fig. 7, Fig. 11, Fig. 12, which will be described later.
The same applies to FIG. Next, with reference to FIG. 5, overdubbing processing as an essential function of a multi-channel PCM recording/playback device will be explained. Overdubbing is a method of recording sound on another channel in synchronization with the playback sound of a previously recorded channel. In FIG. 5, the shaded area 1c of the information track 12 is the overdubbed area, that is, the rerecorded area, and the vertical line indicates the position of the synchronization mark S, and one square corresponds to one frame. . In this way, for the section where the information on the second channel of the information track 12 is newly rewritten, the corresponding redundant track 10a,
Redundant signals 1d and 1e of 10b are also rewritten.

The configuration and information recording format of the multi-channel PCM recording/playback device have been explained so far, but the conventional multi-channel PCM recording/playback device has drawbacks that cause inconvenience under special conditions as shown below.

Figures 6 and 7 are conventional multi-channel
FIG. 6 is a diagram showing an example of inconvenience caused when overdubbing recording is performed using a PCM recording/playback device; in particular, FIG. 6 shows a case where recorded magnetic tape is used, and FIG. The case using tape is shown.

In FIG. 6, 1e indicates a newly recorded section, and 1c indicates an additionally overdubbed section. In a recording state in which signals are newly recorded in all channels on the frame 1d in which signals were previously recorded on the magnetic tape 1, overdubbing is performed from outside the newly recorded section 1e,
Assume that overdubbing is performed extending beyond the newly recorded section 1e. Then, the old record part 1d
Due to the discontinuity between the frame of the new recorded portion 1e and the frame of the new recorded portion 1e, when the block code is reproduced later, it becomes impossible to reconstruct the block code, and an abnormal sound is generated.

On the other hand, as shown in FIG. 7, in a recording state in which new signals are recorded on all channels using an erased magnetic tape in which the signals recorded on all tracks have been erased, recording is performed from outside the recorded section 1e. In this case, the running speed becomes unstable because the synchronization mark that serves as a reference for playback running is not recorded. For this reason, A near the beginning of the range recorded on all channels
It is not possible to record the signal in the correct position at the point,
If the data is played back later, abnormal sounds will be generated because the block code cannot be reconstructed.

Therefore, the main object of the present invention is to provide a multi-channel PCM recording and playback device that can eliminate the above-mentioned disadvantages.

To summarize this invention, when recording for the first time, only the signals recorded on a specific track at the start of recording are erased, a section is provided in which neither erasing nor recording is performed on the remaining tracks, and then recording is performed on all tracks. Then, at the end of recording, a section is provided in which information other than the synchronization mark is recorded incorrectly when it is reproduced immediately before the end of recording, and overdubbing is performed.

The above objects and other objects and features of the present invention will become more apparent from the detailed description given below with reference to the drawings.

FIG. 8 is a schematic block diagram of one embodiment of the present invention. First, the circuit configuration required for this invention will be explained. Multi-channel shown in this figure 8
The PCM recording and playback device has a decoding status check section 36.
The configuration is the same as that shown in FIG. 4 above, except that a reproduction phase check section 37 and a reproduction phase check section 37 are provided. Decoding status check section 3
Reference numeral 6 constantly checks the decoding state of the magnetic tape 1 to detect that uncorrectable errors have occurred frequently. Further, the reproduction phase check section 37 checks whether the phase of the digital signal reproduced from the magnetic tape 1 is within a predetermined range. The detection signal of the decoding state check section 36 is given to the reproduction phase check section 37, and from this reproduction phase check section 37 is given to the overdubbing control section 33 together with the reproduction phase detection signal. The overdubbing control section 33 has a decoding state check section 36.
detects an abnormality in the decoding state, or when the reproduction phase check section 37 detects that the reproduction phase is outside a predetermined range, the switch group 31 is opened to stop overdubbing by the multitrack recording head 32. When the decoding state check section 36 detects that the decoding state is normal and the reproduction phase check section 37 determines that the reproduction phase is within a predetermined range, the overdubbing control section 3
3 closes the switch group 31 and causes the multitrack recording head 32 to perform overdubbing.

FIG. 9 shows the decoding status check section 36 shown in FIG.
FIG. 3 is a detailed circuit diagram of a reproduction phase check section 37 and an overdubbing control section 33. Next, the configuration will be explained with reference to FIG. 9. The uncorrectable signal a detected by the decoding processing circuit 23 is applied to an input terminal 361 of the composite state check section 36. This uncorrectable signal a becomes low level when correction is possible, that is, when overdubbing is possible, and becomes high level when overdubbing is not possible. The uncorrectable signal a is applied to one input terminal of a gate circuit 362, and is inverted by an inverter 363 and applied to one input terminal of a gate circuit 364. Clock b is applied from a clock generator 365 to the other input terminal of each of the gate circuits 362 and 364. Therefore, if correction is possible, gate circuit 362 is opened and clock b is connected to gate circuit 3.
If correction is not possible, clock b is applied to the down input end of the up/down counter 367. A low-level Q output is applied from the up-down counter 367 to the other input terminal of the gate circuit 366, and the gate is opened.
Clock b is applied to the up-power end of up-down counter 367. Updown counter 36
7 is constituted by a hexadecimal counter, for example, and is counted up by clock b when correction is possible, and counted down when correction is not possible.

When the second count value is counted from the Bo output terminal of the up-down counter 367, a carry signal d is output and applied to the reset input terminal of the flip-flop 368, and is also inverted by the inverter 369 and sent to the reset input terminal of the up-down counter 367. given at the end. Therefore, the up-down counter 367 is reset every time it outputs the carry-down signal d. Further, the Q signal as the first count value of the up-down counter 367 is outputted and applied to the aforementioned gate circuit 366, and is also inverted by the inverter 370 and applied to the set input terminal of the flip-flop 368. Therefore, the up-down counter 367 stops counting up when it has counted the first count value. Note that the first count value is selected to be larger than the second count value. Normally, up-down counter 367
If the count value is between the first count value and the second count value and can be corrected, the up-down counter 3
The count value of 67 increases and approaches the first count value, and if it cannot be corrected, it decreases and approaches the second count value. The flip-flop 368 supplies a signal e to the reproduction phase check section 37, which remains at a low level as long as the state in which correction is not possible continues, and which becomes a high level when correction becomes possible.

The reproduction phase check section 37 is constructed in substantially the same manner as the decoding state check section 36 described above, and the reproduction synchronization mark f detected by the time axis correction circuit 22 is applied to an input terminal 371. Gate signal creation section 3
Reference numeral 75 generates a gate signal g that becomes low level if the phase of the reproduction synchronization mark is within a predetermined range. The up/down counter 377 is then increased depending on whether or not the playback synchronization mark f given to the input terminal 371 is within the range of the gate signal g.
The inputs of are switched by gate circuits 372, 374, 376 and inverter 373. The up-down counter 377 counts up if the reproduction synchronization mark f is within the range of the gate signal g, and counts down if it is outside the range.

A gate circuit 381 is connected to the set input terminal of the flip-flop 378.
Detection signal e is applied from the decoding state check section 36 to one input terminal of 1, and falling signal i is applied from the Bo output terminal of the up-down counter 377 to the other input terminal. Therefore, the flip-flop 378 is reset when the up-down counter 377 counts the second count value and outputs a falling signal i and when the reproduction phase check section 37 detects an uncorrectable state. The flip-flop 378 is an up-down counter 37.
7 counts the first count value and outputs a high level signal from the Q output terminal, it is reset. Therefore, the output signal j of the flip-flop 378 becomes low level when overdubbing recording is possible, and becomes high level when overdubbing recording is not possible. The output signal j of this flip-flop 78 is given to the overdubbing control section 33.

The overdubbing control section 33 includes an overdubbing instruction signal generation section 331. This overdubbing instruction signal generating section 33 generates an overdubbing instruction signal k.
is generated and applied to one input terminal of gate circuits 332 and 333. A detection signal is applied from the reproduction phase check section 37 to the other input terminal of each of the gate circuits 332 and 333. Therefore, the gate circuits 332 and 333 provide a low level signal from the reproduction phase check section 37, that is, an overdubbing instruction signal when overdubbing recording is possible, to the signal switching circuit 24 and the switch group 31.

FIG. 10 is a time chart for explaining the operation of FIG. 9.

Next, the specific operation of one embodiment of the present invention will be described with reference to FIGS. 8 to 10. When the uncorrectable signal a becomes low level and becomes a correctable state, the up-down counter 367 included in the decoding status check section 36 counts up the clock b, and when the first count value is reached, the Q output becomes high level. Then, the flip-flop 368 is set and the detection signal e becomes high level. At this time,
Since the gate circuit 366 is closed by the high-level signal of the Q output, the up-down counter 367 continues to hold the first count value. In this state,
When the uncorrectable signal a becomes high level, the up/down counter 367 starts counting down. If the uncorrectable state is short and the correction becomes possible after that, the up-down counter 367 counts up again. In other words, in this example,
Overdubbing is not prohibited when the uncorrectable signal is applied for an extremely short period of time. If the uncorrectable state continues for a long time, the up/down counter 367 counts down and the second
When counting up to the count value , the flip-flop 368 is reset by the output signal d from Bo, and the up-down counter 367 is also reset. As a result, flip-flop 368
The detection signal e from becomes low level. At this time, if the playback phase check section 37 detects that the playback phase is normal and the signal i from the Bo output terminal of the up-down counter 377 is set to high level, the signal i from the decoding state check section 36 Flip-flop 378 is set by detection signal e. Then, the detection signal j from the flip-flop 378 becomes high level, and the input gate circuits 332 and 333 of the overdubbing control section 33
Close. As a result, the overdubbing control section 33
overdubbing is prohibited.

On the other hand, the up-down counter 377 of the reproduction phase check section 37 counts up if the reproduction synchronization mark f is within the gate period of the gate signal g, and counts down if it is outside the gate period. As long as the reproduction synchronization mark f is within the gate period of the gate signal g, the up-down counter 377 continues to count up, and when it reaches the first count value, it stops counting up and resets the flip-flop 378. If the decoding status check section 36 mentioned above
If it determines that the decoding state is normal and sets the detection signal e to a high level, the output of the flip-flop 378 becomes a low level and does not inhibit the overdubbing control section 33 from controlling overdubbing. While the up-down counter 377 continues to hold the first count value, if the reproduction synchronization mark f is out of the gate period, it starts counting down, and when it reaches the second count value, the flip-flop 378 is set and the up-down counter 377 continues to hold the first count value. Counter 377 is reset. When the flip-flop 378 is set, a high level signal j is applied to the overdubbing control section 33, so overdubbing is prohibited.

From the above explanation, when the decoding status check section 36 detects that uncorrectable errors have occurred frequently at the timing shown in FIG. 10, the flip-flop 378 of the reproduction phase check section 37 is set.
At the timing shown in , since there is no error and the phases match, the flip-flop 378 is reset. At the timing shown in FIG.
78 is set. At the timing shown in
Since there are no errors and the phases continue to match, flip-flop 378 is reset.

With the above configuration, overdubbing is forcibly stopped and restarted. In this embodiment, as shown in FIG. 10, there is a delay in detection before recording is stopped, so the inconvenience cannot be completely alleviated. That is, it is necessary to stop recording while the reproduction synchronization mark, which serves as a reference for reproduction running, is correctly detected. To this end, in the present invention, the following considerations are further taken at the start and end of recording.

FIG. 11 is a diagram showing the recording pattern of the end section of all-channel recording recorded by an embodiment of the present invention, and FIG. 12 is a diagram showing the recording pattern of the beginning section of all-channel recording. , 1st
FIG. 3 is a schematic diagram of a time chart for forced stop and restart of overdubbing.

First, as shown in FIG. 11, when all channel recording is finished, only a synchronization mark is recorded, and an information section B is provided in which data that is always detected as an error during reproduction is recorded. Further, as shown in FIG. 12, when starting all-channel recording, only section C of a specific track is erased, and sections are provided in which neither erasing nor storing is performed on the remaining tracks. Thereafter, all channel recording is started from point E in FIG. By adopting such a recording method, only the synchronization mark is recorded when all channel recording is finished, and the information section is recorded with data that will always be detected as an error during playback. An uncorrectable section continues before the end of all channel recording, and at point B shown in FIG.
The composite state check section 36 shown in the figure operates,
It is possible to always stop overdubbing. Furthermore, since we have created a section where only a specific track is erased at the start of recording, and the remaining tracks are neither erased nor recorded, there is always an uncorrectable section before moving from a previously recorded pattern to a newly recorded pattern. continues, and overdubbing can be forcibly stopped at point D shown in FIG.

Next, with reference to FIG. 13, the forced stop and restart of overdubbing will be explained in terms of timing according to an embodiment of the present invention. FIG. 13a shows the recording state of the tape, b shows a state in which overdubbing is being performed with an overdubbing signal, that is, a logic O, and c shows a state in which recording is performed with a recording signal, that is, a logic O. Section F shown in FIG. 13a is a section of a previously recorded pattern, and section G is a section in which a track with a previously recorded pattern and an erased track coexist.
The H section is the section of the pattern newly recorded on all channels, the I section is the section where information other than the synchronization mark is always detected as an error, and the J
The section is a section in which all tracks have been deleted, and K
The section is similar to section G, but as a result, all tracks are erased.

In the above embodiment, the phase control is performed using the playback synchronization mark and the playback run is performed. , similar effects can be obtained with the following configuration.

FIG. 14 is a diagram showing an example of a recording pattern according to another embodiment of the present invention. In FIG. 14, 10c is a servo track, 10e, 1
0f is an information recording track, f is newly recorded information, and g is an erase section. Also,
The blank area is an area in which neither recording nor erasing is performed, and the previous state remains. Then, after erasing all tracks except the servo tracks for a certain period of time in the section shown in Fig. 14, recording of all the tracks including the servo tracks is performed in the section , and recording of the tracks other than the servo tracks is stopped at the timing of . death,
Servo tracks continue to be recorded for a certain period of time in the section, and all tracks are erased.

As described above, according to the present invention, when recording for the first time, a reference signal (playback synchronization mark or servo track information) that serves as a reference for playback running is left, and after providing a period in which other information is erroneous. ,
By starting to record all information and leaving a reference signal that serves as a reference for playback when recording ends, we have created a period in which other information is in an incorrect state. It is possible to have a function to forcibly stop the playback, and it is possible to operate stably without generating abnormal sounds during subsequent playback.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the recording format of a conventional multi-channel PCM recording/playback device. FIG. 2 is a diagram showing a method of adding the redundant track shown in FIG. 1. FIG. 3 is a diagram in which a large number of data shown in FIG. 2 are arranged in the tape running direction, and redundant signals are also added in the tape running direction. Fourth
The figure is a schematic block diagram of a conventional multi-channel PCM recording and playback device. FIG. 5 is a diagram showing tracks that are rewritten during overdubbing. 6th
The figure shows an example of a problem when using a recorded magnetic tape. FIG. 7 is a diagram showing an example of a problem when using an erased magnetic tape. FIG. 8 is a schematic block diagram of a multi-channel PCM recording and reproducing apparatus to which an embodiment of the present invention is applied. FIG. 9 is a detailed circuit diagram of the composite state check section, reproduction phase check section, and overdubbing control section shown in FIG. 8. FIG. 10 is a diagram showing the time chart of FIG. 9. FIG. 11 is a diagram showing a recording pattern in the end section of all-channel recording according to an embodiment of the present invention. FIG. 12 is a diagram showing the recording pattern of the leading section of all-channel recording. FIG. 13 is a diagram showing a time chart for forced stop and restart of overdubbing. FIG. 14 is a diagram showing an example of a recording pattern according to an embodiment of the present invention. In the figure, 1 is a magnetic tape, 21 is a multitrack playback head, 22 is a time axis correction circuit, and 23 is a multitrack playback head.
24 is a signal switching circuit, 25 is a D/A converter, 28 is an A/D converter, 29 is an encoding circuit, 30 is a delay circuit, 31 is a switching group, 32 is a multitrack recording head, 33 is an overdubbing control section, 34 is a travel servo section, 35
3 is a capstan motor, 26 is a composite status check section, 367 is an up-down counter, 368 is a flip-flop, 37 is a reproduction phase check section, 3
77 is an up-down counter, and 378 is a flip-flop.

Claims (1)

[Claims] 1. A multichannel system in which audio signals of multiple channels are converted into digital signals and recorded between synchronization marks on multiple tracks of a magnetic tape.
In a PCM recording/playback device, when recording for the first time, the signal recorded on a specific track among the plurality of tracks is erased, a section is provided in which neither erasing nor recording is performed on the remaining tracks, and then recording is performed on all tracks. A recording system for a multi-channel PCM recording/playback device, characterized in that a signal that causes an error during playback is recorded in a section other than the synchronization mark before the end of recording. 2. Any one of the plurality of tracks is a servo track that records a reference signal for controlling the phase of playback running, and when recording for the first time, all tracks except the servo track are kept constant at the start of recording. After erasing the time,
Necessary tracks including the servo track are recorded, and before the recording ends, recording of tracks other than the servo track is stopped, and the servo track is continued to be recorded for a certain period of time, and all tracks are erased. A recording system for a multi-channel PCM recording/playback device according to claim 1, characterized in that: