JPH0237014B2 - MARUCHICHANNERUPCMROKUONSAISEISOCHI - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a multi-channel PCM recording and playback device, and in particular, to a fixed head type multi-channel PCM recording and playback device.
Related to improving the overdubbing function of PCM recording and playback equipment.

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 information for one audio channel is recorded as a digital signal, and a redundant signal 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, information signals a1 to a8 are recorded on recording tracks 11 to 18, and redundant signals c1 and c2 for error correction.
are recorded on redundant tracks 1a and 1b, respectively. These information signals a1 to a8 and redundant correction signals c1 and c2 have a bit length of b.
To create redundant tracks 1a and 1b, b-bit information signals a1 to a8 are extracted from adjacent positions in the width direction of the tape from the information tracks 11 to 18 described above, and errors are removed from a total of 8b-bit information signals. Obtain correction signals c1 and c2,
This is recorded on redundant tracks 1a and 1b, respectively.

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 signals d1 to d10 are added and recorded every 7b bits to each of information tracks 11 to 18, 1a and 1b. These redundant signals d1 to d10 are usually generated by a CRC code algorithm, and the CRC generated in this way is
A synchronization mark S is further added to the code (information signal + redundant signal) for each track. Hereinafter, the period from the synchronization mark S to the redundant signal di (i=1 to 10) will be referred to as a frame. A collection of 10 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 crystal-accurate clock. For this purpose, the traveling servo section 34
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. The same applies to FIGS. 6 and 9, which will be described later. 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 synchronizing with the playback sound of a pre-recorded channel.
This is a method of recording to a separate 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 manner, for the section where the information on the second channel of the information track 12 is newly rewritten, the corresponding redundant signals 1d and 1e of the redundant tracks 10a and 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.

In other words, if playback becomes impossible for some reason during overdubbing, the playback synchronization mark S
cannot be read, and recording is performed while the vehicle is running erratically. For this reason, even if reproduction becomes possible later, the block code 10 distributed and recorded on each track cannot be reconstructed.

Furthermore, when overdubbing, if the running is disturbed for some reason, the recording will be made in a state that is significantly deviated from the normal position. For this reason, during subsequent reproduction, the block code 10 distributed and recorded on each track cannot be reconstructed. Under the above-mentioned conditions, as shown in Figure 6, a recording pattern like information track 12 occurs, and the block code cannot be reproduced, causing abnormal sounds and preventing stable multi-channel recording. It could not be called a channel PCM recording/playback device.

Therefore, in order to eliminate the above-mentioned inconveniences, the main object of the present invention is to provide a multi-channel PCM recording system that can automatically forcibly stop and restart overdubbing depending on the playback status. The purpose of the present invention is to provide a playback device.

To summarize the invention, a decoding state detection means and a reproduction phase detection means are provided, and when the reproduction phase is outside a predetermined range or an abnormality in the decoding state is detected, overdubbing is stopped and the decoding state is normal. The apparatus is configured to restart overdubbing when the state is reached and the reproduction phase falls within a predetermined range.

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. 7 is a schematic block diagram of one embodiment of the present invention. Multi-channel PCM shown in this figure 7
The recording and reproducing apparatus is the same as that shown in FIG. 4 above, except that a decoding state check section 36 and a reproduction phase check section 37 are provided. The decoding status check unit 36
The decoding state of the magnetic tape 1 is constantly checked to detect if 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. When the decoding status check unit 36 detects an abnormality in the decoding status or when the reproduction phase check unit 37 detects that the reproduction phase is outside a predetermined range, the overdubbing control unit 33 opens the switch group 31 to Stops overdubbing by the track recording head 32. Then, the decoding status check section 36
When the decoding state is detected to be normal and the reproduction phase check section 37 determines that the reproduction phase is within a predetermined range, the overdubbing control section 33 closes the switch group 31 and allows the multitrack recording head 32 to overdubbing.

FIG. 8 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. The uncorrectable signal a detected by the decoding processing circuit 23 is applied to an input terminal 361 of the decoding 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. The low-level Q output from the up-down counter 367 is applied to the other input terminal of the gate circuit 366 to open the gate, and the clock b is applied to the up-input terminal of the 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 _B0 output terminal of the up-down counter 367, a carry signal d is outputted and applied to the reset input terminal of the flip-flop 368, and is inverted by the inverter 369 to reset the up-down counter 367. given to the input 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, when the up-down counter 367 counts up the first count value, the first count value is selected to be larger than the second count value. Normally, the count value of the up-down counter 367 is between the first count value and the second count value, and if correction is possible, the count value of the up-down counter 367 increases and approaches the first count value. , if correction is not possible, the count 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 mark signal g which 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 _B0 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. 9 is a time chart for explaining the operation of FIG. 8.

Next, the specific operation of one embodiment of the present invention will be described with reference to FIGS. 7 to 9. 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 afterwards, the up-down counter 367 counts up again. That is, in this embodiment, 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 will count down.
After counting down to the second count value, the output signal d from B0 causes the flip-flop 368 to
At the same time, the up-down counter 367 is also reset. As a result, the detection signal e from flip-flop 368 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 B0 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,
Input gate circuit 33 of overdubbing control section 33
Close 2,333. As a result, overdubbing by the overdubbing control section 33 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 state check section 36 detects that uncorrectable errors have occurred frequently at the timing shown in FIG.
7 flip-flops 378 are set. 2
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 3, the playback phase check section 37 checks that the playback phases continue to be out of alignment, and the flip-flop 37
8 is set. At the timing shown in FIG. 4, there is no error and the phases continue to match, so flip-flop 378 is reset.

As described above, according to the present invention, it is possible to detect whether the decoding state of a digital signal reproduced from a magnetic tape is normal and whether or not the reproduction phase is within a predetermined range. Since the configuration is such that overdubbing is forcibly stopped if there is an abnormality, overdubbing recording is stopped when the playback condition is poor, and it is possible to prevent abnormal sounds from occurring 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 a state in which overdubbing is performed using a conventional multi-channel PCM recording and playback device. FIG. 7 is a schematic block diagram of one embodiment of the present invention.
FIG. 8 is a detailed circuit diagram of the decoding state check section, reproduction phase check section, and overdubbing control section shown in FIG. 7. FIG. 9 is a waveform diagram for explaining the operation of FIG. 8. 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 decoding processing circuit, 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, 36 is a decoding status check section, 367 is an up-down counter, 368 is a flip-flop, 37 is a playback phase check section, 3
77 is an up-down counter, and 378 is a flip-flop.

Claims (1)

[Claims] 1. In a multi-channel PCM recording/playback device that converts audio signals of a plurality of channels into digital signals and records them on a plurality of tracks of a magnetic tape, the decoding state of the digital signal played back from the magnetic tape. decoding state detection means for detecting the decoding state of the digital signal; reproduction phase detection means for detecting whether the reproduction phase of the digital signal reproduced from the magnetic tape is within a predetermined range; Overdubbing control means for controlling overdubbing of another audio signal with a digital signal on a track; and said decoding state detecting means detecting an abnormality in the decoding state or detecting that said reproduction phase is outside a predetermined range. overdubbing stop means for stopping overdubbing by the overdubbing control means in response to the detection by the reproduction phase detection means; and the decoding state detection means detecting normality of the decoding state and the reproduction phase is predetermined. A multi-channel PCM recording and reproducing apparatus, comprising means for causing the overdubbing control means to restart overdubbing in response to the reproduction phase detection means detecting that the phase is within the range. 2. The decoding state detection means includes: a decoding state detection counter means that performs a counting operation to increase or decrease its count value based on the error correction processing result of the reproduced digital signal; and an output of the decoding state detection counter means. decoding state detection flip-flop means that is set based on a first count value of the decoding state, reset based on a second count value, and outputs a signal representing abnormality or normality of the decoding state from its output terminal. , a multi-channel PCM according to claim 1.
Recording and playback device. 3. The playback phase detection means includes: a playback phase detection counter means that operates to increase or decrease a counted value according to the playback phase of the playback synchronization mark recorded on the magnetic tape; and the playback phase detection counter. a reproduction phase that is set by a first count value of the means output, is reset based on a second count value, and outputs from its output end a signal indicating whether or not the reproduction phase is within the predetermined range; A multi-channel PCM recording and reproducing apparatus according to claim 1, further comprising a detection flip-flop means.