JPH0316704B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention provides a method for converting analog signals such as audio
This invention relates to a running speed control device for a magnetic recording and reproducing device that performs recording and reproducing by encoding using PCM modulation.

Conventional configuration and its problems Below, magnetic tape is used as the magnetic recording medium.
This will be explained using a PCM recorder as an example. Traditionally, PCM
There are two types of recorders: those that use a rotating head to record PCM signals on an inclined track on the magnetic tape, and those that use a fixed head to form tracks in the longitudinal direction of the magnetic tape and record PCM signals. , commercial use used in recording studios, etc.
Among PCM recorders, especially multi-channel PCM
The latter fixed head type is the mainstream for recorders.

Synchronized recording or punch-in/out are important functions required of multichannel recorders. Sync recording means playing back an already recorded channel while simultaneously recording another signal on another channel in synchronization with the playback channel, and punch-in/out means playing a part of an already recorded channel continuously. This refers to the operation of re-recording data while preserving its originality. In conventional analog multi-channel recorders, the above operation was achieved by using the recording head as a playback head. However, in the case of a PCM recorder, it takes until the reproduced digital signal is demodulated to obtain the original analog signal.
Since there is a delay time caused by various digital signal processing circuits until the input analog signal is converted to digital, modulated, and recorded on the magnetic tape, sync recording or punch-in recording using the recording head as a playback head is not possible. Out is impossible in principle. For this reason, the reproducing head is placed upstream of the recording head in the magnetic tape running direction to achieve the above function.

Figure 1 shows its outline. 1 is a magnetic tape running in the direction of the arrow. 2 is a reproduction head; 3 is a reproduction circuit that demodulates the reproduced digital signal and returns it to an analog signal; signal processing time is _d1 . 4 is a monitor speaker, 5 is a microphone, 6 is a delay circuit whose delay circuit is d ₂ , 7 is a recording circuit whose signal processing time is d ₅ , and 8 is a recording head.

For example, in the case of sync recording, where you play back an already recorded accompaniment and record the vocals on another channel while listening to it through a monitor speaker, the accompaniment and vocals are recorded on the final magnetic tape. In order to hear in sync without deviation, L/V = d ₁ + d ₂ + d ₃ (Equation 1), where L: magnetic tape running distance between playback head 2 and recording head 3, V: magnetic tape It only needs to be the running speed. Since d ₁ and d ₃ are determined by the signal processing circuit configuration, the remaining necessary delay time is obtained by d ₂ . Punch-in/out for re-recording a part of an already recorded channel is also performed in a similar manner. That is, if the first equation is satisfied, musical continuity can be ensured before and after the re-recorded portion.

Now, in the case of a PCM recorder, the digital signal is generally divided into a certain number of parts, a synchronization signal, an error detection code, etc. are added to form a frame, and the frame is recorded on a magnetic tape.When playing back, the reproduced digital signal is Based on the synchronization signals separated and extracted from the synchronization signals, signal processing such as wow and flutter removal using a buffer memory and error correction is performed on a frame-by-frame basis. In the case of the above-mentioned sync recording, in which data is recorded on multiple tracks, it is important for playback signal processing that the frame phases of the already recorded track and newly recorded track on the magnetic tape are always almost the same. desirable. Also, in the case of bunch-in-out, it is desirable that the shift in frame phase before and after the connection point between the already recorded portion and the newly re-recorded portion be as small as possible.

The reason for this will be explained below using FIGS. 2 and 3.
In FIG. 2, 9 is a magnetic tape, 10 is an already recorded track, and 11 is a synchronization signal. Also 12
indicates the track on which new sync recording was performed, and 13 indicates its synchronization signal. In FIG. 2, the phase of the synchronization signal 11 of the already recorded track 10 and the synchronization signal 13 of the newly recorded track 12 is D ₁
If the amount of deviation D ₁ is not equal to or less than a certain value for each sync recording, and therefore the phase relationship between the sync signals 11 and 13 cannot be predicted, then during playback, each track will Signal processing is performed according to the phase of the reproduction synchronization signal. This requires supplying timing pulses to the signal processing circuit of each track and providing elements used in the signal processing circuit independently for each track, resulting in an increase in circuit scale.

FIG. 3 is an example of punch-in-out. 14 is a magnetic tape, 16 is a synchronization signal for the already recorded part,
16 is the newly recorded part (shaded area in the figure)
With the synchronization signal, recording starts at point A and ends at point B. In FIG. 3, the phase is shifted by _D2 due to re-recording with respect to the original position of the synchronization signal, and as a result, the continuity of the phase before and after points A and B is disturbed.

Normally, as a means for separating and extracting a synchronization signal from a reproduced signal from a certain track, a method of detecting the synchronization signal by focusing on a continuous and regular pattern is generally widely used. Therefore, the above-mentioned disturbance in the synchronization signal phase leads to failure to detect the synchronization signal.
This is a so-called out-of-synchronization state, and it usually takes several frames to return to a state in which a synchronization signal is normally detected again, and the data in the frames during that time will be erroneous. In other words, the phase of the synchronization signal is disturbed, and what would normally be an error of only one frame becomes an error of several frames.

For the above reasons, sync recording, punch-in
When performing out, it is desirable that the frame phase of the signal already recorded on the magnetic tape and the frame phase of the newly recorded signal be aligned. However, in the actual running of magnetic tape, there is always fluctuation due to wow and flutter, and it is virtually impossible to record with strictly aligned phases. Since a time axis correction operation is performed using a buffer memory to remove this, the phase shift amounts D ₁ and D ₂ in FIGS. There is no problem if the value is small compared to .

Next, the conventional method of adjusting the phase of the synchronization signal will be explained using FIGS. 4 and 5.
In FIG. 4, reference numeral 1 denotes a magnetic tape running in the direction of the arrow in the figure. 2 is a reproduction head, and 3 is a reproduction circuit which demodulates the digital signal reproduced by the reproduction head 2 and outputs it as an original analog signal. A recording circuit 7 digitizes and modulates the input analog signal, and then a recording head 8 records it on a magnetic tape.

Further, 17 is a circuit for separating and extracting a synchronization signal from the reproduced digital signal, and 18 and 20 are respectively supplied with clock pulses M from a reference clock pulse generation circuit 19 to the reproduction circuit 3 or the recording circuit 7.
A clock pulse generation circuit 21 generates the necessary timing pulses in the reference clock pulse generation circuit, and 21 a clock pulse N from a reference clock pulse generation circuit and a reproduction synchronization signal separated and extracted by a synchronization signal separation circuit 17 (or a reproduction clock separated and extracted from reproduction data).
This is a running speed control circuit that controls the running speed of the magnetic tape so that the frequency of B or its frequency-divided output becomes the same.In this example, the running speed of the magnetic tape is It controls the speed.

Now, consider the case where a reproduced digital signal is reproduced in the reproduction head 2 as shown in A in FIG. In the figure, F1 to F27 represent frame numbers, and S represents a synchronization signal portion. B indicates the reproduced synchronization signal separated and extracted from the reproduced digital signal by the synchronization separation circuit. Although not shown in FIG. 4, the normal reproduction of the reproduction signal is detected using, for example, the continuity of the reproduction synchronization signal, and the reproduction system clock pulse generation circuit 18 receives the reproduction signal processing start command C.
Thereafter, the phase of the reproduction system clock pulse E used for reproduction signal processing is determined by the phase matching pulse D using the reproduction synchronization signal B as a reference.

On the other hand, the phase of the recording system clock pulse H that determines the frame phase of the recording signal I is, for example, not shown in FIG. After the recording command F is given with a delayed signal K, the timing is determined by a phase matching pulse G based on the reproduction synchronization signal B. In this example, the frame phase of the signal recorded on the magnetic tape passing in front of the recording head is expressed as J, but the phase relationship between A and J, which is the frame phase of the signal recorded in the front of the reproduction head, is as follows. is caused by the tape running distance between the playback head and the recording head and the length of the frame on the magnetic tape, which is uniquely determined by the system used. For this reason, the phase of the recording system clock pulse is adjusted based on the reproduction synchronization signal B so that the frame phase at the front of the recording head matches the frame phase of the recording signal to be recorded. Therefore, it was actually recorded by the recording start command K (fifth
(Shaded area in the figure) The frame phase on the magnetic tape can be kept almost constant before and after the start of recording.

However, in the above configuration, since the reproduction system clock pulse generation circuit 18, the recording system clock generation circuit 20, and the phase matching pulses D and G are provided independently, the circuit scale is large and the signal path is complicated. It had drawbacks.

Purpose of the Invention In view of the above-mentioned drawbacks, the present invention provides a magnetic recording and reproducing apparatus that can make the frame phase already recorded on a magnetic tape almost equal to the frame phase of a newly recorded signal by using a very simple circuit configuration. The purpose of this invention is to provide a control device.

Composition of the Invention The running speed control device for a magnetic recording/reproducing apparatus of the present invention includes a clock generation circuit that generates a reference clock pulse, and a synchronization signal added to a digital signal by the reference clock pulse, and the recording head records the digital signal on a track on a magnetic recording medium. a reproduction synchronization signal separation circuit for separating and extracting the synchronization signal from a signal reproduced from a track on the magnetic recording medium by a reproduction head disposed upstream of the recording head with respect to the tape running direction; , a phase difference detection circuit that uses the reference clock pulse and the reproduction synchronization signal separated and extracted as input signals and outputs a phase difference output signal according to the phase difference thereof; and a phase difference output signal of the phase difference detection circuit. It consists of a running speed control circuit that controls the running speed of the magnetic recording medium. With this configuration, the phase relationship between the frame phase of the recorded signal and the reference clock pulse that determines the frame phase of the signal to be recorded is directly compared, and the running speed of the magnetic recording medium is controlled to maintain a certain relationship. As a result, the frame phase of the already recorded signal and the frame phase of the newly recorded signal can be kept approximately equal on the magnetic recording medium.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a block diagram showing one embodiment of the present invention, and FIG. 7 is a time chart thereof.

In FIG. 6, 1 is a magnetic tape, 2 is a playback head, 3 is a playback circuit, 7 is a recording circuit, 8 is a recording head, 17 is a synchronization signal separation/extraction circuit, 19 is a reference clock pulse generation circuit, and 21 is a running speed control. The circuit 22 is a capstan, and the above structure is the same as that shown in FIG.

23 detects the phase difference between the reproduced synchronizing signal D outputted from the synchronizing signal extraction circuit 17 and the reference clock pulse M' outputted from the reference clock pulse generation circuit, and outputs a phase difference output Q corresponding to the phase difference. This is a phase difference detection circuit that outputs to the speed control circuit 21.

The operation of the traveling speed control circuit of the magnetic recording/reproducing apparatus configured as above will be explained below. The reproduction signal A reproduced by the reproduction head 2 is demodulated in the reproduction circuit 3 based on the reference clock pulse M' outputted from the reference clock pulse generation circuit and output as an analog signal, and is also input to the synchronization signal separation and extraction circuit 17. . The synchronization signal separation and extraction circuit 17 separates and extracts the synchronization signal from the input reproduced signal A and outputs the reproduced synchronization signal B to the phase difference detection circuit 23.

On the other hand, the recording circuit 7 converts the input analog signal into a digital signal, and outputs a reference clock pulse from the reference clock pulse generation circuit 19.
Based on M', frame configuration such as addition of a synchronization signal is performed, modulated, and recorded on the magnetic tape by the recording head 8. The phase difference detection circuit 23 also detects the reproduced synchronization signal B output from the synchronization signal separation and extraction circuit 17.
and the reference clock pulse M' output from the reference clock pulse generation circuit 19.
A phase difference output Q corresponding to the phase difference is output to the traveling speed control circuit 21. The running speed control circuit 21 controls the rotation speed of the capstan 22 in this example according to the phase difference output Q, and changes the running speed of the magnetic recording medium.

Taking as an example the case where the reproduced signal A is reproduced as shown in FIG. Signal B is output. Although not shown in FIG. 6, when the reproduction signal processing start command C is outputted, the reproduction synchronization signal B and the reference clock pulse M' are determined in advance in the phase difference detection circuit 23, as in the explanation of the conventional example. It is determined whether the phase relationship is ahead or behind, and a phase difference output 5, which is a determination output, is output to the traveling speed control circuit 21. Traveling speed control circuit 21
Based on the phase difference output Q, the running speed of the magnetic tape is increased or decreased in a direction to obtain a predetermined phase relationship between the reproduction synchronizing signal B and the reference clock pulse M'.

In the example shown in FIG. 7, the interval T is an interval in which traveling speed control is prohibited because the reproduction signal processing start command C has not arrived, and in this example, _T2 is the interval in which reproduction synchronization is performed with respect to the reference clock pulse M'. Since the phase of signal B is behind the predetermined relationship, the phase difference output is output and the traveling speed is controlled to be higher than usual, and in _T3 , the phase relationship between the two has become the predetermined relationship. This is the section where travel speed control is canceled again.

On the other hand, in the recording circuit 7, the reference clock pulse
Since the recording signal I is obtained by performing frame configuration such as adding a synchronization signal based on M', the frame phase relationship between the reproduced signal A and the recording signal I is established through the reference clock pulse M' from the _T3 interval onwards. It will be subject to certain regulations.

As mentioned in the explanation of the conventional example, the playback head 2
The frame phase relationship between the reproduced signal A reproduced by the recording head and the recorded signal J at the front of the recording head is uniquely determined by the traveling distance of the magnetic tape between the reproduction head and the recording head and the frame length on the magnetic tape. It is clear that this is predetermined by the system used and that there are no factors that change it other than fluctuations due to wow and flux, so with the above configuration, the frame phase of the recorded signal J at the front of the recording head and the frame phase of the newly recorded signal J are determined in advance. By controlling the running so that the frame phase of the recording signal I is equal to that of the recording signal I,
A recording signal I is recorded on the magnetic tape by a recording start command K.
Even if a track is recorded, the continuity of the frame phase before and after the recording start/end point, or the deviation from the frame phase of the signal of another recorded track, is guaranteed to be within the amount of wow and flutter.

As described above, according to this embodiment, by controlling the running speed of the magnetic tape so that the phase relationship between the reproduction synchronization signal and the reference clock pulse is always kept constant, the clock pulses necessary for the reproduction circuit and the recording circuit are supplied. The frame phase of the recorded signal and the frame phase of the newly recorded signal can be recorded on the magnetic tape using a simple circuit configuration without providing an independent clock pulse generation circuit and a timing pulse path and circuit required for complex phase alignment. They can be made almost equal.

In this example, the track used for control was explained using the data track used when digitizing and recording the input analog signal, but the track used can be the absolute position of the frame (address code) or A similar effect can be obtained even with a control track used for recording information such as sampling frequency.

In addition, although the output form of the phase difference detection circuit 23 is not specified in this embodiment, it is possible to directly convert the phase difference into a voltage value depending on the circuit system of the traveling speed control circuit 21. A phase comparator (φ-V converter) that can be converted into If the circuit system controls the running speed by comparing the phase or frequency of the clock pulse obtained by dividing the frequency into a number of times, the running speed of the magnetic tape can be controlled by increasing or decreasing the frequency division ratio, so the phase difference The detection circuit 23 is configured to output phase delay or lead information as logical information for increasing or decreasing the frequency division ratio.

In addition, “delay” is output information of phase difference detection,
In addition to the binary value of "lead", by setting a range for determining "match" within the allowable amount of phase shift and prohibiting running speed control, the magnetic tape running speed is always controlled by "lag" and "advance" information. By increasing or decreasing the amount, it is possible to prevent the amount of wow and flutter from increasing, and more stable magnetic tape running can be realized.

Effects of the Invention The present invention controls the magnetic tape running speed so that the reproduction synchronization signal separated and extracted from the reproduction signal and the reference clock pulse, which is the reference for the frame structure of the recording signal, always have a certain phase relationship.
With a very simple circuit configuration, the frame phase of the recorded signal and the frame phase of the newly recorded recording signal can always be kept almost equal, and this is of great industrial value.

[Brief explanation of the drawing]

Figure 1 is a block diagram for realizing the sync recording and punch-in-out functions in a PCM recorder, and Figure 2 is a diagram showing the frame phase of the recording signal of each track on the magnetic tape when sync recording is performed. FIG. 3 is a diagram showing the frame phase of a recording signal on a magnetic tape when performing punch-in-out, FIG. 4 is a block diagram showing a conventional circuit configuration, and FIG. 5 is a timing chart of a conventional circuit configuration. FIG. 6 is a block diagram showing the circuit configuration of one embodiment of the present invention, and FIG. 7 is a timing chart of the circuit according to one embodiment of the present invention. 1...Magnetic recording medium, 2...Reproduction head, 3...
...Reproducing circuit, 7... Recording circuit, 8... Recording head, 19... Reference clock pulse generation circuit, 23
... Phase difference detection circuit, 21 ... Traveling speed control circuit, A ... Reproduction signal, B ... Regeneration synchronization signal,
M'...Reference clock pulse, Q...Phase difference output signal.

Claims (1)

[Scope of Claims] 1. A reference clock generation circuit that generates a reference clock pulse, a recording circuit that adds a synchronization signal to a digital signal using the reference clock pulse and records it on a track on a magnetic recording medium by a recording head, and a tape running direction. a reproduction synchronization signal separation circuit for separating and extracting the synchronization signal from a reproduction signal reproduced from a track on the magnetic recording medium by a reproduction head disposed upstream of the recording head; A phase difference detection circuit receives the reproduced synchronization signal separated and extracted by the synchronization signal separation circuit as an input signal and outputs a phase difference output signal corresponding to the phase difference, and magnetic recording is performed using the phase difference output signal from the phase difference detection circuit. 1. A running speed control device for a magnetic recording/reproducing device, comprising a running speed control circuit for controlling the running speed of a medium. 2. Claim 1, wherein the track is a data track for recording PCM signals.
A running speed control device for a magnetic recording and reproducing device as described in 1. 3. A running speed control device for a magnetic recording/reproducing device according to claim 1, wherein the track is a control track for recording an address signal. 4 The phase difference detection circuit receives the reference clock pulse and the reproduction synchronization signal as input signals, and outputs a voltage value corresponding to the phase difference, and the running speed control circuit controls the running speed of the magnetic recording medium according to the input voltage value. A running speed control device for a magnetic recording/reproducing device according to claim 1, characterized in that the device is configured to perform the following.