JPH0544746B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording/reproducing device that enables high-speed retrieval of recorded contents for editing or cueing. Multi-channel used for PCM audio signals (hereinafter referred to as PCM signals)
This relates to a cylinder control method in a PCM device.

Conventional Technology In recent years, standards have been unified for 8mm VTRs, which have a tape format different from that of VHS-based VTRs.
According to it, signal processing of video signals is VHS
This method is the same as the method and β method, but the audio signal is FM and PCM recording, and the control method uses a pilot signal for tracking.
Additionally, the amount of tape wrapped around the cylinder containing the rotary head is approximately 36 degrees more than the conventional 180 degree wrap, which corresponds to the recording amount of PCM.

PCM signal processing converts audio signals input continuously over time into digital signals.
Store in RAM. Thereafter, it is read out from the RAM in a temporally compressed form and recorded in the aforementioned 36-degree area. During playback, the data is compressed in time.
Regenerate the PCM signal, store it once in RAM, and then
The PCM signal stored in the PCM signal is expanded in time and read out. Thereafter, it is subjected to D/A conversion and output as a temporally continuous normal audio signal.

Figure 6 shows the tape format of an 8mm VTR. In the figure, A ₁ , B ₁ , A ₂ ,
_B3 is the recorded magnetization locus recorded by the A head and the B head. As shown in the figure, the PCM signal is recorded in each area of 36 degrees, and the video signal is recorded in each area of 180 degrees + α (α is the margin).

The 8mm VTR was originally developed for recording video and audio signals, but the 8mm VTR can also be used as a dedicated device for recording and playing back only audio signals, that is, as a multi-channel PCM (hereinafter referred to as multi-PCM) device. It is possible.

FIG. 7 shows the recorded magnetization locus when the 8 mm VTR is used as a multi-PCM device that records and reproduces only audio signals. As shown in the figure, PCMs of PAi to PFi (i = 1, 2, 3...) are on each magnetization trajectory.
The signal is recorded. CH1 to CH6 indicate each channel. For example, PCM recorded on CH1
The signal is a signal for a certain period of time of the same song and ID
(Identification) Signal is recorded. Also,
The audio signal recorded on each channel can be recorded as a stereo signal. Therefore, it is possible to record six types of audio signals in stereo broadcasting on the magnetization trajectory shown in FIG.

As is clear from the above explanation, the 8mm VTR can be used as a normal VTR that records and plays back video signals, and as shown in Japanese Patent Laid-Open No. 58-222402, it can be used as a multi-channel VTR that records and plays only audio signals. It is also possible to use it as a PCM device.
Therefore, if an 8mm VTR 1-hour cassette tape is used as a multi-PCM device, when the tape format shown in Figure 7 is adopted, 6 hours worth of tape can be recorded.
PCM recording is possible.

Problems to be Solved by the Invention Incidentally, since multi-PCM devices are capable of long-time recording as described above, editing and cueing functions are essential. That is, on a tape recorded for 6 hours, about 90 songs are recorded with an average of 4 minutes per song, and it would be very inconvenient for the user if he could not search for the beginning freely.

Conventionally, there is a method using a tape counter to provide a cue function. In this method, the number of rotations of the reel is converted into the amount of tape movement.
It is used because it has a relatively simple structure, but the accuracy is very poor because the tape winding diameter changes. Another method is to record a pilot signal exclusively for cueing on the tape and reproduce the pilot signal at the time of retrieval to provide a cueing function. This method requires a head for recording and reproducing the pilot signal, a signal processing circuit, etc., resulting in a complicated configuration.

Various methods can be considered as search methods for editing and cueing in a multi-PCM device, but it would be extremely convenient if ID signals could be used. That is, if the ID signal indicating the recorded content is used as an identification signal for the search, the accuracy is high and there is no need to add a new head exclusively for the pilot signal as described above.

However, in fast forward mode and rewind mode (hereinafter referred to as
(referred to as FF/REW), even if you try to reproduce the ID signal, the relative speed of the tape and rotating head differs between normal playback and FF/REW, and the tape winding diameter also changes during FF/REW. Therefore, since the tape speed is not constant at the beginning, middle, and end of winding, the relative speed is not constant, so the clock reproduction frequency of the digital signal is not constant, and the signal cannot be demodulated accurately. It had a point.

In view of this, the present invention has developed a method for controlling the rotation frequency of the cylinder so that the relative speed between the tape and the rotary head is the same as that during normal playback, so that the ID signal can be accurately demodulated even in FF/REW. The purpose is to provide high-speed searches easily.

Means for Solving the Problems The present invention is configured such that a magnetic tape is wound diagonally around a cylinder containing a rotating magnetic head, and information signals are recorded and reproduced on the magnetic tape as a group of discontinuous recording tracks. A means for temporally compressing and recording an audio signal, a means for temporally expanding and reproducing the temporally compressed audio signal, and a configuration for recording the audio signal together with an identification signal indicating the recorded content. A magnetic recording and reproducing device comprising: a take-up reel rotation period detection means; a supply reel rotation period detection means; and a normal tape speed in a fast forward mode or a rewind mode based on output information of the two reel rotation period detection means. tape speed ratio detecting means for calculating and detecting a double speed ratio of the cylinder; This is a magnetic recording/reproducing device characterized by controlling the number of rotations.

Effects With the above-described configuration, the present invention detects the supply side reel period and the take-up side reel period in FF/REW, performs a predetermined calculation to detect the tape speed, and detects the tape speed corresponding to the tape speed. By controlling the cylinder rotation frequency so that the relative speed between the tape and the rotating head is the same as that during normal playback, the ID signal can be accurately demodulated even during FF/REW, and the digital audio signal This makes it easy to perform high-speed searches.

Embodiment FIG. 1 is a block diagram of an arithmetic processing circuit that realizes the cylinder control system that is a feature of the present invention, in which 1 is a reference oscillator, 2a, 2b, and 2c are reference oscillators and a supply reel (hereinafter referred to as S reel). , a counter whose input is the rotation detector of each cylinder of the take-up reel (hereinafter referred to as T-reel), 3a and 3 are square calculators, 4 is an adder, and 5 is a speed for deriving the double speed ratio of the tape speed. A computing unit 6 is a constant memory for storing the data computed by the adder 4 during recording or normal playback, and 7 is a memory in which values pre-calculated using arithmetic formulas to be described later according to each speed ratio are stored. 8 is a reference value generator that generates a reference value based on the ROM data corresponding to the speed ratio obtained by the speed calculator 5; 9 is a reference value generator 8;
This is a subtracter that subtracts the value of counter 2c, which indicates the value corresponding to the rotational frequency of the cylinder, from the value of , and outputs an error signal to the cylinder control circuit.In this way, the relative constant speed of the tape and rotating head is kept constant. An arithmetic processing circuit 10 is configured to perform the following operations.

FIG. 2 is a diagram showing an embodiment using the cylinder control method of the present invention, in which 10 is the arithmetic processing circuit described above, 11 is a cylinder with a built-in rotary head (not shown), 12 is a magnetic tape, and 13 is a cylinder containing a rotary head (not shown). is S reel, 1
4 is a T reel, 15 is a cylinder rotation detector, 16
1 is an S reel rotation detector, 7 is a T reel rotation detector, 18 is a cylinder control circuit that receives the error signal 10b output from the arithmetic processing circuit 10 and the speed information 10a and controls the cylinder 11, 19a to d
is a post for regulating the running of the tape 12,
The S reel 13, the T reel 14, and the cylinder 11 are rotating in the direction of the arrow, and the tape 12 is being transported in the direction of the arrow.

FF/REW of this embodiment configured as above
The basic principle of the cylinder control method in this mode will be explained below.

Here, V _t = Tape feed speed T _S = Time required for one rotation of S reel 13 T _t = Time required for one rotation of T reel 14 D ₀ = Hub diameter of both reels (not shown) δ = Tape thickness If L = total tape length, T _S ² + T _t ² = 1/C ² ...(1) However, It is expressed as

Here, tape thickness δ, tape total length L, hub diameter
Assuming that D ₀ is substantially constant, it can be seen from equation (1) that there is a correlation between the sum of the squares of the rotation periods of both reels and the tape speed.

Adjust the tape speed during recording or normal playback.
V _t (1), and when running at n times speed is V _t (n), from equation (1), T _S (1) ² + T _t (1) ² = 1/n ² (T _S (n) ² +T _t (n) ² ) ...(2) However, T _S (n) and T _t (n) are the S and T reel rotation periods at n times the speed. In other words, if the tape is running at 30x speed, the value will be 1/900 of the value of T _S (1) ² +T _t (1) ² during recording (or during normal playback). Conversely, when the tape is running at a certain speed, if we detect the S reel cycle and T reel cycle, square them, and then add them together, we can calculate the value by comparing it with that during recording (or normal playback). It can be determined whether the tape is running at double speed.

Next, the relative speed between the rotating head and the magnetic tape will be explained. Figure 3 is a diagram to explain this. V _t (n) = Tape speed at n times speed V _H (n) = Relative speed of 〃 V _H (1) = Relative speed during recording or normal playback W = Recording width θ ₀ = Scanning angle θ _o = n times speed when still D = Cylinder diameter _V = Vertical synchronization signal frequency _V (n) = Cylinder rotation frequency _V when n times speed (1) = When recording Alternatively, the cylinder rotation frequency n=double speed ratio during normal reproduction is shown. From the figure, θ ₀ = sin ^-1 (W/πD/2) ……(3) L ₀ = W/tanθ ₀ ……(4) Ln=L ₀ −n・V _t (1)/2 _V …… (5) θn=tan ^-1 (W/Ln) -tan ^-1 (W/L ₀ -n・V _t (1)/2f
_V ……(6) V _H (n)=πD/2・2 _V (n)−V _t (n)・cosθn =πD _V (n)−V _t (n)・cosθn ……(7) Yotsute , to make the relative speed equal even at n times speed, from equation (7), _V (n)=V _H (1)+nV _t (1)・cosθn/πD ……(8). In equation (8), V _H (1), V _t (1), and πD are determined by the standard and are constants, and cosθn can be calculated from equations (3) to (6) as long as the speed ratio n is known. It can be found using (W is a constant) In other words, if the speed ratio n is known, it is possible to find the rotational frequency of the cylinders whose relative speeds should be made equal.

Next, we installed a magnetic recording/reproducing device using this method in the first
This will be explained with reference to FIG.

FIG. 4 is a diagram for explaining the operation of the counters 2a to 2c in FIG. 1. The number of reference oscillation pulses is counted according to the input pulse width of each rotation detector. As a result, the outputs of the counters 2a and 2b are S, values corresponding to the T reel cycle, T _S and T _t . square calculator 3a,
3b, T _S ² and T _t ² are calculated, and adder 4 calculates T _S ²
+T _t ² is output.

First, the value calculated by the adder 4 during recording (or during normal playback), that is, T _S (1) ² + T _t (1) ²
is stored in constant memory 6. Next, FF/REW
The value similarly calculated by adder 4, T _S
(n) ² +T _t (n) ² is input to the speed calculator 5, and in the speed calculator 5, is calculated, and the double speed ratio n is output to the ROM data 7 and the cylinder control circuit 18. In ROM data 7, the value of the cylinder rotation frequency _V (n) at which the relative speed calculated in advance by equations (3) to (8) is constant is output to the reference value generator 8 for the input double speed ratio n. , the reference value generator 8 outputs a value corresponding to the cylinder rotation frequency _V (n) to the subtracter 9.

On the other hand, since the outputs of the reference oscillator 1 and the cylinder rotation detector 15 are inputted to the counter 2c, the output of the counter 2c is a value corresponding to the rotation period of the cylinder 11, 1/ _V '(n). Then, 1/ _V ′(n) is input to the reciprocal calculator 20, and the reciprocal calculator 20 calculates a value corresponding to the rotational frequency of the cylinder 11, ′ _V (n)
is output to the subtracter 9. The subtracter 9 sends the difference between the cylinder rotational frequency _V (n) to be controlled and the current cylinder rotational frequency ' _V (n), that is, the value of _V (n) - ' _V (n), to the cylinder control circuit 18 to detect an error. Output as a signal.

Generally speaking, cylinder rotation control methods include a free run correction method and a phase lock correction method. The former corrects the cylinder rotation frequency according to the tape speed, while the latter performs free run correction according to the tape speed.
This phase locks the cylinder system and capstan system (or tape drive system in the case of a capstanless system). The former is high-speed search (playback by high-speed forwarding)
However, the latter method is generally used because the noise band can be fixed and a stable image can be obtained.
The latter method is often used in VTRs. However, if we only consider the playback of audio PCM, it is only necessary to make the relative speed of the tape and the rotary head the same as the relative speed during recording during n-times speed playback, and demodulate the ID signal, so phase control can be applied, but there is no limit to that. There is no need to do this, and a substantially constant relative velocity is sufficient.
Therefore, in the cylinder control method of this embodiment,
A description of cylinder phase control will be omitted.

Error signal _V output from the arithmetic processing circuit 10
(n)−′ _V (n) is output to the cylinder control circuit 18,
In the cylinder control circuit 18, this error signal _V (n)−
' The rotational frequency of the cylinder 11 is controlled according to _V (n), and a cylinder drive signal that reduces this difference is obtained.

In this way, the rotation of the cylinder 11 is controlled by the drive signal so that the above-mentioned difference becomes small, and the relative speed between the tape and the rotating head is controlled so that the cylinder rotation frequency _V (n) is the same as that during recording or normal playback. be done.

Here, information 10a indicating another speed ratio of the error signal is input to the cylinder control circuit 18 from the arithmetic processing circuit 10, but this information is necessary for optimally performing cylinder control. Adjust the gain of the control loop based on this.

As described above, information for performing optimal control and control error signals are sent to the cylinder control circuit 18.
a and 10b, and is controlled to keep the relative speed constant. In addition, the cylinder control circuit 18
Since the circuit configuration is similar to the conventional circuit configuration, the specific circuit is not shown here.

In this embodiment, after storing the value of T _S (1) ² + T _t (1) ² in the constant memory 6 during recording (or during normal playback), the value T _S (1) ² + T _t (n) ² is stored. I showed an example of calculating, but 8
The automatic identification mechanism of the tape cassette, which consists of five holes in the millimeter cassette, is used to detect the tape type, tape thickness, etc., and then predetermined T _S (1) ² based on the standard values.
There is no problem with a configuration in which the calculation result of +T _t (1) ² is provided as ROM data and this value is used to calculate T _S (1) ² +T _t (1) ² . In addition, an example was shown in which the reference value generator 8 calculates in advance the value found by equation (8) according to various values of the speed ratio n, and stores it as ROM data. After obtaining the ratio n, (3)
The configuration may be such that the value of _V (n) shown in equation (8) is calculated using equation (6). FIG. 5 is a flowchart showing the calculation procedure from when the speed ratio n is known to when the rotational speed of the cylinder at which the relative speed should be kept constant is derived.

It is well known that microcomputers are capable of performing various calculations, comparisons, input/output control, etc., and the arithmetic processing circuit 10 in FIGS. 1 and 2 may be configured with a microcomputer. It is possible.

As described above, according to this embodiment, if the double speed ratio n is determined from the periods of both the S and T reels, and the rotation of the cylinder is controlled to the rotation frequency calculated from this n using equation (8), the tape speed changes. However, the relative speed between the tape and the rotating head is always constant, that is, the relative speed during recording or normal playback can be maintained, and therefore, the ID signal can be accurately demodulated even in FF/REW. can.

In this embodiment, the codes in equations (5) to (8) are explained based on the case where the tape running direction and the video head scanning direction are the same, but when they are in the opposite direction, the codes are expressed as (5) as follows. ′ to (8)′ can be used for calculation.

Ln=L ₀ +n・V _t (1)/2 _V ……(5)′ θn=tan ^-1 (W/L ₀ −nV _t (1)/2 _V ) ……(6)′ V _H (n )=πD _V (n)+V _t (n)・cosθn ……(7)′ _V (n)=V _H (1)−nV _t (1)cosθn/πD ……(8)′ Effect of the invention As explained above As described above, according to the present invention, it is possible to accurately demodulate the identification signal even during FF/REW, and the identification signal can be used to easily cue and edit, so that it is easy to use for practical use. The effect is significant.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an arithmetic processing circuit of a magnetic recording/reproducing device according to an embodiment of the present invention, FIG. 2 is a block diagram of this embodiment, and FIG. 3 is a tape pattern for explaining the control method according to the present invention. Figure, 4th
The figure is a waveform diagram for explaining the operation of the counters 2a to 2c in Figure 1, Figure 5 is a flowchart for determining the rotational speed of the cylinder to be controlled after the speed ratio n is determined, and Figure 6 is a 8 mm A pattern diagram showing the recording magnetization trajectory when the VTR is used as a normal VTR,
FIG. 7 is a pattern diagram showing the recording magnetization locus when an 8 mm VTR is used as a multi-track PCM device. 10...Arithmetic processing circuit, 11...Cylinder, 1
3... Supply reel, 14... Take-up reel.

Claims (1)

[Claims] 1. A magnetic tape is wound diagonally around a cylinder containing a rotating magnetic head, and an information signal is recorded and reproduced on the magnetic tape as a group of discontinuous recording tracks, and an audio signal is temporally recorded. A magnetic recording and reproducing device comprising means for compressing and recording the temporally compressed audio signal, and means for temporally expanding and reproducing the temporally compressed audio signal, and a configuration for recording the audio signal together with an identification signal indicating the recorded content. Based on the output information of the take-up reel rotation period detection means, the supply reel rotation period detection means, and the both reel rotation period detection means, the speed is determined relative to the normal tape speed in the fast forward mode or the rewind mode. A tape speed ratio detection means for calculating and detecting a speed ratio is provided, and the number of rotations of the cylinder is adjusted based on the output information of the tape speed ratio detection means so that the relative speed between the tape and the rotary head is approximately constant. A magnetic recording/reproducing device characterized by controlling. 2 The supply reel rotation period and take-up reel rotation period during recording or normal playback are T _S (1),
T _t (1), tape speed V _t (1), cylinder rotation frequency f _U (1), vertical synchronization signal frequency f _U , cylinder diameter D, recording width of one field track in tape width direction When is W, the cylinder rotation frequency f _U (n) when the tape is running at n times speed is f _U (n)=V _H (1)+n・V _t (1)・COSθn/πD However, V _H (1)=πDf _U (1)−V _t (1)・COSθ ₁ θ ₁ = tan ^-1 (W/W/tanθ ₀ −V _t (1)/2f _U ) θ ₀ = sin ^-1 (W /πD/2) T _S (n): Supply reel rotation period when running at n times speed T _f (n): 〃 Winding〃 θ _o = tan ^-1 (W/W/tan θ ₀ −n・V _t (1)/2f _U ) A magnetic recording and reproducing apparatus according to claim 1, characterized in that: