JPH0654969B2 - Magnetic recording / reproducing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus (hereinafter referred to as VTR), and more particularly to a signal processing apparatus for high-speed search / reproduction that searches for a desired reproduction portion at high speed during reproduction.

2. Description of the Related Art When the tape reproduction time of a VTR reaches as long as 8 hours as in the VHS system, it is difficult to find and reproduce a necessary portion of the tape. For this reason, a VTR is generally provided with a tape counter. To use this tape counter, it is necessary to reset the tape counter when setting the tape in the VTR.
It is necessary to know the count value of the portion to be reproduced in advance, and it becomes useless if either of them is forgotten. Also, the tape may be set to the VTR from the middle, and in this case, even if the count value of the portion to be reproduced is known, the counter does not correspond to the position of the tape, which is not useful.

There is also a method of using a cue signal and an address signal, but this requires a dedicated head and a dedicated track, and the signal processing becomes complicated, which makes the device expensive and makes it difficult for home use. not appropriate.

The conventional VTR high-speed search playback includes, for example, "NH
K Home Video Technology "(written by NHK Katsuya Yokoyama) (P.188-18)
9).

FIG. 5 is a diagram for explaining an example in which this conventional high-speed search reproduction is used for 8 mm video, and two rotary magnetic heads (not shown) have an angular interval of 180 ° during recording.
Rotation is controlled at a cycle of 30 times per second, which is the frame frequency of the video signal, and the tape 1 is controlled to run in the direction of arrow 2 at a constant speed to form the recording pattern shown in FIG. On the tape 1, one field is recorded as one oblique magnetic track 3A, 3B, and in the tracks 3A, 3B, the numbers 1 to 525 indicate horizontal scanning numbers. (FIG. 5 is a pattern diagram in which an NTSC signal is recorded.). The distance between the start end of an arbitrary track 3 and the start end of the adjacent track 3 (so-called αH) is 1H in the length direction of the track 3 (H is the length of one horizontal scanning period of the track 3). ).

On the other hand, at the time of reproduction, the rotary head is controlled to scan the track 3 in the same manner as at the time of recording, and a reproduced video signal is obtained. In such a VTR, when the running speed of the tape 1 is reproduced three times as high as that at the time of recording, the rotary head is scanned as shown by arrows 4A and 4B. And in this case
According to the scanning of the arrows 4A and 4B, the arrows 4A to 4B
Even when the scan is changed to, the recorded contents can be reproduced even if the time speed is tripled without any disturbance in the interval of the horizontal synchronizing pulse.

However, if this is done, the following inconvenience will occur. That is, when the running speed of the tape 1 is tripled, the running path of the head is indicated by the arrows 4A and 4B, the horizontal scanning period changes, and therefore the frequency of the horizontal synchronizing pulse becomes
Than regular frequency It becomes low (the horizontal scanning period becomes long).

Similarly, when the tape 1 running speed is N times that at the time of recording, the frequency of the horizontal synchronizing pulse is higher than the normal frequency. Just lowers.

Therefore, as can be seen from the equation (1), if the running speed of the tape 1 is increased, the horizontal synchronization of the receiver cannot be achieved, and the recorded contents may not be searched at high speed.

Furthermore, in the 8 mm video, four types of pilot signals of 100 to 165 KHz are used, and the respective signals of H and 3H (H is the horizontal synchronizing signal frequency) which are the difference frequencies of the pilot signals from the adjacent tracks are extracted to obtain the tracking error signal. The method used as is taken. Therefore, if the frequency of the horizontal synchronizing signal changes, it is not possible to properly extract the H and 3H signals by the tuning circuit, and thus it becomes impossible to obtain a good tracking error signal. .

Therefore, in the conventional VTR, the rotational speed of the head is changed so that the frequency of the horizontal synchronizing pulse does not change during high-speed search reproduction. That is, when searching at N times speed, the rotational speed of the head is changed every second. The rotation was controlled at the cycle calculated by the equation (2), and the frequency of the horizontal synchronizing pulse was kept unchanged.

Problems to be Solved by the Invention However, the above configuration has the following problems. Generally, a normal TV receiver is used for a playback monitor of a home VTR, but in this normal TV receiver, the lock range of the vertical oscillation circuit is 5
It is about 7%, which is wider than the lock range of the horizontal oscillation circuit. Therefore, as described above, the conventional VTR utilizes this property to control the rotational speed of the rotary head so that the frequency of the horizontal synchronizing pulse does not change during high-speed search, and the frequency of the vertical synchronizing pulse changes accordingly. However, the wide locking range of the receiver allowed vertical synchronization to be achieved.

However, the demand for accessing a high-speed tape has become stronger as the tape has been recorded for a long time. For example, when performing a high-speed search at 30 times speed, the rotational speed of the rotary head is controlled so that the frequency of the horizontal synchronizing pulse does not change. In other words, from the formula (2), Control, the frequency of the vertical sync pulse is therefore Then, it changes by 10% or more, which exceeds the lock range of the vertical oscillation circuit of the receiver. That is, the conventional VTR can be applied only up to the tape speed (about 13 times speed in the case of 8 mm video of αH = 1) which is allowable in the lock range of the vertical oscillation circuit.

In view of the above point, the present invention has an object to provide a magnetic recording / reproducing apparatus capable of performing high-speed search / reproduction such as 50 × speed.

Means for Solving the Problems The present invention controls the rotational speed of the rotary head during high-speed search to a rotational speed different from that during normal reproduction so that the horizontal scanning frequency of the reproduced video signal becomes substantially the same as during normal reproduction. In the magnetic recording / reproducing apparatus, the memory capable of storing one field of the reproduced and demodulated video signal, the writing and reading of the video signal to and from the memory are controlled, and the writing to the memory is performed by using a tape. When playing back in the same direction at the time of recording at high speed, the video signal for one field of the played back video signal and blank data are added and written, and when playing back in the reverse direction at high speed, only part of the played back video signal A memory control circuit for controlling the writing of a fixed amount of video signal, and the writing to this memory is performed every several fields according to the tape speed. It is a magnetic recording / reproducing apparatus.

With the above-described structure, the present invention controls the rotational speed of the rotary head during high-speed search reproduction to be different from that during standard reproduction, thereby changing the cycle of the vertical synchronizing signal of the reproduced video signal. One field of the demodulated video signal is stored in the memory, and when the tape is played back in the same direction as at the time of recording at high speed, the video signal is added to the memory in addition to the played video signal, and the tape is played back in the opposite direction at high speed. In this case, by discarding a part of the reproduced video signal and storing it in the memory, a certain amount of the video signal in the memory is stored, and the video signal in this memory is sequentially read out, so that the cycle of the vertical synchronization signal is stable. It becomes possible to obtain a signal. Further, since the writing to the memory is performed every several fields according to the tape speed, it is possible to obtain a reproduced image which is easy to see visually in spite of high speed reproduction.

Embodiment FIG. 1 is a block diagram showing a main part of a video signal processing section of a two-head type VTR in an embodiment of the present invention. In FIG. 1, 5A and 5B are magnetic heads, 6A and 6B are re-amplifiers, and 7 is a first switch which is switching-controlled by a head switching signal supplied from a terminal 8. Reference numeral 9 is a demodulation circuit, 10 is a sync signal separation circuit, 11 is an analog-digital converter (hereinafter referred to as A / D converter), 12 is a semiconductor memory, and 13 is a digital-analog converter (hereinafter D / D).
A converter), 14 is a memory control circuit, and 15 is a second
Switch 16 is a video signal output terminal. In FIG. 1, reproduction video signals reproduced by the rotary heads 5A and 5B are amplified by reproduction amplifiers 6A and 6B, respectively.
Are alternately switched over by the switch 7 to produce a continuous reproduced video signal. This reproduced video signal is demodulated by the demodulation circuit 9 and converted into a digital video signal by the A / D converter 11.

On the other hand, the output of the demodulation circuit 9 is also input to the synchronization signal separation circuit 10, and the synchronization signal separation circuit 10 separates and extracts the horizontal synchronization signal, the vertical synchronization signal and the color subcarrier signal in the demodulated video signal, and these are extracted. By operating the memory control circuit 14 based on the signal, the digital output of the A / D converter 11 is written to a predetermined address of the memory 12 in a unit of one field. The memory control circuit 14 also controls the reading of the memory 12, and the digital video signal written in the memory 12 is converted into the original analog video signal by the D / A converter 13, and then the second switch is operated. A video signal is output to the output terminal 16 via the D side of 15. A of the second switch 15
The output of the demodulation circuit 9 is supplied to the side, the switch 15 is connected to the side A during standard reproduction, and the switching is controlled by a system control circuit (not shown). The configuration of the memory control circuit 14 will be described in detail later.

Next, using the present embodiment, the tape is moved in the same direction as when recording.
The operation in the case of performing high-speed search reproduction at 0 times speed will be described. When performing high-speed search playback of 50 times speed, increasing the rotation speed of the capstan motor to 50 times and pinching the tape with the pinch roller to transfer the tape causes the motor to have insufficient torque, and from standard playback to 50 times speed. Since it is very difficult to control a motor over a wide range with good performance, direct tape transfer between reels is used as follows. For example, Japanese Patent Application No. 60-38032 describes a method of controlling a tape at a constant speed without using a capstan motor. In the present invention, description of a tape high speed transfer control method such as 50 times speed is omitted. is doing.

FIG. 2 shows an operation waveform diagram of a main part. A is a head switching signal, B is an R / W signal for controlling writing and reading of the memory 12, C is a video output read from the memory 12, and D is its output. The vertical synchronizing pulse signal of a video output is shown. The operation will be described below with reference to the drawings.

In the high speed search reproduction mode of 50 times speed, the second switch 15 is connected to the D side. As described above, the number of rotations of the head is set so that the frequency of the horizontal synchronizing pulse does not change during the high speed search reproduction. Controlled by. Therefore, the frequency of the vertical sync pulse is 1 / t ₁
Is And changes by about 18.7%.

Therefore, since the vertical sync lock range of the television receiver is exceeded, writing and reading of the memory 12 are controlled to control the vertical sync cycle so that the vertical sync oscillation circuit of the television receiver falls within the lock range. There is.

When the tape runs at 50 times speed and the head is rotated at 35.60 [rps], the number of horizontal scanning lines reproduced is 213.5. Therefore, in the present embodiment, blank data is given to the memory 12 by an amount corresponding to 49 horizontal scanning lines, and a total of 262.
By making the number of horizontal scanning lines five and reading the memory 12 sequentially, a vertically synchronized image is produced.

.., 8 in FIG. 2A are field numbers, and the field 1 is written in the memory 12 and read by the D / A converter 13 in parallel. At this time,
The number of horizontal scanning lines reproduced in the field 1 is 213.5, and the video signals corresponding to these 213.5 horizontal scanning lines are sequentially rewritten in the memory 12. The blank data previously written in the memory 12 remains without being rewritten by the amount corresponding to 49 horizontal scanning lines. At the time of running at 50 times speed, rewriting to the memory 12 is controlled so as to be executed every 6 field cycles as shown in FIG. 2B, for example. The memory 12 is not rewritten until the video signal of the field 7 is written in the memory 12.

Now, the digital video signal stored in the memory 12 in this way is under the control of the memory control circuit 14.
The signals are sequentially read, converted into the original analog video signal by the D / A converter 13, and supplied to the terminal 16 via the D side of the second switch 15. At this time, the vertical scanning period read from the memory 12 is naturally 1 / t at the time t ₁ shown in FIG. 2D because the horizontal scanning line is corrected.
It becomes 60 [sec]. Therefore, the period of t _{2 in which} the vertical scanning period changes most is calculated as follows.

This is a change of about 5% with respect to 60 [Hz],
Enough to enter the lock range of the TV receiver. The example shown in FIG. 2 is an example in which the vertical scanning period for 6 fields is set to the vertical scanning period for about 5 fields, and it suffices to set how many fields the data is rewritten according to the tape speed ratio. The example shown in this embodiment is not uniquely determined.

For example, at the 40 × speed, the blank data prepared in the memory 12 need only correspond to 39 horizontal scanning lines. At this time, as in the case described above, the blank data is rewritten into the memory 12 every 8 fields, and the blank data is stored for 7 fields. Then, even in the 7th field (t _{2 in} the example of FIG. ₂ ) where the vertical scanning period is most deviated, And changes to about 4% with respect to 60 [Hz].

The high-speed search reproduction also requires that the tape be run in the reverse direction for reproduction, and will be described below by taking the case of performing search reproduction at 50 times speed (-50 times speed) in the reverse direction as an example.

The rotation speed of the head is set so that the frequency of the horizontal sync pulse does not change during -50x speed search. Controlled by. The horizontal scanning line reproduced at this time is 31
The number of vertical sync pulses is 3.5, Will be.

Therefore, in the case of reverse search, the number of reproduced horizontal scanning lines is 26
When the number of video signals exceeds 2.5, the video signals after that are cut off and stored in the memory 12 so as to have a total of 262.5 horizontal scanning lines, which are sequentially read out to produce a vertically synchronized image.

FIG. 3 is a diagram showing operation waveforms of a main part at the time of reverse search. E is a head switching signal, F is an R / W signal for controlling writing and reading of the memory 12, and G is an image read from the memory 12. Output, H indicates the vertical synchronizing pulse signal of the video output.

.., 8 in FIG. 3E are field numbers, and the field 1 is written in the memory 12 and read by the D / A converter 13 in parallel. In the case of this -50 × speed search, the number of horizontal scanning lines reproduced in field 1 is 313.5, and the memory 12 sequentially rewrites the video signals corresponding to the first 262.5 horizontal scanning lines. Then, the video signals corresponding to the remaining 51 horizontal scanning lines are truncated. During the -50 × speed search, the rewriting to the memory 12 is controlled to be executed every four field cycles as shown in FIG. 3F, and the field 1 is written in the memory 12. From
The rewriting of the memory 12 is not executed until the video signal of the field 5 is written in the memory 12.

The digital video signals thus stored in the memory 12 are sequentially read out under the control of the memory control circuit 14 and converted into the original analog video signal by the D / A converter 13. It is supplied to the terminal 16 via the D side of the second switch 15. At this time, the memory 12
The vertical scanning period read out from is t ₁ shown in FIG. 3H.
At 1/60 [sec], of course. T ₂ where the vertical scanning period is most shifted is And changes to about 4% with respect to 60 [Hz].

As described above, by adding blank data in the forward search, and by truncating a part of the video signal in the reverse search, it is possible to obtain a stable image with vertical synchronization. Generally, a high-speed search playback image is sufficient if the contents of the tape can be confirmed quickly. If blank data is added in the forward direction search, the bottom of the screen becomes blank in the television receiver, and the video signal truncated in the reverse direction search. Does not pose a practical problem because it cannot be reproduced.

It should be noted that the faster the tape speed for search / playback is, the better the accessibility is. However, it is difficult to confirm the contents of the tape when a high speed search is performed at a speed exceeding 30 times due to human visual problems. In the system in which the video output is switched every several fields as in the present embodiment, there is an effect that the search reproduction image is visually easy to see, and it is very likely that the search speed will increase in the future. Is effective for.

Next, FIG. 4 shows an example of a concrete configuration of the memory control circuit 14 of the embodiment shown in FIG. In FIG. 4, the same components as those in FIG. 1 are designated by the same reference numerals, and a description thereof will be omitted except for the synchronization signal separation circuit 10 and the memory control circuit 14 surrounded by dotted lines. Reference numeral 17 denotes an _SC generation circuit that separates and extracts a color burst signal from the demodulated video signal output from the demodulation circuit 9 and generates a color subcarrier signal that is phase-synchronized with this color burst signal. Reference numeral 18 denotes the color subcarrier signal. A multiplying circuit for multiplying (for example, 4 times), 19 is a horizontal synchronizing signal separating circuit, and 20 is a vertical synchronizing signal separating circuit, which separate each signal from the demodulated video signal input. Reference numeral 21 denotes a first counter which receives the clock signal from the multiplication circuit 18 as a count input and receives the horizontal synchronization signal from the horizontal synchronization signal separation circuit 19 as a reset input, and 22 has a horizontal synchronization signal as a count input and a vertical synchronization signal separation circuit. 20
A second counter which receives the vertical synchronizing signal from the counter as a reset input specifies the write and read addresses of the memory 12 by the outputs of these counters 21 and 22. 23
Is a write / read control circuit (hereinafter referred to as an R / W control circuit), which generates a write pulse and a read pulse for the memory 18 based on the clock signal from the frequency multiplication circuit 18.

The memory control circuit 14 is configured as described above. The demodulated video signal from the double tone circuit 9 (see FIG. 1) is
It is input to the A / D converter 11 and sampled in synchronization with the output clock signal of the multiplication circuit 18 and converted into a digital signal. On the other hand, the R / W control circuit 23 generates a write pulse W delayed by a certain time (memory access time) from the clock signal and a read pulse R slightly delayed from the write pulse W. The digital video signal stored at each address of the memory 12 is sequentially read by the read pulse R generated by the R / W control circuit 23, input to the D / A converter 13, and then the D / A converter 13 Synchronizes with the clock signal of the multiplication circuit 18, latches the input digital signal, converts it into an original analog video signal, and outputs it to the terminal 16 via the second switch D side.

Next, how many fields are rewritten in the memory 12 will be described. As already described in the examples of 50x speed, 40x speed, and -50x speed, the vertical scanning period changes most in the field immediately before rewriting the video signal in the memory 12,
The vertical scanning period of this field should be within the lock range of the television receiver.

Therefore, N _H : Number of horizontal scanning lines per field of video signal to be recorded / reproduced (N _H = 262.5 in the case of NTSC system) _V : Vertical synchronization frequency [Hz] of video signal to be recorded / reproduced
( _V = 60 [Hz] in case of NTSC system) α: H shift of recorded tape pattern [H] (α = 1 [H] in case of 8 mm video SP recording) N: Double speed ratio of tape M: Memory Rewriting period [field] (M is a natural number) ΔV: When the vertical scanning lock range [%] of the monitor receiver is set, the following conditions must be satisfied.

When the tape is searched and reproduced N times in the same direction as when it was recorded, Therefore, it suffices if this period is within the change of ΔV in the period of 1 / _V. Therefore, Summarizing equation (3), In addition, when the tape is searched N times in the reverse direction to that when recording, Therefore, if the expressions (4) and (5) are satisfied, the search reproduction video signal is compressed or expanded by ± 1 field by the memory, and a reproduction image with vertical synchronization can be obtained.

Next, when the reproduced video signal is compressed or expanded by ± J fields, the conditions for obtaining a reproduced image in vertical synchronization are derived.

When the tape is played back N times in the same direction as when it was recorded,
The vertical scanning period that changes the most is Therefore, in the same way as the formula (4) is derived, In addition, when the tape is searched and reproduced N times in the opposite direction to that at the time of recording, in the same way as the formula (5) is derived, Therefore, write the memory in the cycle that satisfies the equations (6) and (7),
By controlling the reading, it is possible to obtain a reproduced image with vertical synchronization.

As described above, by performing the video signal processing of the high-speed search reproduction, it is possible to obtain a reproduction image that is vertically synchronized, and further, the reproduction image is switched at a cycle of several fields to obtain an easy-to-see search reproduction image. You can also

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to obtain a stable reproduction image that is vertically synchronized even during high-speed search reproduction, and the reproduction image is switched only every few fields. There is an advantage that the search image is very easy to see, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a block diagram of a signal processing apparatus according to an embodiment of the present invention, FIGS. 2 and 3 are waveform charts for explaining the operation of the embodiment, and FIG. 4 is a memory shown in FIG. FIG. 5 is a block diagram showing a specific configuration of the control circuit, and FIG. 5 is a relationship diagram between the recording track pattern of 8 mm video and the reproduction scanning locus of the rotary head at the time of reproducing at 3 × speed. 5A, 5B ... rotary head, 9 ... demodulation circuit, 10 ...
Synchronous signal separation circuit, 11 ... Analog-digital converter, 12 ... Memory, 13 ... Digital-analog converter, 14 ... Memory control circuit.

Claims (2)

[Claims] 1. A magnetic tape in which a video signal is recorded at an inclined track formed at a rate of one per field by a rotary magnetic head when traveling at a constant speed at the time of recording, at a higher speed than that at the time of recording. With the magnetic tape running, the rotary magnetic head is controlled to rotate at a rotational speed different from that at the time of recording, and the reproduction is performed by the rotary magnetic head having a horizontal scanning frequency substantially the same as that of standard reproduction. A magnetic recording / reproducing apparatus for obtaining a video signal, the memory capable of storing one field of a reproduced and demodulated video signal, and control of writing and reading of the video signal to and from the memory. When the magnetic tape is reproduced at high speed in the same direction as when recording, the video signal for one field of the reproduced video signal and blank data are added and written. In addition, when performing high-speed playback in the reverse direction, a part of the played video signal is discarded and a fixed amount of video signal is written, and writing to this memory is performed every several fields depending on the tape speed. And a memory control circuit for controlling so that the magnetic recording and reproducing apparatus. 2. The memory control circuit writes a video signal to the memory when the magnetic tape is reproduced at a high speed in the same direction as when recording. In addition, when playing back at high speed in the reverse direction of recording, However, fV: vertical sync frequency of the video signal to be recorded and reproduced [H
z] NH: Number of horizontal scanning lines per field of video signal to be recorded / reproduced α: H deviation of recorded tape pattern N: Double speed ratio of tape M: Memory rewriting cycle [field] (M is natural number) ΔV: Monitor The magnetic recording / reproducing apparatus according to claim 1, wherein the magnetic recording / reproducing apparatus is a memory control circuit that controls so as to satisfy the condition of vertical scanning lock range [%] J: natural number of the receiver.