JPH02261279A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To make a picture of an ultrahigh speed feeding and rewinding reproduction stable by applying write control in response to a tape drive speed and readout control with a prescribed interval and providing a level conversion circuit and a synchronizing signal replacement circuit. CONSTITUTION:A rotary head cylinder control circuit 18 controls a relative speed between magnetic heads 6, 7 and a tape 1 so that a horizontal scanning frequency of a reproduced video signal is nearly the standard frequency at the fast feed reproduction, and a write address generating circuit 14 generates a write address to a memory 11 based on a specific range of a reproduced video signal and a write start address depending on tape drive speed information from a tape drive control circuit 17. Moreover, a readout address generating circuit 15 generates an address to read a data by one field in the memory 11 at a frequency almost equal to the standard value of the vertical scanning frequency and a level conversion circuit 12 brings the specific range in readout data to a prescribed video level and a synchronizing signal replacement circuit 16 replaces the synchronizing signal generated at the output of the circuit 12 subject to analog conversion 13.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a video tape recorder (hereinafter referred to as V
The present invention relates to magnetic recording and reproducing devices such as TR.

In conventional VTRs, fast forward playback and rewind playback are modes in which the user checks what content is recorded on a magnetic tape (hereinafter referred to as tape) while looking at the screen.

Hereinafter, fast forward playback and rewind playback in a conventional magnetic recording/reproducing device will be explained with reference to the drawings.

FIG. 4 is a plan view schematically showing the arrangement of magnetic heads on a rotating head cylinder, R and L are a pair of magnetic heads for long-time recording mode, and R' and L' are standard recording This is a pair of magnetic heads for mode. magnetic head R and R/,
L and L' have the same azimuth angle, magnetic heads R and L' are attached at positions close to each other and constitute a head pair A, and magnetic heads R' and L are also attached at positions close to each other and form a head pair. It constitutes B. Figure 5 (,) is a diagram showing the trajectory of the playback head during fast-forward playback, and (b) is a diagram showing the trajectory of the playback head during rewind playback. Tracks with different azimuths from L (!:R) are recorded alternately on the tape. Head pairs A and B alternately scan over the tape.During fast-forward playback and rewind playback, each head pair A and B scans the R azimuth in accordance with the speed of the tape. The track written in ``A'' and the track written in L azimuth are crossed several times, but since the head vs. person and B are each equipped with an L azimuth head and an R azimuth head, the playback output of the two heads By determining the level of the playback head and selecting the playback head in real time, it is possible to output fast-forward or rewind video.

As can be seen from Fig. 5, the trajectory of the playback head during fast-forward playback and rewind playback is different from that during normal playback, so if the rotary head cylinder is rotated at the same number of revolutions as during normal playback,
The frequency of the horizontal synchronization signal increases or decreases, causing the television receiver to lose horizontal synchronization and causing the screen to drift horizontally. For this reason, the rotational speed of the rotary head cylinder is controlled according to each tape speed so that the frequency of the horizontal synchronizing signal becomes approximately the standard value, thereby creating a stable screen.

Problems to be Solved by the Invention However, in the conventional configuration described above, the number of horizontal synchronization signals in one scanning period (one field) during fast-forward playback and rewind playback increases or decreases as the speed becomes faster. There was a problem in that fast-forward and rewind playback could only be performed at speeds that allowed vertical synchronization of the receiver.

For example, in the standard mode of an NTSC standard VTR, the number of horizontal synchronization signals in one field period during fast forward playback is:
If the speed is n times faster, it becomes 262.5+ (1-n)×1,5
The number of books decreases as the speed increases.

Also, during rewind playback, the faster the speed, the more the number of tracks increases.

In fast-forward playback at 30 times the standard mode, the number of horizontal synchronization signals in one field period is 219, and the period of the vertical synchronization signal is 17% smaller than the standard value.
Some television receivers may cause the screen to drift.

In addition, the faster the tape running speed, the more
The number of tracks crossed by B and B increases in one scan, and the skew distortion on the screen also increases, resulting in an unsightly screen.

In view of the above problems, the present invention uses a field memory in which writing and reading operations can be performed asynchronously, so that the period of the vertical synchronization signal of the output video signal is approximately the standard value at any tape running speed. The present invention provides a magnetic recording/reproducing device that can obtain a stable screen during ultra-high-speed fast forward playback and rewind playback by performing skew correction.

Means for Solving the Problems In order to solve the above problems, the magnetic recording and reproducing apparatus of the present invention includes a tape running control circuit that controls the running direction and speed of the tape, and a horizontal scanning of the reproduced video signal at any tape speed. A rotary head cylinder control circuit that controls the relative speed between the rotary head cylinder and the tape so that the frequency is approximately the standard value, can store at least one field's worth of reproduced video signals, and has asynchronous and independent write and read operations. A write address to the memory is generated from the horizontal and vertical reference signals of the playback video signal based on the specific range of the playback video signal determined by the tape running speed information from the tape run control circuit and the write start address. a write address generation circuit that reads one field of data from the memory at a frequency approximately close to the standard value of the vertical scanning frequency;
A level conversion circuit converts a specific range of data read from the memory to a certain video signal level according to the tape running speed information from the tape running control circuit, and a level conversion circuit generates a synchronization signal based on the read address and converts the level. This device is equipped with a synchronization signal replacement circuit that replaces the synchronization signal with the output data of the circuit.

Effect of the Invention With the above-described configuration, the horizontal and vertical synchronization signals and image signals of the video signal are stabilized during fast-forward playback and rewind playback at any tape running speed, and the screen at an ultra-high tape speed can be displayed on a television. It can be viewed on a receiver.

Example Below, regarding a magnetic recording and reproducing device according to an example of the present invention,
This will be explained with reference to the drawings.

FIG. 1 shows a block diagram of an embodiment of the present invention. In Figure 1, 1 is a tape, 2 is a cassette, 3 is a rotating head cylinder, 4 is a capstan, 6 is a pinch roller, 6.7 is a magnetic head, a signal reproducing circuit, and 9 separates a synchronization signal from a reproduced video signal. Synchronous signal separation circuit, 1o
11 is an AD converter that converts the reproduced video signal from analog to digital; 11 is a memory that stores one field worth of digital video signals; 12 is an AD converter that converts a particular part of the video signal read from the memory 11 to a certain level; level conversion circuit,
13 is a DA converter that converts a video signal from digital to analog; 14 is a write address generation circuit that generates a write address for the memory 11; 15 is a read address generation circuit that generates a read address for the memory 11; 16 is a DA converter 13 17 is a tape running control circuit that controls the rotational speed of the capstan 4; and 18 is a rotating head cylinder control circuit that controls the rotation of the rotating head cylinder 3. be.

The operation of the magnetic recording/reproducing apparatus configured as described above will be described below with reference to FIGS. 1, 2, and 3.

The second is a diagram showing the waveform of the video signal during fast-forward playback and rewind playback, 30, 31, and 32 are the waveforms during fast-forward playback, 3o is the waveform of the playback video signal, and 31 is the memory 1
1 indicates the range to be written, and 32 indicates the waveform of the output video signal. 33, 34° 36 are waveforms during rewind playback,
33 is the waveform of the reproduced video signal, 34 is the range to be written into the memory 11, and 36 is the waveform of the output video signal.

First, the fast forward playback will be explained. The rotating head cylinder control circuit 18 corrects the relative speed between the tape 1 and the magnetic head 6.7 in accordance with information on the tape running direction and speed from the tape running control circuit 17, and adjusts the period of the horizontal synchronizing signal of the reproduced video signal. Since it is set to approximately the standard value, as described above, the faster the speed, the smaller the period of the vertical synchronization signal of the reproduced video signal becomes, as shown in waveform 30. The write address generation circuit 14 counts using the horizontal and vertical reference signals from the synchronization signal separation circuit 9 in accordance with the tape running direction and speed information from the tape running control circuit 17, and generates a waveform 31 internally. .

The range of the waveform 31 is the video data actually written into the memory 11. Then, an address is generated to write the range into the memory 11 from the write start address determined by the tape running information. To explain this operation using FIG. This is an operation in which the data is written to the '7''z position. In the read operation, the read address generation circuit 16 generates an address so that the cycle for reading one field of data from the memory 11 almost matches the cycle of the vertical synchronization signal, and the level conversion circuit 12 performs the read operation according to the tape running information. From the address, a range other than ab-c...X'7'Z and a horizontal blanking period are detected, and the level of the data is converted to the pedestal level. Thereafter, the DA converter 13 converts it into an analog signal, and the synchronization signal switching circuit 16 switches the horizontal and vertical synchronization signals based on the read address. In other words, during fast-forward playback, the number of horizontal scans per field period decreases, so by writing all the video information into memory and creating the missing part with the pedestal level and synchronization signal, the waveform shown in waveform 32 is obtained, which is vertical according to the NTSC standard. The scanning period is corrected to be approximately 1/60 second.

Similar control is performed during rewind playback, but in this case, since the number of horizontal scanning lines increases, the video information before and after az of waveform 33 is discarded to create a signal of waveform 35. Also, by performing memory write and read control asynchronously, skew on the screen can be corrected.

FIG. 3 is a diagram showing an example of the screen of a television receiver when the present invention is used. 40 is a double-sided screen during normal playback, 4
1 is a screen during fast-forward playback, and 42 is a screen during rewind playback. During fast-forward playback, the lack of information is compensated for at the pedestal level, so in this example, a black screen 4 is displayed at the top and bottom of the screen.
3.44 is displayed, but the screen is stable. During rewind playback, some information is discarded, so in this example, the information at the top and bottom disappears, leaving the screen stretched vertically.

In this embodiment, the vertical reference for writing is created from the synchronization signal, but a head switch signal of the rotating head cylinder may also be used. Also, the level of the missing data during fast-forward playback was converted to the pedestal level, but any video level may be used. However, the horizontal and vertical blanking periods must be at the pedestal level /l/. Also,
In this embodiment, the NTSC system has been described, but other broadcasting systems can also be supported. Regarding color signal processing,
This is omitted because similar processing can be performed if color demodulation is performed to a color difference signal or the like. However, with the same configuration as the synchronization signal replacement,
It would be better to have a configuration where the burst signal can also be changed.

As described above, by using field memory to perform write control according to the tape running speed and read control at regular intervals, and by providing a level conversion circuit and a synchronization signal switching circuit, it is stable in any tape direction and speed. You can get a screen like this.

Effects of the Invention As described above, according to the present invention, it is possible to obtain a stable screen even when the tape is run at ultra-high speed, and it is possible to immediately check the contents of the program recorded on the videotape or to It is possible to obtain excellent effects such as being able to quickly search the screen.

[Brief explanation of drawings]

Fig. 1 is a flow diagram of an embodiment of the present invention, Fig. 2 is a waveform diagram of a video signal during fast forward playback and rewind playback, and Fig. 3 is a screen diagram of a television receiver when the present invention is used. , 4th
The figure is a plan view schematically showing the arrangement of the magnetic heads on the rotary head cylinder, and FIG. 6 is a pattern diagram showing the locus of the reproducing head during fast-forward reproduction and rewind reproduction. 9...Synchronization signal separation circuit, 1o...A
D converter, 11... Memory, 12...
Level conversion circuit, 13...DA converter, 14.
...Write address generation circuit, 15...
- Read address generation circuit, 16... Synchronization signal replacement circuit, 17... Tape running control circuit, 18... Rotating head cylinder control circuit. Name of agent: Patent attorney Shigetaka Awano and 1 other person false 3
figure

Claims (1)

[Claims] A magnetic recording and reproducing device that records and reproduces video signals on a magnetic tape using a magnetic head installed in a rotating head cylinder, and includes a tape running control circuit that controls the running direction and speed of the magnetic tape, and a tape running control circuit that controls the running direction and speed of the magnetic tape, and the ability to play back video signals at any tape speed. a rotary head cylinder control circuit that controls the relative speed between the rotary head cylinder and the magnetic tape so that the horizontal scanning frequency of the video signal is approximately at a standard value; and a rotary head cylinder control circuit that is capable of storing at least one field of reproduced video signals and that performs a writing operation. and a memory that can perform read operations asynchronously and independently;
a write address generation circuit that generates a write address to the memory from horizontal and vertical reference signals of the reproduced video signal based on a specific range of the reproduced video signal determined by tape running speed information from the tape running control circuit and a write start address; a read address generation circuit that reads one field of data from the memory at a frequency that is approximately close to the nominal value of the vertical scanning frequency; The present invention includes a level conversion circuit that converts a specific range into a certain video signal level, and a synchronization signal replacement circuit that generates a synchronization signal based on a read address and replaces the synchronization signal with the output data of the level conversion circuit. Features of magnetic recording and reproducing device.