JP2697108B2 - Magnetic recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stable fast-forward reproduction / reproduction using an image memory.
Video tape recorder that enables rewind playback
VTR) and the like.

2. Description of the Related Art In a VTR, there are fast-forward playback and rewind playback as modes for checking what is recorded on a magnetic tape (hereinafter referred to as a tape) while looking at a screen.

Hereinafter, fast forward reproduction / rewind reproduction in a conventional magnetic recording / reproducing apparatus will be described with reference to the drawings.

FIG. 4 is a plan view schematically showing the arrangement of the magnetic heads on the rotary head cylinder. R and L are a pair of magnetic heads for a long time recording mode, and R 'and L' are standard recordings. This is a magnetic head pair for mode. The magnetic heads R and R 'and L and L' have the same azimuth angle, and the magnetic heads R and L 'are mounted near each other to form a head pair A. Also constitute a head pair B at a position close to it. FIG. 5 (a) is a diagram showing the trajectory of the reproducing head at the time of fast-forward reproduction, and FIG. 5 (b) is a diagram showing the trajectory of the reproducing head at the time of rewind reproduction. The head pairs A and B alternately scan over them. During fast-forward playback and rewind playback, each head pair A and B crosses a track written in R azimuth and a track written in L azimuth several times in one scan according to the speed of the tape. Since the head pairs A and B have a head of L azimuth and a head of R azimuth, respectively, the level of the reproduction output of the two heads is determined, and the reproduction head is selected in real time. It is configured to be able to output reverse playback video.

As can be seen from FIG. 5, the trajectory of the reproducing head during fast forward reproduction and rewind reproduction is different from that during normal reproduction.
If the rotating head cylinder is rotated at the same number of revolutions as during normal reproduction, the frequency of the horizontal synchronizing signal increases and decreases, and horizontal synchronization of the television receiver cannot be obtained, and the screen horizontally flows.
For this reason, the rotation speed of the rotary head cylinder is controlled according to each tape speed so that the frequency of the horizontal synchronizing signal is substantially equal to the standard value, thereby providing a stable screen.

However, in the above-described conventional configuration, 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 increases. There is a problem that fast-forward reproduction and rewind reproduction can be performed only at a speed within a range in which the receiver can be vertically synchronized.

For example, in the NTSC standard VTR standard mode, the number of horizontal synchronizing signals in one field period during fast-forward playback is 262.5+ (1-n) × 1.5 when the speed is n times faster, and the number decreases as the speed increases. . At the time of rewind reproduction, the number increases as the speed increases. In fast forward playback at 30 × speed in the standard mode, the number of horizontal synchronization signals in one field period is 219
This is a book, and the period of the vertical synchronizing signal is 17% smaller than the standard value, and the screen may flow depending on the television receiver.

Also, as the tape running speed increases, the number of tracks that the head pairs A and B cross in one scan increases, and the skew distortion on the screen increases, resulting in an unsightly screen.

In view of the above problems, the present invention uses a field memory in which a write operation and a read operation can be performed asynchronously so that the period of a vertical synchronization signal of an output video signal is almost a standard value at any tape running speed. It is another object of the present invention to provide a magnetic recording / reproducing apparatus capable of obtaining a stable screen in ultra-fast fast-forward reproduction and rewind reproduction by performing skew correction.

Means for Solving the Problems In order to solve the above problems, a magnetic recording / reproducing apparatus of the present invention is a magnetic recording / reproducing apparatus which records and reproduces a video signal on a magnetic tape by a magnetic head provided on a rotary head cylinder. And a tape running control circuit for controlling the running direction and speed of the magnetic tape, and controlling the relative speed between the rotary head cylinder and the magnetic tape so that the horizontal scanning frequency of the reproduced video signal becomes almost a standard value at any tape speed. A rotary head cylinder control circuit, a memory capable of accumulating at least one field of reproduced video signals, and capable of asynchronously and independently performing a write operation and a read operation, and a reproduction determined by tape traveling speed information from a tape traveling control circuit; Based on the specific range of the video signal and the horizontal and vertical reference signals of the reproduced video signal based on the write start address A write address generation circuit for generating a write address to the memory; a read address generation circuit for reading data of one field from the memory at a frequency substantially close to the vertical scanning frequency standard; and a tape running speed from a tape running control circuit Among the data read from the memory according to the information, a level conversion circuit for setting a specific range to a certain video signal level, and a synchronization signal generated based on a read address, and replaced with the output data of the level conversion circuit And a synchronous signal switching circuit.

Operation The present invention has the above-described configuration, and enables the horizontal and vertical reproduction of video signals at the time of fast-forward playback and rewind playback at any tape running speed.
The vertical synchronizing signal and the image signal become stable, and it becomes possible to view a screen at an ultra-high tape speed on a television receiver.

Embodiment Hereinafter, a magnetic recording and reproducing apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, 1 is a tape, 2 is a cassette, 3
Is a rotary head cylinder, 4 is a capstan, 5 is a pinch roller, 6 and 7 are magnetic heads, 8 is a video signal reproducing circuit for processing reproduced output signals of the magnetic heads 6 and 7, and 9 is a synchronizing signal from the reproduced video signal. Synchronization signal separation circuit for separation, 10 AD converter for analog-to-digital conversion of reproduced video signal, 11 for 1
Memory for storing digital video signals for the field, 12
Is a level conversion circuit for converting a specific portion of the video signal read from the memory 11 to a certain level, 13 is a DA converter for digital-to-analog conversion of the video signal, 14 is a write address for generating a write address of the memory 11 Generator circuit, 15
Is a read address generation circuit for generating a read address of the memory 11, 16 is a synchronizing signal switching circuit for switching a synchronizing signal among output video signals of the DA converter 13, and 17 is a tape running for controlling the rotation speed of the capstan 4. Control circuit, 18
Is a rotary head cylinder control circuit for controlling the rotation of the rotary head cylinder 3.

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

FIG. 2 is a diagram showing waveforms of video signals at the time of fast-forward playback and rewind playback, where 30, 31, and 32 are waveforms at the time of fast-forward playback, 30 is the waveform of the playback video signal, and 31 is written in the memory 11. The range 32 indicates the waveform of the output video signal. 33,34,35
Represents a waveform at the time of rewind reproduction, 33 represents a waveform of a reproduced video signal, 34 represents a range to be written in the memory 11, and 35 represents a waveform of an output video signal.

First, a description will be given of the fast forward playback. The rotary head cylinder control circuit 18 controls the tape 1 and the magnetic head according to the information of the tape running direction and speed from the tape running control circuit 17.
As described above, the relative speed of 6, 7 is corrected so that the period of the horizontal synchronization signal of the reproduced video signal is almost the same as the standard value. Becomes smaller and becomes a 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 / speed information from the tape running control circuit 17, and generates a waveform 31.
Occurs internally. The range of the waveform 31 is the video data actually written to 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. This operation will be described with reference to FIG. 2. The information of a, b, c,..., X, y, z of the waveform 30 is written in the position of a, b, c,. This is the operation. The read operation is performed in the memory 11
The read address generation circuit 15 generates an address so that the period for reading out the data of one field substantially coincides with the period of the vertical synchronizing signal, and the level conversion circuit 12 calculates a.b from the read address in accordance with the tape running information.・ C ……
The horizontal blanking period is detected outside the range of x, y, and z, and the data is converted to a pedestal level. After that, the signal is converted into an analog signal by the DA converter 13, and the synchronization signal switching circuit 16 switches the horizontal and vertical synchronization signals based on the read address. That is, during fast-forward playback, the number of horizontal scans in one field period is reduced, so that all video information is written to memory, and the missing parts are made up of pedestal levels and synchronization signals, resulting in the waveform shown in waveform 32. The correction is made so that the scanning cycle is approximately 1/60 second.

The same control is performed at the time of rewind reproduction, but in this case, since the number of horizontal scanning lines increases, the video information before and after a to z of the waveform 33 is discarded to form a signal of the waveform 35. The skew on the screen is corrected by asynchronously controlling the writing and reading of the memory.

FIG. 3 is a diagram showing an example of a screen of a television receiver when the present invention is used.
Denotes a screen at the time of fast forward reproduction, and 42 denotes a screen at the time of rewind reproduction. At the time of fast forward playback, the lack of information is compensated by the pedestal level, so in this example, black screens 43, 4
4 appears, but the screen is stable. At the time of rewind reproduction, a part of the information is discarded, and in this example, the information in the upper and lower portions is lost, and the screen is extended vertically.

In this embodiment, the reference in the vertical direction of writing is made from the synchronization signal. However, a head switch signal of the rotary head cylinder may be used. In addition, the insufficient data at the time of fast-forward playback is level-converted to a pedestal level, but any video level may be used. However, the horizontal and vertical blanking periods need to be at the pedestal level. In the present embodiment, the NTSC system has been described, but other broadcasting systems can be supported. The color signal processing is omitted because the same processing can be performed if the color demodulation is performed on a color difference signal or the like. However, it is better to adopt a configuration similar to that of the replacement of the synchronization signal, and to replace the burst signal.

As described above, the writing control according to the tape running speed and the reading control at a constant interval are performed using the field memory, and the level conversion circuit and the synchronizing signal switching circuit are provided, so that the tape can be stabilized in any tape direction and speed. Screen can be obtained.

Effect of the Invention As described above, according to the present invention, a stable screen can be obtained even when the tape is run at an extremely high speed, and the contents of the program recorded on the video tape can be immediately confirmed or desired. An excellent effect such as quick search of the screen can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of one 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 view of a television receiver when the present invention is used. , Fourth
FIG. 5 is a plan view schematically showing the arrangement of the magnetic heads on the rotary head cylinder, and FIG. 5 is a pattern diagram showing the locus of the reproducing head during fast-forward reproduction and rewind reproduction. 9: Synchronous signal separation circuit, 10: AD converter, 11: Memory, 12: Level conversion circuit, 13: DA converter, 14: Write address generation circuit, 15: Read address generation circuit, 16: Synchronous signal switching circuit, 17: Tape running control circuit, 18: Rotating head cylinder control circuit

Claims (1)

(57) [Claims] 1. A magnetic recording / reproducing apparatus for recording and reproducing video signals on a magnetic tape by a magnetic head provided on a rotary head cylinder, comprising: a tape running control circuit for controlling a running direction and speed of the magnetic tape; A rotary head cylinder control circuit for controlling the relative speed between the rotary head cylinder and the magnetic tape so that the horizontal scanning frequency of the reproduced video signal is substantially equal to the standard value even at the tape speed; and storing the reproduced video signal for at least one field. A write operation and a read operation can be performed asynchronously and independently; a specific range of the reproduced video signal determined by the tape traveling speed information from the tape traveling control circuit; .Write address generation for generating a write address to the memory from a vertical reference signal A read-out address generating circuit for reading data for one field from the memory at a frequency substantially close to the standard ground of the vertical scanning frequency; A level conversion circuit that sets a specific range to a certain video signal level, and a synchronization signal switching circuit that generates a synchronization signal based on a read address and switches the synchronization signal to output data of the level conversion circuit. Characteristic magnetic recording / reproducing device.