JPH01194688A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To record a video signal due to a single rotation magnetic head by recording a time base compressed video signal at a field unit through a rotation magnetic head in which the ratio of a scanning period occupied at a rotation period is equal to a time base compression ratio. CONSTITUTION:At the time of recording a video signal, a video signal made into a digital signal by an AD converter 14 is written into a picture memory 15 in accordance with the writing clock signal from a writing reading control circuit 21. The video data for two fields are written into the picture memory 15 and old video data are updated as they are written. For example, when the writing of the video data concerning an even number field is executed, the video data of an odd number immediately before the writing is already completed are read at the K-fold speed of a writing speed. The inverse number of a speed ratio K of a reading speed for the writing speed is equivalent to the time base compression ratio of a time base compressing circuit 13 and equal to 1/K which is just the ratio of the tape scanning period occupied at the rotation period of a rotation magnetic head 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic recording and reproducing apparatus that records time-base compressed signals through a single rotating magnetic head.

[Prior Art] A magnetic recording and reproducing apparatus 1 shown in FIG. 3 is a home video tape recorder using a helical scan method, and a magnetic tape 3 that is wound around the outer periphery of a head drum 2 and runs on a head drum 2. A pair of rotating magnetic heads 2a and 2b within the drum 2 record or reproduce signals while performing diagonal scanning.

[Problems to be Solved by the Invention] The conventional magnetic recording/reproducing device l described above requires at least two rotating magnetic heads 2a, 2b, and when assembling the rotating magnetic heads 2a, 2b into the head drum 2, Assembling requires precision and measures to match the recording and reproducing characteristics of the rotating magnetic heads 2a and 2b.In addition to the changeover switch 4 that can be switched between the recording mode and the reproducing mode, there is also a A changeover switch 7 is required to distribute the recorded signals to the rotating magnetic heads 2a and 2b, and vice versa, to supply signals read from the magnetic tape 3 by the rotating magnetic heads 2a and 2b to the signal reproducing circuit 6. I had a problem.

[Means for Solving the Problems] The present invention solves the above problems, and includes a time-base compression circuit that compresses the time-base of a video signal in units of fields;
A rotating magnetic head in which a ratio of a scanning period to a rotation period is equal to a time-base compression ratio of the time-base compression circuit, and records a time-base compressed video signal supplied from the time-base compression circuit on a magnetic tape in synchronization with scanning; It is characterized in that it is configured by providing.

[Operation] The present invention records a video signal that has been time-axis compressed field by field through a rotating magnetic head in which the ratio of the scanning period to the rotation period is equal to the time-axis compression ratio. enables recording of video signals.

[Example] Hereinafter, an example of the present invention will be described with reference to FIG. 1.2. FIG. 1.2 is a schematic circuit diagram showing one embodiment of the magnetic recording/reproducing apparatus of the present invention, and a diagram showing the relationship between recording signals and track patterns, respectively.

A magnetic recording/reproducing apparatus 11 shown in FIG. 1 is capable of recording video signals continuously without interruption using a single rotating magnetic head 12. In the case of the embodiment, the magnetic tape 3 is wound around the outer periphery of the head drum 2 at an angle of 210 degrees or more. In the preceding stage of the signal recording circuit 5, an AD converter 14 is installed as a time axis compression circuit 13.
A cascade circuit of an AD converter 18, an image memory 19, and a DA converter 20 is connected as a time axis expansion circuit 17 at the subsequent stage of the signal reproducing circuit 7. The connection circuit is connected. As the image memory 15 and 19, one capable of recording video signals for two fields is used, and writing and reading of the signals are controlled in accordance with a clock signal sent from the writing/reading control circuit 21. be done.

First, when recording a video signal, the video signal converted into a digital signal by the AD converter 14 is converted into a digital signal according to the write clock signal from the write/read control circuit 21.
Write to image memory I5.

Video data for two fields is written into the image memory I5, and the old video data is updated at the same time as the writing. For example, when video data for an even field is being written, video data for an odd field that has already been written is read out at twice the writing speed. The reciprocal of the speed ratio of the read speed to the write speed is the time axis compression circuit 13
corresponds to the time axis compression ratio of , which is just the rotation magnetic head 12
is equal to 1/K, which is the ratio of the tape scanning period to the rotation period of .

The video data whose time axis has been compressed to 1/K in this way is D
After being converted into an analog video signal by the A converter 16, it is sent to the rotating magnetic head 12 via the signal recording circuit 5 and the changeover switch 4. In this case, the reading of video data from the image memory 15 is performed just by rotating the magnetic head 1.
2 is rotated in contact with the magnetic tape 3, the time-axis compressed video signal is delivered to a predetermined track on the magnetic tape 3 without too much or too little, as shown in FIG. recorded. Therefore, even if recording is interrupted during the period when the rotating magnetic head 12 is separated from the magnetic tape 3, the continuity of the recorded video signal will not be lost.

On the other hand, during reproduction, the time-base compressed recorded video signal is read out from the magnetic tape 3 in synchronization with the rotation of the rotary magnetic head 12. The video signal, in which the luminance signal is FM demodulated and the chrominance signal is frequency-converted, is sent to the time axis expansion circuit 17 in the signal reproducing circuit 6 . In the time axis expansion circuit 17, the signal is first converted into a digital signal by the AD converter 8, and then written into the image memory 19. In this case, the data read speed of the image memory 19 is set to 17 times the write speed, so the time axis compressed video data is expanded to the time axis before recording.
It passes through the DA converter 20 and is reproduced as the original continuous signal.

In this way, the magnetic recording/reproducing device 11 records a video signal whose time axis has been compressed on a field-by-field basis via the rotating magnetic head 12 in which the ratio of the scanning period to the rotation period, 1/K, is equal to the time axis compression ratio. By recording the time-axis compressed video signal on the magnetic tape 3 in accordance with the scanning period of the rotating magnetic head 2, blank recording is achieved until the rotating magnetic head 12 finishes recording and starts the next scanning. The period can be assigned to the blank period of the video signal caused by time-base compression, thereby making it possible to assign the period to the blank period of the video signal caused by time-base compression, thereby making it possible to assign the period to the blank period of the video signal caused by time-base compression, thereby making it possible to assign the period to the blank period of the video signal caused by time-base compression.

2b requires at least two rotating magnetic heads,
To be able to reduce the number to one, which is the minimum number, and at the same time to fundamentally eliminate problems in reproduced image quality caused by differences in recording and reproduction characteristics of the two rotating magnetic heads 2a and 2b, and countermeasures for this problem. Can be done.

In addition, the time axis expansion circuit 17 performs digital signal processing including time axis correction to remove jitter components included in the reproduced video signal, or performs cyclic noise reduction processing to reduce the field correlation of the video signal. It is also possible to perform noise reduction processing using .

[Effects of the Invention] As explained above, the present invention has a configuration in which a video signal whose time axis is compressed in units of fields is recorded via a rotating magnetic head in which the ratio of the scanning period to the rotation period is equal to the time axis compression ratio. Therefore, by recording the time-axis compressed video signal on the magnetic tape in accordance with the scanning period of the rotating magnetic head, the blank recording period until the rotating magnetic head starts the next scan after finishing recording can be compressed on the time axis. It can be allocated to the blank period of the video signal caused by compression, and as a result, the number of rotating magnetic heads that previously required at least two can be reduced to the minimum number of one, and at the same time, two rotating magnetic heads can also be used. It is possible to fundamentally eliminate problems in playback image quality caused by differences in the recording and playback characteristics of the heads, as well as countermeasures for these problems.Furthermore, it is possible to completely eliminate problems with playback image quality caused by differences in the recording and playback characteristics of the heads. In the process, digital signal processing including the use of image memory is performed to remove jitter components contained in the reproduced video signal, or cyclic noise reduction processing is performed to reduce noise using the field correlation of the video signal. It also has excellent effects such as being able to apply

[Brief explanation of the drawing]

Figures 1 and 2 are a schematic circuit diagram showing an embodiment of the magnetic recording/reproducing device of the present invention and a diagram showing the relationship between recording signals and track patterns, respectively, and Figure 3 is an example of a conventional magnetic recording/reproducing device. FIG. 2 is a schematic circuit configuration diagram illustrating. 391. Magnetic tape, 11. ,,magnetic recording and reproducing device, 1
2. ,,rotating magnetic head,13. ,,Time axis compression circuit.

Claims (1)

[Claims] a time-base compression circuit that compresses the time-base of a video signal field by field; and a time-base compression circuit whose ratio of a scanning period to the rotation period is equal to the time-base compression ratio of the time-base compression circuit, and which is supplied from the time-base compression circuit in synchronization with scanning. A magnetic recording/reproducing device comprising a rotating magnetic head for recording a time-base compressed video signal on a magnetic tape.