Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1998-05-29
2001-01-09
Nguyen, Huy (Department: 2715)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000
Reexamination Certificate
active
06173110
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic recording and reproduction apparatus for recording on and reproducing a video signal from a magnetic tape. More particularly, it relates to a magnetic recording and reproduction apparatus having a video signal recording characteristic correction function capable of recording the video signal in an optimal recording state by testing a characteristic of a magnetic tape and adjusting a recording characteristic according to the tested characteristic.
2. Discussion of the Related Art
Since a video signal which is input to a magnetic recording and reproduction apparatus, such as a video tape recorder (VTR), has a frequency band of 30 Hz to 4.2 MHz, it is difficult to directly record the video signal on a magnetic tape. Therefore, the magnetic recording and reproduction apparatus modulates the input video signal to alter the frequency band of the video signal. Modulation methods, such as amplitude modulation (AM), frequency modulation (FM) and phase modulation, have been used to modulate the input video signal.
The magnetic recording and reproduction apparatus mainly uses a method for frequency-modulating the an input video signal's luminance signal that is appropriate to the magnetic recording channel. The input video signal's chroma signal is converted to a low frequency band, and then mixed with the frequency-modulated luminance signal to be recorded on the magnetic tape.
Since the chroma signal is recorded on the tape in a state of being mixed with the luminance signal, it is similar to a BIAS recording in which the chroma signal frequency becomes small and the luminance signal frequency becomes large. When the mixed signal is recorded on and reproduced from the tape, the luminance and chroma signals are recorded together with an interference component involving third-order distortion.
The interference component involving third-order distortion degrades the picture quality of a reproduced image. The interference component is represented as YC
2
SIN(&ohgr;y−2 &ohgr;c)t, in which Y is the magnitude of a luminance carrier signal, C is the magnitude of a chroma carrier signal, &ohgr;y is an angular frequency of the luminance carrier signal and o)c is an angular frequency of the chroma carrier signal, and t is time. The interference component is demodulated along with the luminance signal component, and appears on a screen in the form of dot interference having an angular frequency of 2 &ohgr;c. Such interference is commonly called cross beat.
In the meanwhile, magnetic tapes have large characteristic deviations due to a difference in magnetic force, and are classified into several grades of tape performance based on the characteristic deviations. Also, heads contribute to characteristic deviation by more than approximately 30%, according to the head's structure and magnetic materials.
As described above, magnetic characteristics of the magnetic tape vary even within a specified range for a standard magnetic recording and reproduction apparatus. Accordingly, there is a drawback in that a video signal can not be properly recorded to comply with the characteristic of the tape.
SUMMARY OF THE INVENTION
In order to solve the problem, an object of the present invention is to provide a magnetic recording and reproduction apparatus having a video signal recording characteristic correction function, capable of recording the video signal in an optimal recording state by testing a characteristic of the tape and adjusting a recording characteristic according to the tested characteristic.
To accomplish the above object of the present invention, there is provided a magnetic recording and reproduction apparatus for recording on and reproducing a video signal from a magnetic tape. The magnetic recording and reproduction apparatus comprises:
a luminance test signal generator for generating a frequency-modulated luminance test signal using a predetermined voltage; a chroma test signal generator for generating a chroma test signal having a lower frequency; a recording level adjusting unit for respectively adjusting levels of the frequency-modulated luminance test signal and the chroma test signal based on corresponding a luminance recording level and a chroma recording level; a recording unit for mixing signals level-adjusted by the recording level adjusting unit to record a mixed test signal on the magnetic tape; a readout and preamplifying unit for reading out the mixed test signal from the magnetic tape and preamplifying the read-out signal; a control unit for adjusting the luminance recording level and the chroma recording level in the recording level adjusting unit based on the mixed test signal applied from the readout and preamplifying unit, determining an optimal luminance recording level and an optimal chroma recording level to record a video signal on the magnetic tape, and supplying the determined luminance recording level and chroma recording level to the recording level adjusting unit.
REFERENCES:
patent: 5083211 (1992-01-01), Dugan et al.
patent: 5579119 (1996-11-01), Mimura
patent: 5598273 (1997-01-01), Kurisaki et al.
patent: 0 481 824 (1992-04-01), None
patent: 0 579 198 (1994-01-01), None
Kim Chul-min
Seki Masamitsu
Nguyen Huy
Samsung Electronics Co,. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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