Facsimile and static presentation processing – Facsimile – Recording apparatus
Patent
1986-10-08
1989-02-28
McElheny, Jr., Donald
Facsimile and static presentation processing
Facsimile
Recording apparatus
H04N 989
Patent
active
048090840
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention can be used for recording/reproducing apparatus such as a VTR and for video signal transmitting apparatus, and is effective for obtaining satisfactory high frequency characteristic of the luminance signal and chrominance signal characteristic.
BACKGROUND ART
Most VTRs used for broadcasting are of 1-inch tape width or 2-inch tape width, and video signal recording system is such that a composite video signal is frequency modulated without any change. In recording/reproducing process, time base variation occurs due to the irregularity in the head rotation, the irregularity in tape travel or the like. This variation is corrected by a time base corrector (TBC) during reproduction by using horizontal sync signal or burst signal in the reproduced video signal. However, since the chrominance signal according to this system is subjected to quadrature modulation in NTSC system by subcarrier of 3.58 MHz to be superimposed upon luminance signal, when frequency modulated, it departs from its modulation carrier, and thus reduction of noise, which is a feature of FM, is not sufficient. Furthermore, chrominance subcarrier suffers from phase variation as much as residual jitter of TBC, and this becomes phase noise and thus the convergence of color vectors is insufficient.
As described in Japanese patent application No. 59-163155, there is a method for improving S/N of amplitude and phase direction of chrominance signal so as to improve the convergence in view of the above. According to this method two components of chrominance signal are also frequency modulated before recording, and time base correction is effected on playback before it is modulated (encoded) by a reference subcarrier to be added to luminance signal to form a composite video signal. According to this method since the chrominance signal (component signal) is also FM recorded at base band, reproduction is effected with good S/N. In addition, since encoding is effected with the reference subcarrier, there occurs no phase noise and thus it is possible to obtain satisfactory reproduced chrominance signal.
A conventional example of this system will be described with reference to FIG. 1. In FIG. 1, the references 1, 2 and 3 are input terminals for luminance signal Y, R-Y signal and B-Y signal; the reference 25, a sync signal generator; the reference 5, time base compressor; the references 4 and 6, frequency modulators; the references 7 and 8, heads, the references 9 and 10, frequency demodulator; the references 11 and 12, TBCs; the reference 14, reference signal input terminal; the reference 15, a sync generator; the reference 16, an encoder; the references 18, 19, 20 and 21, output terminals for Y signal, R-Y signal, B-Y signal and a composite video signal. The Y signal fed to the terminal 1 is modulated by the frequency modulator 4 to be recorded on a tape via the head 7. On the other hand, two chrominance signal components R-Y signal and B-Y signal fed to the terminals 2 and 3 are compressed by the time base compressor 5 in unit of 1 line so that time base becomes one half with a sync signal produced by the sync signal generator 25 using horizontal sync signal included in the Y signal being added to the R-Y signal. As a result, these signals are formed into a single signal such as R-Y.multidot.B-Y.multidot.R-Y.multidot.B-Y . . . (R-Y indicates R-Y signal compressed to 1/2 line) to be modulated by the frequency modulator 6 so as to be recorded on a tape via the head 8. Luminance signal and chrominance signal are recorded on a tape with different tracks being formed by the heads 7 and 8. Y signal reproduced by the head 7 on playback is demodulated by the frequency demodulator 9 and the time base thereof is corrected by the TBC 11. Chrominance signal reproduced by the head 8 is demodulated by the frequency demodulator 10, and the time base thereof is corrected by the TBC 12 and is expanded to its original length. The TBCs 11 and 12 writes a signal into a memory using a write clock generated using horizontal sync signal included
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Morimoto Takeshi
Sekimoto Kunio
Matsushita Electric - Industrial Co., Ltd.
McElheny Jr. Donald
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