JPS6238917B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording method for color video information and a method for reproducing the same.

Various methods have been proposed for recording and reproducing color video information on recording media such as disk records or magnetic tapes, but the color signal processing methods that are in practical use can be roughly divided into color subcarriers. A method of recording and reproducing by modulating the density and hue of the color signal to the amplitude and phase of the color signal (commercial VTR
(or RCA video disk) and a method (TED video disk) in which color signals are recorded and played back line-by-line. Of the former, the RCA method ``embeds'' a subcarrier (modulated with a chrominance signal) in the middle of the luminance band in an interleaved relationship with respect to the line frequency, so both the luminance and chrominance signals are Although it is possible to obtain the desired resolution, as in the case of commercial VTRs, the subcarrier carries the phase component of the color signal as described above, so the influence of phase fluctuations of the recording/reproducing device (hue However, in order to eliminate this problem, it is necessary to remove the time axis fluctuation of the recording/reproducing system or to install a compensation circuit for this time axis fluctuation. On the other hand, in the TED method, the low frequency component of the luminance signal was synthesized based on line-sequential color signals, so the vertical resolution of this low frequency component was not sufficient.

Taking this point into consideration, the present invention provides a novel color video signal recording system that does not impair the resolution of the luminance signal, has a good S/N ratio of the color signal, and is not affected by color unevenness caused by time axis fluctuations. The aim is to provide a system and a method for reproducing the same.

That is, the present invention converts color signals constituting color video information into line-sequential lines, and uses the line-sequential color signals to generate frequencies that are interposed between adjacent signals that are multiples of the line frequency ( _H ). (For example, 195/2 _H ≒ 1.534 ^MHz (NTSC system)) subcarrier is subjected to carrier suppression AM modulation, and this AM-modulated line-sequential color signal is used as the brightness signal within the band of the brightness signal constituting the color video information. We provide a recording method for color video signals in which the composite signal is FM-modulated and recorded as a recording signal, and this recording signal is
FM demodulation is performed to reproduce the brightness signal and the AM-modulated line-sequential color signal synthesized within the band of the brightness signal, and the AM-modulated line-sequential color signal is converted into a multiple of the line frequency ( _H ). A comb filter is applied to a comb filter that exhibits a passing characteristic at a frequency interposed between adjacent ones (for example, 195/2 _H ) and at frequencies spaced apart by an integer multiple of the line frequency, and the output of the filter is Synchronize and detect to create a simultaneous color signal, modulate a color subcarrier with a color difference signal created based on this simultaneous color signal, and synthesize the brightness signal with this modulated color subcarrier to create a composite video signal. The present invention aims to provide a method for reproducing color video signals in which the color video signal is obtained.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the recording method of the present invention. 1 is a video source such as a video camera telecine, from which a brightness (Y) signal and a simultaneous color signal are derived. The brightness signal is applied to a low pass filter 2 having a cutoff frequency of about 3 MHz to remove high frequencies. On the other hand, the simultaneous color signals are supplied to a sequential switch 3 which is driven in synchronization with the line period. The line-sequential color signal output from this switch is band-limited by a low-pass filter 4 having a cutoff frequency of 500 KHz, and then applied to an AM modulator 5. This AM modulator 5 performs carrier suppression AM modulation on the subcarrier from the oscillator 6 using the line-adapted color signal. Here, the exact frequency of this subcarrier ( _C ) is the line frequency ( _H ) in the video signal.
, offset by a fraction of the line frequency (preferably an odd multiple of half the line frequency, e.g.
_C = 1/2×195× _H ≒1534091Hz) is selected.
As described above, the brightness signal with the high frequency component removed and the
The line-sequential color signal output from the AM modulator 5 is added to the adding circuit 7 and applied to the FM modulator 8. This FM modulator is designed to have a synchronization tip at approximately 4 MHz and a white peak at approximately 6 MHz, and its output (recording signal) is recorded on a medium 9, such as a disk or tape. In addition, Karu FM
Looking at the frequency spectrum of the video signal before modulation, as shown in Figure 2, the brightness signal extends from the field frequency (approximately 60Hz) to 3MHz, but it does not necessarily occupy the band continuously. Rather, the energy is concentrated near integer multiples of the line frequency, and the energy becomes more discrete as it goes to higher frequency regions. Energy becomes diluted (see solid line in Figure 2). That is, it is in the vicinity of an odd multiple of half the line frequency, and the above-mentioned subcarrier frequency _C is one such frequency. On the other hand, a signal obtained by carrier suppression AM modulation of a subcarrier using a line sequential color signal also has energy at every integer multiple of the line frequency based on the subcarrier frequency _C , that is, as shown by the dotted line in FIG. Therefore, even if these are combined, they will not interfere with each other as long as the separation means are appropriate. In order to facilitate this separation, before adding both signals, it is preferable to pass them through a so-called C-type or Y-type comb filter, each having a band of _C ±500KHz. in this case,
The upper and lower portions of the occupied band contain only a luminance signal, and the middle portion contains a luminance signal and a line-sequential color signal.

FIG. 3 is a block diagram of one embodiment of the reproduction system of the present invention. After the recorded signal extracted from the recording medium is subjected to well-known preprocessing (not shown), it is provided to the FM demodulator 10, and a composite video signal is derived as its output. This composite video signal passes through a video amplifier 11 and is supplied to a bandpass filter 12 whose passband is _C ±500KHz, and its output is
We derive the line-sequential color signal near 1.53MHz and the luminance signal sandwiched between them. This filter output and the oscillation output from the oscillator 13 whose oscillation frequency ₀ is 5.11 MHz are input to the mixing circuit 14, and among its outputs, the difference frequency between the two inputs (i.e., ₁ =
3.58±0.5MHz) component is separated by a low-pass filter 15. The frequency-shifted signal is then input to a so-called C-comb filter 16 (providing the desired comb filter characteristic for the color signal, with zeros repeated at every even multiple of half the line frequency) and its output. A line-sequential color signal is derived from which the luminance signal component that causes cross color is removed. Then, one of the outputs is input to a mixing circuit 17 together with the oscillation output of the oscillator 13. The signal centered at 1.53MHz, which is the difference component between the two input signals, is almost the same as the color signal component included in the output from the FM demodulator 10, so when the difference between them is taken by the circuit 18, the output is Only the luminance signal component can be derived. This luminance signal is supplied to an adder circuit 19.

The other output of the filter 16 is provided to two 1H glass delay lines 20 and 21 connected in series. Then, the non-delayed, 1H delayed, and 2H delayed signals are transferred to the simultaneous switches 22 and 23 as shown in the figure.
24 (so-called triple switch).
This switch is separated from the video signal by the synchronization separation circuit 25.
By controlling the output of the switch control circuit 26 which is driven by the horizontal synchronizing signal separated by , it is possible to derive a simultaneous color signal as the output of each switch. Each simultaneous color signal is provided to detection circuits 27, 28, and 29, respectively, where it is detected to obtain a video signal. Each signal is provided to the matrix 30, where color difference signals (R-Y) and (B-Y) are created.
The 3.58MHz oscillator 3 uses the color difference signal that is its output.
The output from 1, ie, the subcarrier, is modulated in modulator 32. The modulated output is combined with the luminance signal in the adder circuit 19, and a composite video signal (NTSC) can be derived as the output of the adder circuit.

According to the recording and reproducing method of the present invention as described above,
The subcarrier ( _C = 1.53MHz) in the recording medium contains color information only in its amplitude component,
The S/N ratio is better than when color information is included in both amplitude and phase, such as in RCA video discs and commercial VTRs. In addition, in the latter method, jitter, which is unavoidable especially in home video equipment, appears on the screen as color unevenness, that is, color noise, but in the present invention, such color noise does not occur. Therefore, it is not necessary to add an APC circuit or an AFC circuit to the reproduction circuit to reduce this color noise. The disadvantage of the method of the present invention is that since the color signals are sequential, deterioration of the vertical resolution is unavoidable, but since color signals originally have more resolution in the vertical direction than in the horizontal direction, Even if there is a slight decrease in
Even if it is reduced to 1/3, the effect is hardly noticeable. Furthermore, unlike the TED method, the vertical resolution of the low frequency component of the luminance signal does not deteriorate.

[Brief explanation of the drawing]

Figure 1 is a configuration block diagram of one embodiment of the recording method of the present invention, and Figure 2 shows the recording signal before FM modulation or
FIG. 3, a drawing showing a frequency spectrum after FM demodulation, is a block diagram of an embodiment of the reproduction method of the present invention. 3...Sequential switch, 5...AM modulator, 6
... Oscillator, 8 ... FM modulator, 10 ... FM demodulator, 16 ... C-type comb filter, 20, 21
...1H delay line, 22, 23, 24... Simultaneous switch, 26... Switch control circuit, 27, 2
8, 29...detection circuit, 30...matrix, 3
2...Modulator.

Claims (1)

[Scope of Claims] 1. A line-sequential color signal obtained by line-sequentializing color signals constituting color video information is obtained by AM modulating it with a subcarrier having a frequency near an odd multiple of 1/2 of the line frequency ( _H ). A method for reproducing color video information in which a line-sequentially modulated color signal is combined with the brightness signal within the band of the brightness signal constituting the color video information, and the combined signal is FM-modulated and recorded on a recording medium. FM demodulating the signal extracted from the recording medium into the composite signal, inputting the composite signal to a comb filter that allows only the line sequentially modulated color signal to pass, and converting the output of the comb filter into the composite signal. At the same time, the comb filter outputs are synchronized and detected to create a simultaneous signal, and the color subcarrier is quadrature modulated with the color difference signal created based on the simultaneous color signal, and then added to the subtracted output. A color video information reproduction method that obtains a composite video signal.