JPH0339437B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Field of Use The present invention relates to a carrier color signal transmission system, and particularly relates to a carrier color signal transmission method.
This invention relates to a transmission method for transmitting a carrier color signal with a wider band than the transmission band in a band-limited carrier color signal transmission system such as a VTR.

Conventional technology and its problems Video signal recording and reproducing devices, especially home VCRs, have been developed for broadcasting due to demands for lower prices and smaller size.
Compared to a VTR, the mechanical and electrical systems are simpler, so the relative linear velocity between the tape and the head is slower, and the transmission band is sufficient to record and play back the entire color video signal by frequency modulating it. In addition, there are large fluctuations in the time axis. For this reason, current home use
Most VTRs separate the standard color video signal into a luminance signal and a carrier color signal, and use the luminance signal to frequency modulate (FM) the low frequency carrier wave, as shown in Figure 5.
A frequency-modulated luminance signal with a frequency spectrum as shown in Figure 5 is used, and the carrier color signal is frequency-converted to a lower frequency range to make it less susceptible to reproduction time axis fluctuations. These two signals are frequency-division multiplexed and recorded on a magnetic tape as a low-frequency conversion carrier color signal, and during playback, signal processing operations that are reverse to those during recording are performed to obtain a reproduced color video signal. It is well known that this method is adopted.

However, in order to prevent interference between the luminance signal and the carrier color signal, this method cannot widen the band of the carrier color signal sufficiently; for example, the band of the baseband is only about 300kHz, so This caused deterioration in image quality such as color bleeding.

Therefore, in the present invention, a signal obtained by sampling the carrier color signal alternately every horizontal scanning period (1H) is sent to the transmission system, and the receiving side (reproducing side) extracts the sampling information alternately over 2H or more. An object of the present invention is to provide a carrier color signal transmission method that solves the above problems.

Means for Solving the Problem The carrier color signal transmission method described in claim 1 samples a carrier color signal having a band of f _sc ±f _c (where f _sc is the color subcarrier frequency). and sends it out to the transmission path. Here, the above sampling is a period that satisfies the following inequalities: 1/(N・f _c )<τ ₁ <1/f _c 1/f _sc ≦τ ₂ <τ ₁ (N is an integer greater than or equal to 2) This is performed by gate-outputting the carrier color signal for a period of τ ₂ every τ ₁ , and sampling is performed such that the sampling points of N adjacent lines are shifted from each other by τ ₁ /N in the horizontal scanning direction. It will be done.

Further, in the carrier color signal transmission method described in claim 4, the sampled carrier color signal is supplied via a transmission path, and both of the current line and both before, after, or before and after the current line are provided. A total of N lines of sampled carrier color signals consisting of lines are sequentially and cyclically switched and output every period τ ₁ /N, and the time division multiplexed signal obtained thereby is outputted as the carrier color signal of the current line. .

Effect The present invention according to claim 1 gates out the carrier color signal only during the period τ ₂ of each cycle τ ₁ and sends it out to the transmission path as the sampled carrier color signal, so f _sc ±(1/2) f _s (however, f _s = 1/
Even a transmission line that can only transmit signals in a band of approximately τ ₁ ) can transmit a carrier color signal in a band of f _sc ±f _c . Furthermore, if the amplitude and phase of the sampled carrier color signal are a continuous wave that is approximately constant from period τ ₂ to immediately before the next period τ ₂ , then the same continuous wave as the carrier color signal to be reproduced by the existing reproduction device is assumed. Become.

Further, the present invention according to claim 4 relates to a transmission system (recording system) and a reception system (reproduction system) of a transmission system, and the sampled carrier color signal of N transmitted lines is calculated by τ ₁ /N. By sequentially and cyclically switching and outputting each time, the sampling frequency of the obtained carrier color signal becomes substantially N times the sampling frequency in the transmission system (recording system). Embodiments of the present invention will be described below with reference to the drawings.

Embodiment FIG. 1 shows a block system diagram of an embodiment of the method of the present invention. First, to explain the operation during recording, for example, an NTSC color video signal input to terminal 1 is supplied to Y/C separation circuit 2, while
The signal is supplied to the synchronous separation circuit 4 through the switch circuit 3 connected to the terminal R side. A phase locked loop (PLL) 5 is supplied with the horizontal synchronization signal taken out from the synchronization separation circuit 4, and generates and outputs, for example, a symmetrical square wave having a sampling frequency fs that is phase-locked to the horizontal synchronization signal. Note that the above sampling frequency f _s is a frequency that satisfies the inequality f _c < f _s < 2f _c , and as an example, 38.5f _H (=
605.769kHz; _fH is the horizontal scanning frequency). The output square wave of the PLL 5 is supplied to a duty ratio adjustment circuit 6 using a monostable multivibrator or the like, where it is converted into a pulse train with a repetition frequency f _s where the high-level pulse width is τ ₂ . This pulse width τ ₂ is selected to be shorter than the sampling period τ ₁ (=1/f _s ) and longer than 1/f _sc which is one cycle of the color subcarrier of the carrier color signal.

On the other hand, the carrier color signal in the band f _sc ±f _c (where f _sc is the color subcarrier frequency) separated from the input NTSC color video signal by the Y/C separation circuit 2 is supplied to the switch circuit 7 . The switch circuit 7 has a pulse width τ ₂ and a period τ ₁ from the duty ratio adjustment circuit 6.
A pulse train of is applied as a switching pulse (sampling pulse), and the input carrier color signal is gated out and supplied to the bandpass filter 8 only during a period of pulse width τ ₂ . Therefore, if the pulse width τ ₂ is, for example, one period of the color subcarrier, the output signals of the switch circuit 7 will be as shown in FIG. 2A on each of the lines k-2, k-1, k and k+1. . As can be seen from FIG. 2A, the output signal of the switch circuit 7 is a sampled carrier color signal obtained by sampling the input carrier color signal for each period of τ ₂ with a period of τ ₁ (=1/f _s ). For the two lines, the sampling frequency fs is selected to be the frequency 38.5f _H which is an odd multiple of f _H /2 as described above, so the sampling points are shifted from each other by τ ₁ /2 in the horizontal scanning direction.

The sampled carrier color signal taken out from the switch circuit 7 is a burst wave as shown in FIG. 2A, and this signal is passed through a band filter 8 having frequency characteristics as shown in FIG. converted into waves. As shown in FIG. 3, the bandpass filter 8 has a color subcarrier frequency f _sc (here, 3.58MHz).
The frequency characteristics have been selected so that the frequency components in the band f _sc ±f _s are centered on . In this way, the reason why the sampled carrier color signal is a continuous wave is that a magnetic tape recorded using the recording system of the present invention can be used with an existing magnetic tape that does not have the reproduction system of the present invention.
This is to make it possible to add colors that have a certain degree of practicality even when played back on a VTR.

The recording signal processing circuit 9 is a circuit that performs signal processing according to the existing VTR recording method, and frequency-modulates the carrier wave with the luminance signal extracted by the Y/C separation circuit 2 to obtain a frequency-modulated luminance signal. After frequency-converting the sampled carrier color signal from the bandpass filter 8 to a low frequency band, both signals are frequency-division multiplexed. This frequency division multiplexed signal is supplied to a recording rotary head 11 through a recording amplifier 10.
As a result, a video track is formed and recorded on the running magnetic tape 12a.

Note that instead of using the band filter 8, a memory circuit is used, and the carrier color signal of the period τ ₂ shown in FIG. 2A is written into this memory circuit until the carrier color signal of the next period τ ₂ comes in. During the interval (τ ₁ −τ ₂ ), reading may be performed so that the amplitude is the same as that of the written carrier color signal and the phase is continuous. This method is convenient for digitizing and processing carrier color signals.

Next, the reproduction system will be described. During reproduction, the switch circuit 3 is connected to selectively output the input signal of the terminal P. Signals are recorded on the magnetic tape 12b in the same manner as the signals recorded on the magnetic tape 12a, and the frequency division multiplexed signal is reproduced by the reproducing rotary head 13. This reproduced frequency division multiplexed signal is supplied to the reproduced signal processing circuit 15 via the preamplifier 14, where the existing
Similar to the reproduction system of a VTR, the low frequency converted carrier color signal is returned to the reproduced carrier color signal of the original band, and the frequency modulated luminance signal is FM demodulated to become the reproduced luminance signal. The reproduced carrier color signal is connected to terminal 1 of the switch circuit 16.
6a directly, while the 1H delay circuit 17
and the switch circuit 1 through the phase inversion circuit 18.
It is supplied to the terminal 16a of No. 6. Here, the reason why the phase inversion circuit 18 is used is to set such a phase relationship since the phase of the color subcarrier is inverted every line in the carrier color signal of the NTSC system.

On the other hand, the reproduced luminance signal passes through the switch circuit 3 and the synchronization separation circuit 4, and after the reproduced horizontal synchronization signal is extracted, it is supplied to the PLL 5, where the period τ ₁ is set as described above.
(=1/f _s ) symmetric square wave. The switch circuit 16 is controlled to switch every half cycle τ ₁ /2 of the output square wave of the PLL 5. Therefore, the line k-1 which is 1H (one line) before the current reproduction line k is connected to the terminal 16b of the switch circuit 16.
When a reproduced carrier color signal as schematically shown in FIG. 2C is received, and a reproduced carrier color signal of line k schematically shown in FIG. 2C is input to the terminal 16a, the switch circuit As schematically shown in FIG. 2D, the output reproduced carrier color signal of No. 16 alternates between the sampled carrier color signal of line (k-1) and the sampled carrier color signal of line k every period τ ₁ /2. The time-division multiplexed signal of the current line k is synthesized in time series.

As can be seen from FIG. 2C and D, the output reproduction carrier color signal of this switch circuit 16 is a carrier color signal because the sampling information of two adjacent lines (k-1) and k are close to each other. It is substantially equivalent to a sampled carrier color signal obtained by sampling the signal at a sampling frequency of _2fs . Therefore,
In this case, the Nyquist frequency f _N is f _s /2 (=
302.8845 kHz), but even through a transmission system with a band of about f _sc ±f _N , a band close to f _sc ±2f _N can be substantially obtained, making it possible to widen the band of the reproduced carrier color signal.

The reproduced carrier color signal output from the switch circuit 16 is filtered by a bandpass filter 19 to remove switching noise in the switch circuit 16 (attenuated at a frequency of f _sc ±2f _N to such an extent that this noise does not become a problem), and then mixed. The signal is supplied to a circuit 20, where it is mixed with a reproduced luminance signal, and then outputted to an output terminal 21 as a reproduced color video signal.

Note that even if the sampling frequency fs is not selected to be an odd multiple of f _H /2, the sampling points can be shifted from each other by 1/2 f _s every 1H.
For example, if the sampling frequency f _s is an integral multiple of f _H , the phase of the sampling pulse may be shifted by 180° every 1H.

The above is an example in which the integer N is "2", but next, a case in which N is "3" will be explained with reference to FIG. 4. In this case, the carrier color signal is gated out for a period of τ ₂ every period τ ₁ to obtain a sampled carrier color signal, and the sampling point is set on three adjacent lines k as shown in FIG. 4A. -1,
Sampling is performed at k and k+1 so as to be shifted from each other by τ ₁ /3 in the horizontal scanning direction, and the samples are sent to the transmission path. In the reception system (reproduction system), among the sampled carrier color signals, a total of three lines of sampled carrier color signals, for example, the current line k, the previous line k-1, and the subsequent line k+1, are processed for a period of τ ₁ By sequentially and cyclically switching output every /3, a time division multiplexed signal as schematically shown in FIG. 4B is extracted as a carrier color signal of the current line. The two-time division multiplexed signal effectively has a sampling frequency of 3f _c
is equivalent to the carrier color signal sampled at
Horizontal resolution can be significantly improved.

It should be noted that the present invention is not limited to the above embodiments, but also includes various other modifications. For example, in consideration of line correlation, the value of the integer N is preferably 2 or 3, but in principle it may be 4 or more. The present invention can also be applied to. In addition, the waveform continuation circuit using the band filter 8 and the memory circuit is
When considering only reproduction on a VTR according to the method of the present invention, it may be omitted, and the burst wave as shown in FIG. 2A may be recorded as is. In this case, the reproduced carrier color signal must be a continuous wave, but
The bandpass filter installed in the reproduction system is f _sc ±2f _s (N
= 2) and was sufficiently attenuated (e.g. -40dB)
This can be solved by selecting characteristics.

Furthermore, if the sampling gate time τ ₂ is set to τ ₁ /N, the waveform caused by switching in the reproduction system will be continuous, so the reproduction system only needs a bandpass filter that removes switching noise. Since it is not necessary to obtain , the attenuation amount at f _sc ±2f _s can be used even if it is smaller than in the above case, and the influence of band limitation and deterioration of phase characteristics due to the band filter can be reduced.

Effects of the Invention As described above, according to the present invention, the carrier color signal in the band f _sc ±f _c is distributed such that the sampling points on N adjacent lines are shifted from each other by τ ₁ /N in the horizontal scanning direction. sample, and select the sampling period τ ₁ to be larger than 1/(N・f _c ) and smaller than 1/f _c , and satisfy the inequality 1/f _sc ≦τ ₂ <τ _1. Since the sampled carrier color signal is transmitted by gate outputting for a satisfying period τ ₂ , f _sc
It can pass through a narrowband transmission system that allows signals in the ±(f _s /N) band to pass through, and since the sampled carrier color signal is a continuous wave, it can be used with existing VTRs.
It is possible to add colors with a certain degree of practicality using a reproduction device such as . In addition, since the sampled carrier color signals of N adjacent lines are cyclically switched and output every τ ₁ /N, it is effectively the carrier color signal sampled at a frequency N times the sampling frequency f _s . An equivalent carrier color signal can be obtained, so even if a narrowband transmission system with a band of f _sc ±(f _s /N) is used, a carrier color signal with a wider band than this can be obtained. In particular, since the reproduced carrier color signal can be made wider than the recording band in home VTRs, good image quality with reduced color blurring and blurring can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block system diagram showing an embodiment of the method of the present invention, FIGS. 2 and 4 are diagrams schematically showing examples of a sampled signal and a reproduced carrier color signal, respectively, of the method of the present invention. This figure is a diagram showing an example of the frequency characteristic of the bandpass filter of the recording system in the block system shown in FIG. 1, and FIG. 5 is a diagram showing an example of the frequency spectrum of the recording signal. DESCRIPTION OF SYMBOLS 1... Color video signal input terminal, 2... Y/C separation circuit, 3, 7, 16... Switch circuit, 4... Synchronization separation circuit, 5... Phase locked loop (PLL), 6... Duty ratio adjustment circuit, 8 ...bandwidth filter, 12a, 12b...magnetic tape, 17...
1H delay circuit, 18...phase inversion circuit.

Claims (1)

[Claims] 1. A carrier color signal having a band of f _sc ±f _c (where f _sc is the color subcarrier frequency) is supplied, and 1/(N·f _c )<τ ₁ <1/f _c Sampling is performed by gate-outputting the carrier color signal only during a period τ ₂ for each period τ ₁ that satisfies the following inequality: 1/f _sc ≦τ ₂ <τ ₁ (N is an integer of 2 or more). , and sampling is performed such that the sampling points in N adjacent lines are shifted from each other by τ ₁ /N in the horizontal scanning direction, and the sampled carrier color signal obtained thereby is transmitted. Transmission method of carrier color signal. 2. A patent having means for converting the sampled carrier color signal into a continuous wave in which the sampled carrier color signal is supplied and the amplitude and phase of the sampled carrier color signal during the period τ ₂ are substantially constant until just before the next period τ ₂ Claim 1
Transmission method of the carrier color signal described in Section 1. 3. The carrier color signal transmission system according to claim 1, wherein the period τ ₂ is selected to be τ ₁ /N. 4 A carrier color signal with a band of f _sc ±f _c (where f _sc is the color subcarrier frequency) is supplied, and 1/(N・f _c )<τ ₁ <1/f _c 1/f _sc ≦τ ₂ < τ ₁ (N is an integer of 2 or more) Sampling is performed by gate-outputting the carrier color signal only during a period τ ₂ for each period τ ₁ that satisfies the following inequality, and Sampling is performed such that the sampling points in the N lines are shifted from each other by τ ₁ /N in the horizontal scanning direction, and the sampled carrier color signal obtained thereby is transmitted, and the transmitted sampled carrier color signal is A total of N lines of the sampled carrier color signals, which are the current line and lines before, after, or before and after the current line, are sequentially and cyclically switched and outputted every period τ ₁ /N, thereby obtaining the obtained signal. A carrier color signal transmission method characterized in that a time-division multiplexed signal is output as a carrier color signal of a current line. 5. A patent having means for converting the sampled carrier color signal into a continuous wave in which the sampled carrier color signal is supplied and the amplitude and phase of the sampled carrier color signal during the period τ ₂ are substantially constant until immediately before the next period τ ₂ Claim No. 4
Transmission method of the carrier color signal described in Section 1. 6. The carrier color signal transmission system according to claim 4, wherein the period τ ₂ is selected to be τ ₁ /N.