JPS5816395B2 - Seishigasingouki Rokusaiseisouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a still image memory device that records and reproduces one field or one frame of color video signals using a magnetic disk memory or the like.

In recent years, there has been an active development of still image recording and reproducing devices using magnetic disk memories, magnetic sheet memories, storage tubes, and the like.

Along with this, transmission formats dedicated to still images are being considered based on such memory devices.

The signal formats discussed here are just one example.
The outline is that a still image signal is divided and transmitted during the vertical retrace period of a conventional television signal (such as an NTSC signal), and the receiving side extracts only the necessary signals and records them in the aforementioned image memory in an orderly manner. The purpose of this method is to obtain a still image signal for one field over one frame.

The present invention is an improvement on the problems that occur when recording and reproducing such signals.

The signal format of television signal multiplexed still image broadcasting will be described below as an example of the signal format to which the present invention is applied.

As an example of television signal multiplexed still picture broadcasting (hereinafter abbreviated as SPB broadcasting), the Image Transmission Study Group of the Television Society announced a "multiplexed still picture broadcasting system" on October 19, 1973.

This method divides the still image video signal into one or several scanning lines and inserts it into the vertical blanking period (hereinafter abbreviated as VBL) of the conventional standard television signal format. It transmits data without causing any interference.

A receiver that receives SPB broadcasting is equipped with a video recording device, extracts the required SPB broadcast signal from the transmitted signal, records it sequentially for each one or several scanning lines, and then records it as a still image. Once recording is complete, the still images are continuously played back on the CRT.

The above is an outline of SPB broadcasting. FIG. 1a is a waveform diagram showing an example of time-division multiplexing of a still picture signal (hereinafter abbreviated as SPB signal) to a television video signal.

In FIG. 1a, the first horizontal scanning period (hereinafter, the horizontal scanning period is abbreviated as H) of the television video signal.

) to 20th H and 264th to 284th VB
This is a case where the SPB signal is multiplexed in the 3H sections of the 14th to 16th H and the 277th to 279th H within the L period.

Here, one program is multiplexed from the 14th to the 16th H, and the second
It is devised to multiplex another program from 77H to 279H.

This is to maintain phase continuity of color subcarriers during SPH broadcast reception, as will be described later.

FIG. 1 shows a waveform diagram when SPB broadcasting is received and reproduced, that is, an SPB signal.

FIG. 2 is a diagram showing the recording order of SPB signals on a magnetic disk recorder used as a video recording device of a receiver.

The magnetic disk recorder shown in FIG. 2 rotates at a speed capable of recording 261H scanning lines in one revolution.

In general, standard television signals advance video frames at a rate of 60 fields per second, or 30 frames per second.One frame is expressed in terms of the number of scanning lines, and one field is 262.5 lines per second. There are 525 frames.

Therefore, the magnetic disk recorder shown in FIG.
Standard television signals are also 1.5 in 1 field.
In H, 1 frame, it rotates faster for 3H period.

On a magnetic disk recorder that rotates like this, there is a
The 14th to 16th H of the signal are extracted, and the 1st to 3rd H of the SPB signal are recorded at the positions shown in FIG. 2A, as already shown in FIG.

Subsequently, when the 14th to 16th signals of the next frame arrive, that is, when the time of 525H has elapsed, the second
The magnetic disk recorder in the figure has reached 261H twice and 3H, that is, the position shown in Figure 2.

Therefore, the 4th to 6th H in FIG. 1 are recorded at the positions shown in FIG. 2.

In this way, on the magnetic disk recorder shown in FIG.
Recording is performed sequentially every 3H, and a video signal is recorded such that 261H constitutes one field.

Therefore, 26LH is placed on the magnetic disk recorder in Fig. 2.
To record one field of video signal, 261H÷3
= 87 times or 87 frames of standard television signal (87
frame), it takes 29 seconds.

Also, recording intermittently every frame rather than every field means that the color subcarrier is not transmitted in order to maintain compatibility with standard television signals, as shown in Figure 1a. This is because the phase of the signal is reversed, making it difficult to maintain continuity on the receiver side.

Although the 14th H to 16th H signals of the odd field have been described above, the same applies to the even field 277H to 279H signals.

Now, when recording such SPB signals on a magnetic disk recorder, the common method is to perform FM modulation on the video signal and record it, but when using a small magnetic disk recorder, the recording band is narrow, so the performance is not sufficient. I can't keep good records.

Therefore, the luminance signal and chromaticity signal are separated in advance, and the luminance signal is subjected to FM modulation.

The chromaticity signal is obtained by converting a color subcarrier into a low frequency, superimposing a pilot signal, which serves as a reference for correcting uneven rotation from a motor that rotates a magnetic disk, and subjecting it to FM modulation.

Then, the FM-modulated luminance signal and chromaticity signal are recorded on separate recording tracks.

In this case, since the SPB signal is recorded with a width of 3H for each frame, the pilot signal will have a phase discontinuity every 3H unless the frequency is selected appropriately, and when extracting the pilot signal on the playback side, the phase will change. This causes steps, which appear as color unevenness in the reproduced video signal.

An object of the present invention is to determine a frequency that does not cause a phase step even if 3H is recorded every other frame when determining the frequency of the pilot signal, and to prevent color unevenness from occurring in the reproduced video signal. be.

The present invention will be specifically described below with reference to Examples.

FIG. 3 shows an SPB signal recording and reproducing apparatus to which the present invention is applied.

SPB signal low frequency F wave generator 101 extracted by 3H gate IQ
The signal is separated into a luminance signal and a chromaticity signal by a band p-wave converter 103.

The luminance signal is modulated by the FM modulator 102 and then recorded on the magnetic disk recorder 110.

On the other hand, the chromaticity signal is once converted to a lower frequency by a low frequency converter 104.

This 9 o'clock low conversion carrier is generated by a low frequency conversion carrier generator 108 based on the color subcarrier reproduced by the burst control oscillator 101.

At the same time, a pilot signal generator 109 generates a pilot signal based on the color subcarrier, and an adder 105 superimposes it on the low frequency converted chromaticity signal.

Figure 4 shows the frequency spectrum at this time.

E is a chromaticity signal modulated with a chrominance subcarrier, h is a chromaticity signal subjected to low frequency conversion, and g is a pilot signal.

In FIG. 3C, this superimposed signal is modulated by the iFM modulator 106 and recorded on a recording track different from the luminance signal of the magnetic disk recorder 110.

One of the reasons for low-frequency conversion of the chromaticity signal is that lowering the frequency of the modulation signal of FM modulation is advantageous in terms of recording bandwidth, and another major reason is that once low-frequency conversion is performed, When the signal is regenerated and converted back to its original frequency,
This is to cancel out the phase jitter of the chromaticity signal that is caused by uneven rotation caused by the magnetic disk rotation motor of the magnetic disk recorder 110.

After FM demodulating the chromaticity signal with the FM demodulator 114 shown in FIG. Generates a signal for conversion, high frequency converter 115
A chromaticity signal having the same color subcarrier as the input signal can be obtained by high-frequency converting the reproduced chromaticity signal and passing it through the band p-wave unit 116.

Here, since the phase jitter experienced by the reproduced chromaticity signal is equal to the phase jitter experienced by the reproduced pilot signal, the phase jitter can be canceled out through the process of high frequency conversion.

Furthermore, the reproduced luminance signal is reproduced by an FM demodulator 111 and a low-frequency wave transducer 112, and an adder 113 adds the luminance signal and chromaticity signal to obtain a reproduced color video signal.

Now, the video signal of the SPB signal is recorded every 3H in one frame period, but if we pay attention to the pilot signal superimposed for phase jitter correction at this time, the pilot signal on the recording side is as shown in Figure 5a. It is a continuous signal and there is no phase step.

However, if this pilot signal is recorded for 3H periods every other frame, a phase step will occur every 3H as shown in FIG. 5 unless the frequency of the pilot signal has a certain condition.

By extracting this signal through a resonant circuit on the reproducing side, the phase step is removed as in step C, but instead the waveform becomes different from that of the original pilot signal.

If a carrier wave for high-frequency conversion on the reproduction side is created using a pilot signal having a waveform different from the original waveform in this way, the reproduced video signal will become uneven in color, and a correct chromaticity signal cannot be reproduced.

Therefore, in order to prevent the phase step from occurring in the above-mentioned recorded pilot signal, the pilot signal is
When extracting every H period, the extracted pilot signal needs to be continuous.

In other words, at the end of the extraction of the pilot signal for the 3H period,
The period of the pilot signal must be completed until the next 3H period.

Generally, the period for inserting the SPB signal is m times the horizontal period (
mH), and the period of the inserted SPB signal is n times the horizontal period (
Letting the period of the nHL pilot signal be TL, TL must be a divisor of (m-n)H.

(However, H is the horizontal period.

) If the period of the pilot signal is selected as described above, it is possible to record the pilot signal without a phase step, and it is possible to reproduce the correct chromaticity signal.

According to the present invention, when another video information is transmitted during the vertical retrace period of a conventional television signal, and this information is extracted by a receiver and recorded on a magnetic disk recorder, etc., the recording method is a luminance signal, a chromaticity signal, etc. In order to separate the signals and remove the phase jitter that is applied to the chromaticity signal by the motor that rotates the magnetic disk, it is possible to eliminate the phase step that occurs when recording the pilot signal when a new pilot signal superimposition method is adopted. This makes it possible to reproduce a chromaticity signal with the correct hue.

[Brief explanation of drawings]

FIG. 1 is a signal waveform diagram of a video signal to which the present invention can be applied;
Figure 2 is a pattern diagram in which only the desired signal is extracted from a signal in which another video information signal is newly inserted for several horizontal periods into the vertical retrace period of a conventional television signal and recorded on a magnetic disk recorder. The figure is a circuit diagram showing an embodiment of the video signal recording and reproducing device according to the present invention, FIG. 4 is a diagram showing the frequency spectrum of the chromaticity signal in each part, and FIG. 5 is a diagram showing the frequency spectrum of the pilot signal superimposed on the chromaticity signal in each part. FIG. 3 is a waveform diagram showing waveforms. 101...Low-range offshore wave chart, 102...FM modulator, 1
03...Band F wave device, 104...Low frequency converter, 10
5... Adder, 106... FM modulator, 101...
- Burst control oscillator, 108... Carrier wave generator for low frequency conversion, 109... Pilot signal generator, 110.
...Magnetic disk recorder, 111...FM demodulator,
112... Toshiro Tobaki, '113... Adder, 114
...FM demodulator, 115...High frequency converter, 116.
・・band p-wave unit, 117 ・・pilot signal extractor,
118...Carrier generator for high frequency conversion, 119...3
H gate.

Claims (1)

[Claims] 1. A color video signal consisting of a superposition of a luminance signal and an adjusted chromaticity signal is intermittently inserted with a signal of an integral number n times the horizontal period at a constant period (an integral number m times the horizontal period). In an apparatus for recording and reproducing a signal that is selectively inserted, means for extracting the inserted signal, means for separating a luminance signal and a modulated chrominance signal, and a carrier wave for the separated modulated chrominance signal. means for converting the chromaticity signal to a much lower frequency, a means for superimposing a signal of a constant period on the chromaticity signal, a means for recording the luminance signal, the low-frequency converted chromaticity signal, and the signal number of the constant period in a continuous manner. It has a means for reproducing a signal of one field or one frame, and has a period TL of a signal of a constant period.
A still picture signal recording and reproducing device characterized in that is not an integer fraction of the horizontal period TH, but is an integer fraction of a period (m−n) times the horizontal period TH.