JPH0562873B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a video signal recording and reproducing device, and more particularly to a device that records and reproduces a video signal by frequency multiplexing a first signal containing temporally continuous first information and a video signal. Regarding.

<Description of Prior Art> As this type of video signal recording and reproducing apparatus, there is a video table recorder (VTR) of the type that records and reproduces an FM-modulated audio signal by frequency multiplexing it with a video signal. of
This will be explained using a VTR as an example.

In recent years, so-called teletext broadcasting has started. In line with this trend, it will be desirable to be able to record and reproduce text multiplex signals even in the field of home VTRs.
FIGS. 1A and 1B are diagrams showing the spectrum and waveform of a character multiplex signal, respectively. Generally, the bit rate of a text multiplex signal is 5.73 Mb/S, and the spectrum distribution extends to about 4.5 MHz. In FIG. 1B, 1 is a character multiplex signal, 2 is a color burst signal, and the character multiplex signal is inserted on the pedestal within the vertical blanking period.

Figure 2 is a diagram showing the frequency spectrum of a conventional VTR recording signal that is not multiplexed with FM modulated audio signals, where 4 is a low frequency converted chroma signal, 5
respectively show the spectrum of the FM-modulated luminance signal.

Now, the above-mentioned character multiplex signal can be transferred to this type of VTR.
Consider recording using .

However, if this text multiplex signal is treated as a luminance signal and attempted to be recorded using FM modulation, the bandwidth will be insufficient. Conventional general VTRs for this purpose cannot record such character multiplex signals. Therefore, it is possible to widen the occupied band of the FM modulated text multiplex signal during the period when the text multiplex signal is superimposed, and to make the band occupied by the low frequency converted chroma signal also the occupied band of the text multiplex signal. . That is, when handling a text multiplex signal as a luminance signal, it is sufficient to force the VTR into the black and white video signal recording/reproducing mode and record the text multiplex signal with a spectral distribution as shown in FIG. 3.

On the other hand, FIG. 4 is a diagram showing the frequency spectrum of a recording signal in a VTR that records and reproduces multiplexed FM modulated audio signals. In the figure, 4 indicates the spectrum of the low-frequency converted chroma signal, 5 indicates the FM-modulated luminance signal, and 7 indicates the spectrum of the FM-modulated audio signal. However, in this type of VTR, if the character multiplex signal has a wide occupied band as described above, it will also take over the occupied band of the FM modulated audio signal, causing some of the information contained in the audio signal to be lost. This will result in
This is because the audio signal contains temporally continuous information, so this type of VTR
It was not possible to record multiplexed text signals.

In this way, in a device that frequency-multiplexes and records/reproduces a first signal containing temporally continuous first information and a video signal, both the occupied bands of the first signal and the video signal are It has not been possible to record and reproduce a second signal that requires time-sharing with these signals.

<Object of the Invention> The present invention has been made in view of the above-mentioned drawbacks, and it is a first signal that requires both a first signal containing temporally continuous first information and an occupied band of a video signal. It is an object of the present invention to provide a video signal recording and reproducing apparatus capable of recording and reproducing two signals in a time-sharing manner.

<Explanation based on Examples> The present invention will be described below as a type of recording/reproduction in which an FM modulated audio signal is frequency-multiplexed with a video signal.
This will be explained using an example applied to a VTR.

FIG. 5 is a block diagram showing a recording and reproducing circuit of a VTR as an embodiment of the present invention. In the figure, 8 is a luminance signal input terminal, 9 is an audio signal input terminal, 10 is a chroma signal input terminal, 11, 1
1' is a synchronization separation circuit that extracts only the synchronization signal from the luminance signal, 12 and 12' are output counters that detect the multiplexed period of the character multiplexed signal and output a switching signal, and 13 and 13' are counters, respectively. 12, 12' is used to determine whether or not a character multiplex signal is multiplexed, and a switching signal is applied during the multiplexed period; 14 is an FM modulator that performs FM modulation on the luminance signal;
15 is a high pass filter (HPF); 16 is an HPF with a wider pass band than 15, and has a pass band necessary for recording the character multiplex signal;

17 is a switch connected to the output side of the HPF 16 only during the period when the character multiplex signal is multiplexed by the switching signal output from the discrimination circuit 13;
18 is an FM modulator that modulates the audio signal with FM;
19 is an HPF; 20 and 23 are switches that are connected to the ground side only while the character multiplex signal is being multiplexed; 21 is a frequency conversion circuit that converts the chroma signal to a low frequency; 22 is a low-pass filter (LPF); 24 teeth
An adder that frequency-multiplexes the FM-modulated luminance signal with the FM-modulated audio signal, 25 an amplifier that frequency-multiplexes and amplifies the output of the adder 24 and the low-frequency converted chroma signal, and 26 a recording magnet. 27 is a magnetic head for reproduction, 28 is a reproduction preamplifier, 29 is an FM demodulator for demodulating the FM-modulated luminance signal, 30 is an LPF, and 31 is a character multiplexed signal multiplexed by the output of 13'. A memory 32 stores the character multiplex signal demodulated only during the period.
A band pass filter (BPF) separates only the FM modulated audio signal; 33 is an FM demodulation circuit that demodulates the FM modulated audio signal; 34 is an FM demodulation circuit that demodulates the FM modulated audio signal;
LPF 35 is a sample hold (S/H) circuit for holding the previous value of the demodulated audio signal only during the period when the character multiplexed signal is multiplexed;
6 is a switch that is connected to the output side of the S/H circuit 35 only during the period when the character multiplex signal is multiplexed by the output of the discrimination circuit 13'; 37 is an LPF that separates the low frequency converted chroma signal; and 38 is a separator. 39 is a BPF, and 40, 41, 42, and 43 are playback output terminals for the chroma signal, audio signal, luminance signal, and text multiplex signal, respectively.

The operation of each part according to the above-described configuration will be explained below. The counter 12 detects the horizontal scanning period (g) during which the character multiplex signal is predicted to be multiplexed during recording. This is based on the fact that in teletext broadcasting, the teletext signal is multiplexed onto H during predetermined vertical blanking. Further, the determination circuit 13 confirms that the character multiplex signal is actually multiplexed during this period. Therefore, the discrimination circuit 13 generates a switching signal that is at a high level, for example, only during the period when the character multiplex signal is multiplexed.
Accordingly, the switch 17 is connected to the HPF 16 side, and the signals 20 and 23 are connected to the ground side. That is, this widens the recording band of the character multiplex signal treated as a luminance signal (FM modulated). During the other periods, the brightness signal and the audio signal are each FM-modulated as in a conventional VTR, the chroma signal is frequency-converted to a low frequency range, and these multiplexed signals are sent to the magnetic tape 50 via the amplifier 25 and sent to the head 26. recorded in

During reproduction, the signals recorded on the magnetic tape 50 are reproduced by the head 27 and then amplified by the amplifier 28. The FM-modulated luminance signal or character multiplex signal is demodulated by the FM demodulator 29 and then supplied to the LPF 30. The synchronization signal included in the signal output from the LPF 30 is separated by a synchronization separation circuit 11', and character multiplexing is performed in the same manner as during recording using the synchronization signal separated by the separation circuit 11' and the output signal of the LPF 30. Detect the period during which signals are multiplexed. Discrimination circuit 13'
For example, the switch 36 and the memory 31 are supplied with a switching signal that is at a high level during this period.
Along with this, the memory 31 stores the character multiplexed signal obtained from the LPF 30, and the switch 36
It is connected to the H circuit 35 side.

At this time, in the S/H circuit 35, the demodulated audio signal obtained from the LPF 34 is held at its previous value only during the period when the character multiplex signal is being reproduced, and the lack of the audio signal during this period is compensated for. There is. Also, the low frequency converted chroma signal is
The signal is extracted by the LPF 37, frequency-converted by the frequency converter 38, and output after passing through the BPF 39.

The VTR configured as described above can record and reproduce text multiplex signals, and can also record and reproduce FM modulated audio signals satisfactorily.

In the above embodiment, as a method of compensating for the lack of an audio signal, the level immediately before the missing period is held at the previous value, but if an analog or digital delay circuit is used, for example, the level immediately before and after the missing period can be held as the previous value. It is also possible to perform linear interpolation using Further, by taking a distortion removing means such as passing the audio signal output to the terminal 41 during this period through an LPF with a low cutoff frequency, an even better reproduced audio signal can be obtained.

Furthermore, the present invention is not limited to application to a VTR as in the above-mentioned embodiments, but uses a signal containing temporally continuous information other than an audio signal as the first signal, and uses a wide occupied band other than a text multiplex signal. Of course, the present invention can also be applied to the case where the required signal is the second signal, and the effect is great.

<Description of Effects> As explained above, according to the present invention, the first signal containing temporally continuous first information and the second signal that requires both the occupied band of the video signal can be combined with these. A video signal recording and reproducing device capable of time-division recording and reproducing was obtained.

[Brief explanation of the drawing]

Figures 1A and B are diagrams showing the spectrum and waveform of a character multiplexed signal, Figure 2 is a diagram showing the frequency spectrum of a conventional VTR recording signal that does not multiplex an FM modulated audio signal, and Figure 3 is a diagram showing a character multiplexed signal. Figure 4 shows the recording spectrum of multiplexed signals.
A diagram showing the frequency spectrum of a VTR recording signal,
FIG. 5 is a block diagram showing a recording/reproducing circuit of a VTR as an embodiment of the present invention. 1 is a character multiplex signal, 2 is a color burst signal,
3 is a hedestal level, 4 is a low frequency converted chroma signal spectrum, 5 is an FM modulated luminance signal spectrum, 6 is an FM modulated character multiplex signal spectrum, 7 is an FM modulated audio signal spectrum, 11, 11' is a synchronous separation circuit; 12;
12' is a counter, 13 and 13' are discrimination circuits, 1
7, 20, 23 are switches, 31 is a memory,
35 is a sample hold circuit, and 36 is a switch.

Claims (1)

[Claims] 1. A device for frequency multiplexing and recording/reproducing a first signal containing temporally continuous first information and a video signal, which utilizes a frequency region occupied by both the first signal and the video signal. means for recording and reproducing a second signal containing second information in a time-sharing manner with these, and a means for recording and reproducing a second signal containing second information, and a means for recording and reproducing a second signal including second information, and a means for recording and reproducing a second signal containing second information, and a means for recording and reproducing a second signal containing second information, A video signal recording and reproducing apparatus comprising: means for compensating for the missing portion contained in the reproduced first signal using first information temporally close to the missing portion.