JPH0584711B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a helical scan VTR, and particularly to a VTR suitable for recording and reproducing broadband images.

[Background of the invention]

In recent years, with the development of broadcasting satellites, plans are being made to broadcast higher-band television signals. In order to record and play back such broadcasts at home, a wider band image recording capability is required than that of conventional home VTRs. In order to record and play back broadband signals in a helical scan VTR, it is necessary to increase the relative speed of the head tape, and to achieve this with the same cylinder diameter, currently
A system in which the cylinder rotates at the field period, such as the VTRC format for broadcasting, is more advantageous than the two-head helical scan system used in VTRs, in which the cylinder rotation period and frame period match. However, in order to achieve this with a small diameter cylinder such as a home VTR, it is difficult to load the tape around the cylinder, so it is not possible to set a large tape wrapping angle to the cylinder, and it is difficult to keep the effect of skew on the screen within an acceptable range. Have difficulty. To solve this problem, the recorded video signal can be time-compressed, and one field of the video signal can be compressed during the period when the main head is scanning the tape in a 1.5-head system VTR. However, in this case, the problem is how to record the audio signal accompanying the video signal with high quality.

One solution to this problem is to increase the time compression rate of the video signal and record the audio signal, which has also been time-axis compressed, on the extension of the video signal recording track.
It becomes possible to record and reproduce video signals and high-quality audio signals by reducing the number of magnetic heads required. However, increasing the compression ratio of the video signal too much increases the increase in recording frequency, which in turn leads to a decrease in recording density and deterioration in image quality. In the case of a VTR that takes both NTSC and PAL systems into consideration, it is desirable that an integral multiple of the horizontal scanning line period after time compression correspond to the rotation period of the cylinder. Therefore, due to this restriction, it is desirable to compress the time to about 5/6.
Then, the tape wrapping angle around the cylinder is at least 300°C.
It becomes necessary. In the case of a small-diameter cylinder, the maximum tape wrapping angle around the cylinder is about 330°, so the wrapping angle assigned to the audio signal is just under 30°. If the video signal band is 3MHz, the audio signal band is approximately
It becomes 300KHz. This results in insufficient bandwidth to record high-fidelity PCM audio signals.

[Purpose of the invention]

An object of the present invention is to provide a compact VTR that records and plays back wideband signals, particularly a VTR that can record and playback wideband video signals and high-quality audio signals at the same time, and that is capable of dubbing high-quality audio signals. There is a particular thing.

[Summary of the invention]

The present invention records and reproduces a video signal by time-compressing it using a head, and uses a separate audio signal recording head to record an audio signal compressed at a time-base compression ratio different from that of the video signal. It is characterized by being regenerated.

[Embodiments of the invention]

An embodiment of the present invention will be described based on FIGS. 1 to 6. Figures 1a and b are schematic diagrams of the cylinder section of the present invention, Figure 2 is a diagram showing its head arrangement, Figure 3 is a diagram showing its tape pattern, and Figure 4 is a diagram showing recording signals to the head. 5 is a block diagram of the recording circuit of this embodiment, and FIG. 6 is a block diagram of the reproducing circuit. In FIG. 1, a magnetic tape 1 (hereinafter simply referred to as tape) is guided by tape guides 3 and 4 and is spirally wound around a cylinder 2 at a winding angle θ. The cylinder 2 is composed of a fixed lower cylinder 2b and a rotating upper cylinder 2a. Two double azimuth rotating magnetic heads 5 and 6 (hereinafter simply referred to as double azimuth heads) are fixed to the upper cylinder 2a, and the heads scan by rotation of the upper cylinder. Arrow A in Figure 1 is the running direction of the tape, and arrow B is the upper cylinder 2.
The direction of rotation of a is shown. In this example, the wrapping angle θ is
A value of just over 300° is selected. Double azimuth head 5
is a head exclusively for recording and reproducing audio signals, and the double azimuth head 6 is a head exclusively for recording and reproducing video signals. The double azimuth head 5 is composed of a +azimuth head portion 5a and a −azimuth head portion 5b. The double azimuth head 6 is similarly composed of a +azimuth head portion 6a and a −azimuth head portion 6b. The head track widths of each head portion are equal in this embodiment. As shown in FIG. 2, the heads 5 and 6 are arranged at a predetermined distance in the rotation axis direction (height direction) and circumferential direction. FIG. 2 shows an enlarged view of this part. The head portions 5a and 5b are approximately the same height, and the head portions 6a and 6b are approximately the same height.
are also placed at approximately the same height. The difference in height between heads 5 and 6 must be kept at a constant value in order to obtain a tape pattern to be described later. However, the circumferential spacing of heads 5 and 6 can be chosen freely. Although shown close together in the figure, the heads can be spaced apart, for example 180 degrees apart in the circumferential direction.

FIG. 3 shows the track pattern recorded on the tape. FIG. 3 shows only the tracks recorded during two revolutions of the upper cylinder 2a. That is, the first cylinder's one-turn head 5a records the track 7a, and the head 6a records the track 8a.
The continued single rotation head 5b is the track 7b.
The head 6b records the track 8b. Tracks 7a and 7b record time-compressed audio signals, and tracks 8a and 8b record time-compressed video signals. Each of these tracks is recorded in what is called azimuth overwriting without the card band portion.
A timing chart for these recordings is shown in FIG. Portions 9a, 9b, and 9c of the input video signal 9 are time-base compressed, respectively, and become 9'a, 9'b, and 9'c.
This is the recorded video signal that is output at the timing of . The rotation of the cylinder is controlled so that these periods are within the period during which the head 6 is scanning the tape. Portions 9'a, 9'b, 9'c are recorded alternately on heads 6a and 6b. The same applies to the audio signal, and the portions 10a, 10a of the input audio signal 10,
10b, 10c are compressed in time axis and become 10'a, 1
This becomes a recording audio signal output at timings 0'b and 10'c. The output timing of 10'a, 10'b, and 10'c is 7 in Fig. 3 as the head 5 is different.
The timing is selected so that the parts shown in a and 7b are being scanned, and the heads 5a and 5b are alternately scanned.
recorded. Since heads 5a and 5b or heads 6a and 6b are slightly apart in the circumferential direction, if tracks 8a and 8b and tracks 7a and 7b are output at the same timing with respect to cylinder rotation, the recorded track 8a and 8b, 7a and 7b are slightly shifted in position in the scanning direction. If there is a margin in the wrapping angle of the tape, it is also possible to record with the tape off. If it is necessary to eliminate this shift or to take a so-called H arrangement in the video signal, the output timing of the compressed signal should be changed to 9'a, 9'b, 9'c or 10'a, 10'. 'b,1
Just set it at 0'c and shift it a little every other position.

In this example, the time compression ratio of the audio signal can be within a considerable range (up to 5/6 at the extreme). However, if compression is not performed too much, the increase in bandwidth will be small, but the lengths of tracks 7a and 7b will become longer, and tracks 8a and 8b will become relatively shorter, so there is an optimum point in the system.

Next, the recording circuit will be explained based on the block diagram of FIG. A video signal inputted from an input terminal 11 is synchronously separated by a horizontal sync separation circuit 12, and a clock generated by a clock generation circuit 13 is generated in synchronization with the horizontal sync. The input video signal is sampled by the A/D converter 14 using sampling pulses from the clock generating circuit 13 and converted into a digital signal. The output of the A/D converter 14 is time compressed in the digital signal domain by a time compression circuit 15. This time compression is carried out at the timing shown in FIG. 4 using the output of the cylinder rotation tack signal generator 25 and the time compression pulse of the clock generation circuit 13 as input. The output of the time compression circuit 15 becomes an analog signal time-compressed by the A/D converter 16, which is then passed through the frequency modulation circuit 17, the recording amplifier 18, and the switches 43 and 44 to the heads 6a and 6.
recorded on tape at b. Switches 43 and 44 are switches that are turned ON and OFF alternately every rotation.

The audio signal input to the input terminal 19 is sampled by the A/D converter 20 using the sampling pulse output from the clock generation circuit 13 and converted into a digital signal. After an error correction bit is added to this signal in an error correction bit addition circuit 21, a time compression circuit 22 outputs the output of the tack signal generator 25 and the clock pulse generation circuit 1.
The time compression pulse from 3 performs time compression as shown in FIG. The output of the time compression circuit 22 passes through a modulation circuit 23, a recording amplifier 24, switches 45 and 46, and is recorded on tape by heads 5a and 5b. Switches 45 and 46 are switches that are turned ON and OFF alternately every rotation.

Next, the reproduction circuit will be described with reference to FIG. During playback, the playback output from heads 6a and 6b is amplified by head amplifiers 26 and 27, and switch 2
After being alternately switched by 8, the demodulation circuit 29
It is demodulated by The demodulated signal is a time-compressed video signal. A synchronization signal is separated from this signal by a horizontal synchronization separation circuit 30, and a clock generation circuit 31 which receives this signal as input generates a clock synchronized with the reproduced horizontal synchronization. Using this clock, the time-compressed video signal is sampled by the A/D converter 32 to become a digital signal, and then time-expanded by the time expansion circuit 33.
After being converted into a digital video signal of the original time length,
The signal is returned to an analog signal by the D/A converter 34 and supplied to the video signal output terminal 50.

The reproduced audio signals from the heads 5a and 5b are amplified by head amplifiers 35 and 36, and then switched alternately by a switch 37, and a demodulation circuit 38 demodulates the time-compressed digital audio signal. The output of the demodulation circuit 38 is expanded to the original time length by a time expansion circuit 40, error corrected by an error correction circuit 41, and then converted back to an analog signal by a D/A converter 42, and then sent to an audio signal output terminal 60. is supplied to

In the embodiments described above, the time compression and expansion of the video signal was performed in the digital signal domain.
Of course, this may be done by using an analog memory such as a CCD and using the analog signal as it is without converting it to a digital signal. Furthermore, although the horizontal synchronization signal is used as a time base reference, a dedicated pilot signal may be recorded instead. In addition, a head amplifier was provided for each head in the reproduction circuit, but head 6
Since there is no period when a and 6b and 5a and 5b are reproducing signals at the same time, it is also possible to use a common head amplifier, one for each, and two in total. At this time, there is no need for rapid signal switching, so if necessary, the reproduction head can be switched using a switch. It is also possible to perform this switching within the upper cylinder,
By doing so, it is also possible to reduce the number of channels of the rotary transformer. Of course, if a sufficient S/N ratio can be obtained, it is possible to connect playback heads in series and obtain playback signals of 5a, 5b or 6a, 6b from the same channel, halving the number of channels of the rotary transformer. .

Furthermore, when used as a camera-integrated VTR, time compression of the video signal as shown in FIG. 4 can be performed by controlling the signal output of the video camera using cylinder rotation synchronization pulses using well-known technology. It's obvious.

Furthermore, in the embodiments so far, only audio signals have been considered as the signals to be recorded by the double azimuth head 5, but it is not possible to add digital data accompanying television signals, such as text signals for mass text broadcasting, to this. It is clear that this can be easily done based on the explanations given above.

In the examples so far, we have not specifically described the tape running control method, but this may be a method using conventional control signals, or a method in which a tracking pilot signal is overwritten and recorded on an audio signal or a video signal using a frequency multiplexing method. This may be used to control tape running during playback. Alternatively, a tracking pilot recording area may be provided on the extension of track 7 or 8 in FIG. 3, and the tape running may be controlled by the pilot signal reproduced from this area.

〔Effect of the invention〕

According to the present invention, a time-compressed video signal;
In order to record and play back time-compressed audio signals using a separate double azimuth head, the time compression ratio of the audio signal can be selected over a wide range without increasing the time compression of the video signal. Recording and playback of audio signals becomes possible. In addition, since audio and video are recorded and played back using separate heads, head 5, which is the audio head, and head 6, which is the video head, have different head track width, head gap, and other specifications, and the head that is suitable for each is used. This makes it possible to perform a rational design, and to obtain a VTR capable of recording and reproducing wideband video signals and wideband audio signals.

In addition, in this system, since the audio is recorded and played back in a separate head, dubbing is extremely easy and so-called overwriting and erasing is also possible.Furthermore, the fixed erasing head has a cap corresponding to the tracks 7a and 7b in the width direction. It is also possible to erase with an erase head.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an outline of the cylinder section of an embodiment of the present invention, FIG. 2 is a diagram showing the head arrangement, FIG. 3 is a diagram showing the tape pattern recorded on the tape, and FIG. 5 is a diagram showing the timing of the recording signal, FIG. 5 is a block diagram of the recording circuit, and FIG. 6 is a diagram showing the timing of the recording signal.
The figure is a block diagram of the reproducing circuit. 1... Magnetic tape, 2... Cylinder, 5, 6...
...Double azimuth circuit magnetic head, 7, 8... Track, 15, 22... Time compression circuit, 33, 4
0...Time expansion circuit.

Claims (1)

[Scope of Claims] 1. A video signal time-base compression circuit that compresses the time-base of a recorded video signal; a video signal recording amplifier that amplifies the output signal of the video signal time-base compression circuit; and a rotation reference signal to compress the video signal. a first switch that alternately turns on and off the output signal of the signal recording amplifier; a double azimuth rotary head for video signals to which the output signal of the first switch is alternately input; and a time axis compressor for the recorded audio signal. an audio signal time base compression circuit; an audio signal recording amplifier that amplifies the output signal of the audio signal time base compression circuit; and an audio signal recording amplifier that alternately turns on and off the output signal of the audio signal recording amplifier using the rotation reference signal. The second switch is arranged such that its height in the direction of the rotation axis is different from the double azimuth rotation head for the video signal.
A double azimuth rotary head for the video signal and a double azimuth rotary head for the audio signal whose specifications are different from each other to which the output signals of the switch are input alternately, and a track recorded on the tape by the double azimuth rotary head for the video signal. A magnetic recording/reproducing apparatus characterized in that the track recorded by the double azimuth rotary head for audio signals is formed at a different position in the tape width direction.