JPH07307958A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve the degradation of picture quality such as color nonuniformity caused by the band extension and time-base fluctuation of a reproduced chrominance signal. CONSTITUTION:Color difference signals in two systems of a composite video signal are successively switched for every horizontal period, the color difference signals are thinned, and vertical information is compressed by a compressing means 40. A signal from this compressing means 40 is A/D converted and afterwards written in a frame memory 233 by a write clock FW. After the signal is read out of the frame memory 233 at higher speed than the write clock FW, it is D/A converted, further frequency-modulated and recorded in a PCM area. Then, compressed recorded information is reproduced from this PCM area, demodulated, A/D converted later and written in the frame memory by a clock PBFW. Then, the information is read out of the frame memory by a clock PBFR, which speed is lower than that of this clock PBFW this time, and the compressed recorded information is extended. Further, the chrominance signal is provided by synchronizing line sequential color difference signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus for recording / reproducing video signals, and more particularly to recording / reproducing video signals.
The present invention relates to a magnetic recording / reproducing method for compressing / expanding video information for reproduction.

[0002]

2. Description of the Related Art A VTR or the like converts a video signal into a magnetic signal and records it on a magnetic tape by using a recording head. The recording head or the reproducing head is mounted on the rotary cylinder, and the video signal is recorded / reproduced by the rotation of the rotary cylinder and the mechanism of the head. The rotation of the rotary cylinder is driven by a motor or the like, and is controlled by a control mechanism such as a servo loop system.

Generally, the VTR has standards such as S-VHS and Betacam. In the 8 mm video system, the high band 8 mm system is standardized based on the conventional 8 mm video standard. A rotating 2-head azimuth method is adopted as the recording method. Also, an ATF is used in which a pilot signal is sequentially multiplexed and recorded on a video track, and tracking is performed so as to balance leakage from adjacent tracks during reproduction. For audio signals, PCM For audio signals, PCM
The area is time-compressed and recorded by the video head.

FIG. 5 shows a conventional high band 8 mm type VTR.
The recording / playback method of is shown. In FIG. 5, a luminance signal (hereinafter referred to as Y signal) separated from the composite video signal is supplied to a luminance signal processing circuit 101, and a color signal (hereinafter referred to as C signal) is a band pass filter (hereinafter referred to as BPF) 102.
Through the frequency conversion circuit 103. The Y signal supplied from the luminance signal processing circuit 101 is FM-modulated by the frequency modulation circuit 104, and superposed by the addition circuit 105 on the C signal converted into the low frequency band by the frequency conversion circuit 103.
This signal is amplified by the recording amplifier 106, supplied to the head 107, electro-magnetically converted, and recorded on the magnetic tape 70.

For reproduction, the recorded information on the magnetic tape 70 is converted into an electric signal by magnetoelectric conversion. This electric signal is amplified by the preamplifier 109 and then the filter 110 at the next stage.
After the high frequency component is removed by, the frequency inverse conversion circuit 111 converts the high frequency component into a reproduction color signal frequency. This signal is further supplied to the comb filter 112, crosstalk from an adjacent track is reduced, and is supplied to the BPF in the next stage to reproduce the C signal.

The filter circuit 110 is also provided with a high-pass filter. The high-pass filter removes low-pass components and supplies it to the luminance signal processing circuit 101 to reproduce the Y signal.

By the way, in the above circuit, there is a problem that the reproduction band (-3 dB) can only be about ± 300 KHz due to the format limitation because the data is recorded on the magnetic tape by the frequency low frequency conversion. Therefore, the reproduction state of the color signal is poor due to the narrow band property of the reproduction band of the color signal, and not only horizontal color bleeding occurs but also color unevenness due to the mechanical system is large, resulting in deterioration of reproduced image quality. It was

[0008]

As described above, there is a problem in that the color bleeding occurs due to the narrow band property of the reproduction signal, and the image quality is deteriorated due to the time variation due to the mechanical system.

Therefore, the present invention has been made in view of such problems.
The purpose is to expand the band of the reproduced color signal and improve the deterioration of the image quality such as the color unevenness due to the time axis fluctuation.

[0010]

According to a first aspect of the present invention, there is provided a magnetic recording / reproducing apparatus in which line-sequential switching is performed and a color difference signal obtained by compressing an amount of information in the vertical direction is digitally converted and then framed at a predetermined writing speed. While writing to the memory, the recorded contents are read from the frame memory at a speed higher than the writing speed, and a time axis compression means for compressing the time axis and a P for audio signal recording in an area adjacent to the video area are provided.
After the signal from the time axis compression means is converted into an analog signal in a PCM area of a recording medium having a CM area, the converted signal is frequency-modulated and recorded, and the recording means records the PCM area in the PCM area. After the reproduction / demodulation means for reproducing and demodulating the color difference signal and the reproduction signal from the reproduction / demodulation means are digitally converted, a frame is formed by using a relationship opposite to the relationship between the writing speed and the reading speed of the time base compression means. After writing to and reading from the memory and expanding the time axis, the time axis expanding means for converting the read signal into an analog signal to obtain a color difference signal, and the signal from the time axis expanding means for a horizontal period. Line-sequential switching for each line, and a color signal reproducing means for obtaining a color signal after synchronizing a signal one horizontal cycle before and a current signal are provided. That.

[0011]

In the present invention, the color signal is compressed by the line-sequential switching method in the amount of information, the time axis is compressed / expanded by the time difference between the read / write clocks of the frame memory, and the FM modulation / demodulation wave is used for recording / reproducing. As a result, not only is it possible to expand the band of the color signal, but it is also possible to improve image quality deterioration such as color unevenness due to time axis fluctuations, and to improve image quality characteristics.

[0012]

1 and 2 are block diagrams of recording / reproducing of a high band 8 mm type VTR of the present invention. In FIG. 1, the Y signal separated from the composite video signal is supplied to the luminance signal processing circuit 101, and the C signal is supplied to the frequency conversion circuit 103 through the BPF 102. The Y signal supplied from the luminance signal processing circuit 101 is FM-modulated by the frequency modulation circuit 104, and superposed by the addition circuit 105 on the C signal converted into the low frequency band by the frequency conversion circuit 103. This signal is transferred from the recording area switching circuit 10 to the recording amplifier 10
6A, 106B, and amplifies and supplies the head 107A, 1
It supplies to 07B. In this way, the recording medium 70
Is recorded.

On the other hand, the C signal is also supplied to the compressing means 40, and is decoded into an RY signal and a BY signal by the decoder 41 in the compressing means 40, and is line-sequentially switched and compressed. This line sequential processing is performed by switching the switching circuit 42 for each horizontal period. A high-frequency component of this signal is removed by a low-pass filter (hereinafter referred to as LPF) 31, and the signal is supplied to an analog / digital conversion circuit (hereinafter referred to as A / D conversion circuit) 232. The digital signal of the A / D conversion circuit 232 is written into the frame memory 233 as the clock signal F from the writing means 234.
W is written, and from this frame memory 233, a digital / analog conversion circuit (called a D / A conversion circuit) 23
5 is read by the clock FR of the reading means 236. The reading means 236 includes a reference signal generation circuit 239.
It is possible to set the frequency. Further, the writing unit 234 is also configured to be able to set the frequency similarly to the reading unit.

The above-mentioned A / D conversion circuit 232, writing means 234, frame memory 233, D / A conversion circuit 23.
5, the reading means 236 and the reference signal generation circuit 239 constitute the time axis compression means 200.

Further, the output signal of the D / A conversion circuit 235 has its high frequency component removed by the LPF 37, and the FM modulation circuit 38.
To the recording area switching circuit 20. The recording switching area circuit 20 is composed of SPDT switches 21 and 22, the pole P is connected to the head side, one contact is connected to the FM modulation circuit 37, and the other contact is connected to the adding circuit 105. Has been done. In addition,
The recording area switching circuit 10 switches the recording area between the video area and the PCM area of the magnetic tape 70 by an external control signal (area switching signal).
The recorded information of 0 is magnetoelectrically converted into an electric signal. The heads 107A and 107B are provided with the conventional low-pass conversion filter 1 through the two contacts of the reproduction area switching circuit 10.
10 or an expansion system demodulation circuit 8. Here, the reproduction area switching circuit 10 is composed of SPDT switches 11 and 12 like the recording area switching circuit 20, one contact is connected to the filter 110 and the other contact is connected to the demodulation circuit 8, and each head is connected. 107A, 107
B is connected to the pole via the amplifier circuits 108A and 108B. The reproduction area switching circuit 10 switches between the video area and the PCM area by an external control signal (reproduction area switching signal).

A conventional low-frequency conversion electric signal is amplified by preamplifiers 108A and 108B, a high-frequency component is removed by a filter 110, and then converted to a reproduction color signal frequency by a frequency inverse conversion circuit 111. This signal is supplied to the comb filter 112. The comb filter 112 reduces the amount of crosstalk from adjacent tracks. Furthermore, after passing through the BPF 113 from the comb filter 112, the reproduced C signal is reproduced.

On the other hand, the Y signal, after passing through the filter 110,
It is supplied to the luminance signal processing circuit 114 and supplied to an image receiving unit (not shown).

Further, a frame memory 115 is provided at the subsequent stage of the luminance signal processing circuit 114, and the luminance signal YOUT delayed from this frame memory 115 by one frame is used.
Is output.

On the other hand, the recording data recorded in the PCM area is supplied to the demodulation circuit 8 and filtered (not shown).
The high frequency component is removed by and is supplied to the A / D conversion circuit 2. The output signal of the A / D conversion circuit 2 is written in the frame memory 3 using the writing means 4. The digital data of the frame memory 4 is read by the clock of the reading means 6, converted into analog data by the D / A conversion circuit 5, and the high frequency component is removed by the LPF 9. The writing unit 4 and the reading unit 6 are configured so that the clock frequency can be set.

Further, the LPF 9 is connected to the line sequential switching circuit 310 and the 1H delay circuit 301 of the color reproducing means 300, respectively. This line sequential switching circuit 310
Is composed of two SPDT switches 311 and 312, the pole of which is the color encoder 320 and one of the contacts is LP.
The other is connected to the direct input line from F9 and the other from LPF9 via the 1H delay circuit 330. Then, the line-sequential switching circuit 310 supplies the synchronized color difference signals RY and BY to the color encoder 320, respectively, and the reproduced color COUT is output from the color encoder. The reproduced color signal Cout is supplied to an image receiving unit (not shown) together with the Yout signal.

Next, the operation of FIGS. 1 and 2 will be described with reference to FIGS. FIG. 3A is a high band 8 mm type tape pattern, FIG. 3B is a diagram for explaining a tape loading mechanism, and FIG. 4 is a timing chart showing recording / reproducing timing of color signals.

As shown in FIG. 3, in the high band 8 mm format, 30 ° of the PCM area 72 is 30 ° in the video area 7.
1 180 ° plus loaded. Also,
In this format, P precedes the video area 71.
Recording / reproduction of the CM area 72 is to be performed.

In the recording system, as shown in FIG. 1, the color difference signals R-Y and B-Y are switched by the line-sequential switching circuit 20 every horizontal period (hereinafter referred to as "1H"), and the band-sequential signal is band-passed by the LPF 31. After being limited (cutoff frequency 800 kHz), it is A / D converted by the A / D conversion circuit 232 and written in the frame memory 233.

Next, the signal read from the frame memory 233 is D / A converted by the D / A conversion circuit 235, and the converted signal is band-limited by the LPF 37. This L
The PF 37 removes the clock component from the signal supplied from the D / A conversion circuit 235 with a cutoff frequency of about 5.5 MHz, for example.

Here, the frequency FW of the write clock
And the FR frequency of the read clock is, for example, a frequency (1) that is four times the color sub-carrier frequency (3.58MHz).
Read-out clock at 4.3MHz, this carrier frequency is 1.
It is assumed that the write clock is generated at a frequency (2.4 MHz) divided by 5, and the relationship of FR / FW = 6 is set.

By setting in this way, the signal recorded in one frame can be written with the FW clock, and the reading from the frame memory 203 can be performed at a high speed operation which is 6 times as fast as the writing clock. Done. The signal that has passed through the LPF 37 is frequency-modulated, and passes through the area switching circuit 20 to the heads 107A and 107B.
Is recorded on the magnetic tape 70. Playback each head 1
07A and 107B to video area 71 and PCM area 72
The recorded data in the video area 71 is reproduced into a Y signal and a C signal by a conventional low frequency conversion system. On the other hand, the signal in the PCM area 71 is demodulated by the demodulation circuit 8.
It is supplied to the time axis extending means 1. The time axis extending means 1 is
The writing unit 2, the A / D conversion circuit 3, the frame memory 4, the D / A conversion circuit 5, and the reading unit 6 are included.

The signal supplied to the time axis expansion means 1 is A
A / D conversion is performed by the / D conversion circuit 2, and the data is written in the frame memory 3 by the clock PBFW of the writing means. The written data is read by the clock PBFR of the reading means 6 and D / A converted by the D / A conversion circuit 5. This converted signal is supplied to the LPF 9.

Here, the relationship between the write clock PBFW and the read clock PBFR is set so as to be opposite to the relationship at the time of recording. Playback write clock frequency is PBF
W, playback read clock is PBFR, PBFW / PBFR = 6
To be set.

Therefore, the signal compressed at the time of recording is expanded in the opposite frequency relationship. The expanded signal is reproduced by the line-sequential switching circuit 310 into a signal of two systems of RY and BY, and a C signal is reproduced from this signal.

That is, the line-sequential switching circuit 310 in the color reproducing means 300 performs line-sequential switching to perform synchronization processing, and the color encoder 320 orthogonally two-phase modulates the RY and BY color difference signals. , C signal Cout is obtained.

In the high band 8 mm system, the luminance signal band is secured at 5 MHz (-3 dB) in the base band.
It is well known that the signal is FM-modulated by the frequency modulation circuit 111 and recorded on the magnetic tape 70.

In the present embodiment, the time-axis-compressed color difference signal is frequency-modulated and recorded in the PCM area. For example, the reproduction frequency characteristic of the base band when converted to the band to be used, that is, the Y signal is 4.2 MHz ( -3dB) secured and P
Assuming that 43.75H, which is 1/6 of the number of scanning lines in one field (262.5H) of the CM area 46.5H, can be used, the bandwidth after compression can be 4.2MHz, so the bandwidth of the signal before compression is 4.2. 1/6 of MHZ, 700KHz will be obtained.

The C signal C of the color encoder 320
OUT is delayed by one frame as shown in Fig. 4, so
The Y signal is also delayed by one frame in the frame memory 115, and the timing is adjusted to YOUT.

With the above arrangement, the band of the color signal can be improved, and since the color difference signal is time-compressed and frequency-modulated and recorded, the color unevenness due to the fluctuation of the time axis is strong.

Further, since the PCM area, which is an optional area, is used, the PCM area is compatible with the conventional FM recording system of the low frequency conversion color signal system, and it is possible to obtain improved functions and excellent cost performance. Become.

[0036]

As described above, according to the present invention, the color signal is compressed / expanded by the line-sequential switching method, and the time axis correction and the time axis compression / expansion are performed by the time difference between the read / write clocks of the frame memory. By performing and further recording / reproducing with the FM modulation / demodulation wave, not only the band of the color signal can be expanded, but also image quality deterioration such as color unevenness due to time axis fluctuation can be improved and the image quality characteristics can be improved. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a recording system of a magnetic recording / reproducing apparatus according to the present invention.

FIG. 2 is a block diagram showing an embodiment of a reproducing system of the magnetic recording / reproducing apparatus according to the present invention.

[Figure 3] High band 8mm (a) tape format
(b) It is a figure explaining the mechanism of tape loading.

FIG. 4 is a timing chart of the recording / reproducing system of FIGS. 1 and 2.

FIG. 5 is a block diagram of a conventional magnetic recording / reproducing apparatus.

[Explanation of symbols]

 1 ... Time axis expansion means 40 ... Compression means 70 ... Magnetic tape 71 ... PCM area 72 ... Video area 200 ... Time axis compression means 300 ... Color reproduction means FW ... Write clock (time axis compression means) FR ... Read clock (time Axis compression means) PBFW… Write clock (time axis expansion means) PBFR… Read clock (time axis expansion means)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Michi 3-3-9 Shimbashi, Minato-ku, Tokyo Inside Toshiba Abu E Co., Ltd.

Claims (1)

[Claims] 1. A color-difference signal in which line-sequential switching is performed and the amount of information in the vertical direction is compressed is digitally converted and then written to a frame memory at a predetermined writing speed, while the recorded content is written from the frame memory at a speed faster than the writing speed. Read out and time-axis compressing means for compressing the time-axis and analog-converting the signal from the time-axis compressing means into a PCM area of a recording medium having a PCM area for recording an audio signal in an area adjacent to the video area. Recording means for frequency-modulating and recording the converted signal; reproducing / demodulating means for reproducing and demodulating the signal recorded in the PCM area by the recording means; and digitally reproducing signals from the reproducing / demodulating means. After the conversion, the relationship between the writing speed and the reading speed of the time axis compression means is reversed and the writing and writing to the frame memory are performed. Make out only, after the extension of the time axis,
Further, the time axis expansion means for converting the read signal into an analog signal to obtain a color difference signal, and the signal from the time axis expansion means are line-sequentially switched for each horizontal period, and the signal one horizontal cycle before and the current signal A magnetic recording / reproducing apparatus comprising: a color signal reproducing unit that obtains a color signal after simultaneously performing