JPS61206902A - Magnetic recorder and magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain always reproduced information signal of the best quality even if the reproduced information signal level falls in the same positions of individual inclined tracks, by recording information signals of the same information contents on two adjacent tracks in different orders and reproducing these information signals. CONSTITUTION:A color video signal is digitized by an A/D converter 2 and has the time base compressed from one field period to 1/2 field period by a time base compressing circuit 3. Digital video signals which have the time base compressed to 1/2 are taken out from four field memories in the time base compressing circuit 3 while being switched at every 1/2 field, and two time base compressed information signals out of them are repeated twice in every one-track scan period (one-field period) and are taken out in different orders. A band compressing circuit 4 is provided for reducing the bit rate, and digital signals modulated by a modulating circuit 5 and amplified by a recording amplifier 6 and are supplied to a terminal R of a switch circuit 7 and are supplied to two rotary heads HA and HB.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording device and a magnetic recording/reproducing device, and particularly in a magnetic recording/reproducing device of a two-head helical force scan method, information signals having the same information content are magnetically transmitted by a rotating head. The present invention relates to a recording device for recording on a tape and a recording and reproducing device for recording and reproducing.

Conventional technology 2-head helical force scan type magnetic recording and reproducing bag fi
(VTR), as is well known, the magnetic tape is guided by guide poles and placed on the circumferential side of the rotating head drum at 180 degrees.
It is wound diagonally over a wide angular range, and is run in a fixed direction at a predetermined speed during recording or playback other than still motion playback. A total of two rotating heads are mounted and fixed to the rotating surface of the rotating head drum, facing each other with their gap portions slightly protruding from the circumferential side of the rad drum. A rotating head drum usually has one rotation period.
The magnetic tape is rotated at a number of revolutions for a period equal to a frame (two fields), and during recording, two rotating heads alternately form tracks inclined with respect to the longitudinal direction of the magnetic tape for each field, and information signals ( For example, a frequency-division multiplexed signal of a frequency-modulated luminance signal and a low-frequency conversion carrier chrominance signal) is recorded, and during reproduction, two rotary heads alternately scan the recorded edge track to reproduce the recorded information signal. However, it is well known that the reproduction output of the original information signal is obtained by performing the signal processing opposite to that during recording.

Problems to be Solved by the Invention In the above VTR, since the rotary head drum rotates at high speed, an air layer (so-called air film) is formed between the circumferential side of the rotary head drum and the magnetic tape. However, its thickness is not uniform; it is thickest at the inlet of the rotating head drum where the rotating head begins to slide against the magnetic tape due to the inflow of air flow, and gradually becomes thinner as the magnetic tape travels. It is known that at the outlet of the rotary head drum, where the vibration of the head against the magnetic tape ends, the magnetic tape suddenly becomes thinner due to the negative pressure generated by the outflow of the air flow. For this reason, the rotary head that slides on the magnetic tape suddenly pushes the magnetic tape with a large pressure near the exit portion of the rotary head drum, and then immediately moves away from the magnetic tape, causing the magnetic tape to vibrate. Due to this vibration, the sliding pressing force of the rotary head against the magnetic tape becomes less than a predetermined value at a predetermined position during one track scanning period, resulting in a problem in that the reproduced signal level may drop.

In addition, in home VTRs, due to fluctuations in the running of the magnetic tape or other reasons, the magnetic tape may come into contact with the flange of the tape guide, and the surface of the magnetic layer at the bottom end of the magnetic tape may be destroyed along the length of the tape. A phenomenon in which the magnetic tape bends along the longitudinal direction of the magnetic tape rarely occurs. In such a case, there is a problem that a recording missing portion occurs at a predetermined position such as the first half of a field period during recording, or a reproduced signal missing portion occurs during reproduction.

Furthermore, there is a problem in that the recording signal or reproduction signal level of one of the two rotary heads may be significantly lower than the signal level of the other rotary head due to dust or the like.

Therefore, the present invention records information signals with the same information content in different orders using two rotating heads.

It is an object of the present invention to provide a magnetic recording device and a magnetic recording/reproducing device that solve the above-mentioned problems by reproducing.

Means for Solving the Problems The magnetic recording apparatus according to the present invention uses a time axis compression means to convert information signals to 1/N of one track scanning period (where N is 2).
Among the signals obtained by compressing the time axis by an integer greater than or equal to), the recording means repeats N time axis compressed signals twice per track scanning period, and records the first and second signals in different orders. A time-base compressed information signal having the same information content is recorded on each of two adjacent inclined tracks. The magnetic recording/reproducing apparatus according to the present invention further includes a reproduction means 1 selection means and a time axis expansion means in addition to the above-mentioned time axis compression means and recording means. Of the time-base compressed information signals having the same information content that are sequentially reproduced from two adjacent inclined tracks by the reproduction means, only the signal with the least signal deterioration is selected by the selection means. The time axis is returned to the original time axis by the time axis expansion means.

The signal whose time axis is expanded by the time axis expansion means is selected by the selection means from among two or more time axis compressed information signals having the same information content recorded on adjacent inclined tracks by the recording means. This is the time-base compressed information signal with the least signal deterioration. Therefore, deterioration of the playback signal due to the above-mentioned tape recording, signal loss at the lower end of the magnetic tape caused by the flange of the tape guide in the tape running system, dirt on one of the two rotating heads, etc. Even if a decrease in the recording signal or reproduction signal level occurs, only the time-base compressed information signal reproduced from a position other than the position where the decrease occurs can be selected and reproduced. 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 recording system and reproduction system of the present invention. An embodiment of the recording apparatus of the present invention is shown in FIG. 1 with the configuration of only the recording system.

In FIG. 1, a color video signal input to an input terminal 1 is supplied to an A/D converter 2, where it is sampled and quantized. For this sampling, for example, a sub-Nyquist sampling method is used in which the sampling phase is inverted every two lines as a method that does not require YC separation and does not degrade the horizontal resolution of the luminance signal. The aliased component after sampling is mixed between the luminance signal component and the carrier color signal component.

The digital video signal taken out from the A/D converter 2 is supplied to the time axis compression circuit 3, where the time axis is compressed from one field period to 1/2 field period of 1/2 times the time axis. be done. The time axis compression circuit 3 has four field memories, and sequentially writes digital video signals field by field into these four field memories, and outputs data from the field memory that has already been written, twice as much as when it was written. Read out based on frequency clock pulses. The reading order is 1st for every 1/2 field. 2nd degree 2nd degree. 1st
．． Third. 4th. 4th. The data is read out in the order of each third field memory (in the order of two frame cycles). In this way, the digital video signal whose time axis has been compressed by 1/2 is switched and taken out every 1/2 field from the four field memories in the time axis compression circuit 3 of this embodiment. Two of the time-base compressed information signals are repeated twice every one track scanning period (one field period), and
are taken out in different orders. The output time-base compressed digital video signal of the time-base compression circuit 3 is supplied to the band compression circuit 4.

The band compression circuit 4 is provided to lower the bit rate, and compresses the band by performing, for example, differential pulse code conversion iJ (DPCM) on the digital video signal subjected to sub-Nyquist sampling and time axis compression as described above. (smaller quantization bit number). Furthermore, the band compression circuit 4 extracts the final value of the locally decoded signal from its internal decoder loop, inserts it into a part of the synchronization interval, and transmits it. The modulation circuit 5 is supplied with the output DPCM signal of the band compression circuit 4, and after adding parity for error correction, scrambled N
It is assumed to be an RZ signal. The scrambled NRZ method is DPC
The M signal is an NRZ (non-return-to-zero) signal, but this signal form is affected by low-frequency cutoff by a rotary transformer, so for example, the M-sequence code and DP
By performing addition modulo 2 with the CM signal, even if there are consecutive 1101+ or '1' data in the DPCM data, the probability that '0' or '1'' will continue is extremely small. This method obtains a digital signal, that is, a signal obtained by scrambling an NRZ signal (DPCM signal).

The digital signal modulated and extracted as described above by the modulation circuit 5 is amplified by the recording amplifier 6 and then supplied to the terminal R of the switch circuit 7. During recording, the switch circuit 7 selects and outputs the input signal of the terminal R, and is mounted and fixed on the rotating surface of the -C rotating head drum 8 opposite to each other via a rotary transformer (not shown). if is supplied to rotating heads HA and H8, respectively. Rotating head HA and H
The inclination directions of the gaps with respect to the track width direction are respectively selected to be opposite to each other. The rotating head drum 8 is similar to the conventional 2-head helical scan type VTR.
The magnetic tape 9 is wound obliquely over an angular range of more than 80 degrees, and rotates at high speed, for example, counterclockwise at 30 ros. Further, the magnetic tape 9 is also made to run in a constant direction at a constant speed.

As a result, the digital video signal is transferred to the rotating head HA.
and He, the inclined tracks 11 to t6 etc. shown in FIG. 2 are alternately tl every field.

The data are sequentially formed and recorded in the order of tl, . . . t6, . Here, in FIG. 2, tracks tl, t3゜t
5 is recorded by the rotating head HA, and the track t
l, t4. t6 is recorded by the rotating head H8,
Each track is recorded and formed over one field period. Therefore, on the inclined recording track t1, a signal A1 obtained by compressing the time axis of the first field digital video signal by 1/2 in the first field memory by the first rotary head HA, and a second A signal B2 obtained by compressing the digital video signal of the th field to 1/2 time axis in a second field memory is chronologically combined and recorded in the order of A1→B2. inclined track tl
Adjacent track tl is a track on which recording is formed in one field period by the second rotary head H8 after recording on track tl, and the signals A1 and 82 whose time axis has been compressed to 1/2 of the above are recorded. They are synthesized and recorded in chronological order in a different order: B2→Δ1.

During the next one field period, the first rotary head HA compresses the digital video signal of the third field to 1/2 in the time axis in the third field memory, and outputs the signal C3 and the third field memory. A track t3 is formed in which a signal D4 obtained by compressing the digital video signal of the fourth field by 1/2 in the time axis in the fourth field memory is sequentially recorded.

Then, in the next one field period after recording the third track ahead, the second rotary head Ha forms a track t4 in which the signals C3 and D4 are recorded in a different order from the above. Thereafter, in the same manner as above, the rotary heads HA and H record and form two adjacent tracks.
Time-axis compressed video signals with the same information content are supplied and recorded in different orders to e.

In FIG. 2, TA is an audio track on which audio signals are recorded by a fixed head, and Tc is a control track on which control pulses are recorded by a fixed control head.

In FIG. 1, the above-mentioned audio signal recording/reproducing system and control pulse recording/reproducing system are not shown because they are irrelevant to the gist of the present invention.

Next, the operation during reproduction will be explained. In FIG. 1, the switch circuit 7 is connected to the terminal P side.

Further, the rotary heads HA and HB alternately scan the recorded inclined tracks t1 to 0.degree. C.6 shown in FIG. 2 to reproduce the recorded edge digital signals. The reproduction signals from the rotary heads HA and Ha are transmitted through a rotary transformer (not shown), a switch circuit 7, and a switch circuit (for switching the reproduction signals of the two rotary heads HA and He into continuous signals).
(not shown), and a demodulation circuit 11 through a regenerative amplifier 10 in sequence.
After being restored to the original DPCM signal before being scrambled (so-called descrambling) by known means, time base fluctuations are removed by a time base collector, and then error correction is performed. .

The reproduced DPCM signal taken out from the demodulation circuit 11 is supplied to the video correction/selection circuit 12, where the final value inserted into a part of the synchronization interval and transmitted as described above and the final value decoded from the data are input to the video correction/selection circuit 12. If they do not match, it is determined that an error has occurred, and correction is made in units of several 14 (where H is the horizontal scanning period) using data from one frame before, and correction is made every 1/4 frame. The number of corrections is counted, the minimum section (1/4 frame) of the number of corrections is found, and a gate pulse representing that section is generated.

In this embodiment, as shown in FIG.
Comparing the number of corrections between the first time-base compressed video signals in one frame section, a first gate pulse representing the section with the smaller number of corrections is generated, and a first gate pulse is generated that represents the section with the smaller number of corrections, and also Comparing the number of corrections between the second time-axis compressed video signals in each 1/4 frame section of the second half of one recording track and the first half of the other recording track, the second section represents the section with the smaller number of corrections. Generates a gate pulse. Here, two adjacent recording tracks are rotary heads HA having different azimuth angles.

Tracks recorded by Ha can be easily identified.

The digital signal and gate pulse taken out from the video correction/selection circuit 12 are supplied to the band expansion circuit 13.
After the band is returned to its original size using a DPCM decoder, aliasing components are removed by interpolating only high frequency components from two days ago using an interpolation filter. The time-base compressed DPCM signal taken out from the band expansion circuit 13 is supplied to the time-base expansion circuit 14 together with the first and second gate pulses, where the minimum 1/4 of the signal deterioration indicated by the gate pulses is Only the signal of two sections of one frame has its time axis expanded twice by the reverse operation of the time axis compression circuit 3 and is returned to the original time axis to obtain a reproduced digital video signal of one frame. As a result, the time axis expansion circuit 14 outputs the reproduced digital video signal that is returned to the original time axis and has the least signal deterioration.

This reproduced digital video signal is supplied to a D/A converter 15, converted into an analog color video signal, and then outputted to an output terminal 16.

Note that the present invention is not limited to the above-described embodiments, and various other modifications are possible. for example,
It is sufficient that the two rotary heads record information signals with the same information content in different orders, and therefore the time axis compression ratio may be one integer fraction of a fraction other than 1/2. Furthermore, band compression does not necessarily need to be performed, and it goes without saying that the present invention may be applied to a VTR that forms a track pattern with a guard band other than the azimuth recording/reproducing method. Furthermore, the present invention can be applied to information signals other than color video signals.

Effects of the Invention As described above, according to the present invention, information signals with the same information content are recorded in different orders on each of two adjacent inclined tracks, and these are played back. Deterioration of the reproduced signal due to vibration, damage to the magnetic layer in the longitudinal direction of the magnetic tape due to tape guides, etc., recording due to bending of the magnetic tape, partial loss of the reproduced information signal, dust on one of the two rotating heads, etc. Recorded by.

Even if a drop in the playback information signal level, etc. occurs at the same time at the same position on each inclined track, the signal with the least deterioration of the playback signal can be selected and played back, and the above deterioration of the playback signal can be prevented. It has the advantage that even if the signal occurs in one of the 62 adjacent tracks, a reproduced information signal of the best 8 quality can always be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the device of the present invention;
FIG. 2 is a diagram showing an example of a track pattern recorded, formed and reproduced by the apparatus of the present invention and its recorded information. 1... Color video signal input terminal, 2... A/D converter, 3... Time axis compression circuit, 4... Band compression circuit,
5... Modulation circuit, 8... Rotating head drum, 9...
- Magnetic tape, 11... Demodulation circuit, 12... Video correction/selection circuit, 13... Band expansion circuit, 14...
Time axis expansion circuit, 15...D/A converter, 16...
Reproduction color video signal output terminal, HA...first rotating head, H8...second rotating head.

Claims (2)

[Claims] (1) In a magnetic recording device that records information signals by alternately forming tracks inclined with respect to the longitudinal direction on a magnetic tape by first and second rotary heads, the information signals are recorded during one track scanning period. /N (where N is an integer of 2 or more) times the time axis, and N time axis compressed information signals among the signals extracted from the time axis compression means for each track scanning period. Repeat twice,
and time-base compression of the same information content on two adjacent inclined tracks recorded and formed by the first and second rotary heads by supplying the same information to the first and second rotary heads in different orders from each other. A magnetic recording device comprising: a recording means for recording an information signal. (2) The first and second rotary heads alternately form tracks inclined with respect to the longitudinal direction of the magnetic tape to record information signals, and the first and second rotary heads alternately record information signals. In a magnetic recording and reproducing device that scans a tilted track and reproduces the recorded information signal, time axis compression is performed to compress the information signal to 1/N (where N is an integer of 2 or more) times the track scanning period. and the first and second rotating heads repeat the N time-base compressed information signals among the signals extracted from the time-base compressor twice every one track scanning period and in mutually different orders. recording means for recording time-base compressed information signals having the same information content on two adjacent inclined tracks recorded and formed by the first and second rotary heads; reproducing means for reproducing the recorded time axis compressed information signal by alternately scanning the tilted tracks with the first and second rotary heads; Among the time-base compressed information signals having the same information content to be reproduced, the one with the least signal deterioration -
selection means for selectively outputting the playback time axis compressed information signal;
A magnetic recording and reproducing apparatus comprising: a time axis expansion means for expanding the time axis of the reproduced time axis compressed information signal from the selection means and returning it to the original time axis.