JP2972273B2 - Magnetic recording / reproducing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a two-channel azimuth recording digital VTR having two recording time modes.

[Conventional technology]

Digital VTR is a technical report of the Institute of Television Engineers of Japan 11,24
(1987) As described on pages 13 to 18, the D-1 standard for component signal recording and the D-2 standard for composite signal recording have been standardized. It has been commercialized. These digital VTRs adopt a two-channel recording system in which a signal to be recorded on a magnetic tape is divided into two channels, guided to independent magnetic heads, and two tracks are simultaneously recorded on the magnetic tape. For example, the D-2 standard specifies that digital data such as digital video data obtained by sampling a video signal at a sampling frequency of 14.31818 MHz and 8-bit linear or digital audio data obtained by sampling a 4-channel audio signal at a sampling frequency of 48 KHz and 16-bit linear is used. It is to be recorded. The recording data rate is about 127 Mb / s. If the recording data rate is high, it is necessary to increase the speed of the circuit, and the circuit configuration tends to be difficult. Therefore, the recording signal is distributed to a plurality of channels to reduce the recording data rate per channel.

Further, in the D-2 standard, a guard bandless azimuth recording method is adopted in order to increase the recording density. D-2
The standard recording signal recorded on the magnetic tape has a small low-frequency components, M ² modulated the recording method in which for those with excellent overwriting characteristics are possible.

Also, in the conventional consumer VTR, the VHS system has two recording time modes: a standard mode and a triple mode that can record for a long time with lower image quality than the standard mode, and can be selected according to the purpose. There are advantages that can be done.

Further, Japanese Patent Application Laid-Open No. Sho 62-152283 discloses a conventional technique in which a recording time mode can be selected in a 2-channel guard bandless azimuth recording method. This is not to configure a dedicated magnetic head for each recording time mode, but to correspond to each recording time mode with a small number of magnetic heads.

[Problems to be solved by the invention]

This prior art is not a head configuration in which two heads corresponding to respective channels are installed in one head base, which is a head configuration mainly employed in the conventional two-channel recording. It is installed alone above. For this reason, the efficiency of mounting the head to the rotating cylinder is deteriorated in the construction, and the area occupied by the head inside the cylinder is increased. Therefore, it is necessary to further mount a head for reproduction only, for variable speed reproduction, for erasure, and the like. There is a problem that is relatively difficult.
In addition, in terms of function, when insert editing is performed on data recorded in the long time mode, a track already recorded by the recording head is cut off at the end point of editing, and a predetermined track width cannot be maintained. .

According to the present invention, in a digital VTR of a two-channel guard band azimuth recording system, two recording heads corresponding to two channels are installed on a single head base, and a recording time can be selected. It is an object of the present invention to provide a device in which a predetermined track width is sometimes maintained.

[Means for solving the problem]

In order to be able to select the recording time, the width of the two heads installed on one head base is set to a width almost equal to the track width of the first head in the longest recording mode, and Are set wider than the width of the first head, and in the two tracks obtained by recording on the magnetic tape by these two heads, an unrecorded portion is not generated between the tracks and an overlapping portion is formed. The two heads are provided on the cylinder under the condition that hardly occurs.

Further, in order to perform insert editing normally, in the two heads having different widths, the track to be recorded last when the insert editing is completed is recorded by the narrower head of the two heads. Things.

[Action]

If adjacent heads having head widths different from each other as described above are employed, the recording track pattern in the longest recording mode is such that a track recorded by a wide head is partially cut away immediately after overwriting. As a result, the width of all tracks becomes uniform. Such a track satisfies the condition that the average error generated during reproduction is minimized.

In addition, when performing insert editing in the long-time recording mode, the track recorded immediately before the end of editing is performed by the narrower head, so that the track width uniformity at the end point of editing is maintained, and errors during playback are reduced. Is reduced.

〔Example〕

Hereinafter, examples of the present invention will be described. FIG. 1 is a diagram showing an outline of a digital signal magnetic recording / reproducing system according to an embodiment of the present invention. 1 is a cylinder, 2 is a magnetic tape, 3 is a tape guide, and H1, H2, H3 and H4 are each a magnetic head. The magnetic tape 2 is cylinder 1 by the tape guide 3.
Rolled around 180 ゜. The magnetic heads H1 and H3 have the same head width. The magnetic heads H2 and H4 also have the same head width. Further, the head width of the magnetic heads H1 and H2 is smaller in H1. The head width amounts of the magnetic heads H1, H2, H3 and H4 are respectively set to W _H1 and W _H
Assuming that _H2 , _WH3 and _WH4 , _WH1 (= _WH3 ) < _WH2 (= _WH4 )... (1) Further, the magnetic heads H1 and H3 have the same azimuth angle. The magnetic heads H2 and H4 have the same azimuth angle, but the azimuth angles with the magnetic heads H1 and H2 are opposite to each other and have the same amount of angle. The magnetic heads H1 and H3 are installed on the side surface of the cylinder 1 at positions shifted by 180 °. The magnetic heads H2 and H4 are also set at positions shifted by 180 °. The positional relationship between the magnetic heads H1 and H2 is such that the magnetic heads H1 and H2 are installed on the same head base so as to be located very close to each other. The magnetic heads H1, H2, H3 and H4 scan over the magnetic tape 2 while contacting the magnetic tape 2 as the cylinder 1 rotates. At the time of recording, a recording current is applied to the magnetic heads H1, H2, H3 and H4, and a recording track is formed on the magnetic surface of the magnetic tape 2. Second
FIG. 1 shows a recording pattern of a magnetic tape 2 according to an embodiment of the present invention. T1, T2, T3 and T4 are tracks formed by the magnetic heads H1, H2, H3 and H4, respectively. The tracks are formed without any gap between the tracks T1 and T2 recorded by the magnetic heads H1 and H2. There is almost no overlap between tracks T1 and T2,
The track width of T2 is substantially equal to the head width of the magnetic heads H1 and H2, respectively. The relationship between the tracks T3 and T4 recorded by the magnetic heads H3 and H4 is the same as the relationship between the tracks T1 and T2. In one embodiment of the present invention shown in FIG.
2, the relationship among the head widths W _H1 , W _H2 , W _H3 and W _H4 of _H3 and _H4 is expressed as 3W _H1 (= 3W _H3 ) = 2W _H2 (= 2W _H4 ) (2). At this time, an unrecorded portion occurs between the tracks T2 and T3 and between the tracks T4 and T1. The running speed of the magnetic tape 2 at this time is determined under the condition that if the head width of the magnetic heads H1 and H3 is increased to be the same width as the magnetic heads H2 and H4, the unrecorded portion generated on the magnetic tape 2 at the time of recording just disappears. Things. Hereinafter, the mode in which the tape runs at the tape running speed is referred to as a standard mode.

The system of FIG. 1 will be described again. 4 is a cylinder motor, 5 is a pulse generator, and 6 is a rotation direction. The cylinder motor 4 is a motor that rotates the cylinder 1 in the rotation direction 6. The pulse generator 5 enables the rotation phase of the cylinder 1 to be detected, and generates an electric pulse every time the rotating cylinder 1 reaches a certain rotation phase. 7 is a capstan, 8 is a pinch roller, 9 is a capstan motor, 10 is a frequency generator, 11
Is the running direction. The capstan motor 9 is a motor for rotating the capstan 7. The magnetic tape 2 is sandwiched between the capstan 7 and the pinch roller 8 and runs by the rotation of the capstan 7. At the time of recording or normal reproduction, the magnetic tape 2 runs in the running direction 11. The frequency generator 10 generates a square wave signal having a frequency proportional to the rotation speed of the capstan 7.
This makes it possible to detect the rotational speed of the motor. 12 is a control signal head. At the time of recording, the cylinder 1 rotates, and each time the track T1 is recorded by the magnetic head H1 and each time the track T3 is recorded by the magnetic head H3, a pulse signal is transmitted via the control signal head 12 to the longitudinal direction of the magnetic tape 2. It is recorded on the direction track. In the tape pattern diagram of FIG. 2, reference numeral 21 denotes a control signal track, and reference numeral 22 denotes a control signal. The longitudinal track described above is the control signal track 21,
The pulse signal recorded on the magnetic tape 2 corresponds to the control signal 22. At the time of reproduction, the control signal 22 recorded on the magnetic tape 2 is reproduced by the control signal head 12. At this time, the control signal 22 becomes a reference signal of the tape running system, and based on this, the tape speed,
Capstan rotation phase control and the like are performed. 13 is a servo circuit, and 14 is a system control circuit. The servo circuit 13 obtains the mode information of the current system operation from the system control circuit 14 and controls the operation of the tape traveling system in accordance with the information. Regarding the control of the cylinder 1, the servo circuit 13 drives the cylinder motor 4 so that the rotation of the cylinder 1 is always maintained at a constant rotation phase based on the generated signal of the pulse generator 5. For control of tape running during recording, use the system control circuit.
The tape running speed information is obtained from 14 and the capstan motor 9 is driven so that the frequency of the signal generated by the frequency generator 10 becomes a value corresponding to the speed information.
At the same time, the servo circuit 13 generates a control signal 22 to be recorded via the control signal head 12. Regarding the control of the tape running at the time of reproduction, the control signal 22 reproduced from the control signal head 13 and the pulse generated by the pulse generator 5 are synchronized,
In addition, the speed of the capstan 7 is controlled so that the tape speed becomes constant.

15 is an input signal, 16 is an encode circuit, 17 is a changeover switch, 18 is a decode circuit, and 19 is an output signal. Input signal 15
Are generated by the encoding circuit 16 for a two-channel recording signal. When the system according to the present embodiment is compatible with a digital VTR, the input signal 15 corresponds to a video signal. At this time, the encoding circuit 16 digitizes the input video signal by A / D conversion, and rearranges the digital signal. Further, an error correction code, a synchronization signal and an index signal are added to the digital video signal, and a recording signal divided into two channels is generated. The two recording signals are introduced into the magnetic heads H1 and H3 and the magnetic heads H2 and H4, respectively, by receiving the control signal from the system control circuit 14 and turning the changeover switch 17 to the R side. Will be recorded. At the time of reproduction, the signals recorded on the magnetic tape 2 are reproduced as two-channel reproduction signals by the magnetic heads H1 and H3 and the magnetic heads H2 and H4. Further system control circuit
The switch of the changeover switch 17 is set to P by the control signal from 14.
As a result, the two reproduced signals are introduced into the decoding circuit 18. The decoding circuit 18 performs signal processing such as waveform equalization of a reproduction signal, clock reproduction, error correction processing, deshuffling, and channel synthesis, and then performs D / A
By the conversion, a video signal as the output signal 19 is obtained.

Reference numeral 20 denotes recording time mode information. Recording time mode information
Reference numeral 20 is obtained by the user selecting from two or more recording time modes. At the time of recording, the system control circuit 14 having obtained the recording time mode information 20 operates the tape traveling system via the servo circuit 13 at a tape traveling speed corresponding to the recording time mode.

Here, it is assumed that there are two types of recording time modes: a standard mode in which the recording time is short, and a long time mode in which the recording time is 1.5 times longer than the standard mode.

As described above, FIG. 2 shows the recording pattern when recording is performed at the tape running speed in the standard mode, but the recording pattern in the long-time mode is as shown in FIG. Since the tape running speed in the long mode is 2/3 times that in the standard mode, the recording interval of the control signal 22 is narrowed accordingly. The track T2 formed by the magnetic head H2 is partially overwritten by the track T3 formed by the magnetic head H3 that scans the magnetic tape 2 next, and the track width of the track T2 is reduced. Similarly, the track T4 formed by the magnetic head 4 is also reduced in track width by the track T1 formed by the magnetic head H1 to be scanned next. Also, the relationship between the tracks T1 and T2 formed by the magnetic heads H1 and H2 is that the magnetic heads H1 and H2 are located on the cylinder 1 very close to each other.
As in the case of the standard mode in the figure, there is almost no overlap between tracks and almost no unrecorded portion. Magnetic head
The same applies to tracks T3 and T4 formed by H3 and H4. As a result, the track widths of the tracks T1, T2, T3 and T4 formed in the long recording mode become equal. This is an advantageous condition in a long-time recording mode in which a data error easily occurs. Since the S / N ratio of the reproduced signal correlated with the data error rate is proportional to the square root of the track width, the data error rate decreases on average if the track width is not uneven and a uniform track is formed. It is.

In the long-time recording mode, overwriting between adjacent tracks occurs. However, by selecting a modulation method in which a frequency distribution is concentrated as a recording signal on the magnetic tape 2 and a signal having a low low frequency component is small, overwriting is performed. It is possible to sufficiently ignore the influence of the residual components of the signal recorded before the recording. In the standard mode in the present embodiment,
An unrecorded portion, a so-called guard band, or an imbalance in track width occurs. As described above, the case where there is no guard band and the track width is uniform is a condition advantageous for an average data error. The data recorded in this manner is hereinafter referred to as a standard mode standard tape.

The use of a standard mode standard tape in the present system will now be considered. The system can play standard mode standard tapes. However, when insert editing is performed using the standard mode standard tape, the second configuration is used in this head configuration.
As shown in the figure, since an unrecorded portion occurs, a part of the track originally recorded remains, and the error error rate during reproduction is significantly deteriorated.

Therefore, if the head width of the magnetic heads H2 and H4 is increased to adopt a head configuration in which an unrecorded portion does not occur during recording, no inconvenience occurs in insert editing in the standard mode. FIG. 4 shows a magnetic tape recording pattern of a magnetic head configuration in which an unrecorded portion does not occur in the standard mode. The description of the control track in the tape pattern will be omitted hereinafter. At this time, the relation between the head widths W _H1 , W _H2 , W _H3 and W _H4 of the magnetic heads H1, H2, H3 and H4 is 3W _H1 (= 3W _H3 ) = W _H2 (= W _H4 ) (3) It is assumed that tracks recorded by the respective magnetic heads during recording hardly overlap. The recording tape pattern in the long time mode according to this head configuration is the same as that shown in FIG.

FIG. 5 shows a standard mode standard tape insert-recorded with this head configuration. If the magnetic heads H1 and H2 are tracked as shown in FIG. 5 with respect to the track T of the standard mode standard tape to be inserted, the track originally recorded at the start and end of the insert editing remains. Disappears.

In addition, in the insert editing in a head configuration in which an unrecorded portion is generated in the recording in the standard mode described above, the inconvenience of generating an error at the time of reproduction by installing a flying erase head prior to the magnetic head to be recorded. Can be eliminated.

Next, the insert editing in the long time mode will be described. In the long time mode, the tracks T2 and T4 recorded by the wide magnetic heads H2 and H4 are partially overlapped by the narrow heads H1 and H3 to form tracks T1 and T3. A recording pattern having a wide track width can be obtained. Therefore, as shown in FIG. 3, in the method in which the recording current is simultaneously guided to adjacent magnetic heads and recorded, a wide track is generated at the end of recording. If insert editing is performed in this state, a wide track is recorded at the end of insert editing, and there is a problem that overwriting is performed on tracks that should not be inserted.

Therefore, in order to perform insert editing in the long-time mode in the present head configuration, at the end of insert edit, by flowing a recording current only to the narrower magnetic head of the two magnetic heads that scan the magnetic tape in the same manner, The track width is uniform on the recording tape pattern.

FIG. 6 shows a magnetic tape recording pattern when insert editing is performed by this method in the long time mode. The hatched portions in the figure indicate the inserted tracks. Then, the track is recorded by the magnetic head H1 and the insert editing is completed. At this time, the adjacent wide magnetic heads H2 do not record tracks.

However, since insert editing of a video signal is performed in units of fields or frames, the above-described insert method may not be possible depending on the method of recording information for fields and frames.

In the recording in the standard mode of the present invention, two tracks having different track widths are alternately recorded. Since a wider track can record a larger amount of information than a narrow track, it is conceivable to record signals with different amounts of information on each track. For example, the HDTV system has a screen aspect ratio different from that of the current NTSC system.However, when the vertical direction of the HDTV system is adjusted to the NTSC system, the HDTV image information necessary to compose the NTSC system screen has the same width. The related information is recorded on a wide track and the sub information is recorded on a narrow track, such as writing on a wide track and writing the remaining high-vision image information on a narrow track. It is possible.

〔The invention's effect〕

According to the present invention, in a digital signal recording / reproducing apparatus, two or more recording time modes can be selected with the minimum number of magnetic heads, so that the cost can be reduced by reducing the number of components. Furthermore, since the configuration of the magnetic head is such that two magnetic heads are mounted on one head base, the efficiency of the head mounting process is improved. In addition, since the track width recorded on the magnetic tape in the long-time recording mode can be made uniform, the average error generation rate is most advantageous.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a system configuration of one embodiment of the present invention, FIG. 2 is a diagram showing a recording pattern of a magnetic tape in a standard time recording mode of one embodiment of the present invention, and FIG. FIG. 4 is a diagram showing a recording pattern of a magnetic tape in a long time recording mode according to one embodiment of the present invention, FIG. 4 is a diagram showing a recording pattern of a magnetic tape in a standard time recording mode of one embodiment of the present invention, and FIG. FIG. 6 is a diagram showing a recording pattern of a magnetic tape at the time of insert editing in a standard time recording mode of one embodiment. FIG. 6 is a diagram showing a recording pattern of a magnetic tape at the time of insert editing in a long time recording mode of one embodiment of the present invention. FIG. 1 ... cylinder, 2 ... magnetic tape 4 ... cylinder motor, 7 ... capstan 8 ... pinch roller, 9 ... capstan motor 13 ... servo circuit 14 ... system control circuit H1, H2, H3, H4 ... magnetic head

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 5/782 G11B 5/09 G11B 27/08

Claims (3)

(57) [Claims] A cylinder, means for rotating the cylinder, means for winding a magnetic tape around the cylinder, means for running the magnetic tape by changing at least two kinds of running speeds, and means installed on the cylinder. A plurality of magnetic heads,
Means for recording / reproducing digital signals using the plurality of magnetic heads, wherein the plurality of magnetic heads are arranged such that an interval between the first magnetic head and the second magnetic head is equal to the outer circumference of the cylinder;
A first magnetic head and a second magnetic head having different azimuth angles from one another, wherein the first magnetic head and the second magnetic head have different azimuth angles; The head width of the first magnetic head is smaller than the head width of the second magnetic head, and the first track recorded on the magnetic tape by the first magnetic head is applied to the magnetic tape by the second magnetic head. A magnetic recording / reproducing apparatus, wherein the plurality of magnetic heads are installed so as to record at a position ahead of a second track to be recorded. 2. The recording apparatus according to claim 1, wherein, when recording the digital signal, the magnetic tape traveling speed is set so that the first track and the second track are formed to have the same track width as a result of overwriting by the plurality of magnetic heads. 2. The magnetic recording / reproducing apparatus according to claim 1, wherein the minimum speed is set. 3. The magnetic recording medium according to claim 1, wherein in the case of insert recording, a final recording track is formed by the first magnetic head having a narrow head width among the plurality of magnetic heads. Recording and playback device.