JPH0542723B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a magnetic recording and reproducing system, and in particular to a system that allows digital signals to be recorded and reproduced without being compressed, and also capable of recording and reproducing digital signals even when they are compressed. [Technical Background of the Invention and Problems Therewith] A digital video tape recorder has been developed that converts a television signal into a digital signal and records it on a magnetic tape through a helical scan rotating head. This type of digital video recorder handles a wide band of digital signals, so research is being conducted on how to increase the recording density on magnetic tape, and on how to increase the recording density by compressing the band of the original signal. It is being done. For example, “Television Society Technical Report VVI54-2, 7
"Page 12" reports on band compression of television signals. Also, regarding standards for digital video tape recorders, "Digital Video Recording on the Proposed Format from Sony" (SMPTE Journal,
May 1983, p. 562). In addition, coding methods and variable speed playback in digital video tape recorders have also been announced.
(1983 National Conference of the Television Society) As mentioned above, if there is a device that converts the television signal into a digital signal and a device that compresses the digital signal, the digital video tape recorder can convert the uncompressed signal and the compressed signal. There is a growing demand for devices that have the ability to handle any type of signal. [Object of the Invention] The present invention has been made to address the above-mentioned circumstances, and is capable of recording and reproducing both uncompressed and compressed digital video signals without complicating the system. Another object of the present invention is to provide a magnetic recording/reproducing method that can handle this case without changing the rotational speed of the video head. [Summary of the Invention] In the present invention, when recording a compressed signal, compared to recording an uncompressed signal, the tape speed is reduced without changing the rotational speed of the video head.
Moreover, in this case, a method is used in which a plurality of video heads are sequentially arranged in the rotational direction and thinned out, and thereby, in the case of uncompressed signal recording,
When looking at both track patterns in the case of compressed signal recording, there is almost no difference in the track width, and the relative speed between the tape and the video head is also kept almost the same. Therefore, compression,
Tape compatibility can be obtained both with a video tape recorder equipped with an expansion device and dedicated to recording compressed signals, and with a video tape recorder dedicated to recording and reproducing uncompressed signals. [Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the basic configuration of a rotary head device according to the present invention, FIG. 2 shows a tape track pattern when a digital video signal is not compressed, and FIG. 3 shows a tape track pattern when a compressed digital video signal is recorded. It shows the tape track pattern during playback. In FIG. 1, reference numeral 11 denotes a disk for a video head that rotates in the direction of arrow N. On the outer periphery of this disk 11, a video head A is arranged on a diameter perpendicular to the disk 11.
1, A2 and B1, B2 are attached. Here, there is a step in the direction of the rotation axis between the pair of video heads A1, A2 and the video heads B1, B2. This step difference is approximately the same as the track width. The tape 12 is run in sliding contact with the drum in an oblique direction around the drum of this rotary head device. FIG. 2 shows a track pattern when an encoded digital video signal is recorded without compression.
The illustrated arrow (Vt) means the tape running direction, TP means the track pitch, TW means the track width, and CTL means the control signal track. The recording/playback order of video heads A1, A2, B1, B2 when uncompressed is as follows:
2, A1, B1, A2, B2, etc. are set to be repeated. Therefore, if the track portions of each video head are shown with the same reference numerals, the second
The result will be as shown in the figure. Next, the process of forming the track pattern described above together with the rotational position of the video head will be explained.
The result will be as shown in the figure. Tracks indicated by solid lines are recorded tracks. Next, when reproducing the signals recorded as described above, each video head A1, A2, B1, B2
From this, a signal is obtained as shown in FIG. Since the trace progress during playback is the same as during recording, the explanation will be made with reference to FIGS. 4 and 5. Period T1 in FIG. 5 corresponds to state a in FIG. 4, and the progress of period T2 The time point corresponds to state b in FIG. 4, the time point at which period T3 has elapsed corresponds to state c in FIG. 4, and the time point at which period T4 has elapsed corresponds to state d in FIG. 4. The reproduced signal is a digital video signal in which the data from the preceding track is sequentially input to, for example, a shift register and converted into serial data. PS in Figure 5 is
This is a head switching signal corresponding to a pair of video heads, and corresponds to the rotational phase of the head disk. One frame of television signal data is composed of 12 channels (head outputs). Next, video head control when recording and reproducing compressed video signals will be explained. FIG. 3 shows a track pattern when a compressed signal is recorded. In this case, the recording and playback order of video heads A1, A2, B1, and B2 is as follows: video head A2 (recording), video head B2, A
1 (no recording; thinning), video head B1 (recording), video head A2, B2 (no recording; thinning), video head A1 (recording), video head B
1, A2 (no recording; thinning), video head B2
(recording), video heads A1 and B1 (no recording; thinning), and video head A2 (recording). Therefore, when the recording tracks of each video head are designated by the same reference numerals, the recording tracks of video heads A2, B1, A2, B2, A2, . . . are sequentially formed as shown in FIG. Such a recording track can be obtained by reducing the tape running speed to 1/3 of that when not compressing, even though the rotational speed of the rotary head is the same as when not compressing. Therefore, the interval between control pulses recorded on the control track (CTL) when recording a compressed signal is 1/3 of the interval between control pulses when recording an uncompressed signal, in terms of tape length. When the signals recorded in this manner are reproduced, the signals are obtained from the video heads A1, A2, B1, and B2 as shown in FIG.
The trace progress during playback is the same as during recording, and playback outputs are obtained in the order of video heads A1, B2, A2, B1, A2, . . . . In this case, data for one frame of the television signal is composed of four channels (head outputs). Table 1 below shows various conditions for processing uncompressed signals and compressed signals in the digital video tape recorder.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to record and play back both uncompressed and compressed digital video signals, and in this case, it is possible to record and play back both uncompressed and compressed digital video signals. It is possible to provide a magnetic recording and reproducing method that can be handled without any changes and the system can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a simplified configuration diagram of a head device according to an embodiment of the present invention, FIGS. 2 and 3 are explanatory diagrams of a track pattern formed in an embodiment of the present invention, and FIG. FIGS. 5 and 6 are explanatory diagrams for explaining the formation order of the track patterns shown in the figure, and are explanatory diagrams of reproduction output signals according to the method of the present invention. A1, A2, B1, B2...video head, 11
...disk, 12...tape.

Claims (1)

[Claims] 1. In a helical scan digital video tape recorder that converts a television signal into a digital signal and performs recording and playback, there are two cases when recording an uncompressed signal of the digital video signal to be recorded.
In the case of recording a compressed signal, the rotational speed of the video head is not changed; in the case of compressed signal recording, the tape speed is set to an integer fraction of that in the case of uncompressed signal recording; and in the case of uncompressed signal recording, A plurality of video heads are controlled to form a recording track sequentially according to a sequential arrangement in the rotational direction, whereas in the case of the compressed signal recording, the plurality of video heads are thinned out in a sequential arrangement in the rotational direction. A magnetic recording and reproducing method characterized in that recording tracks are formed under control.