JPS6061973A - Magnetic recording and reproducing system - Google Patents

Abstract

PURPOSE:To perform the searching accurately with low cost and then automatically and quickly when necessary by forming the program searching information through N tracks (N>=2) with a track defined as the information unit and applying such signal processing that gives the significant difference to the record/reproduction characteristics original to the corresponding device. CONSTITUTION:Both tracks A and B are defined as a group, and the retrieving information is given only for a prescribed period immediately before the picture information with said one group defined as a unit. For this information applying means, non-record state of signal is formed according to a prescribed style. In other words, no-record parts 30 where no signal is recorded at all are formed in a prescribed section for each unit of a group on a magnetic tape 1. When the tape 1 is reproduced at a high speed, the parts 30 produce just noises. Then no envelope curve is obtained at a part corresponding to the part 30 for a reproduced waveform of a scanning line 20 of a head A. With addition of the parts 30 to the tape 1, an envelope curve signal appears every 2T compared with conventional time T. Thus the retrieving information is available by making use of the difference between T and 2T.

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 cassette video tape recorder that records signals on a magnetic medium by azimuth recording, which enables high-speed signal retrieval. A magnetic recording and reproducing system like this [The backbone of invention! ! I] Conventionally, as an example of a magnetic recording/reproducing system employing an azimuth recording system, there is a rotating two-head type video tape recorder (hereinafter referred to as VTR). In such a VTR, cueing is performed using, for example, a rotation pulse generated from a winding reel of a magnetic tape as a reference, this rotation pulse being applied to a counter, and based on the counter value. In this case, the time required for one rotation at the start and end of winding is significant (for example, in the Vl-1s method, it is 26φ and 80φ, respectively, and at low speed, the time ratio is 1:3), so the same 1 count value However, there was a problem that the time intervals were different, making it difficult to use. In addition, since search information corresponding to the image signal is not recorded on the tape, the absolute position of the tape is unknown and only relative positions can be used. For this reason, when searching and locating the same location many times, positional deviations occur little by little, or positional deviations occur due to expansion and contraction of the tape.

By the way, when considering the usage of conventional VTRs, it is generally considered that they are often used in a long-time recording/playback mode (6-hour mode). Furthermore, it is rare for one program to be recorded on one tape, and the length is as long as 30 minutes, and a program of 60 minutes has six contents. Of course, it is quite conceivable to record more content than that. In this way, conventional rotary two-head VTR devices do not have high-speed image search information recorded on the tape, so they not only have inaccurate cueing but also
This method has a disadvantage in that the user has to search while looking at the images. In this case, the search speed is generally about 1/10 of the real time, and it may take more than 10 minutes, which is not practical. The only way to avoid this is to use a large number of short-duration tapes.
In this case, there is a drawback that the number of cassettes increases.

[Part of the Invention] Therefore, the main purpose of the present invention is to realize one information unit in a predetermined M track, form search information in N information units, and achieve high-speed playback signals and high-speed reproduction signals obtained by normal recording. To provide a magnetic recording and reproducing system which performs signal processing to give a level difference to the cue part of a magnetic tape so that it can be distinguished from a reproduced signal at the time of retrieval, and enables high-speed cueing by this level difference.

The above objects and other objects and features of the present invention will become more apparent from the detailed description given below with reference to the drawings.

[Description of Embodiments] First, in explaining the present invention in detail, a conventional rotary two-head azimuth recording system will be explained.

FIG. 1 is a diagram showing the recording signal format of a magnetic tape by conventional rotary two-head azimuth recording, FIG. 2 is a diagram showing the azimuth angle of two rotary heads, and FIG. 3 is a diagram showing the conventional rotary two-head azimuth recording. FIG. 3 is a diagram illustrating an output example of an envelope signal when a signal recorded by the method is reproduced at high speed.

Now, suppose that one of the two rotating heads is distinguished as the A head and the other as the B head, the magnetic tape 1 is wound around the rotating drum by more than 180 degrees, and the A head and the B head are respectively scanned on the magnetic tape 1. Then, as shown in FIG. 1, tracks A and B are alternately formed on the magnetic tape 1. At this time, in order to reduce crosstalk between tracks, (90 + θ) 0 and (90 - θ) are
) The A head and B head are tilted at 0. This inclination angle θ is generally called the azimuth angle.

Next, when the tape is fed at high speed in this recording state, the third
The result will be as shown in the figure. In FIG. 3, scanning line example 20
is for the A head, and scanning line example 21 is for the B head. The scanning output signals of the A head 20 and the B spatula and dome 21 have waveforms as shown in FIGS. 3(a) and 3(b).

That is, when the A head scans the magnetic tape 1, an envelope signal 5- is obtained only in the A track portion, and with the B head, an envelope signal 5- is obtained only in the B track portion. This is due to the fact that the A track and B track have different azimuth angles.

However, in this state, if the image signals of two programs are recorded continuously, there is no break in the envelope signal, so information that can be used as a search cue signal cannot be obtained.

FIG. 4 is a diagram showing a magnetic tape on which signals are recorded according to an embodiment of the present invention and its high-speed waveform. Since significant search information cannot be obtained by simply recording and reproducing signals continuously as in the past, in one embodiment of the present invention, A
The track and the 8-track are made into one layer, and search information is added only to a predetermined period immediately before the image content in units of -5 groups. As this information providing means, for example, a non-recorded state of a signal is formed according to a predetermined format. That is, in FIG. 4, a non-recorded portion 30 in which no signals are recorded is formed in a predetermined section of the magnetic tape 1 for each layer. If this is reproduced at high speed, the non-recorded portion 30 will only generate noise, and the reproduced waveform of the head scan $1120 will be the fourth
As shown in Figure (0).

6- The envelope line of the portion corresponding to the non-recorded area 30 is not crossed, and similarly, the reproduced waveform of the B head scanning line 21 is as shown in FIG. 4(d).
It becomes as shown in . For reference, FIG. 4(e) shows a reproduced waveform by the A-head scanning line 20 in the conventional system. As is clear from a comparison between the waveform shown in FIG. 4(C) and the waveform shown in FIG. 4(e), the appearance period of the envelope signal is is now every 2T, compared to every time T in the conventional case. Therefore, this difference can be used as search information. However, since a signal equivalent to the unrecorded area 30 may be generated due to scratches or dust on the magnetic tape 1, in one embodiment of the present invention, two or more unrecorded areas 30 and recorded areas are alternately formed. This improves reliability.

By the way, when recording an image signal on the magnetic tape 1, 1
The number of tracks recorded per second is 60 in the NTSC system, and 30 in group units, so 15 pairs of 2T interval signals are obtained per second.

This time may be arbitrarily set depending on the usage power of the signal.

Furthermore, in the above embodiment, a simple signal recording and non-recording section were provided for each group, but it is also possible to control the recording section and the non-recording section by making them correspond to, for example, a binary code. . In other words, the binary code "11" is stored in the recording section, "
If we assume that "0" is the unrecorded part, then for the 9th image content, we can define the recorded part, unrecorded part, unrecorded part, and recorded part for each group, corresponding to rloolJ in binary code. , it is possible to perform appropriate processing in high-speed playback mode and restore rloolJ. Furthermore, these combined controls are also possible. In addition,
A non-recording state can be easily achieved by controlling the magnetic head to short-circuit or open it.

Furthermore, in one embodiment of the present invention, the recorded portion and the unrecorded portion are provided only at a predetermined time immediately before the image content, so that the recorded image in the portion other than the search information is not affected at all. There is no.

In addition, technically, it is possible to perform high-speed cueing control using the essential main head without using means such as an auxiliary head, and there is an advantage that the desired function can be realized at low cost.

In addition, although the above-mentioned example explained the case where a non-recording part was introduced, the present invention is not limited to this, and the same effect can be achieved by recording a signal of, for example, 100 kHz in place of the non-recording part. It is sufficient to perform signal processing that provides a level difference from the original recording/reproducing characteristics. Further, in the above-described embodiment, the case where the A track and the B track are controlled as one unit has been described, but the object of the present invention can be achieved even if only the A track is used. In this case, cue information is simply not obtained in the B track portion.

[Effects of the Invention] As described above, according to the present invention, cueing information is formed using N (N≧2) tracks, with one track as an information unit, and the recording and reproducing characteristics inherent to the device are used to generate the unit information. Since signal processing is introduced to give a significant difference between the two, it is possible to obtain an apparatus that is inexpensive and capable of automatically and quickly locating the cue in some cases.

10-

[Brief explanation of drawings]

Fig. 1 is a diagram showing the recording signal format of a magnetic tape in conventional rotary two-head azimuth recording, Fig. 2 is a diagram for explaining the azimuth angle, and Fig. 3 is a diagram showing the format of recording signals on a magnetic tape recorded by the conventional recording method. FIG. 6 is a diagram illustrating an output example of an envelope signal when a signal is reproduced at high speed. FIG. 4 is a diagram showing magnetic recording and its high-speed reproduction waveform in one embodiment of the present invention. In the figure, 1 is a magnetic tape, 20 is a scanning line of the head at high speed, 21 is a scanning point of the B head at high speed, and 30 is a signal non-recording area. Agent Masuo Oiwa 10-

Claims (1)

[Claims] In a magnetic recording and reproducing method for recording and reproducing signals using a discontinuous track configuration, an information rate of 1 is achieved in a predetermined M track, search information is formed in N pieces of information, and this Signal processing that gives distinguishable level differences to the recording and playback characteristics specific to the generation of information units.
A magnetic recording and reproducing method that is characterized by being applied to the cue section of a magnetic tape to enable high-speed cueing.