JPH054721B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an FM audio multiplexing VTR that records audio signals as well as video signals using a rotating head.

[Background of the invention]

Conventional home VTRs have a dedicated audio track separate from the video track, and record audio signals on tape using a fixed head. In this case, good sound quality cannot be obtained because the tape speed is slow (for example, 11 mm/s in VHS 6-hour mode). In response, the audio signal is FM modulated, as shown in Figure 1.
Consideration has been given to multiplexing the FM audio signal 3 into a band between the FM-modulated luminance signal 1 and the low-frequency converted chroma signal 2. In this case, the sound quality is greatly improved, but a major drawback is that dubbing (re-recording only the audio later) is difficult.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art and to provide an audio multiplexing magnetic recording and reproducing apparatus that can perform FM audio multiplexing and also perform post-recording.

[Summary of the invention]

In order to achieve the above object, the present invention provides an audio signal head in addition to a video signal head, and records the audio signal on the guard band portion of the video track, thereby enabling dubbing.

[Embodiments of the invention]

The present invention will be explained in detail below based on specific examples. FIG. 2 shows the head arrangement according to the present invention, in which two video heads 5 and 6 with different azimuths face each other at approximately 180° on the drum 4, and two video heads 5 and 6 face each other at approximately 180° at a distance of a certain angle θ. There are two audio heads 7, 8 with different azimuths. The direction of rotation of the drum 4 is indicated by an arrow 9. Different azimuth angles are indicated by + and - symbols.

The following explanation will be given with reference to the 2-hour and 6-hour modes of the NTSCVHS system. The track pitch is as follows: 2-hour mode Tp ₂ =60 μm, 6-hour mode Tp ₆ =20 μm. Also, the track width Tv of the video head is generally selected to be about half of Tp ₂ (60 μm) in the 2-hour mode. That is, Tv=30 μm. This is determined to avoid reading adjacent tracks in the 6-hour mode and to reduce S/N deterioration in the 2-hour mode. In this case, no guard band occurs in the 6-hour mode, and a guard band of about 30 μm occurs in the 2-hour mode.

First, the case of the 6-hour mode will be described. Since there is no guard band, the audio signal and video signal are overwritten. Since the luminance signal in the video signal has a high frequency and is easily erased, the recording order is such that the audio signal is recorded first, and then the video signal is overwritten. In this case, the condition that the audio head does not erase the recorded track of the previous video head is to provide a step Td between the audio heads 7 and 8 with respect to the video heads 5 and 6, as shown in FIG. Here, Td=θ°/180°×Tp ₆ ... For example, when θ=90°, Td=1/2Tp ₆ =10 μm. The track pattern in this case is shown in FIG. 100 is a tape. The track width Ts of the audio head is set to Ts in order to minimize adjacent interference.
= Tp ₆ = 20 μm.

In the example shown in FIG. 4, after recording with the audio head S+, overwriting is performed with the video head V+. The head rotation direction is 9, and the tape running direction is 10.
If the condition of the formula is satisfied, the lower edge of the recording track of the video head V+ and the lower edge of the recording track of the audio head S+ will match and become 11. S-, V
The same applies to - as in the case of S+ and V+. Note that the azimuth angle of the video head is ±
6°, and the azimuth angle of the audio head can be chosen to be, for example, ±20°.

FIG. 5 shows a recording pattern when recording in a two-hour mode using the above-mentioned head.
If the conditions of the formula are satisfied, the tracks of S+ and V+, S-
The tracks of and V- do not overlap. That is, Tp ₂ =
Since 60 μm and Tv=30 μm, a guard band 12 of 30 μm exists, and the audio signal is recorded in this portion. Therefore, since the audio signal can be recorded without erasing the video signal, dubbing becomes possible.

After-recording in the 6-hour mode can be recorded using a fixed head on an audio-only track as before. In this case, the recording audio signal output is switched by a 2-hour and 6-hour changeover switch, and the recording current is applied to the rotary audio head in the 2-hour mode and to the fixed audio head in the 6-hour mode.

In addition, in the present invention, the head preceding V+ is S+,
The head preceding V- is designated as S-, but V+
The same thing can be said if the head preceding V- is S- and the head preceding V- is S+. The azimuth angles and combinations of video and audio heads shall be chosen to minimize video to audio and audio to video interference.

〔Effect of the invention〕

As described above, according to the present invention, the audio performance of a VTR can be greatly improved by FM audio multiplexing, and in the 2-hour mode, post-recording can be performed by FM audio multiplexing, which is extremely effective.

Although the above explanation has been given for the case of NTSC of the VHS system, it can be widely applied to the case of PAL or other recording systems in which a card band exists.

Also, during dubbing, the video head is in playback mode,
Since the audio head is in recording mode, crosstalk from the audio system to the video system can be a problem when a rotary transformer is used. An effective countermeasure against this problem is to extract the video head output using a rotary transformer and the audio head output using a slip ring.

[Brief explanation of the drawing]

Fig. 1 is a spectrum diagram showing an example of the luminance signal, chroma signal, and audio signal bands; Fig. 2 is a plan view showing an example of the arrangement of the video head and audio head on the drum according to the present invention; and Fig. 3 is a diagram showing the arrangement of the audio head and the audio head. FIG. 4 is a front view showing the steps of the video head, FIG. 4 is a track pattern diagram in a 6-hour mode in the present invention, and FIG. 5 is a track pattern diagram in a 2-hour mode in the present invention. 1...Brightness signal, 2...Chroma signal, 3...Audio signal, 5, 6...Video head, 7, 8...Audio head.

Claims (1)

[Scope of Claims] 1. A rotary head for video signals, a rotary head for audio signals, and a fixed head for audio signals are separately provided, and the audio signals to be dubbed are transferred at a normal speed where a guard band is formed between the video tracks. In the long-time speed mode in which no guard band is formed, a switch is provided to switch and supply the audio signal to the rotary head and the fixed head respectively, and during dubbing, the rotary head for the video signal is set to the playback mode, and the mode is the same as that during recording. The tape is run in the speed mode, and in the normal speed mode, the audio signal rotary head is set to recording mode, and the switch supplies the audio signal to be dubbed to the audio signal rotary head, and in the long speed mode, the audio signal is 1. An audio multiplexing magnetic recording and reproducing apparatus, characterized in that the fixed head for audio signals is set in a recording mode, and the switch supplies the audio signal to be dubbed to the fixed head for audio signals.