KR920006746Y1 - High audio quality seeking circuit for vtr - Google Patents

Abstract

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Description

High quality automatic tracking circuit of video player

1 is a circuit diagram showing an example of a conventional automatic tracking circuit.

2 is a circuit diagram showing another example of a conventional automatic tracking circuit.

3 is a graph showing a weighted average difference of audio and video FM signals according to another example of a conventional automatic tracking circuit.

4 is an explanatory diagram showing trace states of audio and video heads.

5 is a graph showing a high frequency level according to the trace state of the audio and video head.

6 is an automatic tracking circuit diagram of the present invention.

7 is a detailed view of the priority circuit of FIG.

* Explanation of symbols for main parts of the drawings

25: priority circuit

The present invention relates to a high quality automatic tracking circuit for reproducing an audio signal in an optimal state in a video player such as a video tape recorder for playing a program recorded on a video tape. A high quality automatic tracking circuit of a video player adapted to a hi-fi type video player for playing back recorded audio signals.

The conventional automatic tracking circuit uses only the video FM signal (hereinafter abbreviated as VFM) reproduced by the video head on the video track or the audio FM signal (hereinafter abbreviated as AFM) reproduced by the audio head, or both VFMs. At the same time, automatic tracking was performed.

That is, FIG. 1 is a circuit diagram showing an example of a conventional automatic tracking circuit. As shown therein, the VFM reproduced by the image head VH1 is amplified by the preamplifier 1 through the rotation transformer T1. The envelope detector 22 detects the envelope of the VFM, and the sample holder 3 samples and holds the envelope of the VFM under the control of the microcomputer 4 and inputs it to the microcomputer 4.

FIG. 2 is a circuit diagram showing another example of the conventional automatic tracking circuit. As shown in FIG. 2, the VFM and AFM reproduced by the video head VH11 and the audio head AH11 are rotated using the rotation transformers T11 and T12. Amplified by the preamplifiers (11) and (12), and the envelope detectors (13) and (14) detect the envelopes of the VFM and AFM, and input them to the analog / digital converters 15A and 15B of the microcomputer 15. It was configured to.

In the conventional automatic tracking circuit having such a configuration, the microcomputer 14 or 15 performs automatic tracking by selecting any one of AFM and VFM. When the tracking of video and audio tracks is slightly off, the automatic tracking is normally performed. This is possible, but if the tracking is significantly out of the way AFM can not automatically track, only VFM can not accurately find the center of the voice track has a problem that can not play AFM with high fidelity.

As shown in FIG. 3, the composite envelope is obtained by taking the weighted average of AFM and VFM, and the maximum point of the composite envelope is traced to compensate for the above-mentioned conventional problems and reproduce the AFM with high fidelity. There is one problem, but in the current system where the width of the voice track is narrow, there are intermittent problems.

That is, as shown in FIGS. 4 and 5, the width of the image track is wide at 49 mu m, and the widths of the image heads VH1 and VH11 which are commonly used are 49 mu m in the first SP head, and the second SP head. Is 60µm wide, so it is possible to auto track with VFM, but there is no difference in envelope size of VFM between 70% tracking and 100% tracking of video head (VH1, VH11) Therefore, if the automatic tracking using VFM alone, the automatic tracking stops at the level of 70-80%, and the high fidelity video player fails to play AFM with high fidelity.

In addition, the voice track is narrow to 16 mu m, and the width of the voice head AH11 is usually narrow to 26 mu m, so that the tracking is considerably deviated and the AFM is 0%.

Therefore, the AFM's envelope power is lost, and the microcomputer 15 automatically tracks a few steps and determines that the AFM has no envelope change, and determines that it is in a normal state, and the automatic tracking is stopped, so that the AFM cannot be reproduced even with high fidelity. Is caused by.

Therefore, an object of the present invention is to allow the audio head to accurately track the voice track by selectively giving priority to the VFM and the AFM according to the state of the video head and the audio head tracking the video head and the audio head. It is to provide an automatic tracking circuit that can regenerate AFM even in high fidelity.

That is, the present invention performs automatic tracking by giving priority to VFM with wide response range when tracking is much off, and giving priority to AFM with low response range near tracking center point, so tracking automatically tracks center point accurately. Done.

Hereinafter, the automatic tracking circuit of the present invention will be described in detail with reference to the attached drawings 6 and 7 as follows.

6 is an automatic tracking circuit diagram of the present invention. As shown therein, the VFM and AFM reproduced by the video head VH21 and the audio head AH21 are rotated through the rotation transformer T21 and T22, and the preamplifier 21 is shown in FIG. After amplifying at (22), the envelope detector 23 and 24 detected the envelope, and the priority circuit 25 selected the envelopes of VFM and AFM according to their levels and input them to the microcomputer 26.

FIG. 7 is a detailed view showing an embodiment of the priority circuit 25 of FIG. 6, and as shown therein, the output terminal of the envelope detector 23 is connected to the resistor R2 through the resistor R1, and The connection point was connected to the microcomputer 26 through the diode D1, and the output terminal of the envelope detector 24 was connected to the microcomputer 26 through the diode D2.

Referring to the effect of the present invention configured as described above are as follows.

The VFM and AFM reproduced by the video head VH21 and the audio head AH21 are amplified by the preamplifiers 21 and 22 through the rotation transformers T21 and T22, respectively, and the amplified VFMs and AFMs are envelope detectors. After detecting the envelope in (13) and (14), and inputting the detected DC output to the priority circuit 25, the priority circuit 25 selects the DC outputs of the input VFM and AFM envelopes according to their levels, In this case, the priority circuit 25 inputs the envelope detector 23 and the envelope DC output of the AFM detected by the envelope detector 24 through the diode D2. Will be entered at (26).

In this way, if the VFM envelope DC output level of the envelope detector 23 and the AFM envelope DC output level of the envelope detector 24 are substantially the same among the envelope DC outputs input to the microcomputer 26 through the priority circuit 25, that is, If the tracking is slightly off, the envelope DC output of the VFM output from the envelope detector 23 is distributed to the resistors R1 and R2 of the priority circuit 25 so that the DC output is reduced. Since the envelope DC output of the AFM of 24) is large, priority is given to the envelope detector 24 near the tracking center.

Therefore, since the envelope DC output of the AFM of the envelope detector 24 is input to the microcomputer 26 through the diode D2 of the priority circuit 25, the microcomputer 26 automatically performs tracking according to the input AFM envelope DC output. To perform.

On the other hand, when the VFM envelope DC output at the envelope detector 23 is larger than the AFM envelope DC output level at the envelope detector 24, i.e., when tracking is significantly deviated as shown in FIG. 4, the envelope detector At (23), the VFM envelope DC output is input to the microcomputer 26 through the resistors R1 (R2) diode D1 of the priority circuit 25, while the AFM envelope DC output of the envelope detector 24 is Since the priority circuit 25 selects the VFM envelope DC output of the envelope detector 23 first, the microcomputer 26 performs automatic tracking according to the envelope DC output of the input VFM.

When tracking is near the center during VFM automatic tracking, the envelope DC output of the VFM becomes smaller than the envelope DC output of the AFM, and the priority is given to the AFM envelope DC output of the envelope detector 24 having a narrow response in the priority circuit 25. Since the envelope DC output of the VFM is interrupted and the AFM envelope DC output of the envelope detector 24 is input to the microcomputer 26 through the diode D2, the microcomputer 26 is connected to the AFM envelope DC output. Therefore, if the tracking is stopped at the center of AFM during the automatic tracking and tracking, the high quality voice signal is output.

As described above, the present invention selects an audio FM signal with a narrow response and automatically tracks when tracking is slightly out of focus when tracking video and audio signals in a video player. It is possible to provide the effect of reproducing and outputting high-quality audio signal by first selecting the video FM signal so as to automatically track and selecting the audio FM signal with a narrow response range in the center range during tracking.

Claims (2)

The VFM and AFM reproduced by the video head VH21 and the audio head AH21 are amplified by the preamplifiers 21 and 22 through the rotation transformers T21 and T22, and the VFMs by the envelope detectors 23 and 24. And an automatic tracking circuit of an image player which automatically tracks the tracking according to the envelope level at the microcomputer 26 after detecting the envelope of the AFM, wherein the detector is detected between the square detectors 23 and 24 and the microcomputer 26. Automatic tracking circuit of a video player characterized in that it comprises a priority circuit (25) for selectively giving priority according to the envelope VFM and AFM DC output, The resistor circuit (1) according to claim 1, wherein the priority circuit (25) selects the VFM DC output first when the tracking is much off, and preferentially selects the AFM DC output when the tracking is slightly off. D1) (D2), the automatic tracking circuit of the video player characterized in that the configuration.