JPS6252705A - Dropout compensating circuit - Google Patents

Abstract

PURPOSE:To attain dropout compensation attended with natural listening by using a normal sound subjected to level correction so as to replace high fidelity sound in response to a signal level of the high fidelity sound just before a dropout takes place when the dropout takes place in the high fidelity sound. CONSTITUTION:When a dropout takes place in a high fidelity sound, a dropout compensation circuit 11 changes a gain of a voltage controlled amplifier circuit 12 in response to a signal level of the high fidelity sound just before the dropout takes place, which is detected by a level detection circuit 13 and the high fidelity sound is replaced by conventional sound subject to level correction. Even when the conventional sound is recorded automatically at a prescribed signal level by an automatic level control circuit at recording, different from the simple replacement of the dropout by the conventional sound, the disconvenience where the signal replacement to the dropout is conducted attended with level fluctuation giving displeasure to ears is avoided and the dropout compensation attended with very natural listening is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dropout compensation circuit that replaces the dropout portion of high-fidelity audio with normal audio.

[Prior Art] A video tape recorder that performs FM modulation on an audio signal, uses a frequency band intermediate between the FM modulated luminance signal and the low frequency conversion chromaticity signal, and multiplexes the recording onto a video track is a high-fidelity audio signal. In addition to normal audio recorded on audio tracks along the side edges of the magnetic tape, it is also possible to simultaneously record signals from different sound sources as high-fidelity audio. However, in terms of -i, high-fidelity audio and normal audio often record the same audio, and due to differences in recording methods such as rotating magnetic heads and fixed magnetic heads, or FM modulation recording and AM modulation recording, the reproduced audio differs. Differences in sound quality are inevitable.

However, even normal audio, which is inferior in sound quality, has a characteristic that dropouts occur less frequently than high-fidelity audio. Taking advantage of this characteristic, it is possible to replace normal audio with high-fidelity audio at the dropout part of high-fidelity audio. Sometimes used. The dropout compensation circuit 1 shown in FIG. 2 is a system that replaces the dropout part of high-fidelity audio with normal audio, and connects the output of the normal audio circuit 2 connected to the fixed magnetic head 2a and the rotating magnetic head 3a. The output of the high-fidelity audio 3 is selectively guided to the audio output terminal 7 via an analog switch circuit 5.6 which opens and closes in reverse operation according to the output of the dropout detection circuit 4. Since the dropout detection circuit 4 outputs a low level signal when detecting a dropout, the dropout detection circuit is normally connected to the analog switch circuit 5 provided between the audio circuit 2 and the audio output terminal 7 via an inverter circuit 8. 4 outputs are provided.

[Problems to be Solved by the Invention] The conventional dropout compensation circuit 1 described above is configured to simply switch the dropout portion to normal audio when a dropout occurs in the high-fidelity audio signal. In the case of normal audio recorded after level correction by an automatic level control circuit (not shown), the signal levels of the level-corrected normal audio and high-fidelity audio do not continue smoothly at the dropout part, causing listeners to On the other hand, the signal level of the reproduced audio changes unnaturally, giving the illusion that it is difficult to listen to.

[Means for Solving the Problems] This invention solves the above-mentioned problems. Hi-Fi audio and normal audio, which have different sound quality based on the difference in recording method for the same audio, are separately supplied. a dropout compensation circuit that replaces a dropout portion with normal audio when a dropout occurs in audio, the amplifier circuit having a variable gain that amplifies the normal audio;
The signal level of the high-fidelity audio is detected, the gain of the amplifier circuit is changed according to the detected signal level, and the signal level of the normal audio that is replaced with the high-fidelity audio during the dropout period is changed to the signal level of the high-fidelity audio immediately before the dropout occurs. The gist is that a level detection circuit is provided to match the level.

[Operation] When a dropout occurs in high-fidelity audio, the present invention replaces the high-fidelity audio with normal audio whose level is corrected according to the signal level of the high-fidelity audio immediately before the dropout, providing an extremely natural hearing sensation. This makes it possible to compensate for accompanying dropouts.

[Example] Hereinafter, an example of the present invention will be described with reference to FIG. 1. FIG. 1 is a circuit diagram showing an embodiment of the dropout compensation circuit of the present invention.

In FIG. 1, the dropout compensation circuit 11 includes a voltage control amplifier circuit 12 between the normal audio circuit 2 and the analog switch circuit 5, and a level detection circuit 13 that detects the output level of the high-fidelity audio circuit 3. The configuration is such that the gain of the control amplifier circuit 12 is variable.

The voltage control amplifier circuit 12 can be switched between a normal audio mode and a high-fidelity audio mode by a changeover switch 14 connected to its gain control terminal, and terminals 14n and 14h corresponding to each mode are connected to voltage dividing circuits. 15 and the level detection circuit 13 are connected. The voltage divider circuit 15 divides the power supply voltage of the DC power supply 1,000 B into resistors R1 and R2.
In order to apply a constant voltage to the terminal 14n by dividing the voltage by
The gain of is fixed to a constant value.

The level detection circuit 13 includes a buffer amplifier circuit 16 connected to the output terminal of the high-fidelity audio circuit 3, and an output terminal of the buffer amplifier circuit 16 connected to a switch 17a and a capacitor C.
The buffer amplifier circuit 1 consists of a sample-and-hold circuit 17 that performs sampling and holding by
8 is applied to the terminal 14h via the resistor R3.

The switch 1.7a in the sample/hold circuit 17 is opened by the dropout detection signal of the dropout detection circuit 4, and is in an open state during the period when the dropout error 1~ occurs, but is otherwise closed. .

Assume that the selector switch 14 is now switched to the high-fidelity audio mode. In this case, the gain of the voltage control amplifier circuit 12 will always change depending on the output of the level detection circuit 13, but during the period when the analog switch circuit 5 is open, the output of the voltage control amplifier circuit 12 will be It is not led to the output terminal 7.

Here, when a dropout occurs in the high-fidelity audio, the output of the dropout detection circuit 4 causes the analog switch circuit 5 to close instead of the analog switch circuit 6. Therefore, the audio output terminal 7 is connected to the voltage control amplifier circuit 12 via the analog switch circuit 5.

In this case, the switch 17a of the sample-and-hold circuit 17 in the level detection circuit 13 opens when dropout occurs, so the capacitor C stores the high-fidelity audio signal level immediately before the dropout occurs. For this reason, the voltage control amplifier circuit 12 whose gain is controlled according to the output voltage of the level detection circuit 13 detects normal audio so that an output level comparable to the signal level of high-fidelity audio immediately before dropout occurs is obtained. Amplify with an appropriate degree of amplification.

The normal audio amplified by the voltage control amplifier circuit 12 is replaced with the missing part of the high-fidelity audio during the dropout period, but at that time, the audio signal guided to the audio output terminal 7 before and after the dropout occurs. There are no jarring level fluctuations, and a natural hearing sensation without the possibility of dropouts can be obtained.

In this manner, when a dropout occurs in high-fidelity audio, the dropout compensation circuit 11 adjusts the voltage control amplifier circuit 12 according to the signal level of the high-fidelity audio immediately before the dropout detected by the level detection circuit 13. By changing the gain of normal audio with level correction.

Because the configuration replaces high-fidelity audio, even if normal audio is automatically recorded at a constant signal level by the automatic level control circuit during recording, the dropout portion can be simply replaced with normal audio. Unlike the case,
There is no inconvenience that signal replacement for dropouts is performed with jarring level fluctuations, and dropout compensation with extremely natural hearing sensation is possible.

[Effects of the Invention] As explained above, according to the present invention, when a dropout occurs in high-fidelity audio, the high-fidelity audio is replaced by normal audio whose level is corrected according to the signal level of the high-fidelity audio immediately before the dropout occurs. Even if the normal audio is automatically recorded at a constant signal level by the automatic level control circuit during recording, it is possible to simply replace the dropout part with the normal audio. In contrast, there is no inconvenience that signal replacement for dropouts is accompanied by jarring level fluctuations, and excellent effects such as dropout compensation with extremely natural hearing sensation are possible.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a dropout compensation circuit of the present invention, and FIG. 2 is a circuit diagram showing an example of a conventional dropout compensation circuit. 2... Normal audio circuit, 3... Hi-fi audio circuit,
4... Dropout detection circuit, 5.6... Analog switch circuit, 11... Dropout compensation circuit,
12... Voltage control amplifier circuit, 13... Level detection circuit.

Claims (1)

[Claims] A dropout compensation circuit that separately supplies high-fidelity audio and normal audio that have sound quality differences based on differences in recording methods for the same audio, and replaces the dropout portion with normal audio when a dropout occurs in the high-fidelity audio. , a variable gain amplifier circuit that amplifies the normal audio, detects the signal level of the high-fidelity audio, and changes the gain of the amplifier circuit according to the detected signal level,
A dropout compensation circuit comprising: a level detection circuit that matches the signal level of normal audio to be replaced with high-fidelity audio during a dropout period to the signal level of high-fidelity audio immediately before the dropout occurs.