KR0132042B1 - Normal sound reproducing circuit for high-speed reproducing mode - Google Patents

Abstract

Disclosed is a normal audio outputting circuit when winding a tape with high speed. The circuit comprises 4 audio heads(L,R,L',R'), 4 input terminals which receives play-back signals from the 4 audio heads(L,R,L',R'), a comparator(26) which compares the envelopes of the play-back signals and generates "high" or "low" signals, a head switch(22) which applies a signal output from a pair of the audio heads(L',R') according to a head switching pulse to a terminal(-) of the comparator as a "low" or "high" signal, and selectively applies the signal output from another pair of audio heads(L,R) to another terminal(+) of the comparator as a "low" or "high" signal, and a head A switch which is connected to an end of the head switch(22) and judges the tape play-back speed as a standard speed or a long time speed according to the output signal of the comparator(26). Thus, normal audio is output when winding the tape with high speed.

Description

Normal sound output circuit at high speed

1 is a schematic block diagram showing processing of an audio signal during high speed travel of the prior art.

2 illustrates an audio four head in accordance with the present invention.

3 is a schematic block diagram showing audio signal processing at high speed playback according to the present invention;

4 is a diagram showing the operation of the head switching switch of the preamplifier of FIG.

5 is a table showing head selection by recording / playback and special playback modes.

6 illustrates a hi-fi head traces an audio track during special playback of the present invention.

* Explanation of symbols for main parts of the drawings

10: 4-head signal input 20: Preamplifier

30: demodulator 40: sample / fold circuit

22: head switch 24: head A switch

26: comparator

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice output circuit of a VCR, and more particularly, to a VCR audio output circuit which outputs normal sound when a special playback of a VCR Hi-Fi tape is performed, for example, at a double or triple speed. will be.

When playing back a conventional VCR hi-fi tape at high speed, as shown in FIG. 1, a high speed audio input signal is sampled through the sampling circuit 1, remodulated by the modulation circuit 2, and then again the filter 3 Audio is output via At this time, assuming that the tape running speed is high, for example, a double speed, the audio input signal frequency is also doubled so that audio is abnormally output. Therefore, in the conventional high-fidelity tape high-speed playback, the audio output is muted to remove such abnormal sounds.

An object of the present invention is to allow a user to listen not only to a screen reproduced at a high speed during the special high-speed playback of such a VCR hi-fi tape but also to a corresponding voice as a normal sound.

In order to achieve this object, the present invention uses two to four conventional VCR hi-fi audio heads. In addition, the present invention allows the four audio heads to be switched in the preamplifier so that the frequency characteristics are not increased even though the tape speed is increased and the audio signal is input at high speed.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

2 is a diagram illustrating an audio four head according to the present invention.

The present invention is constructed by adding two heads L 'and R' to two conventional heads L and R. By adding two audio heads as described above, normal sound can be heard even at high speed playback. A more detailed description thereof is as follows.

3 is a schematic diagram showing audio signal processing during high speed playback according to the present invention. The operation of the present invention during high speed reproduction, for example, at double speed reproduction will be described as follows.

The signal 10 reproduced from each of the four heads R, L, R ', and L' according to the present invention is a signal having a weak level, and is provided to the preamplifier 20 and amplified to a predetermined level.

The signals amplified from each of the four audio heads are connected by head switching pulses (PG pulses) to form a nearly continuous signal capable of demodulation. This signal is passed to an audio signal processing request 50 comprising a demodulation circuit 30 and a sample / hold circuit 40.

The demodulation circuit 30 in the audio signal processing circuit 50 is divided into a left signal (1.3 MHz) and a right signal (1.7 MHz) by a band pass filter (BPF) and then made into a shape of an audio signal by demodulation. This demodulated signal is delayed by a delay (not shown) and then passed to the sample / hold circuit 40. The sample / hold circuit 40 is to compensate for noise caused by switching. The sample / hold circuit 40 detects noise generated when the voice signal is discontinued when the voice signal is dropped out or when the head is replaced by the dropout detector. The noise waveform is held just before that to remove noise. Therefore, the signal output from the sample / hold circuit 40 can be output as a normal sound even at high speed reproduction, for example, at double speed reproduction.

FIG. 4 is a diagram illustrating the operation of the head switching switch of the preamplifier 20 shown in FIG. In the description, signals from four audio heads L, R, L ', and R' will be referred to as (L, R, L ', and R').

The signals reproduced from these four audio heads L, R, L ', and R' are provided to the preamplifier 20, and the signals from each head are head-changed pulses (PG pulses) synchronized with the rotation of the rotating cylinder. Is connected to the demodulator (30).

First, the normal playback time, the head switch 22 is switched by the head switching pulse to selectively output the signal reproduced from each head, in this case, only the head (R ', L') in the standard speed (SP) mode In the long-term speed (SLP) mode, only the heads R and L are used. That is, in the standard speed mode SP, the head switching pulse is applied only to the switches for switching the heads R 'and L' of the head switch 22 to switch signals reproduced from the heads R 'and L'. By providing the audio circuit 50 through the head A switch 24, normal reproduction is achieved. That is, when playing in the standard speed (SP) mode, only the signals switched by the heads R 'and L' are input to the negative terminal of the comparator 26, and the signals from the heads R and L are Since the positive terminal of the comparator 26 is not input to the positive terminal, the positive terminal is always at the '0' level, and thus the comparator 26 always outputs a 'low' signal. Therefore, since the 'low' signal is applied to the head A switch through the microcomputer (not shown), the head A switch 24 is connected to the standard speed SP terminal to receive the reproduction signals from the heads R 'and L'. It is output to the audio circuit 50.

In the long-term speed (SLP) mode, the head switching pulse is applied to a switch for switching the heads R and L of the head switch 22 so that the normal regeneration is performed by switching only the heads R and L. This works the same for recording. That is, when playing back in the long speed speed (SPL) mode, only the signal switched by the heads R and L is input to the negative terminal of the comparator 26, and the signal from the heads R 'and L'. Since is not input to the positive terminal of the comparator 26, the positive terminal is always at the '0' level, thereby the comparator 26 will always output a 'high' signal. Accordingly, since the 'high' signal is applied to the head A switch through a microcomputer (not shown), the head A switch 24 is connected to the speed SLP terminal for a long time to output the signal from the head R and L to the audio circuit 50. ) To allow long-term speed (SLP) playback.

That is, as described above, the head A switch 24 is set to switch between the standard speed SP mode and the long time speed SLP mode. That is, when the head A switch 24 is high, the long-time speed mode is also operated in the standard speed mode when it is low.

On the other hand, during special playback (e.g., playback at double speed), the following two cases operate. First, when the head switch is low due to the head switching pulse, a pair of heads L 'and R of the audio heads are selected, and the envelope of the signal detected from the head is negative (-) and (+) terminals of the comparator 26. Is entered. At this time, when the envelope of the head L 'is large, the comparator 26 outputs a low signal, and when the envelope of the head R is large, a high signal is generated. The output of the post comparator 26 is sent back to the head A switch 24 of the preamplifier 20 via a microcomputer (not shown). Therefore, the mode switching between the standard speed SP and the long time speed SLP causes the head A switch 24 to send a signal of the head having a large envelope to the audio head 50. Second, when the head switch 22 is high by the head switching pulse, another pair of audio heads R 'and L' is selected and the envelope of the signal detected from the head is negative (-), (+ Is inputted to the terminal to perform the same operation as when the heads L 'and R are selected.

5 is a table summarizing and displaying the heads selected for each of the modes described above.

Although the above description has been given by way of example during reproduction, the same applies to recording.

6 is a diagram illustrating an example in which the hi-fi head traces an audio track during the special reproduction of the present invention, when the audio signal is read, the normal sound is output because the frequency does not change even during the special reproduction.

By using the configuration and the circuit of the present invention as described above, the normal sound is reproduced even during the special reproduction of the VCR hi-fi audio signal, so that the voice can be heard along with the high speed video screen.

Claims (1)

In the high fidelity audio output circuit of the hi-fi audio circuit for outputting the normal audio sound during the high speed playback at the double speed in processing the high fidelity audio signal reproduced in the hi-fi audio circuit of the VCR, four audio heads ( L, R, L ', R'); A comparator 26 having four input terminals receiving reproduction signals from the four audio heads L, R, L ', and R', and generating a high or low signal by comparing envelopes of the reproduction signals; According to a switching pulse, the signal from the pair of audio heads R 'and L' is switched to a low or high signal and connected to one end of the comparator, and from the other pair of audio heads R and L. A head switch 22 selectively connected to the other end of the comparator 26 as a signal low or high signal, and connected to one end of the head switch 22 and according to an output signal of the comparator 26. An audio head switching circuit 20 composed of a head A switch 24 for setting a reproduction speed as a standard speed or a long time speed; And an audio signal processing circuit (50) for demodulating the output of the head A switch (24) of the audio head switching circuit (20) and compensating for noise generated during the switching operation of the switch (24). Normal sound output circuit at high speed of hi-fi audio circuit.