KR950006955B1 - Hifi/mono auto selecting apparatus and method for vcr - Google Patents

Abstract

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Description

Hi-Fi / Mono Auto Selector and Method of Video Cassette Recorder

1 is a block diagram of a hi-fi / mono selector of a conventional video cassette recorder.

2 is a waveform diagram of an essential part of a hi-fi / mono selector of a conventional video cassette recorder.

3 is a block diagram of a hi-fi / mono automatic selection apparatus of a video cassette recorder according to the present invention.

4a and b are flowcharts of a hi-fi / mono automatic selection method of a video cassette recorder according to the present invention.

* Explanation of symbols for main parts of the drawings

10: hi-fi detection circuit 20: mono detection circuit

30: detection circuit 40: selection circuit

50: control circuit

The present invention relates to a video cassette recorder, and more particularly, to a video cassette recorder for automatically selecting and outputting a Hi-Fi audio signal and a mono audio signal detected from a video tape according to a tape state. To a hi-fi / mono automatic selection device and method.

As part of a method for improving the audio quality of a video cassette recorder (hereinafter referred to as a VCR), a hi-fi VCR using a hi-fi video tape has been developed.

1 is a block diagram of an audio processing circuit of a conventional hi-fi VCR. As shown, the left and right audio signals recorded on the hi-fi video tape are respectively detected by the left and right hi-fi audio heads LH (RH) in the hi-fi detection circuit 10 and applied to the preamplifiers Amp1 and Amp2. The pulse P1 of FIG. 2 is an audio signal detected at the left head LH, and the pulse P2 is an audio signal detected at the right head RH. In the preamplifiers Amp1 and Amp2, the left and right hi-fi audio signals are amplified, filtered by the bandpass filters BPF1 and BPF2, and applied to the switching circuit 11. At this time, a switching signal such as the pulse P3 of FIG. 2 is applied to the switching circuit 11, and when the high level switching signal is applied, the left audio signal P1 of the band pass filter BPF1 is output and The audio signal P2 of the band pass filter BPF2 is outputted when the switching signal is applied. Therefore, the signal applied from the switching circuit 11 to the hi-fi audio processing circuit 11 may be in a state in which the left audio signal P1 and the right audio signal P2 are combined together with the pulse P4.

At this time, even in a hi-fi VCR, a mono detection circuit 20 for detecting an audio signal of a general mono VCR is provided. The mono detecting circuit 20 is configured so that the head H for general audio detects an audio signal recorded on an audio track of a video tape as shown, and the audio signal detected at the head H for audio is equalized. Amp3) and the main amplifier (Amp4) to amplify and output.

In such a configuration, when playing back a high-fidelity video tape having a poor recording state, the user can listen to the mono audio detected by the mono detection circuit 20 rather than having the user listen to the hi-fi audio detected by the hi-fi detection circuit 10. The sound quality will be further improved.

To this end, the detection circuit 30 and the selection circuit 40 have been conventionally used. That is, the detection circuit 30 compares the envelope waveform of the hi-fi audio signal of the hi-fi detection circuit 10 with a predetermined reference value and outputs a detection signal when it is lower than the predetermined reference value.

The selection circuit 40 outputs the mono audio signal of the mono detection circuit 20 when the detection signal is applied from the detection circuit 30, and the hi-fi audio signal of the hi-fi detection circuit 10 when the detection signal is not applied. Is configured to output

That is, the sound quality of the hi-fi audio signal output from the hi-fi detection circuit 10 deteriorates the sound quality when the envelope waveform is lowered, thereby outputting the mono audio signal of the mono detection circuit 20.

However, the above-described prior art outputs a mono audio signal by the switching action of the selection circuit whenever the envelope waveform of the hi-fi audio signal detected in the hi-fi video tape is lowered, so that the recording state of the audio signal is locally poor. When the tape is played back, a mono audio signal and a hi-fi audio signal are output alternately, and thus a deterioration of listening feeling occurs.

In addition, since the switching noise is generated in the audio signal every time the switching of the selection circuit occurs, there is a problem that the sound quality deteriorates.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to determine a recording state of an audio signal of a videotape for a predetermined time and to improve the quality of the hi-fi audio signal or a mono audio signal by forcing a stable output for a predetermined time. To provide a hi-fi / mono auto selector and method of the VCR.

A feature of the present invention for achieving the above object is a video cassette recorder capable of selectively outputting a hi-fi audio signal and a mono audio signal, comprising: hi-fi detection means for detecting and outputting a hi-fi audio signal from a video tape; Mono detecting means for detecting and outputting a mono audio signal from a video tape; Detection means for outputting a detection signal when the envelope waveform of the hi-fi audio signal detected by said hi-fi detection means is below a predetermined reference value; Control means for selectively outputting a mono selection signal or a hi-fi selection signal by determining a frequency of output of the detection signal of the detection means for a predetermined time; A hi-fi / mono automatic of a video cassette recorder having selection means for outputting a mono audio signal of the mono detection means upon application of the mono selection signal and outputting a hi-fi audio signal of the hi-fi detection means upon application of the hi-fi selection signal; Selective means device.

According to another aspect of the present invention, a detection signal is generated when an envelope waveform of a hi-fi audio signal detected from a magnetic tape is equal to or less than a predetermined reference value, a hi-fi audio signal is output when a hi-fi audio signal is generated, and a mono audio signal is output when a mono selection signal is generated. A high fidelity mono audio selection method of a video cassette recorder, comprising: outputting a mono selection signal by increasing a coefficient value each time a detection signal is generated; Determining whether the mode selection mode occurs when no detection signal is generated, outputting a mono selection signal in the mono selection mode, and outputting a hi-fi selection signal in a non-mono selection mode every predetermined time; Determining whether the value counted in the first step is equal to or greater than a predetermined value; Setting a mono selection mode when the coefficients and values are greater than or equal to a predetermined value, and releasing the mono selection mode when the coefficients and values are less than or equal to a predetermined value; And a second process of performing the step of resetting the count value every predetermined time after performing the above steps.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram of a hi-fi / mono autoselecting apparatus of the VCR according to the present invention, and the same reference numerals as those of FIG. The invention is a hi-fi composed of left and right audio head (LH) (RH) preamplifier (Amp1) (Amp2) band pass filter (BPF1) (BPF2) switching circuit 11 and hi-fi audio processing circuit 13 as shown. It includes a detection circuit 10, and includes a mono detection circuit 20 serving as a general audio head HD1 equalization amplifier Amp3 and a main amplifier Amp4.

The present invention also includes a detection circuit 30 for outputting a detection circuit when the envelope waveform of the hi-fi audio signal output from the hi-fi detection circuit 10 is smaller than a small reference value, and the detection circuit 30 includes a control circuit. 50 are connected.

The control circuit 50 is usually composed of a microcomputer and performs the same operation as the flowcharts of FIGS. 4A and 4B. The flowchart of FIG. 4 is mentioned later.

The selection circuit 40 connected to the control circuit 50 outputs the mono audio signal of the mono detection circuit 20 when the mono selection signal is applied from the control circuit 50 and detects the hi-fi when the hi-fi selection signal is applied. The circuit 10 is configured to output a hi-fi audio signal.

The operation of the control signal 50 described above will be described with reference to FIG. 4. FIG. 4A is a flowchart performed by the control circuit 50 every 10 msec. As shown in the figure, a signal is input in step S1, and if it is detected by detecting whether the rising or falling edge is detected in step S2, if it is detected, the count value is increased by one and in step S2 Proceed. In step S2, it is determined whether the detection signal is applied from the detection circuit 30, and if the detection signal is not applied, the flow advances to step S6 to apply a mono selection signal to the selection circuit 40.

At this time, if the detection signal is applied in step S4, it is determined whether the mono flag is set in step S5. If the mono flag is set, the process proceeds to step S6 to output a mono selection signal.

However, if the mono flag is not set in step S5, the flow advances to step S7 to output the hi-fi select signal.

In FIG. 4B, the flowchart performed by the control circuit 50 every 10 sec is shown.

As shown in the figure, if the value counted in step S3 in step S7 is greater than or equal to a predetermined value, for example, 10, the process proceeds to step S8, and in step S8, the above-mentioned mono flag is set. .

However, if the result of the determination in step S7 is smaller than 10, the flow advances to step S9 to set the mono flag to the reset state. After the steps S8 and S9 are performed, the process proceeds to step S10 to reset the count value.

As can be seen from the above description, the control circuit 50 counts the input detection signal every 10 msec and selects mono only when the detection signal is applied or when the mono flag is set (i.e., set to the mono mode). Output the signal. At this time, the monoflag is set when the count value of the detection signal reaches a predetermined value as shown in FIG. 4B.

Therefore, when the count value of the detection signal is greater than or equal to the predetermined value, the control circuit determines that the hi-fi audio signal is poorly recorded on the video tape and outputs the mono selection signal.

In addition, since the control circuit 50 performs the above-described processes every predetermined time, when the hi-fi audio signal is badly recorded only on a part of the video tape, the control is performed when the signal recorded in the other part other than the part is reproduced. The circuit 50 will output a hi-fi select signal.

As described above, the present invention detects the state in which the hi-fi audio signal is recorded on the video tape every predetermined time and outputs the hi-fi or mono audio signal according to the recording state. The sound quality can be improved by preventing switching, and there is an effect of preventing switch noise caused by the selection circuit switch action.

Claims (2)

A video cassette recorder capable of selectively outputting a hi-fi audio signal and a mono audio signal, comprising: hi-fi detection means for detecting and outputting a hi-fi audio signal from a video tape; Mono detecting means for detecting and outputting a mono audio signal from a video tape; Detection means for outputting a detection signal when the envelope waveform of the hi-fi audio signal detected by said hi-fi detection means is below a predetermined reference value; Control means for selectively outputting a mono selection signal or a hi-fi selection signal by determining a frequency of output of the detection signal of the detection means for a predetermined time; A hi-fi / mono automatic of a video cassette recorder having selection means for outputting a mono audio signal of said mono detection means when said mono selection signal is applied and outputting a hi-fi audio signal of said hi-fi detection means when said hi-fi selection signal is applied; Selector. The detection signal is generated when the envelope waveform of the hi-fi audio signal detected from the magnetic tape is equal to or less than a predetermined reference value, and the hi-fi audio signal is output when the hi-fi audio signal is generated, and the mono audio signal is output when the mono selection signal is generated. A mono audio selection method, comprising: increasing a coefficient value each time a rising and falling edge signal is generated; Determining whether the mono selection mode is applied when the hi-fi detection signal is not generated, outputting a mono selection signal in the mono selection mode, and outputting a hi-fi selection signal in the mono selection mode every predetermined time; Determining whether the value counted in the first process is greater than or equal to a predetermined value, setting a mono selection mode when the coefficient and the value are greater than or equal to a predetermined value, releasing the mono selection mode when the predetermined value is less than or equal to the predetermined value, and And a second step of performing the step of resetting the count value every predetermined time after the execution.