JPS6226674A - Sound drop-out compensating device - Google Patents

Abstract

PURPOSE:To improve the compensating performance of a sound drop-out by providing a drop-out detecting means and a compensating means to compensate the omitted part of the sound signal in response to a drop-out detecting signal. CONSTITUTION:When the first drop-out detecting circuit 13 of the drop-out detecting means 5 detects the drop-out when the drop-out generating period is in the setting period of 50 micro seconds or above and less than 1 millisecond, the first drop-out detecting signal S1 corresponding to the drop-out generating period is inputted, and in response to this, the sound signal level is held and corrected by holding circuits 15 and 16 of a compensating means 6. When the second drop-out detecting circuit 14 detects the drop-out in which the drop-out generating period exceeds the setting period of 1 millisecond or above, the second drop-out detecting signal corresponding to the generating period is outputted, and in response to this, muting is executed and corrected by muting circuits 17 and 18 or the compensating means 6. Thus, the high performance sound drop-out compensation can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an audio dropout compensation device suitable for a video disc player, a video tape recorder, or the like.

<Prior Art> In video disc players and the like, playback signals may drop out due to scratches on the video disc or dust attached thereto. Such dropouts are a major cause of damage not only to the reproduced video but also to the audio.

General methods for compensating for video and audio losses due to such dropouts are as follows.

That is, regarding the video signal, dropout compensation is performed by replacing the video signal at the time when the dropout occurs with a video signal from one horizontal scanning period before the time, which has a high correlation with the video signal. In the case of a video signal, since it is a visual signal, such a method can sufficiently compensate for dropouts. On the contrary,
Since the audio signal is auditory, the audio signal is corrected to compensate for the dropout by simply muting the audio signal from the point at which the dropout occurs, or by increasing the hold.

However, in the conventional dropout compensation for audio signals, regardless of the length of the dropout occurrence period, compensation was performed by regularly muting or holding. For some reasons, it may not be possible to sufficiently eliminate the effects of dropout.

For example, in the method of correcting by applying a hold to the -temperature, the period during which a dropout occurs is set in advance as a fixed period, and when a dropout occurs, the correction is performed by applying a hold for that period of occurrence. When the dropout occurrence period is relatively long, for example, several tens of milliseconds, it is not possible to sufficiently remove the noise associated with the dropout. When a dropout occurs for a long time like this, it is preferable to correct it by applying muting, since although the sound is eliminated, it also eliminates noise.

On the other hand, in the method of correcting by applying muting regularly, the occurrence period is medium length, for example, several hundred microseconds, and the occurrence period is when the audio signal rises from the zero level, or when the sound signal rises from the zero level or When a dropout occurs at the timing of a dropout, if muting is applied at that timing, the level of the audio signal suddenly drops to zero level, which is undesirable because the audio suddenly becomes silent. Therefore, in such a case, it is preferable to correct by applying hold rather than muting.

<Object of the Invention> The present invention has been made in view of the above points, and provides high-performance audio by selecting and performing a dropout correction method according to the length of the dropout occurrence period. An object of the present invention is to provide a dropout compensation device.

<Structure of the Invention> In order to achieve the above-mentioned object, the present invention provides a first dropout detection signal that outputs a first dropout detection signal corresponding to the dropout occurrence period when the dropout occurrence period is within a set period. Dropout detection means comprising a dropout detection circuit, and a second dropout detection circuit that outputs a second dropout detection signal corresponding to the dropout occurrence period when the dropout occurrence period exceeds the set period. , a hold circuit that holds the audio signal level before the dropout occurs in response to the first dropout detection signal, and a muting circuit that mutes the audio signal in response to the second dropout detection signal. The device is configured to selectively perform muting or holding depending on the length of the dropout occurrence period to compensate.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of one embodiment of the present invention. In the figure, ■ is a pickup, 2 is a preamplifier that amplifies the reproduced signal from pickup l, 3 is an FM demodulation circuit, and 4 is a video signal processing circuit that performs predetermined signal processing such as dropout correction and jitter correction of the video signal. , 5 is a dropout detection means for detecting a drop alert based on the reproduced signal from the FM demodulation circuit 3, and 6 is a first . Second dropout detection signal S1. Compensation means for compensating for missing portions of the audio signal in response to S2; 7 and 8 are bandpass filters (BPF) for both channels that separate audio carriers; 9 and 10 are FM demodulation circuits; 11 is a de-emphasis and noise reduction circuit; This is an audio signal processing circuit that performs processing such as Kunyong.

The dropout detection means 5 includes a dropout detection circuit 12 that detects dropout based on the reproduced signal and outputs a dropout detection signal S, and a dropout detection circuit 12 that detects dropout based on the dropout detection signal S of the dropout detection circuit 12. A first dropout detection circuit 13 that outputs a first dropout detection signal Sl corresponding to the dropout occurrence period when the dropout occurrence period is within a set period, and a dropout occurrence period exceeding the set period. A second dropout detection circuit 14 outputs a second dropout detection signal S2 corresponding to the dropout occurrence period.

The compensation means 6 includes hold circuits 15 and 16 that hold the audio signal level before the dropout occurs in response to the first dropout detection signal S1, and hold circuits 15 and 16 that hold the audio signal level before the dropout occurs in response to the second dropout detection signal S2. It consists of muting circuits 17 and 18 for muting.

In this example, short dropouts of about a few microseconds do not affect the playback audio, so dropouts of medium length of about several hundred microseconds can be corrected without correction. The system holds the audio signal level before a dropout occurs, and performs muting for relatively long dropouts of about several tens of milliseconds.

Therefore, in this embodiment, the above-mentioned setting period in the detection means 5 is selected to be 50 microseconds or more and less than 1 millisecond.

Therefore, the first dropout detection circuit 13 of the dropout detection means 5 has a dropout occurrence period of 50
When it is within the set period of microseconds or more and less than 1 millisecond,
In other words, when a dropout over a medium length is detected, the first
A dropout detection signal S1 is output, and in response to this, the audio signal level is held and corrected by the hold circuits 15 and 16 of the compensation means 6. Further, when the second dropout detection circuit 14 detects a long dropout in which the dropout occurrence period exceeds the set period of 1 millisecond or more, the second dropout detection circuit 14 outputs a second dropout detection signal corresponding to the dropout occurrence period. In response to this, muting is performed by the muting circuits 17 and 18 of the compensating means 6 for correction.

FIG. 2 is a signal waveform diagram of each part for explaining the operation of the embodiment of FIG. 1, and the operation of the audio dropout compensating apparatus having the above configuration will be explained with reference to FIG. The reproduced signal picked up by the pickup 1 is amplified by a preamplifier 2, demodulated by an FM demodulation circuit 3, and then supplied to a video signal processing circuit 4, a dropout detection means 5, and a bandpass filter 7.8, respectively.

Dropout detection circuit 1 of dropout detection means 5
2, all dropouts including dropouts of less than 50 microseconds are detected and the dropout detection signal S shown in FIG. They are applied to second dropout detection circuits 13 and 14, respectively. The video signal processing circuit 4° C. performs dropout correction on the video signal based on this dropout detection signal S, and further performs predetermined signal processing such as jitter correction to form a standard television signal.

The first dropout detection circuit 13 of the dropout detection means 5 detects a moderate dropout with a dropout occurrence period of 50 microseconds or more and less than 1 millisecond, and detects the first dropout shown in FIG. 2(B). Out detection signal S
1 is applied to the hold circuits 15 and 16 of the compensation means 6, respectively. The second dropout detection circuit 14 of the dropout detection means 5 detects a dropout with a long dropout occurrence period of 1 millisecond or more and generates a second dropout detection signal S2 as shown in FIG. 2(c). Compensation means 6
muting circuits 17 and 18 respectively.

On the other hand, in the audio system, the PM carriers of each channel are separated by the bandpass filter 7.8 and the signal S3 shown in FIG. 2(D) is outputted, and the FM demodulation circuit 9. The audio signal S4. which is demodulated by IO and shown in FIG. 2(E)CF)(H). An audio signal having portions S5 and 97 is output. Note that here, these audio signals S4. S5,97
The dropout occurrence periods tl, t2 . This is an enlarged view of the portions corresponding to t3, and in the audio signal 84 portion shown in FIG. 2(E), the relatively short period t of less than 50 microseconds is shown.
Dropout occurred over the course of 1, and as shown in Figure 2 (F
) In the audio signal 85 portion shown in FIG. In this case, dropout occurs over a period t3 of 1 millisecond or more.

Hold circuits 15 and 16 of the compensation means 6 hold the audio signal level in response to the first dropout detection signal Sl. For example, the audio signal 85 portion in FIG. 2(F) is held by the hold circuits 15 and 16 for a dropout occurrence period t2, and is output as the audio signal S6 shown in FIG. 2(G). . Further, the muting circuits 17 and 18 of the compensation means 6 perform muting in response to the second dropout detection signal S2. For example, in the audio signal 87 portion of FIG. 2(H),
Muting is performed over the dropout occurrence period t3 and output as the audio signal S8 shown in FIG. 2(1).

In this way, dropouts of less than 50 microseconds that have no effect on the playback audio are not compensated for, and dropouts of medium length greater than 50 microseconds and less than 1 millisecond are compensated for. Hold is applied to compensate, and if the dropout is longer than 1 millisecond, muting is applied to compensate, so unlike the conventional example, hold or muting is applied across the board. It is possible to reduce the influence of dropout compared to correction.

That is, for example, it is possible to sufficiently remove dropout noise even when the period during which dropout occurs is relatively long, on the order of tens of milliseconds, compared to the conventional example in which a hold is applied to correct the dropout noise. In addition, the dropout period is moderately long, on the order of several hundred microseconds, compared to the conventional example in which the dropout is corrected by applying muting to the audio signal (1 rises from zero level, or Even if a dropout occurs at the falling timing, the level of the audio signal will not suddenly drop to zero level, making it possible to perform high-performance audio dropout compensation.

In the above-mentioned embodiment, the setting period was selected to be 50 microseconds or more and less than 1 millisecond, but it is not limited to this, and it goes without saying that it may be selected as appropriate.

<Effects of the Invention> As described above, according to the present invention, the dropout detection means outputs the first and second dropout detection signals according to the length of the dropout occurrence period based on the reproduced signal; The first signal from the dropout detection means. compensating means for compensating for a missing portion of the audio signal in response to a second dropout detection signal, the dropout detecting means being configured to compensate for a dropout occurrence period when the dropout occurrence period is within a set period. a first dropout detection circuit that outputs the corresponding first dropout detection signal; and a second dropout detection circuit that outputs the first dropout detection signal corresponding to the dropout occurrence period when the dropout occurrence period exceeds the set period.
a second dropout detection circuit that outputs a dropout detection signal, and the compensation means includes a hold circuit that holds the audio signal level before the dropout occurs in response to the first dropout detection signal; 2, it includes a muting circuit that mutes the audio signal in response to the dropout detection signal, so it is possible to selectively perform muting or holding to compensate for the length of the dropout occurrence period. Compared to the conventional method in which correction is performed by uniformly applying holding or muting, the influence of dropouts can be reduced, and high-performance audio dropout compensation can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
FIG. 2 is a signal waveform diagram for explaining the operation of the embodiment shown in the figure;
Figure (A) shows the dropout detection signal S, Figure 2 (B) shows the first dropout detection signal S1, and Figure 2 (C) shows the second dropout detection signal S.
The dropout detection signal S2, FIG. 2(D) is the output signal S3 from the bandpass filter 7.8, and FIG. 2(E) is the output signal S3 from the FM demodulation circuit 9.8. Audio signal S4 including the dropout occurrence period tl among the audio signals output from IO, FIG. 2(P)
is the audio signal S5 including the dropout occurrence period t2 among the audio signals output from the FM demodulation circuit 9.10, and the second
Figure (G) shows the audio signal S6 after holding and correcting the audio signal S5, and Figure 2 (H) shows the dropout occurrence period t of the audio signal output from the F'M demodulation circuit 9.10.
FIG. 2 (I) is a waveform diagram of the audio signal S8 after muting and correcting the audio signal S7. 5... Dropout detection means, 6... Compensation means,
13.14...1st. a second dropout detection circuit;
15.16... Bold circuit, 17.18... Muting circuit, Sl, S2 - 1st. Second dropout detection signal.

Claims (1)

[Claims] (1) An audio dropout compensation device for compensating for missing parts of an audio signal caused by dropouts, the device comprising first and second dropouts according to the length of the dropout occurrence period based on the reproduced signal. dropout detection means for outputting a detection signal; and compensation means for compensating for a missing portion of the audio signal in response to the first and second dropout detection signals from the dropout detection means, The means includes a first dropout detection circuit that outputs the first dropout detection signal corresponding to the dropout occurrence period when the dropout occurrence period is within the set period; a second dropout detection circuit that outputs the second dropout detection signal corresponding to the dropout occurrence period when the period exceeds the dropout occurrence period, and the compensating means detects the dropout in response to the first dropout detection signal. An audio dropout compensating device comprising: a hold circuit that holds an audio signal level before occurrence of an audio dropout; and a muting circuit that mutes the audio signal in response to the second dropout detection signal.