JPH054356U - Image quality switching device - Google Patents

Abstract

(57) [Summary] [Purpose] When playing a rental soft tape,
Automatically changing at least the characteristics of the video signal processing circuit to improve the quality of the reproduced image. [Structure] Whether or not a soft tape is a soft tape is determined by using the presence or absence of a copy guard additional signal added to the soft tape, for example, by using the number of sync signals from the sync separation circuit 2 during a predetermined period. Based on this result (by the microcomputer 3), the characteristics of the video processing circuit 4 are automatically changed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an image quality switching device when playing a rental soft tape.

[0002]

[Prior Art]

 Rental of soft tapes (tapes on which movies etc. have been pre-recorded) has become widespread, but with such rental soft tapes, since the number of times of playback is large, there is noise in the playback signal due to demagnetization effects, etc. It will be noticeable. Therefore, conventionally, a video tape recorder provided with a characteristic selection switch for changing the reproduction characteristic of a video signal during reproduction of a rental soft tape has been sold (for example, Radio Technology June 1989 issue). See pages 177 to 178).

[0003]

[Problems to be solved by the device]

 However, in the above video tape recorder, since the characteristic changeover switch has to be manually operated, it is not only inconvenient, but even if there is a means for changing the folding angle characteristic, the user does not notice it. If it is not, there is a drawback that the playback quality cannot be improved.

[0004]

[Means for Solving the Problems]

 In consideration of the above points, the present invention provides an image quality switching device that automatically operates a characteristic switching switch when a rental tape is being reproduced. That is, it comprises a discriminating means for discriminating whether or not it is a soft tape based on the reproduced signal, and a means for changing the characteristics of the video signal or the audio signal based on the output of the discriminating means.

[0005]

[Action]

 Therefore, whether or not it is a soft tape is automatically discriminated from the state of the reproduced signal, and the characteristic of the video signal or the audio signal is changed based on the discrimination result, so that it is possible to prevent malfunction in the switching of image quality. it can.

[0006]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. 1 is a block diagram showing the configuration of the embodiment, FIG. 2 is a waveform diagram showing a part of a video signal recorded on a soft tape, and FIG. 3 is a diagram showing a sync signal from a video signal recorded on a soft tape. It is a waveform diagram showing the separated waveform.

In FIG. 1, reference numeral 1 is an input terminal of a demodulated video signal (luminance signal), 2 is a synchronization separation circuit, 3 is a microcomputer constituting a discriminating means, 4 is a video signal processing circuit, and 5 is a video signal processing circuit. This is a processing circuit for an audio signal.

In the video signal processing circuit 4, the characteristics such as the noise cancellation amount, the output level, and the frequency characteristic can be switched in at least two stages in accordance with a command from the outside. Further, in the audio signal processing circuit 5, the characteristics such as the frequency characteristic and the output level can be switched in at least two stages in accordance with the command from the outside.

A synchronization signal separated by the synchronization signal separation circuit is supplied to the microcomputer 3, which is the determination means. The sync separation circuit separates the sync signal from the input video signal according to the amplitude level.

Here, the video signal recorded on a so-called soft tape will be described. As shown in FIG. 2, a copy guard signal (pseudo synchronization signal) is recorded on the soft tape in the blanking period of the video signal for the purpose of preventing dubbing. This signal has an amplitude from the white peak of the video signal to the level of the sync tip.

Details of the signal for copy guard are as follows. That is, a pseudo sync signal having a width of 2 μs is inserted 9.4 μs after the timing of the leading edge of the horizontal sync signal, and then a signal of 100 IRE level continues for 3.7 μs. After that, the pedestal level continues for 1.8 μs (this period is a pseudo sync front porch). Then, five pseudo sync signals, five signal levels, and four pseudo sync front pouches are inserted during one horizontal period.

The synchronization separation output of the portion where the copy guard signal is inserted is as shown in FIG. That is, an extra sync signal is inserted within one horizontal period. Therefore, the discriminating means can detect whether or not it is a soft tape by detecting the extra synchronizing signal.

In practice, the microcomputer 3 makes the determination by counting the number of rising edges in the output of the synchronous separation circuit during the blanking period. That is, when the count value is larger than the predetermined threshold value, it is determined that the tape is a soft tape.

The result determined by the microcomputer 3 is sent to the video signal processing circuit 4 and the audio signal processing circuit 5. When it is determined that the soft tape is reproduced, the video signal processing circuit 4 increases the amount of noise cancellation (increases the amount of cancellation), lowers the output level, and executes high frequency cut in the frequency characteristic. By doing this, even with a rental soft tape that has been played many times, it is possible to automatically play the improved screen instead of the noisy screen.

Also, regarding the audio signal, when it is detected that it is a soft tape, the sound quality at the time of reproduction can be improved by changing the frequency characteristic of the audio processing.

Further, as a method of detecting the soft tape, in addition to the method of counting the number of synchronization signals in the above-described predetermined period, the determination can be made by measuring the time interval from edge to edge of the synchronization signal. You can Further, from the signal waveform as shown in FIG. 2, when this video signal is reproduced, the AGC voltage fluctuates greatly in a short period (using this fluctuation, dubbing is prevented). Therefore, it is possible to determine whether the tape is a soft tape or not by detecting the fluctuation of the AGC voltage.

[0017]

[Effect of the device]

 As described above, according to the present invention, whether or not the tape is a soft tape is determined by the presence or absence of the added copy guard signal, and the characteristics of the video signal processing are changed according to the result, so that it is automatically performed. It is practical because the characteristics of the soft tape can be changed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment.

FIG. 2 is a waveform diagram showing a part of a video signal recorded on a soft tape.

FIG. 3 is a waveform diagram showing a waveform obtained by separating a sync signal from a video signal recorded on a soft tape.

[Explanation of symbols]

 2 sync signal separation circuit 3 microcomputer (discriminating means) 4 video signal processing circuit 5 audio signal processing circuit

Claims (1)

Claims for utility model registration Claims: 1. Detecting means for detecting a soft tape at the time of reproduction in relation to a copy guard signal added to the soft tape, and video signal processing based on this detecting means. An image quality switching circuit comprising means for changing the characteristics of the circuit.