JPH077484B2 - Video tape recorder with integrated camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a camera-integrated video tape recorder for multiple recording of FM audio signals on video information.

(B) Conventional technology A camera-integrated video tape recorder called 8 mm video is disclosed on pages 39 to 47 of the March 1985 issue of the magazine "TV Technology" published by Electronic Technology Publishing Co., Ltd. As shown in the figure, the sound collected by the microphone provided at the bottom of the electronic viewfinder is FM-modulated and frequency-multiplexed with the video information, and the frequency of the audio signal is limited like other camera-integrated video tape recorders. It records a wideband audio signal without recording.

(C) Problems to be Solved by the Invention However, in the case of the 8 mm video described above, since the audio signal to be recorded has a wide band, the horizontal deflection output of the electronic viewfinder leaks and mixes into the audio signal line, Constant frequency noise corresponding to the horizontal sync frequency occurs in the audio signal. Since the constant frequency noise itself has a high frequency and a low level, it does not cause any problem during reproduction.

However, the FM audio signal at the time of reproduction is made a continuous signal by the switching accompanying the head output switching, and the previous value is held at the switching noise generation timing in order to eliminate the switching noise. The pre-hold output is effective for low frequency components, but high frequency components become spike noise through the noise reduction circuit. The spike noise increases in level with the constant frequency noise as a bias, and produces an offensive sound.

(D) Means for Solving the Problems Therefore, in the present invention, a trap circuit for trapping the horizontal synchronizing frequency is provided in the preceding stage of the FM modulation circuit in order to remove the constant frequency noise that becomes the bias of the spike noise. Is characterized by.

(E) As a result, constant frequency noise in the audio signal is trapped, so that constant frequency noise does not occur in the reproduced audio signal,
Spike noise in the output of the noise reduction circuit is not biased.

(F) Example Hereinafter, the present invention will be described according to an example.

First, the present embodiment adopts the present invention to a camera-integrated video tape recorder (8 mm video) of a system in which an FM audio signal is frequency-multiplexed with video information and recorded on a video track.

FIG. 1 is a circuit diagram of a recording side main part of this embodiment. The audio signal to be recorded is usually obtained from a microphone (1) fixed to the bottom of an electronic viewfinder (not shown). This audio signal is input to the amplifier (3) via the external microphone terminal (2). The external microphone terminal (2) is formed at the bottom of the electronic viewfinder, and a microphone jack is inserted to input an audio signal to the amplifier (3) instead of the built-in microphone (1). The output of the amplifier is input to the voice processing IC (5) through the horizontal synchronizing signal frequency trap circuit (4). This IC (5) has a switch (5a) to select external input audio signal or trap output.
And an AGC circuit (5b) for inputting the switch output and a buffer circuit (5c) for inputting the AGC output. However, the external input terminal and its line are located away from the electronic viewfinder. The AGC output is input to the noise reduction circuit (7) set to the recording mode through the low pass filter (6). The noise reduction circuit (7) emphasizes high frequencies during recording. The noise reduction output is input to the FM modulation circuit (8) and converted into an FM audio signal. This FM audio signal is frequency-multiplexed and recorded on a video track by a well-known recording circuit together with video information composed of an FM luminance signal and a low frequency conversion color signal. Therefore, in this embodiment, even if the constant frequency noise corresponding to the horizontal synchronizing frequency leaked from the electronic viewfinder is mixed in the signal line in the preceding stage of the amplifier (3), it is removed by the trap circuit (4). .

Therefore, when reproducing the audio signal by reproducing the video tape from which the constant frequency noise corresponding to the horizontal synchronizing frequency is removed, the reproduced FM audio signal is the FM demodulation circuit (9) as shown in FIG.
Entered in. The demodulated output is input to the pre-holding circuit (10), and pre-holding is performed to remove switching noise at the head switching timing. The noise reduction circuit (7) in the reproduction mode which inputs the pre-hold output suppresses the high frequency component. However, the noise reduction circuit (7) does not have a constant phase shift characteristic for each frequency at the same time, and as a result, spike noise is formed in the pre-holding portion. This spike noise does not exhibit a bias effect unless the constant frequency noise is present, and is inconspicuous.

(G) Effect of the Invention According to the present invention, therefore, the trap circuit blocks recording of constant frequency noise, so that spike noise in the reproduced voice width is not conspicuous and the effect is large.

[Brief description of drawings]

Each of the drawings shows an embodiment of the present invention. FIG. 1 shows a main circuit diagram of a recording circuit, and FIG. 2 shows a main circuit diagram of a reproducing circuit. (4) …… Trap circuit, (8) …… FM modulation circuit,
(7) …… Noise reduction circuit.

Claims (1)

[Claims] 1. A microphone or an external microphone terminal is arranged in the vicinity of an electronic viewfinder, an FM audio signal obtained by inputting an audio signal to an FM modulation circuit is frequency-multiplexed with video information, and recording tracks are alternately recorded by a pair of video heads. The video tape recorder with a built-in camera, wherein a trap circuit for trapping a frequency corresponding to a horizontal synchronizing signal is provided in the preceding stage of the FM modulation circuit.