JPH028459Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a video and audio recording/reproducing circuit.

In order to improve the sound quality of VTRs, we installed a pair of heads for audio signals in addition to a pair of heads for video signals on the rotating drum, and in addition to the head for PCM in addition to the video signal.
(Pulse code modulation) has been proposed, but since this recording method creates video tracks and audio tracks alternately, special playback of still images, etc. is not possible. If this was done, the playback head would also scan the audio track, and there was a risk that the audio signal would be mixed into the image as noise, degrading the image quality.

In view of the above points, the purpose of this invention is to
Ideal for use with VTR devices that record in PCM format, the PCM signal can be removed for playback, and clear playback images can be obtained even during special playback such as still image playback. The purpose of the present invention is to provide a video and audio recording/playback device.

Hereinafter, embodiments of the present invention will be described based on the drawings.

Figure 1 shows the overall block diagram. D is a rotating drum, and on its outer periphery are provided a pair of heads VH for video signals and a pair of heads PH for audio signals, which are converted into PCM along with the video signals. The recorded audio signals can be recorded and played back. In such a recording/reproducing system, in the present invention, the audio signal recording/reproducing circuit 1 processes the audio signal to set the synchronization signal leading edge level of the audio signal to a level different from the synchronizing signal leading edge level of the video signal. It is now possible to record the information.

Reference numeral 2 designates the entire video signal recording and reproducing circuit, which is configured to cut off the video output signal path for a predetermined period of time by detecting the difference in the leading edge level of both recorded synchronization signals.

Next, we will explain a specific circuit configuration example and an example of its operation. First, when recording video and audio, the input section
The video signal input from the VI is input to the head VH via the video signal modulation/demodulation circuit 3, and the video signal is recorded.The audio signal input from the input section PI is pulse-coded by the PCM processor 4, and then The signal is input to a DC offset circuit 5 for offsetting the PCM frequency domain, passes through a pseudo video signal modulation/demodulation circuit 6, and is recorded as an audio signal via a head PH. Now, focusing on the waveforms of both recording signals, FIG. 2a shows the frequency distribution of the video signal whose reference level is PL, and A is a synchronization signal whose tip level is set to FL. Note that HL indicates the peak level. On the other hand, c indicates a PCM signal offset to a higher frequency by the DC offset circuit 5,
This frequency offset sets the leading level of the synchronizing signal A' to FL'. Note that the peak level is set to HL'. As a result, as is clear from the figure, the leading level of the synchronizing signal A' of the audio signal is the leading level of the synchronizing signal A of the video signal.
It will be recorded at a different level than FL.
During special playback during still image playback, the leading levels of both synchronizing signals are determined by the separation circuit 7 connected to the playback output side of the video signal modulation/demodulation circuit 3, and only the leading level of the synchronizing signal on the video signal side is detected. Switching means S provided in the video output signal path is turned on for a predetermined period of time maintained by the retrigger mono multivibrator 8 connected to the next stage.
It is controlled so that only the video signal is output, and the audio signal is not output to the output VO side.

By performing the above processing, harmful audio components (PCM) are generated during special playback such as still image playback.
It is possible to obtain a clear image without being outputted. In this case, the DC offset circuit 5 is used as a synchronous clamp circuit, and only the leading level of the synchronous signal A'' is set to a different level as shown in Fig. 2b, or the leading level of the synchronous signal is set to a different level than that for video. Of course, the same discrimination process can be performed even if the switching means S is set to a low frequency and the opening/closing relationship of the switching means S is reversed.In addition, during normal playback, the DC offset audio signal is used. (PCM) is restored to its original level by the DC offset restoration circuit 9 and reproduced, so no problem occurs.

According to the video and audio recording and reproducing circuit according to the present invention, the recording and reproducing circuit is capable of recording and reproducing a PCM audio signal together with the video signal, and the leading level of the synchronization signal of the audio signal is By recording the signal at a level different from the leading level of the synchronizing signal, and detecting the difference between the leading levels of the two synchronizing signals during special playback, the video output signal path is blocked for a predetermined period of time and the audio signal is output. Since it is configured so that it is not output, not only can normal playback be performed, but even during special playback such as still image playback, there is no possibility that audio signal noise will be mixed into the image, and the reproduced image will be clear and clear. can be obtained.

[Brief explanation of the drawing]

The figure shows a video and audio recording and reproducing apparatus according to the present invention, with FIG. 1 being an overall block diagram and FIG. 2 being a diagram illustrating the principle of operation. 1: Audio signal recording and reproducing circuit as a recording circuit, 2: Video signal recording and reproducing circuit as a reproducing circuit, A: Video signal synchronization signal, A': Audio signal synchronization signal, D: Rotating drum, 5: DC offset circuit, S: switching means.

Claims (1)

[Claims for Utility Model Registration] In addition to the pair of video signal heads provided on the rotating drum, a pair of audio signal heads are provided so that PCM audio signals can be recorded and played back along with the video signals. A recording circuit that is a recording and reproducing circuit for setting and recording a leading level of a synchronizing signal of an audio signal to a level different from a leading level of a synchronizing signal of a video signal;
A separation circuit that detects one of the synchronization signals based on the level difference between the two synchronization signals during special playback, and switching that uses the output from the separation circuit to block the video signal output signal path for a predetermined period of time so as not to output the audio signal. A recording/reproducing circuit comprising: a reproducing circuit comprising means.