JPS62195701A - Reproducing device for video signal and pcm audio signal - Google Patents

Abstract

PURPOSE:To prevent any hindrance on a video reproducing operation due to mis-discrimination by discriminating a PCM recording tape based on a discriminated pilot signal and making the discrimination ineffective at the video reproduction. CONSTITUTION:Since a pilot detection circuit 18 might detect a low frequency conversion chrominance signal in error in reproducing a video recording tape, a circuit detecting the presence of a reproduced video signal is provided at the video reproduction so as to not cause the muting. That is, an output of a de-emphasis circuit 8 of a luminance reproduction system is given to a SYNC presence discrimination circuit 21 to discriminate the presence of a synchronizing signal SYNC. A synchronizing signal is detected at the video reproduction and an output of the discrimination circuit 21 goes to a high level. The output is inverted to a low level by an inverter 22, an AND gate 19 is closed by the inverted output, resulting that an output of the pilot detection circuit 18 having a possibility is mis-detection at the video reproduction is cut off by the AND gate 19 to turn off the muting function.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for reproducing video signals and PCM audio signals.

[Summary of the invention]

When reproducing either a video signal or a PCM audio signal from a recording medium, it is determined that the recording medium has recorded a PCM audio signal based on the discrimination pilot signal recorded together with the PCM audio signal, and the video signal is reproduced. The above-mentioned discrimination is invalidated when the discrimination pilot signal and the video signal are overlapped on the frequency axis, so that even if an erroneous discrimination occurs, the playback operation will not be affected.

[Conventional technology]

8 Two-rotation head V called IIN VTR
With TR, the tape wrapping angle on the drum should be 1800 or more (
For example, it is known to time-divisionally record a video signal (180°) and a time-compressed PCM audio signal (36°). Add another 36 degrees to the video section
It can also be used as a PCM audio recording area with a total of 6 channels by dividing it into 5 segments (sections).

When playing back a videotape or a multi-channel PC
It is determined whether it is an M tape, and if it is a PCM tape, the monitor screen is turned off (muting). Therefore, for example, in the multi-channel PCM area (other than the first channel) of a tape on which a video signal is recorded,
When a CM signal is additionally recorded, a band-shaped noise band corresponding to the PCM recording area appears on the playback screen, but if it can be determined that multi-channel PCM has been recorded, muting will not cause such a strange playback screen. .

One way to determine whether the tape is multi-PCM recorded is to record 228.748K l in the PCM area.
lz discrimination pilot signals (continuous waves) are multiplexed and recorded.

[Problem that the invention seeks to solve]

This pilot signal is selected to have a frequency that does not interfere with the modulated recording signal of the PCM signal. However, when playing back a tape on which a video signal has been recorded, the lower sideband of the low frequency converted chroma signal (743Kl(z)) and the pilot signal in the playback signal are overlapping, causing misjudgment and causing multi-PCM recording. The muting of the monitor screen sometimes made playback of ordinary video recording tapes difficult.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a reproduction system that prevents erroneous discrimination of viroft signals.

[Means for solving problems]

Video signal or PC on a discontinuous trunk, such as a VTR
This is a device for reproducing a recording medium on which M audio signals are recorded, and when reproducing PCM audio, it is necessary to mute the monitor output and make the screen completely blank.

Therefore, based on the discrimination pilot signal recorded together with the PCM audio signal, a discrimination circuit discriminates that the recording medium is a recording medium on which a PCM audio signal has been recorded. A detection circuit for detecting the video signal is provided, and when the video signal is detected, the operation of the discrimination circuit is turned off.

In a preferred embodiment, the detection circuit is a circuit for detecting synchronization or chroma signals in the reproduced video signal. Furthermore, when an FM audio signal is multiplexed and recorded together with a video signal, the carrier of this FM audio signal may be detected.

〔Example〕

FIG. 1 is a block diagram of a reproduction system of an 8 m+n VTR to which the present invention is applied. As is well known, this type of VT
The recording pattern of R's trasokuhi is video + AF corresponding to 1806 of the rotating head drum as shown in Figure 2.
It consists of an M (audio FM) section and a 36'' PCM audio section.The video+AFM section can be further divided into 5 equal parts and used as a multi-channel PCM recorder with a total of 6 channels.

When used as a VTR, as shown in the signal band diagram in Figure 3, the FM luminance signal (deviation 4.2 to 5
．． 4 Mllz) and 743Kllz are band-separated and recorded, and 1
．． 5 Insert the Mllz FM audio signal. In addition, the 4-frequency tracking pilot signal is set to lOO~15.
0KI (enter into the z band.

FIG. 4 shows the band when used as a multi-channel PCM recording 1, which covers a wide band of several to several M Ilz. In order to distinguish that the tape is a multi-PCM recording tape, a 228.7 KHz discrimination pilot signal is multiplexed and recorded. Since the frequency of this discrimination signal overlaps with the lower sideband of the low frequency converted chroma signal of the VTR recording tape, the image cutoff function during multi-PCM playback may malfunction as described above.

FIG. 1 shows an embodiment in which such malfunctions do not occur. First, the playback outputs of the rotary heads 1a and 1b are led to changeover switches 3a and 3b through preamplifiers 2a and 2b, and the A and B channels are integrated and Video playback system and PCM
Signals are distributed to the reproduction system.

In the video reproduction system, the Y filter 4 and the C filter 5 separate the luminance signal and the chroma signal, the luminance signal passes through the limiter 6, is demodulated by the demosulator 7, is high-frequency corrected by the de-emphasis circuit 8, and then is added to the adder 9. is derived. On the other hand, Chroma Shingetsu is 3.58 with frequency converter 10.
The signal is converted into Ml1z, passed through a bypass filter 11, added to the luminance signal by an adder 9, and then passed through a mute intensifier 12 (or a cutoff switch) to be derived as a reproduced video signal.

Furthermore, the FM audio signal AFM inserted between the bands of the FM luminance signal and the chroma signal is separated by an AFM filter 14, demodulated by a demodulator 15, and then derived as a reproduced audio signal.

The reproduced PCM signals obtained from the changeover switches 3a and 3b are demodulated by the PCM decoder 16, converted into analog audio signals by the D/A converter 17, and derived.

The following determination circuit is provided to determine whether PCM reproduction is being performed. That is, the reproduced PCM signal is also led to the pilot detection circuit 18, and when a multi-channel PCM recording tape is reproduced, a discrimination pilot signal of 228.7 K11z is detected.

When the pilot signal is detected, the output of the detection circuit 18 becomes high level and is applied to the tens field detection circuit 20 through the AN1ζ gate 19. This detection circuit 20 compensates for malfunctions of the pilot detection circuit 18, and uses a microprocessor or the like to determine whether the pilot detection output continues for more than ten fields. When the determination result is obtained, the muting 12 is turned off at its output, and the output of the video signal to the monitor is prohibited.

As mentioned above, the pilot detection circuit 18 may erroneously detect the low frequency converted chroma signal when playing back a video recording tape, so the following circuit is provided to detect the presence or absence of a playback video signal during video playback. This prevents muting (cutoff of the monitor screen) from occurring. That is, the output of the de-emphasis circuit 8 of the brightness reproduction system is
The signal is applied to the NC presence/absence determining circuit 21 to determine the presence/absence of the synchronizing signal 5YNC. During video playback, a synchronizing signal is detected and the output of the discrimination circuit 21 becomes high level. This output is inverted to a low level by an inverter 22, and the AND gate 19 is closed with this inverted output.

As a result, during video playback, the output of the biloft detection circuit 18, which may cause false detection, is blocked by the AND gate 19, and the muting function is turned off.

Note that the presence or absence of a reproduced video signal may be detected using a chroma signal or a color burst signal. That is, in the chroma reproduction system shown in FIG.
3, and this filter output is discriminated by the level discrimination circuit 24. If the chroma signal is present in the reproduced signal, the output of the level discrimination circuit 24 will be at a high level. This output is given to the color reproduction system as an automatic color killer signal ACK,
When the signal is applied to the inverter 22 in the discriminative pilot detection section described above, the AND gate 19 is closed by the low signal output from the inverter 22. Therefore, as described above, muting of the monitor image does not occur even if the discrimination pilot detection section malfunctions during video playback.

Furthermore, the muting function of the monitor image may be disabled (inoperable) by determining the presence or absence of an audio FM signal obtained together with the video signal from the rotary head. In this case, the output of the AFM filter 14 shown in FIG. 1 is led to a carrier detection circuit 25 to detect the presence or absence of a 1.5 MHz FM carrier. When there is a carrier, the output of the detection circuit 25 is at a high level, so if this output is inverted by the inverter 22 and supplied to the AND gate, the muting function is disabled and there is no risk of malfunction.

FIG. 5 is a time chart showing playback signals. During normal video playback, PCM signals and video signals are obtained alternately from heads 1a and 1b as shown at A and B. Furthermore, when reproducing a multi-PCM tape, PCM signals of each channel are reproduced as shown in a and b. If the PCM signals of the second and fourth channels are additionally recorded on a tape on which video signals have already been recorded, as shown in Figure 5 a and b, even if the video signals remain in the shaded area, they will be multiplexed to each PCM channel. The monitor image is muted by the detection of the discrimination pilot signal, so that a screen with bar noise in the PCM band does not appear. Furthermore, when the video signals shown in FIGS. 5A and 5B are reproduced, the detection of the book discrimination pilot signal is disabled, so there is no possibility that the monitor screen will be muted due to erroneous detection.

- [Effects of the Invention] As in the case of the present invention, when the present invention is configured to determine that it is a PCM recording tape based on the identification pilot signal recorded together with the PCM audio signal, this determination is invalidated during video playback. Therefore, the video playback operation will not be affected by misjudgment. Therefore, the discriminating pilot signal may overlap the frequency band of video recording and can be at an optimal frequency.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention.
Figure 2 is a spectrum diagram of the video recording band, Figure 3 is a spectrum diagram of the PCM recording band,
FIG. 4 is a recording pattern diagram on the tape, and FIG. 5 is a reproduction signal time chart. In addition, in the symbols used in the drawings, 1----------One rotation head 18---111--------------------- Pilot detection circuit 20-1-- −−−−・−−−−−−10-odd field detection circuit 21−−−−−−−−−−−−1−−
-3Y N C presence/absence determination circuit 24
---1--Level discrimination circuit 25--
-----------This is a carrier detection circuit.

Claims (1)

[Claims] 1. A device for reproducing a recording medium in which a video signal or a PCM audio signal is recorded on discontinuous tracks, the device playing back a recording medium in which a video signal or a PCM audio signal is recorded on discontinuous tracks, wherein the PCM audio signal is reproduced based on a discrimination pilot signal recorded together with the PCM audio signal. A video signal and a PCM comprising: a discriminating circuit for determining that the recording medium is a recording medium that has recorded a PCM; a detecting circuit for detecting the video signal; and a circuit for turning off the operation of the discriminating circuit based on the output of the detecting circuit. Audio signal playback device. 2. The video signal and PCM audio signal reproducing apparatus according to claim 1, wherein the detection circuit is a circuit for detecting a synchronization signal in a video signal. 3. The video signal and PCM audio signal reproducing apparatus according to claim 1, wherein the detection circuit is a circuit for detecting a chroma signal in a video signal. 4. The video signal and PCM audio signal reproducing apparatus according to claim 1, wherein the detection circuit is a circuit for detecting an FM carrier of an FM audio signal frequency-multiplexed with the video signal. .