JPH0898129A - Video tape recorder - Google Patents

Abstract

PURPOSE: To eliminate a flicker of display and to output main sound at the time of duplex sound broadcasting to eliminate unpleasant pop sound. CONSTITUTION: A duplex broadcast discrimination signal and a stereo broadcast discrimination signal from a sound multiplex signal demodulation circuit 18 are given to a station selection microcomputer 44. At the time of errorneous discrimination, the number of the change times of the discrimination signals becomes more than two within prescribed time. At the time of a normal operation, it becomes less than one. When the state of errorneous discrimination continues for ten times, the station selection microcomputer 44 judges that a discrimination result in the sound multiplex signal demodulation circuit 18 is errorneous. When a normal state continues for ten times on the other hand, the discrimination result is judged to be correct. When the discrimination result is judged to be errorneous, a compulsory monaural signal is outputted from the station selection microcomputer 44 to the sound multiplex signal demodulation circuit 18, and a broadcasting mode is compulsorily set to a monaural mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video tape recorder, and more particularly to a video tape recorder for demodulating, for example, an audio multiplex signal.

[0002]

2. Description of the Related Art In television sound multiplex broadcasting, a sound multiplex signal contains three types of signals, namely, a main sound signal, a sub sound signal and a control signal. It distinguishes between stereo broadcasting and dual audio broadcasting. Since the maximum frequency excursion of the control signal is 2 kHz, the S / N ratio deteriorates in a weak electric field area, an abnormal pulse is input, and an audio input signal near the control signal frequency causes the monaural broadcast and stereo broadcast to be mixed. The discriminating circuit for discriminating between heavy audio broadcasting may malfunction. Also, in CATV and the like which have been increasing recently, the audio carrier level is lowered with respect to the video carrier as a countermeasure against the audio beat of the adjacent channel, so that the malfunction of the broadcast discrimination occurs.

A conventional video tape recorder 1 is shown in FIG. Referring to FIG. 6, the television audio multiplex signal is
FM demodulation is performed from the antenna 2 through the tuner circuit 3 and the IF circuit 4, and is input to the audio multiplex signal demodulation circuit 5. From the audio multiplex signal demodulation circuit 5 to the audio circuit 6
An Lch audio signal and an Rch audio signal are provided as audio signals. Separately, from the audio multiplex signal demodulation circuit 5, a stereo broadcast discrimination signal and a dual broadcast discrimination signal (a monaural broadcast when neither a stereo broadcast discrimination signal nor a dual broadcast discrimination signal is present) are selected by the microcomputer 7 Entered in. In accordance with this discrimination signal, a broadcast mode indicating whether it is monaural broadcasting, stereo broadcasting, or dual audio broadcasting is displayed on the display tube 8, or if the discrimination signal is a dual broadcasting discrimination signal, a video tape The recording method of the horizontal track is switched to recording only the Lch audio signal (main audio signal) (normally, Lch + R
Record the mixed signal of ch).

Therefore, every time the audio multiplex signal demodulation circuit 5 malfunctions, the display on the display tube 8 is switched and flickers, and in spite of the dual audio broadcasting, it is erroneously determined to be stereo broadcasting and the main audio is recorded on the horizontal track. When a mixed signal of audio and sub-audio is recorded, the main audio and the sub-audio are mixed and output at the time of output despite the double audio broadcasting. Further, there is a problem that an unpleasant popping sound is generated each time the broadcast mode is switched due to a malfunction of the audio multiplex signal demodulation circuit 5.

Further, conventionally, only the sync signal is separated from the video signal of the video circuit 9a by the sync separation circuit 9b.
The tuning microcomputer 7 discriminates the presence / absence of a received broadcast based on the presence or absence of the synchronization signal. When it is determined that there is no station, a mute signal is sent from the channel selection microcomputer 7 to the video circuit 9a.
Also, the signal is output to the mute input terminal (not shown here) of the audio multiplex signal demodulation circuit 5 so that video and audio are not output.

However, normally, in a weak electric field, the sound of the image and the sound is significantly deteriorated. That is, even if the image is sufficiently satisfactory, the voice is often unsatisfactory. For this reason, in the conventional technology that determines the presence / absence of a received broadcast based on the presence / absence of a synchronization signal regardless of the audio performance, it is determined that the received broadcast is a station even if the audio is abnormal. And sound was sometimes output.

Therefore, a main object of the present invention is to provide a video tape recorder which operates well even if the broadcast mode is erroneously discriminated. Another object of the present invention is to provide a video tape recorder capable of outputting only a broadcast having good video and audio.

[0008]

SUMMARY OF THE INVENTION A first aspect of the present invention is directed to a tuner capable of receiving a television signal, a broadcasting mode discrimination based on the television signal from the tuner, and a discrimination signal and an audio signal depending on the discrimination result. In a video tape recorder equipped with an audio multiplex signal demodulation circuit for outputting, a correct / wrong judgment means for judging whether the judgment result of the audio multiplex signal demodulation circuit is correct based on the judgment signal, and forcibly audio multiplex when the judgment result is incorrect. It is a video tape recorder characterized by comprising switching means for switching an audio signal from a signal demodulation circuit to a monaural output.

A second aspect of the invention is a tuner capable of receiving a television signal, an audio multiple signal demodulation circuit which determines a broadcast mode based on a television signal from the tuner and outputs a determination signal and an audio signal according to the determination result. , And a video tape recorder provided with a discriminating means for discriminating presence / absence of a received broadcast based on a video signal. Further, the control means is a video tape recorder characterized in that the presence / absence of the received broadcast is determined in consideration of whether the determination result is correct or incorrect.

[0010]

According to the first aspect of the present invention, the correct / wrong judgment means judges whether the judgment result in the voice multiplex signal demodulation circuit is correct or not. At this time, if the number of changes of the discrimination signal is equal to or larger than the threshold value within a predetermined time and the state is continuously confirmed a predetermined number of times, the discrimination result in the audio multiplex signal demodulation circuit is determined to be incorrect. Then, the switching means forcibly switches the audio signal from the audio multiplex signal demodulation circuit to monaural output.

According to the second aspect of the invention, the discriminating means considers the presence / absence of the video signal, that is, the synchronizing signal, and whether or not the discrimination result in the audio multiplex signal demodulation circuit is correct.
Determine the absent station. At this time, the correctness of the determination result is determined by the correctness determination means as in the first aspect of the invention. The determining means determines that the received broadcast is stationed only when the synchronization signal is present and the determination result is correct.

[0012]

According to the first aspect of the present invention, when the broadcast mode is erroneously determined, it is automatically and forcibly switched to the monaural mode. Therefore, the flicker of the display disappears. Further, at this time, since the monaural sound having the same band as the main sound is recorded on the horizontal track, the main sound is eventually recorded in the case of the dual sound broadcasting actually. Therefore, at the time of output, the desired main audio is output even in the dual audio broadcast. Further, there is an effect that an unpleasant popping sound that occurs each time the broadcast mode is switched is eliminated. In this way, good voice can be obtained and unwanted movements can be eliminated.

According to the second aspect of the present invention, by considering whether the judgment result is correct or incorrect as a condition for judging the presence / absence of a received broadcast, it is possible to determine that the broadcast is abnormal even if the sound is abnormal. Therefore, it is possible to determine that only a broadcast having good video and audio is regarded as a station and output only good video and audio. The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0014]

Embodiment FIG. 1 shows a video tape recorder 1 of this embodiment.
Indicates 0. In the video tape recorder 10, the television audio multiplexed signal is transmitted from the antenna 12 to the tuner circuit 14 and the I circuit.
The signal is demodulated by FM through the F circuit 16 and input to the audio multiplex signal demodulation circuit 18. The voice multiplexed signal demodulation circuit 18 is configured, for example, as shown in FIG.

The multiplexed signal from the IF circuit 16 is input to the audio multiplexed signal demodulation circuit 18 shown in FIG. The multiplexed signal includes a main audio signal, a sub audio signal and a control signal. The multiplexed signal is the LPF 22,
The BPFs 24 and 26 separate the main audio signal, the sub audio signal, and the control signal. The main audio signal is input to the matrix circuit 30 via the de-emphasis circuit 28. Further, the sub audio signal is the sub audio signal FM detection circuit 32.
After FM detection by the de-emphasis circuit 34
Is given to the matrix circuit 30 via the.

Further, the control signal from the BPF 26 is AM-detected by the control signal AM detection circuit 36 and given to the mode discrimination circuit 38. Based on this AM detection signal, it is determined whether it is a stereo broadcast or a dual audio broadcast. Furthermore, BP
The sub audio signal from F24 is the sub audio carrier discrimination circuit 40.
, The sub-voice carrier is extracted and given to the mode discriminating circuit 38. With this sub-voice carrier,
It is determined whether it is monaural broadcasting or other broadcasting, that is, stereo broadcasting and dual audio broadcasting. The reason why the sub audio carrier discriminating circuit 40 is provided and the sub audio carrier is used for the mode discrimination is to more accurately discriminate between stereo broadcasting and dual audio broadcasting.

A dual broadcast discrimination signal or a stereo broadcast discrimination signal is output from the mode discrimination circuit 38, and these discrimination signals are given to the matrix circuit 30 and
Channel selection microcomputer 44 via terminals 41 and 42, respectively
Given to. In the matrix circuit 30, processing is performed according to the discrimination signal from the mode discrimination circuit 38, and the terminal 46
Lch audio signal (main audio signal) from terminal 4
Rch audio signals (sub audio signals) are output to audio circuits 50 from 8 respectively. Further, a horizontal track switching signal is output from the tuning microcomputer 44 to the audio circuit 50. From the audio circuit 50, L
The ch signal, the horizontal track signal, and the Rch signal are output.

The voice multiplexed signal demodulation circuit 18 also includes a mode switch 52. Then, the tuning microcomputer 44
If it is determined that the broadcast mode determination in the audio multiplex signal demodulation circuit 18 is incorrect, a signal indicating a malfunction, that is, a forced monaural signal is output from the channel selection microcomputer 44 to the mode switch 52, and in response to the forced monaural signal. The mode switch 52 outputs a signal to the mode determination circuit 38, and the mode determination circuit 38 switches the mode to the forced monaural mode. For example, when neither the dual broadcast discrimination signal nor the stereo broadcast discrimination signal is output, the monaural mode is set.

Further, the matrix circuit 30 has terminals 54.
A mute signal may be given from the. As a result, the audio signal from the matrix circuit 30 is muted. This mute signal is used in the embodiment of FIG. 4 described later. Returning to FIG. 1, a broadcast mode such as monaural broadcast, stereo broadcast, or dual audio broadcast is displayed on the display tube 56 according to an instruction from the channel selection microcomputer 44.

The main operation of the channel selection microcomputer 44 of such a video tape recorder 10 is shown in FIG. By the operation of FIG. 3, it is determined whether or not the determination result of the broadcast mode in the audio multiplex signal demodulation circuit 18 is correct. As a premise, it is assumed that the number of times the discrimination result, that is, the discrimination signal is switched during the fixed period T is A times. The fixed period T is equal to or longer than the double broadcast / stereo broadcast discrimination time t. Stereo broadcasting control signal is 982.5Hz, dual broadcasting control signal is 922.5Hz.
Since it is Hz, it is considered that the discrimination time t is about 1 msec, and T = 10 msec in this embodiment.

In step S1 shown in FIG. 3, first,
The threshold value B of the number of consecutive confirmations is set to 10, and the number of consecutive confirmations C of erroneous determination and the number of consecutive confirmations D of normal operation are set to 0
Set to. Next, in step S3, 10 msec
It is determined whether or not A ≦ 1. 10 ms during normal operation
The number A of switching of the double broadcast discrimination signal and the stereo broadcast discrimination signal during ec is less than or equal to 1 each. On the contrary, at the time of erroneous discrimination, the discrimination signal is switched twice or more. Therefore, in normal operation, step S3 becomes "YES",
Go to step S5.

In step S5, the number of consecutive confirmations D of normal operation is incremented by "1", the number of consecutive confirmations C of erroneous discrimination is reset to "0", and the process proceeds to step S7. In step S7, it is determined whether or not the condition that A is 1 or less continues B times (B = D). "YE
If "S", the discrimination signal is normal, that is, the discrimination result is judged to be correct, the forced monaural signal is turned off in step S9, and the process ends.
If the condition of "O", that is, A is not more than once, has not been continued B times, the process returns to step S3.

On the other hand, if step S3 is "NO", that is, if an erroneous determination is made, the process proceeds to step S11. Step S
In 11, the continuous check count C for erroneous determination is incremented by "1", the continuous check count D for normal operation is reset to "0", and the process proceeds to step S13. In step S13, whether the number C of consecutive confirmations of misjudgment continues B times (B =
C)) or not. If "YES", it is determined that the misjudgment is made, the forced monaural signal is output in step S15, and the process ends. Step S13 is "NO"
In case of, it returns to step S3.

In this way, the dual broadcast discrimination signal and the stereo broadcast discrimination signal output from the audio multiplex signal demodulation circuit 18 are input to the channel selection microcomputer 44 to determine whether the audio multiplex signal demodulation circuit 18 is malfunctioning. To do. And
When malfunctioning, a forced monaural signal is output from the channel selection microcomputer 44 to the mode switch 52 of the audio multiplex signal demodulation circuit 18, and the mode is switched to the forced monaural mode. Then, on the horizontal track, monaural audio is recorded during monaural broadcasting, main audio is recorded during dual broadcasting, and L + R mixed signals are recorded during stereo broadcasting.
Therefore, at the time of output, since monaural audio is output for monaural broadcasting, main audio is output for dual broadcasting, and L + R is mixed and output for stereo broadcasting, main audio and sub audio are output as in the conventional case. The malfunction of mixing and outputting can be prevented. Further, since the broadcast mode is fixed to the monaural mode, it is possible to prevent an undesired operation such as flicker on the display of the display tube 56 disappearing, and further eliminating an unpleasant popping sound generated each time the broadcast mode is switched.

Next, FIG. 4 shows a video tape recorder 10 'of another embodiment. Video tape recorder 10 '
Is a video circuit 58 to which the video signal from the IF circuit 16 is input, and a sync separation circuit 6 that separates the sync signal from the video signal from the video circuit 58 and sends it to the channel selection microcomputer 44.
Equipped with 0. The video circuit 58 and the sync separation circuit 60 are not shown in FIG. 1, but it goes without saying that the video tape recorder 10 of FIG.
Further, unlike the video tape recorder 10, the video tape recorder 10 'does not output a forced monaural signal from the channel selection microcomputer 44 to the audio multiplex signal demodulation circuit 18, but the channel selection microcomputer 44 demodulates the video circuit 58 and the audio multiplex signal demodulation. A mute signal is given to the circuit 18 in accordance with the result of the presence / absence determination. Since other configurations are similar to those of the video tape recorder 10 shown in FIG. 1,
By giving the same reference number, the duplicated explanation is omitted.

The operation of discriminating presence / absence of a received broadcast in the channel selection microcomputer 44 of the video tape recorder 10 'shown in FIG. 4 will be described with reference to FIG. The operation shown in FIG.
Since it largely overlaps with the operation shown in, the overlapping steps will be briefly described. Step S2 shown in FIG.
1, B = 10 and C = D = 0 are set, and it is determined in step S23 whether A ≦ 1. "YE
If "S", the process proceeds to step S25, D is incremented by "1", C is reset to "0", and step S is performed.
Proceed to 27. In step S27, it is determined whether B = D. If "NO", the process returns to step S23, and if "YES", the process proceeds to step S29. In step S29, it is determined whether or not there is a sync signal. If there is a sync signal, the mute signal is not output in step S31. That is, the process proceeds to step S31 when it is determined that the determination signal is normal, that is, the determination result is correct and there is a synchronization signal. In this case, it is determined that the received broadcast is stationed. Then, the mute signal is turned off, and the mute signal is not given to the video circuit 58 and the audio multiplex signal demodulation circuit 18. As a result, good video and audio are output as they are. And it ends.

On the other hand, if step S23 is "NO", the process proceeds to step S33, C is incremented by "1", D is reset, and the process proceeds to step S35. In step S35, it is determined whether or not B = C,
If "NO", the process returns to step S23, and if "YES", the process proceeds to step S37. Step S29 is "N
Also in the case of "O", the process proceeds to step S37. That is, in all cases other than the case where the discrimination signal is normal and there is the synchronizing signal, the process proceeds to step S37, it is determined that the received broadcast is non-station, and the channel selection microcomputer 44 Supplies a mute signal to the video circuit 58 and the audio multiplex signal demodulation circuit 18. As a result, the video signal and the audio signal are muted, the video and the audio are not output, and the process ends.

Thus, the video tape recorder 10 '
Then, in determining the presence / absence of a station, not only the condition based on the video signal (synchronization signal) but also the determination signal output from the audio multiplex signal demodulation circuit 18, that is, the determination result in the audio multiplex signal demodulation circuit 18 is considered. When it is determined that there is no station, a mute signal is given to the video circuit 58 and the audio multiplex signal demodulation circuit 18 to mute the video signal and the audio signal so that the video and the audio are not output. Therefore, it is possible to improve so that only the received broadcast with good video and audio can be output.

The operations shown in FIGS. 3 and 5 are performed, for example, every time the channel is switched.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of a voice multiplexed signal demodulation circuit of this embodiment.

FIG. 3 is a flowchart showing main operations of the embodiment shown in FIG.

FIG. 4 is a block diagram showing another embodiment of the present invention.

5 is a flowchart showing main operations of the embodiment shown in FIG.

FIG. 6 is a block diagram showing a conventional technique.

[Explanation of symbols]

 10, 10 '... Video tape recorder 12 ... Antenna 14 ... Tuner circuit 16 ... IF circuit 18 ... Audio multiple signal demodulation circuit 44 ... Channel selection microcomputer 50 ... Audio circuit 56 ... Display tube 58 ... Video circuit 60 ... Sync separation circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04N 5/765

Claims (5)

[Claims] 1. A tuner capable of receiving a television signal,
And a video tape recorder including an audio multiplex signal demodulation circuit that determines a broadcast mode based on a television signal from the tuner and outputs a determination signal and an audio signal according to the determination result, wherein the audio based on the determination signal An authenticity determination means for determining whether the determination result of the multiplex signal demodulation circuit is correct, and a switching means for forcibly switching the audio signal from the audio multiplex signal demodulation circuit to monaural output when the determination result is incorrect. Characteristic video recorder. 2. A tuner capable of receiving a television signal, an audio multiplex signal demodulation circuit which determines a broadcast mode based on the television signal from the tuner, and outputs a determination signal and an audio signal according to the determination result, and In a video tape recorder provided with a discriminating means for discriminating presence / absence of a received broadcast based on a video signal, correct / erroneous judgment means for judging whether the discrimination result in the audio multiplex signal demodulation circuit is correct or not based on the discrimination signal. Further preparation,
The control means further determines whether the received broadcast is stationed or absent in consideration of whether the determination result is correct or incorrect.
Video tape recorder. 3. The video tape recorder according to claim 2, wherein the discriminating means determines that the received broadcast is local only when the discrimination result is correct and the video signal is detected. 4. The correctness determination means determines that the determination result in the audio multiplex signal demodulation circuit is incorrect if the number of changes of the determination signal within a predetermined time is equal to or more than a threshold value. The video tape recorder according to any one of 3 above. 5. The correct / wrong determination means determines the determination result in the audio multiplex signal demodulation circuit when the state in which the number of changes of the determination signal within a predetermined time is equal to or more than a threshold value is continuously confirmed a predetermined number of times. The video tape recorder according to any one of claims 1 to 3, which is determined to be erroneous.