JP3386997B2 - VTR - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a VTR having a built-in speaker. 2. Description of the Related Art A conventional technique will be described with reference to FIG.
FIG. 2 is a block diagram of a conventional circuit. In FIG.
21 is a head amplifier circuit, 22 is a chroma APC circuit, 2
3 is an EQ circuit, 24 is an FM demodulation circuit, 25 is a noise canceller circuit, 26 is a Y / CMIX circuit, 27 is a head amplifier circuit, 28 is a band-pass filter circuit, 29 is an FM demodulation circuit, 30 is an expansion circuit, and 31 is an expansion circuit. DOC circuit, 3
2 is a noise canceller circuit, 33 is a speaker amplifier circuit, and 35 is a chroma signal processing circuit. [0003] First, the video reproduction system will be described. The reproduced signal output from the head is amplified by the head amplifier circuit 21 and then supplied to the chroma APC circuit.
After being processed by the chroma signal processing circuit, the reproduced chroma signal is Y / C
It is supplied to the MIX circuit 26. The reproduced F amplified by the head amplifier circuit 21
After the frequency characteristic of the M signal is corrected by the EQ circuit 23,
After being returned to the original video signal by the FM demodulation circuit 24 and the noise signal being removed by the noise canceller circuit 25, the Y /
The CMIX circuit 26 combines the luminance signal and the chroma signal,
It is supplied to the video output terminal and the RF converter circuit. On the other hand, in the audio reproduction system, an L-channel audio reproduction line of a Hi-Fi signal will be described. A reproduction signal output from a head is amplified by a head amplifier circuit 27, and then amplified by a band-pass filter circuit.
After taking out the FM carrier (1.3 MHz ± 50 kHz), it is restored to the original audio (compressed) signal by the FM demodulation circuit 29, and the audio signal expanded by the expansion circuit 30 is subjected to dropout compensation by the DOC circuit 31. After the noise is removed by the noise canceller circuit 32, the signal is supplied to the audio output circuit and the speaker amplifier circuit 33, and the audio signal amplified by the speaker amplifier circuit 33 is supplied to the speaker. In the conventional circuit, the vibration of a vibration source, for example, a speaker, coincides with the resonance frequency of the set and causes a large vibration. There was a problem of causing jitter. When such a problem occurs, the reproduction volume level is reduced by a manual volume. According to the present invention, the reproduced audio level can be automatically adjusted so that horizontal jitter does not occur in the reproduced video signal. In a VTR according to the present invention, a vertical synchronous pickup circuit provided between an FM demodulation circuit and a noise canceller circuit of a video reproduction system, and a pickup picked up by the vertical synchronous pickup circuit. A vertical synchronization connection reference DC generator for generating a reference DC voltage from a vertical synchronization signal; a vertical period extraction circuit for extracting a vertical period from an output signal of the FM demodulation circuit; and a horizontal circuit for extracting horizontal synchronization from an output signal of the vertical period extraction circuit. A sync extraction circuit, a sync tip connecting voltage generator for connecting the horizontal sync sync chips, and generating a connecting voltage waveform;
The reference DC voltage from the vertical synchronization connection reference DC generator is compared with the sync tip connection voltage waveform from the sync tip connection voltage generator, and the voltage difference is compared with a preset reference voltage. And a comparator that outputs
A control signal generator that receives the output signal of the comparator to generate a control signal, a volume variable circuit that receives the control signal and varies a volume incorporated in a sound reproduction system, and an output signal of the volume variable circuit. A speaker amplifier circuit to amplify,
And a speaker driven by an output signal of the speaker amplifier circuit. [0010] With this, the volume level is varied according to the jitter level, and in the case of tape audio reproduction containing a large amount of resonance frequency components, the level is suppressed to a level that does not cause a moderate amount of jitter. In addition, an automatic sound volume changing circuit for returning the sound volume to the normal sound volume is built in, so that an optimum sound volume and a good reproduced image can be obtained. FIG. 1 is a block diagram showing an embodiment of the present invention.
It will be described based on. FIG. 1 is a schematic block diagram. In FIG. 1, reference numeral 1 denotes a head amplifier circuit;
Is a chroma APC circuit, 3 is an EQ circuit, 4 is an FM demodulation circuit, 5 is a noise canceller circuit, 6 is a Y / CMIX circuit, 7 is a vertical synchronization pickup circuit, 8 is a vertical period extraction circuit, and 9 is a vertical synchronization connection reference. DC generator, 10
Is a horizontal synchronization extracting circuit, 11 is a sync chip connection voltage generator, 12 is a comparator, 13 is a control signal generator, 14
Is a head amplifier circuit, 15 is a band pass filter circuit, 16 is an FM demodulation circuit, 17 is an expansion circuit, and 18 is DO
C circuit, 19 is a noise canceller circuit, 20 is a volume variable circuit, 34 is a speaker amplifier circuit, 34 is a speaker amplifier circuit, and 35 is a chroma signal processing circuit. First, in the reproducing system, the reproduced signal output from the head is amplified by the head amplifier circuit 1 and supplied to the chroma APC circuit 2, and then processed by the chroma signal processing circuit 35. / CMIX circuit 6
Supplied to Reproduced FM amplified by head amplifier circuit 1
The signal is frequency-corrected by an equalizer (EQ) circuit 3 and then returned to an original video signal by an FM demodulation circuit 4.
The signal is supplied to the noise canceller circuit 5 and to the vertical synchronous pickup circuit 7 and the vertical period extracting circuit 8. After the noise component is removed by the noise canceller circuit 5, the luminance signal and the chroma signal are mixed by the Y / CMIX circuit 6 and supplied to the video output terminal and the RF converter circuit. After only the vertical synchronizing signal is extracted from the reproduced luminance signal supplied to the vertical synchronizing pickup circuit 7, a DC voltage to which the vertical synchronizing end is connected is generated by the next vertical synchronizing reference DC generator 9. This is supplied to the comparator 12 as a reference DC voltage. After all the horizontal synchronization in the vertical period is extracted from the reproduced luminance signal supplied to the vertical period extraction circuit 8, only the horizontal synchronization is extracted in the next horizontal synchronization extraction circuit 10, and the next sync chip is connected. The voltage generator 11 generates a voltage waveform connecting the horizontal sync chips, and a horizontal jitter change appears in this waveform. The voltage waveform at the sync tip connection voltage generator 11 is supplied to a comparator 12 and compared with the reference DC voltage from the vertical synchronization connection reference DC generator 9 to detect the difference voltage. The comparator 12 compares the preset reference voltage with the difference voltage, and determines whether the horizontal sync chip variation due to jitter is large or small. If it is determined that the voltage is large, a voltage corresponding to the magnitude level is supplied to the control signal generator 13. If it is determined to be smaller, it is not supplied. The control signal generator 13 generates a control signal corresponding to the voltage level input from the comparator 12 and supplies the control signal to the volume control circuit 20. That is, when the jitter is large, a control signal for lowering the volume level is supplied from the control signal generator 13 to the volume variable circuit 20 corresponding to the voltage level corresponding to the level. The reproduced sound varied by the volume varying circuit 20 is amplified by a speaker amplifier circuit 34 and then supplied to a speaker. On the other hand, the reproduced audio supplied to the audio output circuit is supplied from the volume variable circuit 20. That is, the variable sound volume operates only on the reproduced sound supplied to the speaker amplifier circuit 34 and the speaker built in the VTR. According to the present invention, when the mechanical section of the VTR vibrates due to the vibration of the speaker built in the VTR and the horizontal jitter occurs in the reproduced video signal due to the influence of the vibration, the interval of the horizontal synchronizing signal changes. In accordance with the above, the audio level supplied to the speaker is reduced to suppress the horizontal jitter and maintain the maximum volume level within a range where the video is not adversely affected, thereby obtaining the optimal volume and a good reproduced image. be able to.

[Brief description of the drawings] FIG. 1 is a block diagram of the present invention. FIG. 2 is a block diagram of a conventional example. [Explanation of symbols] 1 Head amplifier circuit 2 Chroma APC circuit 3 EQ circuit 4 FM demodulation circuit 5 Noise canceller circuit 6 Y / CMIX circuit 7 Vertical synchronous pickup circuit 8 Vertical period extraction circuit 9. Vertical reference transition DC generator 10 Horizontal synchronization extraction circuit 11 Sync tip connecting voltage generator 12 Comparators 13 Control signal generator 14 Head amplifier circuit 15 Bandpass filter circuit 16 FM demodulation circuit 17 Extension circuit 18 DOC circuit 19 Noise Canceller 20 Volume control circuit 34 speaker amplifier circuit 35 Chroma signal processing circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 5/76-5/956 H04R 3/00

Claims (1)

(57) [Claim 1] A vertical synchronization pickup circuit provided between an FM demodulation circuit and a noise canceller circuit of a video reproduction system, and a vertical synchronization signal picked up by the vertical synchronization pickup circuit. A vertical synchronization connection reference DC generator for generating a reference DC voltage, a vertical period extraction circuit for extracting a vertical period from an output signal of the FM demodulation circuit, a horizontal synchronization extraction circuit for extracting horizontal synchronization from an output signal of the vertical period extraction circuit. A sync tip connection voltage generator for generating a connection voltage waveform for connecting the horizontal synchronization sync chips, a reference DC voltage from the vertical synchronization connection reference DC generator and a sync tip connection from the sync tip connection voltage generator The voltage difference is compared with a preset reference voltage, and the voltage difference is compared with the reference voltage. A control signal generator that receives the output signal of the comparator and generates a control signal; a volume variable circuit that receives the control signal and varies a volume incorporated in an audio reproduction system; A VTR comprising: a speaker amplifier circuit for amplifying an output signal of the volume variable circuit; and a speaker driven by the output signal of the speaker amplifier circuit.