JPH07118115B2 - VTR tracking correction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a VTR tracking correction device.

[Conventional technology]

As shown in FIG. 4, the VTR tracking correction device has an error in which the frequency of the frequency generator FG that generates a signal having a frequency corresponding to the rotation speed of the capstan motor is compared with a predetermined reference voltage by the frequency voltage conversion circuit. Detect the voltage.

Then, the transistor TR1, the variable resistor VR1 which is a tracking adjuster, the capacitor C1, and the output pulse of the sampling pulse circuit configured by the RS flip-flop circuit FF1 and the other one have the predetermined reference voltage Vref as an input signal. It is supplied to the comparator circuit 13.

The output signal of the comparator circuit 13 adds the error voltage to the error voltage detected by the speed control means in the phase voltage conversion circuit 14 that converts the phase difference from the control signal CTL generated during reproduction into a capstan motor. The VTR tracking correction was performed by correcting the speed and phase of the capstan motor by feeding back.

[Problems to be Solved by the Invention]

Due to the expansion and contraction of the tape to be played back and the subtle difference in the mechanical running system and playback circuit between the recording device and the playback device, the trace timing of the head may shift during playback of the tape and tracking noise may appear on the screen or voice, In order to correct this, I manually operated the tracking adjuster to make adjustments so that there was no tracking noise. However, this tracking adjustment is automated, and when the recording device and playback device are different, as shown in FIG. As shown in, the best point of video playback tracking and the best point of audio playback tracking may differ, but by selecting and operating the priority switch, playback at the best point of video playback tracking and audio playback The aim is to allow playback at the best point of tracking to be selected.

[Means for Solving the Problems]

In order to solve the above problem, in the present invention, each detection means for detecting the envelope of the reproduced signal of the video signal and the audio signal by the detection circuit, and the detection signal by the detection means is quantized by the sampling pulse. Each A / D conversion circuit means, each means for supplying the same quantized quantized signal to the interface circuit which transmits and receives data to and from the microprocessor, and the quantized signal is divided into blocks at predetermined intervals. Each detecting means, each detecting means for detecting the minimum value by the sampling means at least at three or more places for each block formation, the sampling signal which is the minimum value by the detecting means, and stored in the microprocessor. The respective means for comparing the stored data in the microprocessor and the data stored in the microprocessor based on the result of the comparison. If small, each means for converting the data stored and held in the microprocessor into the same sampling signal, and each means for outputting the data of the phase correction amount corresponding to the converted sampling signal from the same microprocessor, Each means for outputting the data of the phase correction amount stored and held in the microprocessor from the same microprocessor when the data of the sampling signal held in the microprocessor is larger based on the comparison result; Means for supplying data to the phase control circuit controlling the capstan motor of the VTR via the interface circuit, by comparing the data of the two phase correction amounts and varying the phase correction amount based on the smaller data. VTR tracking correction, and By operating the first switch of the first switch and the second switch connected to the VST capstan motor of the VTR via the interface circuit, the minimum value data of the phase correction amount with respect to the envelope of the video reproduction signal is operated. Is supplied to the phase control circuit that controls the VTR, and by operating the second switch, the minimum value data of the phase correction amount with respect to the envelope of the audio reproduction signal is controlled by the capstan motor of the VTR via the interface circuit. It is possible to perform VTR tracking correction by changing the phase correction amount so that the detection output of the envelope of the video and audio reproduction signals is maximized. .

[Action]

In the VTR tracking correction device according to the present invention configured as described above, the envelope of the reproduced signal of the video signal and the audio signal is detected by the detection circuit, and the detection signal by the detection circuit is quantized by the A / D conversion circuit. To do.

The quantized quantized signal is supplied to the interface circuit that transmits and receives data to and from the microprocessor,
A means for dividing the quantized signal into blocks for each frame, and at least a video start portion, a video end portion, and a video start portion of the next field are included in each frame as shown in FIG. 3B. The minimum value is detected by means of sampling at three or more points.

The minimum value sampling signal by the detection means is compared with the data stored and held in the microprocessor, and as a result of the comparison, if the sampling signal is smaller in the data stored and held in the microprocessor, the microprocessor The data stored and held in the processor is converted into the same sampling signal.

When the same sampling signal has a larger amount of data stored and held in the microprocessor, the phase correction amount data stored and held in the microprocessor is output from the microprocessor.

Based on the comparison result, the data of the phase correction amount is supplied to the phase control circuit controlling the capstan motor of the VTR via the interface circuit to perform the tracking correction of the cassette VTR.

Further, the minimum value of the detection output of the envelope of the video reproduction signal is maximized by operating the first switch provided in connection with the interface circuit, and the audio reproduction is operated by operating the second switch. The minimum value of the detection output of the signal envelope is set to the maximum value, and the VTR tracking correction can be performed by changing the phase correction amount so that either reproduction state is prioritized and the optimum state is obtained. .

〔Example〕

Hereinafter, a VTR tracking correction device according to the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a VTR tracking correction device according to the present invention, in which an FG pulse corresponding to the frequency of a frequency generator FG that generates a signal of a frequency corresponding to the rotation speed of a capstan motor is generated. The signal amplified by the pulse amplifier and compared with the signal amplified by the FG pulse amplifier is compared with the specified reference voltage by the frequency-voltage conversion circuit, and if the specified rotation speed of the capstan motor is different, the rotation error voltage To detect.

Then, the playback FM picked up by the video signal head
The video signal is supplied to the video preamplifier amplification circuit 5 via the rotary transformer, and the reproduced FM video signal amplified by the video preamplifier amplification circuit 5 is FM video envelope detection circuit 6
Is detected at to detect the envelope of the FM video signal.

In the present embodiment, the envelope of the FM video signal is sampled by the video A / D conversion circuit 7 at a sampling frequency of 200 μs, and the quantized signal is transmitted / received to / from the microprocessor 3 by the interface circuit 4. Supply to.

In addition, the reproduced FM sound signal picked up by the sound signal head is supplied to the sound preamplifier amplification circuit 8 through the rotary transformer, and the reproduced FM sound signal amplified by the sound preamplifier amplification circuit 8 is detected by the FM sound envelope detection circuit 9 Is detected at to detect the envelope of the FM audio signal.

The envelope of the FM audio signal is about 200 μs in this embodiment.
The signal sampled and quantized by the audio A / D conversion circuit 10 at the sampling frequency of
Interface circuit 4 that sends and receives data to and from
Supply to.

Then, when tracking correction is required as in the flowchart shown in FIG. 5A, in the present embodiment, the determination is made by the interrupt flag of 1 scan that makes 1 scan between 1 frames, and the interrupt flag of 1 scan is determined. When it occurs, as shown in FIG. 5 (b), one scan is interrupted, the minimum value detected by the means for sampling the audio envelope signal is transferred to the audio envelope minimum value area, and the audio envelope minimum value area is set. initialize.

Then, the video envelope signal transfers the minimum value detected by the sampling means to the video envelope minimum value area, and initializes the video envelope minimum value area to 1
Clear the scan interrupt flag.

Then, it is determined whether or not the tracking correction state is in the optimum correction state. If the result of the determination is that the tracking correction state is not in the optimum correction state, the minimum value of the audio sampling signal input as shown in FIG. 5 (c). The data is compared with the data stored and held in the microprocessor 3,
As a result of the comparison, when the input audio sampling signal is smaller than the data stored and held in the microprocessor 3, the data stored and held in the microprocessor 3 is converted into the input audio sampling signal.

If the input audio sampling signal is larger than the data stored and held in the microprocessor 3, the microprocessor 3 outputs the data of the phase correction amount stored and held in the microprocessor.

Then, the minimum value data of the input video sampling signal is compared with the data stored and held in the microprocessor 3, and as a result of the comparison, the input video sampling signal is smaller than the data stored and held in the microprocessor 3. In this case, the data stored and held in the microprocessor 3 is converted into the input video sampling signal.

If the input video sampling signal is larger than the data stored and held in the microprocessor 3, the data stored and held in the microprocessor 3 is output from the microprocessor 3.

In the case of normal reproduction, the audio sampling data and the video sampling data in the microprocessor 3 are compared,
The smaller data is supplied as minimum value data of the microprocessor 3 to the interface circuit 4 which transmits and receives data to and from the microprocessor 3.

Further, when the video priority switch 11 connected to the interface circuit 4 is operated, only the minimum value of the video sampling data in the microprocessor 3 is transferred to the interface circuit 4 transmitting / receiving the data to / from the microprocessor 3. In addition, when the voice priority switch 12 is operated, only the minimum value of the voice sampling data in the microprocessor 3 is supplied to the interface circuit 4 transmitting / receiving data to / from the microprocessor 3.

The output data corresponding to each of the normal reproduction state, the state in which the video priority switch is operated, and the state in which the audio priority switch is operated, supplied from the interface circuit 4, of the mono-multivibrator circuit 2 which is a phase control circuit. Change the pulse width.

The phase voltage change circuit 1 that compares the phase of the output pulse of the mono-multivibrator circuit 2 with the control signal CTL generated during reproduction outputs the phase error voltage corresponding to the input phase difference.

The same phase error voltage and the rotation error voltage are added to amplify the same error voltage in the error amplifier circuit, and the voltage amplified in the same error amplifier circuit is supplied to the motor drive circuit to drive the capstan motor. The feedback circuit corrects the speed and phase of the capstan motor.
It is not a method of detecting only a specific point and maximizing the total value detected, as shown in, and at least three or more points are detected for each same frame, and tracking is performed so that the minimum value detected is maximal. Since the correction is performed, the amount to be corrected can be made uniform during one scan as shown in FIG. 3 (b).

〔The invention's effect〕

As is clear from the above examples, the VTR according to the present invention
The tracking correction device was reproduced from the video signal head.
The FM video signal envelope and the FM audio signal envelope reproduced from the audio signal head are detected, the detected signal is quantized by the A / D conversion circuit, and sampling is performed at least three times or more within one scan. The minimum value of the sampling signal is compared with the sampling data held in the microprocessor, and the pulse width of the mono-multivibrator, which is the phase control circuit, is changed by the small data based on the comparison result, or the video priority switch When is operated, only the minimum value of the video sampling data is used, or when the audio priority switch is operated, the pulse width of the mono-multivibrator, which is the phase control circuit, is changed only by the minimum value of the audio sampling data. Then, the phase difference between the same pulse width and CTL is detected by the phase voltage conversion circuit as the phase error voltage, Since the phase of the capstan motor is controlled by the same phase error voltage, the envelope between the upper part of the tape and the lower part of the tape in one scan becomes uniform, and a stable TV image without noise can be obtained, and the image is reproduced. Even if the best tracking point for audio playback and the best tracking point for audio playback differ, select the priority switch to operate and select the best playback point for video playback or the best tracking point for audio playback. This is a tracking correction that allows reproduction at points to be selected.

Moreover, since the automatic VTR tracking correction circuit does not include the tracking adjuster, troubles caused by the tracking adjuster can be eliminated.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing a relationship between a phase of a mono-multivibrator circuit (MMV) and an envelope output, FIG. 3 is a tracking correction explanatory diagram, and FIG. Is a block diagram of a conventional tracking correction device, and FIG. 5 is a flowchart. In the figure, 1 is a phase voltage conversion circuit, 2 is a mono-multivibrator circuit, 3 is a microprocessor, 4 is an interface circuit, 5 is a video preamplification circuit, 6 is an FM video envelope detection circuit, and 7 is an A / D conversion circuit. , 8 is an audio preamplifier circuit, 9 is an FM audio envelope detection circuit, and 10 is
A / D converter circuit, 11 and 12 priority switch, 13 comparator circuit, 14 phase voltage converter circuit, FF1 RS flip-flop circuit, TR1 transistor, C1 capacitor, VR1 variable resistor, Vref reference voltage , FG is a frequency generator and CTL is a control voltage.

Claims (2)

[Claims] 1. A rotational speed of a capstan motor is detected as a frequency, the frequency is converted into a voltage by a frequency-voltage conversion circuit, the voltage is compared with a reference voltage to obtain an error voltage, and the rotational speed of the motor is determined. In tracking correction that is controlled, a first envelope detection circuit that outputs a detection signal of a video reproduction signal, a first A / D conversion circuit that converts the detection signal into a digital signal, and a detection signal of an audio reproduction signal A second envelope detection circuit for outputting the signal, a second A / D conversion circuit for converting the detection signal into a digital signal, a memory circuit for recording required correction data, and a signal from the first A / D conversion circuit. Compared with the first reference data,
If the signal from the 1st A / D conversion circuit is judged to be small,
A first comparison circuit that outputs a signal from the 1A / D conversion circuit and outputs correction data from the storage circuit when it is determined to be large, and a second comparison circuit that is set as a signal from the second A / D conversion circuit Comparing with the reference data, when the signal from the second A / D conversion circuit is determined to be small, the signal from the second A / D conversion circuit is output, and when it is determined to be large, the correction data from the storage circuit And a third comparison circuit that outputs the data determined to be small by comparing the respective data output from the first and second comparison circuits with the data from the comparison circuit. A pulse generation circuit for controlling a pulse width based on the pulse width to output a pulse signal, a phase comparison circuit for outputting a phase error signal between the pulse signal and a reproduction control signal, and a circuit for adding the phase error signal to the error voltage Composed of and
VTR tracking correction device. 2. A first switch circuit for selecting the first comparison circuit and a second switch circuit for selecting the second comparison circuit are provided.
The VTR tracking correction device according to claim 1, wherein the pulse generation circuit is controlled based on the data from the selected comparison circuit.