JPH0462148B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for recording video signals and audio signals or other signals on the same track in a time-division manner, for example in a helical scan VTR such as 8 mm video. The present invention relates to a recording timing pulse generator that generates pulses for determining a recording start position.

Figure 1 shows an example of a helical scan VTR tape format and its corresponding timing chart.

In FIG. 1, 1 is the track of channel 1 on the tape, and 2 is the track of channel 2 on the tape. In this tape format, 7
CLOCK indicates the beginning of PCM data area 8
The width is determined by the part called RUN IN (or, in PCM audio, it is called the preamble).
1.4° (=2.0H), 8 is the PCM data area with a width of 26.32° (=38.4H), and 9 is the f5 recording area (in PCM, it is called the postamble indicating the end of the PCM data area. ).

Note that f5 here is a single frequency (229KHz) that is recorded to fix the head at a constant height when recording with dynamic track hollowing (DTF).

10 is the part that reproduces the f5 recorded in one head as crosstalk, and the combined width of area 9 and area 10 is 2.06° (= 3.0H), and each area 9 and 10 requires 1H or more. . 11 is called the V-P guard, and it covers the rear video area and the front video area.
It is separated from the PCM audio area. The width of this part is 2.62° (=3.8H). 12 is an area for storing video signals and has a width of 180° (=128.6H). Reference numeral 13 indicates an overlap area where the video signals of channel 1 and channel 2 are overlapped by about 5 degrees and recorded in advance in order to prevent a gap between the video signals and a portion without a video signal from appearing on the screen.

The above is an example of a tape format, and as mentioned above, the feature is that recording signals must be switched with an accuracy of 1H (63.5 μs).

In order to realize the tape format described above, a highly accurate timing pulse is required in which the signal is switched at least every 1/2 fh.
The methods for creating the reference signal are as follows: (1) Create a PG pulse that detects the position of the drum and an optical FG pulse that detects the rotational speed of the drum by dividing the frequency using a counter, etc., (2) Create an external signal instead of the FG pulse. A possible solution would be to equip the system with a stable oscillation circuit.

However, in the above-mentioned methods <1> and <2>, the FG pulse simply counts external oscillation pulses to create timing, and during PCM after-recording, variations in VTR set and drum motor speed fluctuations can occur even with the same set. PCM that indicates the end point of recording an audio signal as the tape expands and contracts.
Postamble 9 may enter the video area, resulting in it appearing as noise on the screen. Furthermore, if the V-P guard 11 is made wide enough to prevent such a situation, the PCM or video data area will become shorter, and the margins of other parts will be cut. .

Furthermore, in the method described in <2> that uses an external oscillator instead of the FG pulse, even during normal recording, the rotation of the drum and the pulse of the external oscillator are not synchronized, so the oscillation pulse when the drum is rotating normally teeth,
As shown in 4 in Figure 2, the correct timing can be determined by counting a predetermined number, but if the motor speed fluctuates or the tape expands or contracts, the external oscillation pulse relative to the tape speed will be 15. It becomes like this. Therefore, since the signal is switched at a specified number of pulses, the position of the recorded signal on the tape is, for example, 14, and the PCM postamble 9 invades the video area 12, causing the video of one scanning line portion of the screen to be switched. Signals cannot be recorded. Also,
Conversely, it is also possible that the PCM audio area 8 becomes narrower than specified, and the recording position and reproduction position of f5 on the adjacent track will not match, and DTF will not be applied.

As described above, in the methods <1> and <2> described above, the relative positions of the PCM audio area 8 and the PCM postamble 9 may change, making it extremely difficult to maintain compatibility with other devices. There are difficult drawbacks.

This invention was made in order to eliminate the above-mentioned drawbacks, and provides a recording timing pulse generator that has excellent compatibility, and the relative positions of the signals do not change even when the drum motor speed fluctuates or the tape expands and contracts. The purpose is to provide.

Embodiments of the present invention will be described below with reference to the drawings. In Fig. 3, 16 is a drum motor;
17 is a PG magnet, 18 is a PG and FG mounting wheel, 19 is a slit that transmits the light of the light emitting element 21, and 20 is a coil that generates an induced voltage when the PG magnet 17 passes below, and this induced pulse becomes the PG pulse. Reference numeral 21 denotes a light emitting element 21 for optical FG, which is made of, for example, an LED. 2
Reference numeral 2 denotes a light receiving element that detects the light transmitted through the slit 19, and uses a photo transistor or the like, and outputs this as an FG pulse.

23 is a drum PG that amplifies the minute PG pulse generated by the coil 20, makes both the positive and negative of the PG pulse generated by the S and N poles of the magnet 17 positive, and shapes it so that it can drive the gate of the next stage.
It is a pulse amplifier. In addition, 24 is the light receiving element 2
2 is an active filter that extracts only the necessary fundamental wave component from the harmonic components contained in the FG pulse generated in 2, and 25 amplifies the output of the active filter 24 and shapes it into a rectangular wave.
This is an FG waveform shaping circuit. Reference numeral 26 denotes a recording timing pulse generator that generates recording timing pulses 6 using the output 3 of the drum PG pulse amplifier 23 and the output 4 of the FG waveform shaping circuit 25 as reference clocks.

FIG. 4 shows an embodiment of a recording timing pulse generator according to the present invention. In this embodiment, a flip-flop 28 generates the start point of the PCM preamble 7 and the start point of the PCM postamble 9, and generates enable signals 32 and 33 that stop the counter from operating at any point other than these two start points. , 29 are provided. 31 is
A presettable counter 30 for determining the starting point of the PCM postamble 9 is a presettable counter 30 for determining the starting point of the PCM preamble 7, and each output is as shown in 5 and 6 in FIGS. 1 and 5. 34 is the output pulse of the counter 31
This is a gate that performs an OR with pulse 9a of PCM postamble 9, so that timing pulse 6 for f5 recording is determined by whichever has the earlier timing between the output of counter 31 and pulse 9a of PCM postamble 9. It's something you make. Therefore,
During normal recording, the pulse 9a of the PCM postamble 9 does not enter the gate 34, and only the output of the counter 31 is input to the gate 34, and becomes the timing pulse 6 as it is.

FIG. 5 is an example of a recording timing chart.

Next, the operation will be explained with reference to FIGS. 3, 4, and 5. First, in FIG. 3, when the PG and FG mounting wheel 18 connected to the spindle of the drum motor 16 rotates 30 times per second, an induced electromotive force is generated between the PG magnet 17 attached to the wheel 18 and the coil 20. Then, a PG pulse is created. Since the PG magnets 17 are installed on the wheel 18 at 180° intervals,
The PG pulse has a frequency of 60Hz. In addition, a slit 1 opened on the concentric circumference of the wheel 18
9 through the slit 19 above the wheel 18.
The light emitted by the light emitting element 21 provided directly above reaches the base of the light receiving element 22, and the light receiving element 22 outputs an output in response. In this method, the frequency of the extracted FG pulse can be increased as the number of slits 19 increases, but in reality there is a limit to the FG frequency depending on the response speed and directivity of the light receiving element 22.

The minimum FG frequency required to realize tape formats 1 and 2 in Figure 1 is the horizontal synchronization period (1H = 63.5μsec, frequency is fh
= 15.75KHz), that is, considering that there are parts 9, 10, and 11 that are switched every 1H, the error is within an allowable range if it is 2fh. Therefore, the FG frequency is 31.5 KHz, and it is appropriate to use the optical FG pulse described above to achieve this level of high resolution.

Now, the PG pulse obtained as above is
The pulse amplifier 23 amplifies the signal to a level that can drive the next stage gate IC. On the other hand, the FG pulse is
The signal passes through a narrow-band active filter 24 that passes only the FG pulse frequency (31.5 KHz for 2fh), and is amplified and waveform-shaped by a waveform shaping circuit 25 so that it can drive the next stage gate IC. In this way, PG pulse 3 and FG pulse 4 are obtained.
Both pulses 3 and 4 enter the next recording timing pulse generator 26. This recording timing pulse generator 26 determines the recording start point of the audio signal, detects the recording end point of the audio signal based on it, and generates a write timing pulse of f5. It is shown in Figure 4.

Next, the operation of the circuit shown in FIG. 4 will be explained with reference to FIG. 5 as well.

First, PG pulse 3 is input to the CLEAR terminal of presettable counter 30. Every time the PG pulse 3 is input, the counter 30 clears the previous count and starts counting anew. When PG pulse 3 is input, FG pulse 4 input to the CK terminal is counted, and when the count number preset by data inputs Da to Dd is reached, pulse 5 is output from the CARRY-OUT terminal.
is output. This output pulse 5 is input to the CLEAR terminal of the next counter 31, and similarly, the number of output pulses set by the data inputs Da to Dd is input from the CK terminal.
When FG pulse 4 is counted, CARRY
OUT output occurs.

Generation of a recording timing pulse only once can be achieved by using the two counters 30 and 31 as described above, but in reality, it is necessary to output these two timing pulses many times. Flip-flops 28 and 29 are for that purpose. Below, 28 is FF1, 29 is FF2
It is abbreviated as

In other words, for FF1, 28, the output Q, 32 is in the "H" state from the input of PG pulse 3 until the pulse 5, which determines the starting point of the PCM preamble 7, is input to the CLK terminal. By inputting this to the ENABLE1 terminal of the counter 30, the counter 30 is enabled to count. Immediately after this pulse 5 is input to FF1, 28 until the next PG pulse 3 is input,
The outputs Q and 32 of FF1 and 28 become “L” state,
This makes the counter 30 uncountable,
The CARRY OUT output is not output. By repeating this operation, only the necessary portions are counted (see 32 in FIG. 5).

Next, the CARRY OUT output of counter 30 is
When input to FF2, 29, the CARRY OUT output of counter 31 becomes CLK of FF2, 29 in exactly the same way.
The Q output 33 of the FF2, 29 is in the "H" state until input to the terminal, and the counter 31 is in a countable state. From the time the CARRY OUT output of the counter 31 is input until the next pulse 5 is input, the outputs Q and 33 of the FF2 and FF29 are in the "L" state, so the counter 31 is in a state where it cannot count.

In this way, as shown in Fig. 5, 33,
It is possible to count the FG pulses 4 from the start point of the PCM preamble 7 to the start point of the PCM postamble 9 and output the necessary timing pulses repeatedly. Therefore, counters 30, 31
By changing the settings of the data inputs Da to Dd, a circuit that can repeatedly output arbitrary timing pulses can be realized.

However, in this embodiment, one counter is used to output one timing pulse, but since the data input is 4 bits, only a maximum of 16 pulses can be counted. If more counts are required, the required number of identical counters must be connected in series.

The output pulse of the counter 31 is input to the OR gate 34, and during PCM after recording,
Pulse 6 is ORed with pulse 9a of PCM postamble 9 and indicates the recording end point of the audio signal.
(f5 recording timing pulse).

In the above example, an optical FG is used as the reference pulse generator, so a high frequency can be obtained as the FG pulse, and a presettable counter is used, so it is easy to set the optimum specified number of pulses. As a result, highly accurate recording timing pulses can be created.

As described above, according to the present invention, the recording start point of the audio signal is determined using the PG pulse and the FG pulse, the recording end point of the audio signal is detected by counting the FG pulses, and the detected pulse and the after recording Compare it with the signal indicating the end point of the audio signal that has already been recorded.
Since the f5 signal is forcibly written with the earlier pulse, the f5 (PCM
postamble) does not enter the video signal recording area.

Therefore, even if the speed of the drum motor or the tape tension varies, the relative positions between the signals do not change, so there is no need for mutual adjustment between the devices.

[Brief explanation of the drawing]

Figure 1 shows an example of the tape format of a helical scan VTR and its corresponding timing chart, and Figure 2 shows an example of a drum format.
A diagram for explaining the relationship between the speed of the motor and the pulse width relative to the tape; Figure 3 is a configuration diagram of the essential parts of an iris scan type VTR to which this invention is applied; Figure 4 is a diagram according to the invention. FIG. 5 is a circuit diagram showing one embodiment of the recording timing pulse generator, and its timing chart is shown in FIG. 3...PG pulse, 4...FG pulse, 5...recording start position detection pulse, 6...f5 recording start position detection pulse, 7...CLOCK RUN IN (PCM preamble), 8...PCM data area, 9...
f5 recording area (PCM postamble), 12...
Video signal recording area, 16...Drum motor,
26... recording timing pulse generator, 28,
29...Flip flop, 30, 31...Presettable counter, 34...OR gate.
In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1 A device that generates pulses indicating the recording position of the pilot signal of a tape format in which an audio signal, a video signal, and a pilot signal located between these two signals are time-divisionally recorded on the same track, The recording start point of the audio signal is determined by the PG pulse that detects the position of the drum and the FG pulse that detects the rotational speed of the drum.
The pulse indicating the recording end point of the audio signal created by counting FG pulses based on this recording start point is compared with the signal indicating the end point of the audio signal already recorded during after-recording. , a recording timing pulse generating device, characterized in that a pulse indicating the pilot signal recording position is generated at a timing which is earlier in time.