JPS62298987A - Time code signal recorder - Google Patents

Abstract

PURPOSE:To demodulate a time code signal from the first word without an error by recording the time code signal after a synchronizing word is recorded at the top of a magnetic tape. CONSTITUTION:A microcomputer 1 outputs the instruction to turn on a recording reproducing changing-over switch 6 to a recording side, the instruction to travel a magnetic tape 8 at the ordinary speed to a capstan motor 9 and a time code signal recording condition is obtained. The microcomputer 1 supplies the data of a synchronizing word as time code data to record to a time code signal generating device 2. The time code signal generating device 2 applies biphase-modulation to the supplied time code data and supplies them to a recording amplifier 3. The signal supplied to the recording amplifier 3 is recorded through a recording reproducing changing-over switch 6 and a recording reproducing head 7 to the magnetic tape 8. Thereafter, the time code signal corresponding to the video signal is recorded together with the video signal.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to an apparatus for recording a time code signal representing positional information by recording a video signal and an audio signal together with a magnetic tape or the like. It is something.

In editing a conventional VTR, time code signals are recorded on cue tracks, audio tracks, etc. in order to position the editing tape. An example of this time code signal is an SMPTE time code signal. The SMPTE time code signal assigns an address to a video signal in units of frames. FIG. 3 shows an example of the μs MPTE signal. As shown in Fig. 3, one word of the SMPT E signal consists of 8Q bits, 32 bits represent the frame number 2 seconds 1 minute 1 hour, and 32 bits are used as user's bits as empty bits for the user. , the remaining 16 bits are allocated to the synchronization word. The synchronization word is provided at the end of each word and is used to detect the end of the time code word and the running direction of the tape.

Then, as shown in FIG. 3, these data are modulated by the pi-phase mark method and recorded on the magnetic tape. In pi-phase mark modulation, a level change occurs at each bit synchronization, and when the bit value is "1", a level change occurs at the center of synchronization, and when the bit value is "0#", there is no level change at the center of synchronization. With the modulation method, the clock signal can be easily extracted from the reproduced signal, but even if the clock signal is the same binary value, the polarity may be different.

As an example of a method for demodulating this time code signal, a demodulation circuit has been proposed that performs demodulation based on the length of the previous bit, as shown in Japanese Patent Laid-Open No. 11231/1983. This demodulation circuit has the characteristic that it can accurately reproduce the time code signal even if the tape speed changes.

Problems to be Solved by the Invention If a time code signal is recorded in correspondence with a video signal from the very beginning of a magnetic tape, the time code signal is sequentially recorded on the magnetic tape from the beginning of one word of the time code signal. go. When this time code signal is demodulated by a demodulation circuit that performs demodulation based on the length of the previous bit as shown in the conventional example, the starting bit cannot be demodulated because there is no previous bit. Further, at the very beginning, no level change can be detected because nothing has been recorded before that point. Therefore, the starting point of a bit cannot be determined, the length of that bit cannot be detected, and the next bit cannot be demodulated. If one bit cannot be demodulated, that one word cannot be demodulated. Further, even when the first bit can be demodulated, the processing is delayed because the focus cannot be determined as the first bit of the word until the subsequent 8Q bits' are demodulated.

In view of the above problems, the present invention provides a time code signal recording device that records a time code signal so that a time code demodulation circuit can demodulate one word of the time code signal recorded at the beginning of a magnetic tape. It is.

Means for Solving the Problems In order to solve the above problems, the present invention provides a recording section for recording a time code signal representing an address of an information signal to be recorded on a magnetic tape in the longitudinal direction of the magnetic tape; a time code signal generator that generates a time code signal;
A detector that detects when a time code signal is not recorded before the position where the time code signal starts to be recorded on the magnetic tape, and it is possible to record the time code signal at the position before the time code signal and read the time code signal immediately after it. and a reference signal generator that generates a reference signal, and records the reference signal at a position before recording the time code signal when the detection means detects that the time code signal is not recorded. This is a time code signal recording device characterized by having means and money.

Effect of the Invention The present invention has the above-described configuration, and provides a reference signal that makes it possible to record a time code signal on a magnetic tape at a position before the time code signal is started and read out the time code signal immediately after the time code signal is recorded. By recording the time code signal at a position before recording the time code signal and then recording the time code signal, the time code signal can be read out without error.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. In FIG. 1, 1 is a microcomputer (hereinafter referred to as a microcomputer) that controls each device, 2 is a time code signal generator that performs pi-phase modulation of time code data supplied from the microcomputer 1, 3 is a recording amplifier, and 4 is a A playback amplifier that plays back the time code signal, 5 a time code signal demodulator, 6 a time code signal recording/playback switch, 7 a time code signal recording/playback head, 8 a magnetic tape, and 9 a capstan motor for running the tape. ,
10 is a tachometer that detects whether the tape is running.

The operation of this embodiment configured as described above will be described.

When an operation command is input to the microcomputer 1, the microcomputer 1 outputs a command to rewind the magnetic tape 8 to the capstan motor 9. The capstan motor 9 operates according to the instructions from the microcomputer 1.
An attempt is made to rewind the magnetic tape 8. If the magnetic tape 8 is the starting end, it will not be rewound.

The microcomputer 1 uses the signal from the tachometer 1o to generate the magnetic tape 8.
If the magnetic tape 8 is not rewound, it is determined that the magnetic tape 8 is the starting end, and a command to stop the magnetic tape 8 is output to the capstan motor 9.

This stop command from the microcomputer 1 causes the capstan motor 9 to stop, and a new time code signal recording operation begins. Further, when the magnetic tape 8 is rewound, the microcomputer 1 switches the recording/reproduction changeover switch 6 to the reproduction side at the same time as the rewinding. Then, the recording/reproducing head 7 is connected to the magnetic tape 8.
The time code signal recorded in the time code signal is reproduced and supplied to the time code signal demodulator 6 via the recording/reproduction changeover switch and the reproduction amplifier 4. The time code signal demodulator 5 demodulates the supplied time code signal and supplies demodulated data to the microcomputer 1. However, unless the time code signal is recorded on the magnetic tape 8, demodulated data cannot be obtained. When demodulated data cannot be obtained, a new time code signal recording operation is performed. Once the demodulated data is obtained, the time code signal to be continuously recorded is recorded in synchronization with the recorded time code signal.

Next, the recording operation of a new time code signal will be explained below.

The microcomputer 1 outputs a command to set the recording/reproduction changeover switch 6 to the recording side, and outputs a command to the capstan motor 9 to run the magnetic tape 8 at a normal speed. With the above steps, the time code signal recording state is entered.

The microcomputer 1 outputs the time code data recorded in the time code signal generator 2 and the code '001111111111.
110f=(data of synchronization word) is supplied. The time code signal generator 2 performs pie-phase modulation on the supplied time code data and supplies it to the recording amplifier 3. The signal supplied to the recording amplifier 3 is recorded on the magnetic tape 8 via the recording/reproducing switch 6 and the recording/reproducing head 7.

Then, along with the video signal, a time code signal corresponding to the video signal is recorded.

The model of the time code signal recorded as described above is
As shown in the figure. In this way, the synchronization bit is followed by a time code signal. When this time code signal is completely reproduced and demodulated, since the previous bit is not recorded in the first bit, no change in level from the previous bit can be obtained, the length of the bit cannot be detected, and of course demodulation is not possible. The second bit cannot be demodulated because the length of the previous bit cannot be detected, but in this case, the length of 7) can be detected. After the third bit, demodulation is possible because the length of the previous bit has been detected, and the synchronization word is detected by the presence of 12 consecutive 1's. Since the first time code signal is generated later, it can be demodulated from the first time code without error. Also,
Since the synchronization word is demodulated first, the subsequent time code M CD start bit can be quickly detected.

As described above, if the time code signal is recorded after the synchronization word is recorded at the beginning of the magnetic tape, the time code signal can be demodulated from the first word without error, and there is no need to change the demodulation circuit. do not have.

In this embodiment, the reference signal is a synchronization word, but any signal representing a break in the time code signal may be used. Further, a signal having the same signal form as the time code signal may be used as the reference signal.

Effects of the Invention As described above, according to the present invention, the time code signal can be demodulated from the beginning of the tape without error, and is very useful.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a model diagram for explaining the embodiment, and FIG. 3 is a waveform diagram of an SMPTE time code signal. 1... Microcomputer, 2... Time code signal generator, 3... Recording amplifier, 4...
・Reproduction amplifier, 5...Time code signal demodulator, 6...Record/playback selector switch, 7...Record/playback head, 8...Magnetic tape, 9...・Capstan motor, 1o...tachometer. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2: 100 eyes

Claims (4)

[Claims] (1) A time code signal generator that generates a time code signal representing the address of the information signal to be recorded on the magnetic tape, a recorder that records this time code signal in the longitudinal direction of the magnetic tape, and a start of recording the time code signal. At the same time, a detector detects whether or not a time code signal is recorded before the recording start position, and a reference signal is generated that makes it possible to record at a position before the time code signal and read out the time code signal immediately after. When the reference signal generator and the detector detect that no time code signal is recorded,
A time code signal recording device comprising means for recording the reference signal at a position before recording the time code signal. (2) The time code signal recording device according to claim 1, wherein the reference signal is a synchronization word of the time code signal. (3) The time code signal recording device according to claim 1, wherein the reference signal is a signal having a signal form of a time code signal. (4) The time code according to claim 1, wherein the detector detects the time code signal by reproducing the time code signal at a predetermined position for a predetermined time with a time code signal regenerator and detecting whether or not a time code signal is obtained. Signal recording device.