JPS63122086A - Time code signal recorder - Google Patents

Abstract

PURPOSE:To correctly read a time code signal at an editing point by recording a time code signal in a level different from a normal signal level at an editing point. CONSTITUTION:Under the control of a system controller 1, an editing point detector circuit 2 detects an editing point, and outputs a pulse having a width equal to one bit of a time code signal, corresponding to this outputting, a time code signal is outputted from a time code signal generator circuit 3. A level control circuit 4 doubles the level of a time code signal outputted from the circuit 3 during a time in which pieces of said pulses are outputted from the circuit 2, and the doubled signals are recorded in a magnetic tape 7. In the reproducing operation, this doubled level is detected and a time code reproduced signal is corrected, thus a time code can be read accurately at an editing point without using the bit of a time code signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an apparatus for recording a time code signal representing positional information on a magnetic tape or the like together with a video signal and an audio signal.

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 SMPTIC time code signal assigns an address to a video signal in units of frames. FIG. 8 shows an example of the SMPTIC signal. As shown in Fig. 8, one word of the SMPTIC signal consists of 80 pits, 32 bits represent the frame number 2 seconds 2 minutes 2 o'clock, 32 bits are used as user bits and are used as empty bits for the user, and the remaining bits represent the frame number 2 seconds 2 minutes 2 o'clock. 16 pits are assigned 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. 8, these data are modulated by a so-called biphase mark method and recorded on a magnetic tape. In biphase mark modulation, the level changes every bit period,
When the bit value is ``1'', a level change occurs at the center of the cycle, and when the bit value is ``o'', there is no level change at the center of the cycle.This modulation method allows the clock signal to be easily extracted from the reproduced signal. Even if they have the same binary value, their polarity may differ.

In VTR assembly editing, this time code signal is also spliced and recorded together with the video signal. At this time, since the time code signal is biphase mark modulated, the bits immediately after the editing point are recorded with the same polarity as the bits before the editing point, as shown in Figure 6, and the bit rate is It may be difficult to read the time code correctly because the level change cannot be obtained.

To solve this problem, there is a recording time code signal generator proposed in Japanese Patent Publication No. 19075/1983. A block diagram of this recording time code signal generator is shown in FIG. 8, and an operation waveform diagram is shown in FIG. 7, and will be explained.

CLl generated from the time code data generator 2o,
Cu2. The signals ST and TD are input to the time code generator 21, and the signal ST shown in FIG. 7 becomes "
The bit value of the Tn via (indicated by “H”) is the previous “n-1”
Controlled by the polarity of the bit, the polarity of the following Tn+1 bit is constant.If the OTn bit is used as the user's pit immediately before the time code, the polarity of the last bit of the word is fixed, and the polarity of the next bit to be connected can be fixed. .

In other words, the time code signal can be recorded with the polarity matched at the editing point.

Problems to be Solved by the Invention However, in the time code signal generator shown as a conventional example, one bit of the time code signal is used as a bit for fixing the end bit of a word of the time code signal. If the signal information cannot be expressed and the user has been using that bit, the bit position must be changed or the use must be stopped.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a time code signal recording device that can read a time code signal without difficulty at an editing point without using the bits of the time code signal.

Means for Solving the Problems The present invention provides a time code signal generation circuit that generates a bi-phase modulated time code signal, and detects an edit point for recording a time code signal following the recorded time code signal. and a control circuit that controls the level of the time code signal supplied from the time code signal generation circuit based on the output of the detection circuit.

According to the above-described configuration, the present invention records the time code signal at a level different from the normal level only at the editing point, and when the time code signal is played back, detects this level and corrects the time code playback signal. As a result, the time code signal can be read out correctly even at the editing point.

Embodiment FIG. 1 shows a block diagram of a time code recording device according to an embodiment of the present invention. In Figure 1, 1
is a system controller (hereinafter referred to as system controller) that controls the operation of the VTR, and controller 2 is driven by an editing start signal from system controller 1, stores the time code of the editing point, and once rewinds the tape, then starts playback operation. The time code that is played back is compared with the stored time code, and when they match (edit point), the time code is changed to 1.
3 is a time code signal generation circuit that generates a bi-phase modulated time code signal; 4 is a level control circuit that controls the level of the time code signal; 6 is a recording amplifier. , 6 is a recording head, and 7 is a magnetic tape.

The operation of the time code recording device of this embodiment configured as described above will be described below with reference to the waveform diagram of FIG. 2. When editing on a VTR, you usually rewind several frames from the editing point, play back the recorded video signal, match the phase of the head with the recorded video signal, play up to the editing point, and then start the new video. Record the signal.

At this time, the time code signal is also reproduced at the same time, and the clock of the bit period of the time code is also synchronized.

This entire operation is controlled by the system controller 1. The edit point is detected by the edit point detection circuit 2, and the time code signal generation circuit 3
A signal indicating an edit point is supplied to the cursor.

In other words, the edit point detection circuit 2 may be
A pulse with a bit width is output as shown in Fig. 2B, and a time code signal whose starting level is H'' is outputted from the time code signal generation circuit 3 as shown in Fig. 2.Then, the level control circuit 4, the output of edit point detection circuit 2 is H''
Only during this period, the time code signal "H" supplied from the time code signal generation circuit 3 is doubled, and is output as shown in FIG.
is recorded on the magnetic tape 7.

FIG. 3 shows a block diagram of an apparatus for reproducing a time code signal recorded as described above. In FIG. 3, 7 is a magnetic tape, 8 is a playback head for playing back the time code signal recorded on the magnetic tape 7, 9 is a playback amplifier, 10.
11 are v, respectively.

A comparator with a comparison voltage of v2, 12.13 is a monostable multivibrator (hereinafter abbreviated as MM) that outputs a pulse at both the rising and falling edges of the supplied signal, 14 is an OR gate, and 16 is a timer. This is a code reading circuit.

The reproduction operation will be explained below with reference to the waveform diagram in FIG. The time code signal reproduced from the magnetic tape 7 by the reproduction head 8 is sent to comparators 10 and 11 via a reproduction amplifier 9.
supplied to If the supplied time code signal is as shown in Figure 4 B, the comparison voltage V of the comparators 10 and 11 is
1. V2 is the level shown in FIG. Comparators 10 and 11 output a 41 HI+ level when the voltage is higher than V, V2, respectively, and therefore a signal such as c shown in FIG. 4 is supplied to MMs 12 and 13. MM12,13
Then, pulses are output at the rising and falling edges of the signal, and signals as shown in FIG.
A signal as shown in FIG. 4f is supplied. As shown in the waveform of FIG. 4f, pulses representing edges can be obtained at the editing points, and since the time code signal has information at the edges, the time code signal can be read out correctly.

It can also be clearly inferred from this example that editing points can be easily checked.

In this embodiment, the level of the time code signal at the editing point is twice the normal level, but other levels may of course be used.

As described in detail, according to the present invention, the time code signal can be read without difficulty at the editing point without using the bits of the time code signal, and its practical effects are significant.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a time code signal recording device according to an embodiment of the present invention, and FIG. 2 is an operation waveform diagram of the same embodiment.
FIG. 3 is a block diagram of an embodiment of a device for reproducing a time code signal recorded according to the present invention, FIG. 4 is an operational waveform diagram of the same reproducing device, and FIG. 6 is a waveform diagram for explaining the conventional technology. Figure 6 is a block diagram of a conventional recording time code signal generator, Figure 7 is an operating waveform diagram of a conventional recording time code signal generator, and Figure 8 is an example of the content and waveform of an SMPTE time code signal. FIG. 1...System controller, 2...Edit point detection circuit, 3...Time code signal generation circuit, 4...
...Level control circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Fig. 2 Fig. 4 I Nose, Fig. 5 Fig. 1 Condition 1.

Claims (1)

[Claims] a time code signal generation circuit that generates a bi-phase modulated time code signal; a detection circuit that detects an edit point for recording a time code signal following the recorded time code signal; and a control circuit for controlling the level of the time code signal supplied from the time code signal generating circuit.