JPH04320193A - Burst flag pulse generating circuit - Google Patents

Abstract

PURPOSE:To attain dubbing recording with excellent color reproducibility in a still video dubbing device. CONSTITUTION:A color signal C with a color burst signal CB added thereafter is inputted to a comparator 102, and when a level of the color burst signal CB is larger than a threshold level of the comparator, A monostable multivibrator circuit 103 sends a burst flag pulse BFP to a decode circuit 27. A monostable multivibrator circuit 104 activates the monostable multivibrator circuit 103 only for a period when the color burst signal CB is in existence.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burst flag pulse generation circuit, which is incorporated into a recording system of a still video dubbing apparatus to perform dubbing recording with good color reproducibility.

0002

2. Description of the Related Art In recent years, a technique for still recording color video signals on a flexible disc-shaped magnetic sheet called a video floppy has been known. This video floppy has a diameter of approximately 50 mm and a track pitch of 100 μm.
, 50 arcuate tracks are recorded concentrically with a track width of 60 μm. For example, the rotation speed is 3600 rpm
It is. As a signal source, an imaging device using a solid-state imaging device, an image pickup tube, or the like, or a television system is used, and still images are recorded by field recording or frame recording. When recording a color video signal, the luminance signal is FM-modulated on the carrier including the synchronization signal, and
Record in a high frequency band of MHz or higher. For FM modulation, in the case of normal band mode shown in Figure 4, the sync chip level is 6MHz and the deviation is 1.5M.
Hz, and in the high band mode shown in FIG. 5, the sync tip level is 7.7 MHz and the deviation is 2 MHz. Further, the chroma signal is recorded in a low frequency band of 2.5 MHz or less by FM modulating the carrier using a color difference line sequential method. However, the RY signal is subjected to FM modulation with a carrier center frequency of 1.2 MHz, and the BY signal is FM modulated with a carrier center frequency of 1.3 MHz.

Although not shown in FIGS. 4 and 5, 1
A signal (DPSK) in which a carrier of 3fH (fH is the horizontal scanning frequency) is DPSK-modulated with data such as the shooting date
signal) is also frequency multiplexed with an FM luminance signal and an FM chroma signal and recorded on a video floppy.

By the way, there is a desire to dub and record a color video signal recorded on a video floppy by an electronic still camera or other recording device onto a new video floppy. A still video dubbing device was developed to meet this demand. The playback system of the previously developed still video dubbing device is shown in FIG. 6, and the recording system is shown in FIG. The reproduction system and the recording system may be built into one device, or both systems may be provided in separate devices and the signals may be transmitted via a line.

First, a reproduction system of a still video dubbing apparatus will be explained with reference to FIG. video floppy 1
It is assumed that an FM luminance signal and an FM chroma signal in the format shown in FIG. 4 or 5 are recorded. The video floppy 1 is rotated by a servo mechanism (not shown) at a constant speed of, for example, 3600 rpm and at a predetermined rotational phase, and the magnetic head 2 is rotated by a head transport device (not shown).
is positioned on an arbitrary track of the video floppy 1. The amplitude of the FM color video signal reproduced by the magnetic head 2 is corrected by the AGC amplifier 3, and the Y/C
The separation circuit 4 separates the FM composite luminance signal Y+S (FM) including the synchronization signal S and the FM line sequential color difference signals R-Y, B-Y.
(FM).

The FM demodulation circuit 5 receives the FM composite luminance signal Y+
S(FM) is FM demodulated and a baseband composite luminance signal Y+S is output. The composite luminance signal Y+S is subjected to de-emphasis processing in a de-emphasis circuit 6, further subjected to averaging processing in an arithmetic mean circuit 7, and then sent to a YC mix circuit 8.

On the other hand, the FM demodulation circuit 9 FM demodulates the FM line sequential color difference signals RY, BY (FM) and outputs baseband line sequential color difference signals RY, BY. The line-sequential color difference signals R-Y, B-Y are de-emphasized by a de-emphasis circuit 10, synchronized by a color-difference synchronization circuit 11, and the two color-difference signals R-Y, B-Y are input to an encoding circuit 12. . The encoding circuit 12 encodes the color subcarrier (3.5
8MHz) is balanced and modulated to generate a carrier color signal (chroma signal) C.
Generate and output. The encode circuit 12 receives a burst flag pulse BFP from the pulse generating circuit 13, and outputs a color burst signal (3.58 MHz) CB when the burst flag pulse BFP is at a high level. The pulse generation circuit 13 detects the horizontal synchronization signal and outputs a burst flag pulse BFP, which is a high-level signal, over a period determined by the standard as a period in which the color burst signal CB should be located, with the horizontal synchronization signal as a reference. do. Therefore, the color burst signal CB is output from the encoding circuit 12 during a period that meets the standard.

The chroma signal C and the color burst signal CB are filtered by a color filter circuit 14, amplified by an amplifier 15, and then superimposed on a composite luminance signal Y+S by a YC mix circuit 8. The color burst signal CB is then inserted at a predetermined position in the back porch during the horizontal blanking period. From YC mix circuit 8, NTS
A C-type composite color video signal V is output, and this composite color video signal V is added with necessary character information in a character mix circuit 16, and then amplified in an amplifier 17 and sent to a terminal A. When performing dubbing recording, the composite color video signal V arriving at terminal A is sent to terminal B of the recording system shown in FIG.

Next, the recording system of the still video dubbing apparatus will be explained with reference to FIG. The composite color video signal V input to the terminal B is separated by the Y/C separation circuit 21 into a composite luminance signal Y+S, a chroma signal C, and a color burst signal CB. The composite luminance signal Y+S is amplified by an amplifier 22, subjected to pre-emphasis processing by a pre-emphasis circuit 23, and FM-modulated by an FM modulation circuit 24 to become an FM composite luminance signal Y+S (FM), which is sent to an adder 25.

Chroma signal C and color burst signal CB
is amplified by the amplifier 26 and sent to the decoding circuit 27. At this time, the pulse generation circuit 28 detects the horizontal synchronization signal, and uses the horizontal synchronization signal as a reference to generate the color burst signal C.
A burst flag pulse BFP, which is a high level signal, is sent to the decoding circuit 27 over a period determined by the standard as a period in which B should be located. The decoding circuit 27 extracts the signal sent from the amplifier 26 and demodulates it as a reference signal during the period when the burst flag pulse BFP is input. That is, when the burst flag pulse BFP is input, the color burst signal CB is sent from the amplifier 26, so the chroma signal C is demodulated using the color burst signal CB as a reference, and the color difference signals R-Y, B-Y are generated. generate. Two color difference signals R
-Y and BY become line sequential color difference signals R-Y and BY in the color difference line sequentialization circuit 29. Line sequential color difference signal R-Y, B
-Y is subjected to pre-emphasis processing by the pre-emphasis circuit 30 and is then processed by the FM modulation circuit 31 as the FM line sequential color difference signal R.
-Y, BY(FM).

The FM composite luminance signal Y+S (FM) and the FM line sequential color difference signals R-Y, B-Y (FM) are superimposed by an adder 25, amplified by an amplifier 32, and then sent to a predetermined location on a video floppy 34 by a magnetic head 33. recorded on the track.

As described above, dubbing recording can be performed by using the reproduction system shown in FIG. 6 and the recording system shown in FIG. 7.

[0013]

[Problems to be Solved by the Invention] In dubbing recording, burst signals are added to the playback device afterwards, so the position of the burst signals may deviate from the standard due to circuit delay characteristics or adjustment errors. It may include nozzles before and after. Furthermore, since the recorder generates the burst flag pulse from the synchronization signal, its position is fixed. As a result, if the position of the burst signal of the input signal shifts, the relative position of the burst signal and burst flag pulse will shift, resulting in a different number of cycles or the inclusion of the aforementioned nozzle, resulting in poor decoding characteristics and poor color reproducibility. Become.

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, it is an object of the present invention to provide a burst flag pulse generation circuit that improves color reproducibility even when the position and number of cycles of a color burst signal deviates from the standard position and number of cycles. shall be.

[0015]

[Means for Solving the Problems] The configuration of the present invention for solving the above problems is such that a chroma signal with a color burst signal added thereto is inputted, and means for detecting the color burst signal from the chroma signal is provided. a burst flag that sends a burst flag pulse having a pulse width shorter than a period determined by standards as a period in which a color burst signal should exist to a decoding circuit that decodes the chroma signal based on the color burst signal; The pulse generation circuit includes, as the detection means, a comparator that outputs a comparator output when the value of the input signal exceeds a preset threshold, and a pulse generator that outputs the burst flag pulse from the time when the comparator output is output from the comparator. 1 monostable multivibrator, the first monostable multivibrator is activated from the rising edge of the horizontal synchronization signal to the falling edge of the burst flag pulse, and the first monostable multivibrator is operated during the remaining period. and a second monostable multivibrator that is brought into a non-operating state.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a burst flag pulse generation circuit 100 according to an embodiment of the present invention. This burst flag pulse generation circuit 100 is incorporated into a recording system of a still video dubbing apparatus, as shown in FIG. The recording system in FIG. 2 has the same configuration as the conventional recording system shown in FIG. 7 in which the pulse generation circuit 28 is replaced with a burst flag pulse generation circuit 100, and the circuit in FIG. 2 has the same function as that in FIG. Common reference numerals are given to circuits that serve the same purpose, and redundant explanations will be omitted.

In FIG. 1, the color burst signal CB and chroma signal C (see FIG. 3(a)) are input from the amplifier 26 to the amplifier 101 of the burst flag pulse generation circuit 100, and the amplitude of the chroma signal C is 2 [VPP]. is amplified. The threshold value of the comparator 102 is set to 2/3 of the amplitude of the amplified color burst signal CB, and the time point when the amplitude of the color burst signal CB exceeds the threshold value (this time point is the time from the beginning of the color burst signal CB). comparator output 102a is sent to monostable multivibrator 103. When the monostable multivibrator 103 receives the comparator output 102a, it enters a quasi-stable state and outputs a burst flag pulse B from the Q terminal.
FP (see Figure 3(d)) is output. In this case, the pulse width of the burst flag pulse BFP (
period) T2 is the color burst signal CB insertion period T1
Monostable multivibrator to be shorter than 10
The time constant of 3 is adjusted. Specifically, the pulse width of the burst flag pulse BFP is set to 2 μs. Such a burst flag pulse BFP is sent to the decoding circuit 27.

On the other hand, when the horizontal synchronizing signal HD (FIG. 3(c)) rises, the monostable multivibrator 104 sets the mask signal MASK output from the Q terminal to a high level.
The time constant is adjusted so that the mask signal MASK becomes low level at the time the burst flag pulse BFP falls. The mask signal MASK is sent to a monostable multivibrator 103 and D flip-flops 105 and 106. Since the mask signal MASK is at a low level during the period when the chroma signal C exists, even if the chroma signal C is input to the comparator 102 and the comparator output 102a is output, the monostable multivibrator 1
03 is in an inactive state due to the mask signal MASK being at a low level, so it does not output the burst flag pulse BFP. In other words, when the color burst signal CB is input, the burst flag pulse BF
P is output, but even if the chroma signal C is input, the burst flag pulse BFP is not output.

The D flip-flop 105 outputs a pulse having the same waveform as the burst flag pulse BFP (FIG. 3(e)) and sends it to the NAND gate 107. Further, the D flip-flop 106 outputs a pulse shown in FIG. 3(f) when the burst flag pulse BFP falls, and sends it to the NAND gate 107. For this reason, Nand Gate 107 is
When the burst flag pulse BFP falls, a clear pulse CLR (FIG. 3(g)) is output. This clear pulse CLR is a monostable multivibrator 104, D
Since it is sent to the flip-flops 105 and 106, when the burst flag pulse falls, it is sent to the monostable multivibrator 104 and the D flip-flops 105 and 10.
6 is cleared.

As described above, the burst flag pulse generation circuit 100 of the present invention generates the burst flag pulse BFP based on the color burst signal CB itself rather than the horizontal synchronization signal of the luminance system. Even if the insertion position of the color burst signal CB deviates from the standard position, the relative position between the color burst signal CB and the burst flag pulse BFP remains constant. Therefore, the decoding circuit 2 in FIG.
7, the color burst signal CB can always be extracted in the same phase state when receiving the burst flag pulse BFP, and therefore the chroma signal C can be extracted with good color reproducibility.
can be decoded. Furthermore, the burst flag pulse BFP is output after the value of the color burst signal CB exceeds the threshold of the comparator 102, and the pulse width of the burst flag pulse BFP is shorter than the period during which the color burst signal CB exists. The decoding circuit 27 can always extract the color burst signal CB with the same number of cycles, and even if noise occurs before and after the color burst signal CB, it will not extract this noise and can decode with good color reproducibility. can do. Furthermore, during the period when the color burst signal CB is not present, the monostable multivibrator 104 performs a masking operation, so that even if a chroma signal or the like is input, the burst flag pulse BFP will not be output by mistake.

[0021]

According to the present invention, as specifically explained above in conjunction with the embodiments, since the color burst signal itself is detected and the burst flag pulse shorter than the color burst signal period is generated, the color burst signal Position of·
Even if the number of cycles deviates from the standard position and number of cycles, the relative phase between the color burst signal and the burst flag pulse is always the same, so the standard signal in the decoder is always the same, improving color reproducibility.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a burst flag pulse generation circuit of the present invention.

FIG. 2 is a circuit diagram showing a recording system of a still video dubbing device incorporating a burst flag pulse generation circuit.

FIG. 3 is a waveform diagram showing signal waveforms of a burst flag pulse generation circuit.

FIG. 4 is a characteristic diagram showing frequency characteristics of normal band mode.

FIG. 5 is a characteristic diagram showing frequency characteristics of high band mode.

FIG. 6 is a block diagram showing a reproduction system of the still video dubbing device.

FIG. 7 is a block diagram showing a conventional playback system of a still video dubbing device.

[Explanation of symbols]

100 burst flag pulse generation circuit 101 amplifier 102 comparator 103, 104 monostable multivibrator 105,
106 D flip-flop 107 Nand gate

Claims (1)

[Claims] Claim 1: A chroma signal with a color burst signal added thereto is input, and the apparatus has means for detecting the color burst signal from the chroma signal, and has a means for detecting the color burst signal from the chroma signal. A burst flag pulse generating circuit that sends a burst flag pulse having a pulse width shorter than a period of time for which the chroma signal is input to a decoding circuit that decodes the chroma signal with reference to the color burst signal, a comparator that outputs a comparator output when the value exceeds a preset threshold; a first monostable multivibrator that outputs the burst flag pulse from the time the comparator output is output from the comparator; a second monostable multivibrator that keeps the first monostable multivibrator in an active state until the falling point of the burst flag pulse and keeps the first monostable multivibrator in an inactive state for the remaining period; A burst flag pulse generation circuit comprising: