JPH01288076A - Magnetic recording and reproducing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording/reproducing apparatus which performs a clamping operation during FM recording on, for example, a high-definition VTR.

[Prior art] For example, the video signal band, such as the NTSC signal, is about 4
．． 2 Mllz's current television signal (hereinafter referred to as TV
In a rotary head type magnetic recording/reproducing apparatus (hereinafter referred to as a VTR) that records and reproduces video signals (hereinafter referred to as signals), one field of video signals is generally recorded on one track.

On the other hand, one method for recording wideband video signals on a VTR, such as a high-definition signal with a luminance signal bandwidth of 20 MHz, or a high-definition signal (MUSE signal) with a bandwidth compression method of approximately 8.1 MHz. There is a so-called multi-channel recording method in which an input wideband video signal is divided into N channels, an integer of 2 or more, and the bandwidth of each channel is reduced and recorded. In this multi-channel recording system, for example, L-field video signals are recorded by N-channel heads.

Figure 3 shows a VT that performs multi-channel recording as described above.
A block diagram of the recording system of R is shown. Note that here N=2,
That is, the case of the two-channel recording method will be explained.

In FIG. 3, (1) is an A/D converter, (2) is a recording processing section, (:11) and (32) are first . The second D/A converters (41) and (42) are the first D/A converters (41) and (42). The second low-pass filters (51) and (52) are the first. The second clamp circuits (71) and (72) are connected to the first clamp circuits (71) and (72). second FM modulator, (
81).

(82) is the first. A second recording amplifier, (3) has a first pre-emphasis, (4) has a second pre-emphasis,
(IIA) is a magnetic head for channel A, and (HB) is a magnetic head for channel B.

FIG. 4 is a signal waveform diagram for explaining the operation of FIG. 1 horizontal scanning period (indicated in units of 10).The numbers in Figure (a) mean line numbers. However, a Y signal and a Cw multiplied signal Cn signal exist for each line.

The Y signal and the Cw multiplied signal Cn signal are quantized by the A/D converter (1) in FIG. 3, and then input as digital signals to the recording processing section (2). In this step, a two-channel video signal, which becomes the actual recording signal to the VTR, is digitally created.

That is, in the recording processing section (2), as shown in FIG.
The field specifies that the Y signal and Cw multiplied signal of odd line numbers in a) are distributed as channel A (hereinafter referred to as CHA), and the Y signal S and Cn signal of even line numbers are distributed as channel B (hereinafter referred to as CHB). The Y signal in IH units and the Cw times signal in CHA are at least valid horizontal scanning period, that is, the Y signal period obtained by time axis expansion of the video signal waveform portion in IH excluding the horizontal blanking period. (Ty) and the C signal period (Tc
) and the horizontal blanking signal (HBL) of the recording signal consisting of the horizontal synchronization signal (113) of negative polarity and the burst signal (BS) are time-division multiplexed and expressed as an analog signal for convenience as shown in Fig. 4 ( 28 as shown in b)
The first place video signal (CIIA) is created by the recording processing section (2).

Also, for CHH, the Y signal and Cn signal of even line numbers are time-axis expanded and compressed in the same way as the video signal (CIIA) mentioned above, and are time-division multiplexed with the horizontal blanking signal (HBL). , Figure 4(c)
A 2H unit video signal (CIIB) as shown in FIG.

The digital data corresponding to the above-mentioned two-channel video signals ((:1lA) and (CHII) outputted from the recording processing unit (2) will be inputted to the circuit block from now on, so the following will be described below. 1, one video signal (CIA) will be explained.

The digital data corresponding to the video signal (CIA) output from the recording processing section (2) is manually inputted to the first D/A converter (31) and converted into an analog signal, and then passed through the 10th-pass filter (hereinafter referred to as the 1st LPF). ) (41) to the first clamp circuit (51). This 71
The Sl clamp circuit (51) is connected to the first FM modulator (7) in the subsequent stage.
This is a circuit for making the relationship between the video signal waveform and the carrier frequency constant in 1), which holds the tip of the negative polarity horizontal 1'1lJJ signal (H5) of the video signal (C1 (A)) at a constant voltage. It is.

By the way, the horizontal synchronization signal Cll5 of the video signal (CHA)
) is a period (Tc) other than this horizontal synchronization signal (IIs)
Compared to the video information that changes in the range from black level to white level, the first clamp circuit (5
In I), for example, by providing a predetermined threshold value, the position of the horizontal synchronizing signal (IIs) can be easily detected. By using a clamp pulse created from the detection result, the leading edge of the horizontal synchronizing signal (H3) of the video signal (C+IA) can be held at a constant voltage using a known method.

Accordingly, the clamped analog video signal (CIIA) output from the first clamp circuit (51) is input to the first pre-emphasis (3) in the next stage, where the high frequency is emphasized, and then sent to the first FM modulator ( 71) and is input to FM
This becomes a signal and is recorded on a magnetic tape (not shown) by a magnetic head (HA) via a first recording amplifier (81). Here, the first pre-emphasis (3) is performed on the VTR.
In order to improve the playback S/N by suppressing triangular noise that occurs more frequently in the high frequency region when FM demodulated during playback, a clamped video signal (CIA) output from the Ml clamp circuit (51) during recording is used. This is a circuit for applying high-frequency emphasis in advance. FIG. 5 shows an example of the configuration of the first pre-emphasis (3), which is composed of a capacitor (C) and a resistor (R).

The VT, which is not shown in the block diagram of FIG.
After FM demodulation in the R reproduction system, the first pre-emphasis (
Noise in the high frequency region is suppressed by restoring it to the original state using a high frequency suppression circuit having the opposite characteristics of 3), that is, de-emphasis. Note that the second pre-emphasis (4) also has the same configuration as the first pre-emphasis (3), but the explanation will be omitted here.

FIG. 6 shows the input/output characteristics of pre-emphasis, and is the input video signal to the first pre-emphasis (3) shown in FIG. 6(a) or FIG. 5. When such a video signal is input, From the first pre-emphasis (3) to Figure 6 (C)
As shown in , a high-frequency emphasized signal waveform having only an overshoot (O8) at a location corresponding to the emphasis amount mO is output.

Also, unlike this example, the first pre-emphasis (3
) has phase-linear characteristics, and if the emphasis amount is the same mO as the upper side, the emphasis output will have a preshoot (PS) and an overshoot (O3). , which exist above and below the peak of the emphasis whisker, as shown in Figure 6 (b).In other words, even if the emphasis amount mO is the same, in the case of phase linear emphasis, the amplitude of the output or the amplitude of the output as shown in Figure 5 It will be smaller than in the case of circuit configuration.So, FM change g!4
If the later frequency shift bands are the same, the amount of emphasis in the case of the phase linear type can be made larger than in the case of the emphasis shown in FIG. 5, which has the advantage of improving the noise suppression effect.

Therefore, when implementing analog phase linear emphasis in il pre-emphasis (3) in Fig. 3,
It is possible to realize this by using a delay line as disclosed in the 1966 Institute of Electrical Communication Engineers National Conference No. 990, but it is difficult to satisfy the desired emphasis characteristics with high precision, and the Since the processing section (2) is treated as digital processing, it is practical to connect the phase linear emphasis to the recording processing section and implement digital processing. Namely.

In place of the analog first pre-emphasis (3) in FIG. 3, it would be more realistic to adopt a configuration in which a digital phase-linear emphasis is provided at the subsequent stage of the recording processing section (2).

[Problems to be Solved by the Invention] In the conventional VTR configured as described above, a digital phase-linear type emphasis system having a high noise suppression effect is arranged after the recording processing section (2). ,
Since phase linear emphasis is performed at the stage of digital processing, the output after digital emphasis can be expressed in analog form as shown in Figure 6(b).In other words, in phase linear emphasis, preshoot and over A negative horizontal synchronizing signal (I
Is) and the video signal part can only be distinguished by amplitude, so the clamp pulse cannot be easily detected in the clamp before FM modulation, and the configuration for performing the specified clamp operation becomes complicated. There was a problem.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a VTR that can reliably and accurately perform a clamping operation at a predetermined position during FM recording.

[,! Means for Solving N] The VTR according to the present invention creates a clamp pulse in advance in a recording processing section that processes an input wideband video signal into a recording signal by digital processing, and
Depending on the variation in the group delay characteristics of the low-pass filter that inputs the D/A-converted analog signal after the digital pre-emphasis output, which is placed after the recording processing section,
The present invention is characterized in that the phase of the clamp pulse is digitally adjusted so as to be at an appropriate clamp position in a clamp circuit before FM modulation.

[Operation] According to the present invention, by adjusting the phase of a clamp pulse in a fixed phase state generated in advance in accordance with individual variations in the delay time of the low-pass filter, for example, by l clock units of the clock signal, Clamping operation can always be performed at a predetermined position.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

Fig. 1 is a block diagram of a recording system of a VTR according to an embodiment of the present invention. Explanation will be omitted.

In FIG. 1, (21) and (22) are the 1st and 2nd digital emphasis, respectively, and (31) and (32) are the 1st and 2nd digital emphasis, respectively. tjIJ2D/A converter, (41), (
42) are the first. 2nd LPF, (s1), (52
) are the first. Second clamp circuit, (61), (6
2) are respectively the first. second phase adjuster, (71),
(72) is the first. Second FM modulator, (81), (82)
are the first. 2nd recording amplifier, (HA), (11B
) are magnetic heads.

Next, the operation of the above configuration will be explained.

The digital data of the input wideband video signal quantized by the A/D converter (1) is converted into a third digital data in the recording processing section (2).
Processing is performed in the same manner as in the conventional example shown in the figure, and two-channel video signals (CHA) and (CHB) are output.

Figure 2 (a) is a convenient representation of the input wideband video signal, and Figures (b) and (C) are two-channel video signals (CHA) output from the recording processing unit (2).
8 and (COB) digital data expressed in analog form. Note that the burst signal is omitted in FIGS. 2(b) and 2(C).

The digital data corresponding to the two-channel video signals (C)IA) and (CHB) from the recording processing unit (2) are each output from, for example, a symmetric acyclic digital filter (hereinafter referred to as an FIR filter). The signal is input to a first digital emphasis (21) and a second digital emphasis (22). Here, the first. Second digital emphasis (21), (22)
is composed of multipliers, adders, etc., and achieves a phase linear emphasis characteristic by appropriately selecting filter coefficients. Therefore, if the digital output data of il, i2 digital emphasis (21), (22) is expressed in analog form, as explained in FIG. 6, it will be as shown in FIG. (IIs) and the video signal portion cannot be distinguished by amplitude.

Therefore, in addition to the digital data of the two-channel output video signal (CIIA) and (CHB), the recording processing unit (2) outputs the digital data in phase synchronization with these data as shown in Fig. 2 (e).
) clamp pulse (cpo) at a fixed position, such as
is output at the same time, and this clamp pulse (CPO)
first and second FM modulators (71) as original signals,
The first section before (72). Second clamp circuit (51)
, (52) are performed for each channel.

However, in reality, the first. The output data of each of the second digital emphasis (21) and (22) is transmitted to the first stage of the next stage. After being input to the second D/A converters (11) and (32) and converted into a two-channel analog signal with phase linear emphasis, 2nd LPF
After being band-limited by (41) and (42), the signals are input to the first and second clamp circuits (51) and (52).

・In this case, 1. 2nd L P F (41), (42
) Since there is some variation in the delay time between the input and output signals,
A clamp pulse ( If the signals are clamped as they are at CPO), the two-channel recording signals (CIA) and (CHB) will be deviated from the predetermined clamping positions, making it impossible to perform a normal clamping operation.

Therefore, the clamp pulse (
CPO) is the first. The signals are input to second phase adjusters (61) and (62), respectively. This first. Second phase adjuster (61
) and (62) are each composed of a shift register, a selector, etc., and adjust the phase of the clamp pulse (cpo) in units of, for example, l clocks of a clock signal (not shown), so that the first . Two-channel recording signals (CIA) and (C
IIB) corresponding to each predetermined clamp position.
．． Second clamp pulse (CPl).

Create (CF2).

After the first clamp pulse (CPI) and the second clamp pulse (CF2) cause the first clamp circuit (51) and the second clamp circuit (52) to perform a clamp operation, the first clamp pulse (CPI) and the second clamp pulse (CF2) perform a clamp operation. The second FM modulators (71) and (72) turn the signal into an FM signal, and the first . ″Second recording amplifier (81)
, (82), the magnetic head (HA), (HB
) to a magnetic tape (not shown).

[Effects of the Invention] As described above, according to the present invention, a digital video signal subjected to digital phase linear emphasis is
/A conversion, clamping the analog recording signal obtained through the LPF, and inputting it to the next stage FM modulator,
Even if there are individual variations in the delay times of the LPFs, the configuration uses clamp pulses whose phases are adjusted to reach a predetermined clamp position according to the variations in the delay times of the LPFs, so accurate positioning can be achieved. It is possible to perform the specified clamping operation with precision.
This has the effect of reliably recording FM on a VTR.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a recording system of a VTR according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram for explaining its operation, FIG. 3 is a block diagram of a conventional VTR recording system, and FIG. 4 is a block diagram of a recording system of a conventional VTR.
The figure is a signal waveform diagram for explaining conventional operation, and FIG. 5 is a configuration diagram showing an example of a conventional analog emphasis system.
FIG. 6 is a signal waveform diagram for explaining phase linear emphasis. (1)...A/D converter, (2)...recording processing section,
(21), (22)...Phase linear type digital emphasis, (31), (:12)...D/A converter, (41), (42)...LPF, (51) ,(5
2)...Clamp circuit, (61), (62)...
Phase adjuster, (71), (72)...FM modulator, (
81), (82)...recording amplifier. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A/D converter that inputs the video signal and this A/D
A recording processing section that creates a digital recording signal and a clamp pulse from digital video signal data that is the output of the converter, and a digital emphasis circuit that performs phase linear emphasis on the digital recording signal that is one output of this recording processing section. , a D/A that converts a digital recording signal having a phase linear emphasis characteristic, which is the output of this digital emphasis circuit, into an analog signal.
A converter, a low-pass filter that inputs the analog recording signal that is the output of this D/A converter, and a clamp pulse that is the other output of the recording processing section, which adjusts the phase of the clamp pulse according to the variation in the delay time of the low-pass filter. A phase adjuster that outputs a clamp pulse whose phase is adjusted to a predetermined clamp position, and a clamp that clamps the analog recording signal that is the output of the above-mentioned low-pass filter at a predetermined position using the phase-adjusted clamp pulse that is the output of this phase adjuster. A circuit, an FM modulator that inputs a clamped analog recording signal that is the output of this clamp circuit and outputs an FM signal, and a recording amplifier that records the FM signal that is the output of this FM modulator. A magnetic recording/reproducing device characterized by: