JPH05183938A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve the picture quality of reproduced images by recording and reproducing chroma signals over a wide band by holding the frequency characteristic of an entire recording and reproducing system for chroma signals at a sien roll off characteristic. CONSTITUTION:After the chroma signals are sampled and the band is compressed, those signals are converted to low frequency and outputted to a magnetic head together with luminance signals and therefore, the chroma signals are recorded on a prescribed magnetic recording medium. In the case of reproducing, the chroma signals are extracted from reproduced signals S1 of the magnetic head, interpolated and outputted after extending the band. In the case of reproducing, prescribed reference signals P1 and SC are extracted from the reproduced signals S1, the signal level of the reference signals P1 and SC is detected and based on the signal level detected result of the reference signals P1 and SC, the frequency characteristic of the reproduced signals S1 is corrected so that the frequency characteristic of the entire recording and reproducing system for the chroma signals can be the sien roll off characteristic. Thus, the dispersion in the frequency characteristics of electromagnetic converting systems can be corrected, and the chroma signals can be recorded and reproduced while compressing the band.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Field of Industrial Application Conventional Technology (FIG. 9) Problem to be Solved by the Invention (FIG. 9) Means for Solving the Problem (FIGS. 1 and 7) Action (FIGS. 1 and 7) Example (1) Overall Configuration (FIG. 1) (2) Configuration of Filter Circuit (FIGS. 2 to 8) (3) Effect of Embodiment (4) Other Embodiment Effect of Invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus, and can be applied to, for example, a video tape recorder for converting a chroma signal into a low frequency band for recording.

[0003]

2. Description of the Related Art Conventionally, in a video tape recorder, a luminance signal is frequency-modulated and a chroma signal is converted into a low frequency band for recording, whereby a video signal can be efficiently recorded and reproduced. There is.

That is, as shown in FIG. 9, in the video tape recorder 1 of this type, the video signal SV is set to AG.
After receiving it in the C circuit 2 and correcting the signal level here, YC
The separation circuit 3 separates the luminance signal and the chroma signal. Further, in the video tape recorder 1, the luminance signal processing circuit 4 frequency-modulates the luminance signal Y to convert it into a recording signal YFM, whereas the band pass filter circuit (BPF) 5
The chroma signal C is given to the ACC circuit 6 via the, and the signal level is corrected there and output to the emphasis circuit 7.

As a result, in the video tape recorder 1, after the chroma signal is subjected to the emphasis processing by the emphasis circuit 7, the conversion circuit 8 performs low-frequency conversion. Further, the video tape recorder 1 outputs the low-pass converted chroma signal to the adder circuit 10 via the low-pass filter circuit (LPF) 9, and adds the tracking control pilot signal ATF and the recording signal YFM. Further, in the video tape recorder 1, the output signal of the adder circuit 10 is output to the magnetic head 12 via the amplifier circuit 11,
As a result, recording tracks are sequentially formed on the magnetic tape 13 and a video signal is recorded on the recording tracks.

On the other hand, in the reproducing system, the output signal of the magnetic head 13 is amplified by the amplifier circuit 14, and then the brightness signal is demodulated by the brightness signal processing circuit 15. On the other hand, for the chroma signal, the video tape recorder 1 extracts the chroma signal component from the output signal of the amplifier circuit 14 in the low-pass filter circuit 16 and corrects the phase characteristic,
The ACC circuit 17 corrects the signal level. At this time, the low-pass filter circuit 16 simultaneously corrects and outputs the phase and frequency characteristics of the chroma signal.

Further, in the video tape recorder 1, the output signal of the ACC circuit 17 is given to the conversion circuit 18,
Here, after the original frequency band is converted, it is output to the de-emphasis circuit 21 through the band pass filter circuit 19 and the comb type filter circuit 20 sequentially. Here, in the video tape recorder 1, after the chroma signal is de-emphasized, it is added to the luminance signal by the adder circuit 22, and the video signal SV is output through the adder circuit 22.

[0008]

By the way, in this type of video tape recorder, the frequency band of the luminance signal has been expanded to improve the image quality. On the other hand, it is considered that the image quality of the chroma signal can be improved if the frequency band can be expanded.

In this case, in the luminance signal recorded on the high frequency side on the magnetic tape, the frequency band can be relatively easily expanded while maintaining compatibility with the conventional format. On the other hand, the chroma signal is recorded in a low frequency band on the magnetic tape and has a limited frequency band, which makes it difficult to expand the band while maintaining compatibility.

The present invention has been made in view of the above points, and an object thereof is to propose a magnetic recording / reproducing apparatus capable of improving the image quality of a reproduced image as compared with the prior art.

[0011]

In order to solve such a problem, according to the present invention, the chroma signal C is sub-sampled, band-compressed, low-frequency converted, and output to the magnetic head 12 together with the luminance signal YFM. , Chroma signal C
Is recorded on a predetermined magnetic recording medium 13, and at the time of reproduction, a chroma signal C is extracted from the reproduction signal S1 of the magnetic head 12, and the chroma signal C is interpolated to expand the band and output. During reproduction, the predetermined reference signals P1 and SC are extracted from the reproduction signal S1, and the reference signals P1 and SC are extracted.
Signal level of the reproduced signal S1 is detected based on the signal level detection result of the reference signals P1 and SC so that the frequency characteristic of the entire recording and reproduction system of the chroma signal C becomes the sine roll-off characteristic. ..

[0012]

When reproducing, a predetermined reference signal P is reproduced from the reproduction signal S1.
1 and SC are extracted, and the frequency characteristic of the reproduced signal S1 is corrected based on the signal level detection result of the reference signals P1 and SC so that the frequency characteristic of the entire recording / reproducing system of the chroma signal C becomes the sine roll-off characteristic. For example, even if the frequency characteristic of the electromagnetic conversion system varies, the entire frequency characteristic can always be maintained at the sine roll-off characteristic, and the chroma signal can be band-compressed for recording and reproduction.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings.

(1) Overall Structure In FIG. 1 in which parts corresponding to those in FIG. 9 are assigned the same reference numerals, numeral 30 indicates a video tape recorder as a whole, which converts a chroma signal C into a color difference signal for processing.

That is, in the video tape recorder 30, after the chroma signal C is converted into the color difference signals U and V by the color difference signal conversion circuit 31, it is given to the sub-sampling circuit 32, where it is subjected to offset sub-sampling to compress the band. To do.

Further, in the video tape recorder 30, the output signal of the sub-sampling circuit 32 is given to the chroma signal processing circuit 33, where it is converted into a chroma signal format for low frequency conversion. As a result, the video tape recorder 30
In the above, the output signal of the chroma signal processing circuit 33 is output via the low-pass filter circuit 9A, and the chroma signal is band-compressed and recorded in the frequency band conventionally defined by the format.

On the other hand, in the reproducing system, the reproducing signal S1 of the magnetic head 12 is amplified by the amplifying circuit 14 and then A
The TF circuit 34A detects the tracking control pilot signal ATF. As a result, in the video tape recorder 30, the ATF circuit 34A generates a tracking error signal, and tracking control is performed based on the tracking error signal.

The reproduction chroma signal processing circuit 35 extracts the chroma signal component from the reproduction signal S1 via the low-pass filter circuit 34, and then converts it into a color difference signal and outputs it.

The sub-sampling circuit 36 sub-samples and outputs the color difference signal output from the reproduction chroma signal processing circuit 35, and the interpolation circuit 37 performs interpolation processing using the color difference signal of the front line or the rear line. The image information thinned out by the sub-sampling circuit 32 is interpolated.
The comb type filter circuit 38 corrects the frequency characteristic of the output signal of the interpolation circuit 37 and suppresses the noise component of the output signal by using a field memory.

As a result, the video tape recorder 30 concerned
In the above, the output signal of the comb type filter circuit 38 is converted into the chroma signal by the output conversion circuit 39 so that the chroma signal can be reproduced.

(2) Configuration of Filter Circuit By the way, when recording and reproducing a chroma signal by sub-sampling as described above, it is necessary that the frequency characteristic of the entire recording / reproducing system is maintained at the cosine roll-off characteristic in the chroma band. Become. Specifically, in order to obtain the cosine roll-off characteristic while maintaining the compatibility with the conventional format, FIG.
As shown in, the center frequency is 743 [kHz] and ± 700 [k
[Hz], the characteristic that the attenuation rate is almost infinite is required.

However, this type of video tape recorder 1
There is a feature that the frequency characteristic of the electromagnetic conversion system changes according to the type of magnetic tape and the running speed of the magnetic tape.
That is, as shown in FIG. 3, this type of electromagnetic conversion system has a characteristic that the amplitude characteristic on the low frequency side is reduced by −6 [dB / oct], and the low frequency converted chroma band (frequency 743 [kHz
z), the amplitude characteristic changes.

In this case, as shown in FIG. 4, in the conventional video tape recorder, the chroma signal is separated through the trap filter circuit for suppressing the frequency-modulated audio signal, so that the frequency characteristic shown in FIG. , And this characteristic changes depending on the magnetic tape or the like.

According to the result of actual measurement as shown in FIG. 6, when the metal tape is reproduced in the standard time recording mode (denoted by symbol L1) and when the metal tape is reproduced in the long time recording mode (symbol L2). It is understood that the frequency characteristic on the low frequency side changes when the standard tape is reproduced in the standard time recording mode (represented by symbol L3).

This frequency characteristic changes even when the standard tape is reproduced in the recording mode for a long time, and there is a difference between the case of the vapor deposition type metal tape and the case of the coating type metal tape. I knew that it could change. In practice, if such a variation of the amplitude characteristic is about 1 [dB] in the chroma band, the Nyquist theorem cannot be satisfied at the time of sub-sampling, and there is a problem that the quality of the reproduced image is significantly deteriorated.

Therefore, in this embodiment, the video tape recorder 30 uses the low-pass filter circuit 34 to correct variations in the characteristics of the electromagnetic conversion system.

That is, as shown in FIG. 7, in the low-pass filter circuit 34, the output signal S1 is supplied to the band-pass filter circuits 44 and 46, and the output signal S
1 is applied to the FIR type filter circuit 48.

Here, the bandpass filter circuit 44 has four
Various types of ATF tracking control pilot signal A
A predetermined pilot signal P1 is extracted from TF and output. On the other hand, the bandpass filter circuit 46 uses the carrier signal (that is, the frequency 7
43 [kHz]) SC is separated and output. The signal level detection circuit 49 detects the signal levels of the pilot signal P1 and the carrier signal SC, and outputs the detection result to the coefficient switching circuit 50.

The coefficient switching circuit 50 switches the amplitude characteristic of the filter circuit 48 based on the detection result, so that even if the characteristic of the electromagnetic conversion system changes, the output signal S0 of the filter circuit 48 has a predetermined frequency characteristic. To maintain. That is, in the filter circuit 48, five stages of delay circuits D1 to D5 are connected in series, the output signals of the delay circuits D1 and D5 are added by the adder circuit 52, and the delay circuit D
The adder circuit 54 adds the output signals of 2 and D4.

Further, the filter circuit 48 includes an adder circuit 52.
And 54 and the output signal of the delay circuit D3 are respectively received by the amplifier circuits 56, 58 and 60, where they are weighted based on the output signal of the coefficient switching circuit 50.
Addition is performed by the addition circuit 62. As a result, in the filter circuit 48, the phase characteristic of the reproduction signal S1 is held at a constant value, and the frequency characteristic of the output signal S1 is corrected so that the signal levels of the pilot signal P1 and the carrier signal SC have a predetermined ratio. Output.

As a result, the video tape recorder 30 concerned
In, the frequency characteristics of the chroma signal are corrected and output with the amplitude characteristics shown in FIG.

Further, at this time, the filter circuit 48 corrects the phase characteristic of the reproduced signal and outputs the corrected signal, thereby operating as a phase equalization filter circuit for the chroma signal.

After correcting the characteristic change of the electromagnetic conversion system in this manner, in the video tape recorder 30, the band pass filter circuits 40 and 41 change the frequency characteristic of the recording / reproducing system with respect to the chroma signal to the cosine roll-off characteristic. Set to. At this time, the band pass filter circuit 40 is set in advance so that the frequency characteristic extends to the low frequency side so as to compensate for the low frequency side frequency characteristic of the electromagnetic conversion system. Further, together with the band pass filter circuit 41, the group delay characteristic 0 [nse
c) is set.

Further, bandpass filter circuits 40 and 4
1 is selected so that the frequency characteristic from the sub-sampling circuit 32 to the sub-sampling circuit 36 has the root roll-off characteristic, so that the frequency characteristic of the recording / reproducing system with respect to the chroma signal has the cosine roll-off characteristic. Has been done. This allows video tape recorder 3
At 0, the wide band chroma signal can be sub-sampled and recorded / reproduced, whereby the quality of the reproduced image can be improved by the amount of widening the band of the chroma signal.

At this time, in the video tape recorder 30, the low-pass filter circuit 34 corrects the characteristic change of the electromagnetic conversion system on the basis of the pilot signal P1 and the carrier signal SC, so that the frequency characteristic of the chroma band is always cosine rolled off. It is possible to obtain reproduced images with improved image quality compared to conventional ones, even if the magnetic tape, recording / reproducing mode changes, or even if the magnetic head wears and the characteristics change. it can. Further, it is possible to obtain high compatibility with conventional format video tape recorders.

(3) Effects of the Embodiments With the above arrangement, the frequency characteristic of the electromagnetic conversion system is corrected with reference to the signal levels of the pilot signal and the subcarrier signal, and the frequency characteristic of the chroma band becomes the cosine roll-off characteristic. By setting so that the wideband chroma signal can be band-compressed and recorded and reproduced, thereby improving the image quality of the reproduced image as compared with the conventional one while maintaining the compatibility with the conventional video tape recorder. be able to.

(4) Other Embodiments In the above embodiments, the case where the chroma signal is converted into the color difference signal and processed is described, but the present invention is not limited to this, and the chroma signal is processed as it is. You may do it.

Further, in the above-mentioned embodiment, the case where the variation of the electromagnetic conversion system is corrected and the phase equalization is performed by the low-pass filter circuit has been described, but the present invention is not limited to this, and the variation correction of the electromagnetic conversion system and the phase equalization are performed. The equalization may be executed individually.

Further, in the above-mentioned embodiment, the case where the variation of the electromagnetic conversion system is corrected on the basis of the pilot signal for the ATF tracking control and the sub-carrier signal has been described, but the present invention is not limited to this and, for example, separately. A dedicated reference signal may be provided and the variation of the electromagnetic conversion system may be corrected based on the reference signal.

Further, in the above-mentioned embodiment, the case where the present invention is applied to the video tape recorder to record and reproduce the video signal on the magnetic tape has been described. However, the present invention is not limited to this, and various magnetic recording media can be used. It can be widely applied to magnetic recording / reproducing devices for recording / reproducing video signals.

[0041]

As described above, according to the present invention, the frequency characteristic of the reproduced signal is corrected so that the frequency characteristic of the entire recording / reproducing system of the chroma signal becomes the sine roll-off characteristic with reference to the predetermined reference signal. By doing so, it is possible to correct the variation in the frequency characteristics of the electromagnetic conversion system, thereby band-compressing the wide band chroma signal and recording / reproducing, thereby improving the image quality of the reproduced image as compared with the conventional one. Obtainable.

[Brief description of drawings]

FIG. 1 is a block diagram showing a video tape recorder according to an embodiment of the present invention.

FIG. 2 is a characteristic curve diagram showing a cosine roll-off characteristic.

FIG. 3 is a characteristic curve diagram for explaining variations in an electromagnetic conversion system.

FIG. 4 is a characteristic curve diagram for explaining a trap filter circuit for trapping an audio signal.

FIG. 5 is a characteristic curve diagram for explaining a variation in overall characteristics including a trap filter circuit.

FIG. 6 is a characteristic curve diagram showing actual measurement results.

FIG. 7 is a block diagram showing a low-pass filter circuit.

FIG. 8 is a characteristic curve diagram showing characteristics of a low-pass filter circuit.

FIG. 9 is a block diagram showing a conventional video tape recorder.

[Explanation of symbols]

1, 30 ... Video tape recorder, 5, 40, 41 ...
… Band pass filter circuit, 9, 16 …… Low pass filter circuit, 12 …… Magnetic head, 13 …… Magnetic tape,
32, 36 ... Sub-sampling circuit, 37 ... Interpolation circuit.

Claims (1)

[Claims] 1. A chroma signal is sub-sampled, band-compressed, low-pass converted, and output to a magnetic head together with a luminance signal to record the chroma signal on a predetermined magnetic recording medium. In a magnetic recording / reproducing apparatus for extracting a chroma signal from a reproduction signal of a magnetic head, interpolating the chroma signal, and expanding and outputting the band, in reproduction, a predetermined reference signal is extracted from the reproduction signal, and the reference signal is extracted. Is detected, and the frequency characteristic of the reproduction signal is corrected based on the signal level detection result of the reference signal so that the frequency characteristic of the entire recording and reproduction system of the chroma signal becomes the sine roll-off characteristic. Characteristic magnetic recording / reproducing device.