JPS6031372A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve the S/N and to reduce the bit number at A/D conversion by providing a nonlinear circuit emphasizing the small amplitude component of a luminance signal to the pre-stage of a time axis compression circuit. CONSTITUTION:A luminance signal is inputted to a luminance signal nonlinear emphasis circuit 5 from an input terminal 3. An output of the circuit 5 is inputted to a memory 9 for time axis compression via an A/D converter 7. The circuit 5 has a characteristics applied with a large emphasis to the luminance signal of a low level and applied with nearly no emphasis to a luminance signal of a high level. Thus, the A/D converter sets more minute quantized steps of the low level signal and does not set minute step for high level. Then the suppression of the quantized noise at low level input is attained. Further, the output of the circuit 5 is converted by a sampling frequency 10-20MHz at the A/D converter 7. The bit number per word is, e.g., 6-7bits through the oeration of the circuit and the resolution equivalent to 8 bits visually is obtained.

Description

Detailed Description of the Invention (Field of Application) The present invention is directed to A/D (Analog/Digital)
Concerning a magnetic recording/reproducing device that compresses and records at least a luminance signal in the time axis using a semiconductor analog memory, magnetic recording is particularly aimed at improving S/N and reducing costs by reducing the number of bits during A/D conversion. Regarding a playback device.

(Background) A conventional magnetic recording/reproducing device will be explained using a magnetic recording/reproducing device that records an NTSC video signal as an example.

FIG. 1 is a diagram illustrating frequency allocation of signals recorded in a conventional example. In the figure, 1 is a low frequency conversion color signal, and 2 is an angle modulation luminance signal.

One method of a conventional magnetic recording/reproducing apparatus is to perform angle modulation on a luminance signal, convert the color signal to a lower frequency side of the angle modulation frequency, and record the signals by frequency multiplexing the respective frequencies.

When recording a carrier color signal in this manner, the phase of the carrier color signal changes due to jitter that occurs during recording and reproduction by a magnetic recording and reproducing device. As a result, a change in hue occurs, causing deterioration in image quality.

On the other hand, there is a method in which the chrominance signal and the luminance signal are compressed on the time axis using an analog-to-digital conversion circuit or a semiconductor analog memory, and then time-division multiplexed recording is performed.
Let me explain about ζ.

FIG. 2 is a diagram illustrating signals recorded on a magnetic recording medium. In the figure, a is a luminance signal, b is a video signal to be recorded, and C is a color signal.

As shown in the figure, Jin's method compresses the time axis of the luminance signal a to, for example, about 415 times. On the other hand, the color signal C is, for example, a line sequential color difference signal R-Y/B-Y.
Compress the time axis to about 5. Then, each signal is time-division multiplexed, angle-modulated, and recorded.

In this way, the color difference signal is recorded with angle modulation. In this case, changes in hue due to jitter can be significantly reduced and image quality can be improved. Furthermore, by time-division multiplexing the luminance signal and the color signal, it is possible to suppress beat interference due to mutual frequency interference, which occurs in the frequency multiplexing method.

However, in this time-division multiplex recording system, in order to time-base compress the v# variable magnification signal and color signal, for example, a CCD (Change
-Coupled -Device) and other semiconductor analog memories are A/I) (Analog/Di
(digital) converter requires digital memory, D/A converter, etc.

In this case, the S/N of these semiconductor analog memories.

Or 11, the S/N ratio at the time of A/D conversion becomes a problem.

Furthermore, since devices such as A/D converters, D/A converters, and digital memories are relatively expensive, there is also the problem of increased costs.

(Purpose) The purpose of the present invention (J) is to improve the S/N ratio in a magnetic recording/reproducing device that compresses the time axis of at least a 54-degree signal using analog-to-digital conversion or a semiconductor analog memory such as a CCD. In addition, when A/D conversion is used to compress the time axis, the number of bits can be reduced, and accordingly, the circuit scale and cost can be reduced.

(Summary) The present invention focuses on the fact that the visual sense is not as sensitive to minute changes in a high-luminance signal as it is to minute changes in a low-luminance signal. , is characterized in that it is provided with a circuit that nonlinearly emphasizes the small amplitude component of the luminance signal. Another feature of the present invention is that a horizontal synchronization signal does not have as much information in its amplitude as a video signal, and a nonlinear circuit for suppressing the horizontal synchronization signal is provided in the preceding stage of the time axis compression circuit. be.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows an embodiment of a recording system circuit that performs time axis compression using A/D conversion according to the present invention. In the figure, 3 is a luminance signal input terminal, 4 is a chrominance signal input terminal, and 5 is a luminance signal nonlinear emphasis circuit.

6 is a color signal non-linear emphasis circuit, 7 is the first A
8 is a second A/D converter, 9 is a first memory, and 10 is a second memory. Also, 11 is the first D
12 is a second D/A converter; 13 is a luminance signal non-linear de-emphasis circuit; 14 is a chrominance signal non-linear de-emphasis circuit; 15 is a switch; 16
is a time division multiplexed video signal output terminal.

Next, the circuit operation of this embodiment will be explained.

A luminance signal of the video signal is input from a luminance signal input terminal 3 to a luminance signal nonlinear emphasis circuit 5. This luminance signal non-linear emphasis circuit 5 has characteristics such as those shown in FIG.
It has the characteristic that no emphasis is applied to high-level luminance signals.

In order to apply such emphasis, in an A/D converter that performs linear quantization, the quantization step for low-level signals is carefully set, and the quantization step for high-level signals (the quantization step is not set so finely). By doing this, it is possible to suppress quantization noise at low level input.In addition, at this time, quantization noise at high level input increases, but when high level input Since the noise is less visually noticeable and the large amplitude level is advantageous in terms of S/N, it does not lead to deterioration of image quality.

The same effect can be obtained even when an analog memory such as COD is used as the time axis compression circuit, for example.

The luminance signal non-linear emphasis circuit 5 outputs a sampling frequency of 10 to 20 in the first A/D converter 7.
It is converted into a digital code at M cycles/sec. At this time, the number of bits per word is, for example, 6 to 7 bits by applying the non-linear emphasis described above, and a resolution visually equivalent to 8 bits can be obtained.

10th) The digital code that is the output of the A/D converter 7 is written into the first memory 9. The written digital code (well, it is read out at a frequency n times the writing frequency and input to the first D/A converter 11. Since the digital code is read out at a frequency n times the writing frequency, the first
The output signal of the D/A converter 11 is transmitted to the first A/D converter 7.
In other words, the signal input to the input signal is compressed to 17n on the time axis, in other words, the frequency is multiplied by n.

For example, in a method that compresses the brightness signal and color signal together and time-division multiplexes them, the value of n (for example, 615
~4/3 is suitable. In this case, the time-axis compressed luminance signal and color signal have approximately the same band. However, the present invention is not limited to just this case.

The output signal of the first D/A converter 11 is input to a luminance signal nonlinear de-emphasis circuit 13. This luminance signal non-linear de-emphasis circuit 13 has characteristics opposite to those of the luminance signal non-linear emphasis circuit 5, and restores the input luminance signal to its original level and outputs it.

On the other hand, the color signal is input from the color signal input terminal 4 to the color signal nonlinear emphasis circuit 6. As shown in FIG. 5, this color signal nonlinear emphasis circuit 6 applies a large emphasis to an input signal of small amplitude.

The output of Iroi No. 88 nonlinear FFF 9 circuit 6 is the second
The signal is input to the A/D converter 8 and converted into a digital code. Then, it is written into the second memory 10.

The digital code written in the second memory 10 is read out at a frequency of m at the time of glance, and then the second D/A
It is input to converter 12. The output signal of the second D/A converter 12 is a signal whose time axis is compressed to 1/'m and whose frequency is m times the input signal of the second A/D converter 8.

In this case, if the time axis compression ratio of the luminance signal is selected to the above-mentioned value, a value of 4 to 6, for example, is suitable as the value of m. However, the present invention is not limited to this case.

The output of the second D/A converter 12 is applied to a color signal nonlinear de-emphasis circuit 14.

The color signal nonlinear de-emphasis circuit 14 has characteristics opposite to the color signal non-linear de-emphasis circuit 6, and the input signal is de-emphasized to its original level and output.

The luminance signal, which is the output signal of the luminance signal non-linear de-emphasis circuit 13, which is time-axis compressed to 1/n, and the color signal, which is the output signal of the non-linear de-emphasis circuit 14, which is the chrominance signal, which is time-axis compressed to 1/m, are the switch. 15+
The signals are inputted, time-division multiplexed, and output to the time-division multiplexed video signal output terminal 16.

This becomes the signal to be recorded.

In the above embodiment, the luminance signal non-linear emphasis circuit 5 applies a large emphasis to the low level of the input luminance signal and a small emphasis to the high level. Then, this emphasized luminance signal is converted into a digital signal by an A/D converter 7.

Therefore, according to this embodiment, A/D with the same number of bits
Compared to A/D conversion without applying emphasis using a converter, it is possible to improve the S/N ratio at low-level inputs that are visually noticeable. In other words, when trying to improve the S/N ratio of low-level input, conventional methods
Whereas it was necessary to increase the number of bits of the D converter, in this embodiment, the S
Since the /N ratio can be improved, the S/N ratio can be improved using an A/D converter with the same number of bits as before.

Conversely, in order to reduce the conventional S/N ratio, the number of bits of the A/D converter can be reduced in this embodiment.

Therefore, in this embodiment, the number of bits of the A/D converter can be reduced compared to the conventional device, making it possible to reduce the circuit scale and cost.

In the above embodiment, the circuit configuration is such that the switch 15 is placed after the non-linear de-emphasis circuit 13, but the cass switch 15 is placed after the first O/A converter 11. Furthermore, a circuit configuration in which the switch 15 is placed after the first memory 9 and performs time division multiplexing in the digital code area is also possible.

Circuit diagrams in that case are shown in FIGS. 6 and 7, respectively. In these circuit diagrams, the characteristics of the nonlinear de-emphasis circuit 17 are the same as those of the luminance signal non-linear de-emphasis circuit 13. In addition, other codes (J No. 31
indicates the same thing as.

Since the operation of these circuits is the same as that in Figure 3,
The explanation will be omitted.

In the circuit shown in Figure 6, the non-linear de-emphasis circuit 17
D/
The A converter 11 can also be reduced to one.

In addition, the above-mentioned 3. 6th. In the circuit shown in FIG. 7, when a signal obtained by time-division multiplexing of a luminance signal and a color signal is guided to an angle modulation circuit (not shown) by the switch 15 and converted into an FM signal, a non-linear de-emphasis circuit is used. 13.14.17 may be deleted.

Next, an example of a reproduction system circuit will be described. FIG. 8 is a block diagram illustrating one embodiment of a reproduction system circuit.

In the figure, 18 is a time division multiplexed video signal input terminal, 19
is a luminance signal non-linear emphasis circuit, 20 is a color signal non-linear de-emphasis circuit, and 21 is the first A/
A D converter, 22 a second A/D converter, 23 a first memory, and 24 a second memory. Further, 25 is a first D/A converter, 26 is a second D/A converter, 27 is a luminance signal non-linear de-emphasis circuit, and 28 is a chrominance signal non-linear de-emphasis circuit 29 is a brightness signal output terminal.

30 is a color signal output terminal.

The operation (ζ) of this embodiment will be explained according to the diagram.

For example, a time division multiplexed video signal reproduced from a VTR is input from a time division multiplexed video signal input terminal 18 to a luminance signal nonlinear emphasis circuit] 9 and a color signal nonlinear emphasis circuit 20. In this video signal, the luminance signal and color signal are each 1/n.

This is a time-base compressed and time-division multiplexed signal of 17m.

Here, the Cζ/luminance signal nonlinear emphasis circuit 19 has the same characteristics as the luminance signal nonlinear emphasis circuit 5 of the recording system circuit 19.

The output of the luminance signal nonlinear emphasis circuit 19 is input to the first A/D converter 21, and the luminance signal portion is converted into a digital code. In this case as well, similar to the recording system circuit, visual resolution equivalent to s bit can be obtained using, for example, a 6 to 7 bit A/D converter.

The digital code that is the output of the first A/D converter 21 is written into the first memory 23, and the digital code that is the output of the first A/D converter 21 is
is read out at the frequency of The signal is then input to the first D/A converter 25. At this time, the output of the first D/A converter 25 is a luminance signal whose time axis is expanded n times with respect to the input of the first A/D converter 21 and restored to the original time axis. This luminance signal is input to a luminance signal nonlinear de-emphasis circuit 27, restored to its original level, and output.

On the other hand, the video signal input to the color signal nonlinear emphasis circuit 20 is outputted with the small amplitude component emphasized. This color signal nonlinear emphasis circuit 20 has the same characteristics as the recording system circuit and the color signal nonlinear emphasis circuit 6.

The output of the color signal nonlinear emphasis circuit 20 is input to the second A/D converter 22, and the color signal portion is converted into a digital code and written into the second memory 24. The digital code written in the second memory 24 is read out at a frequency of 1/m at the time of writing, and is transferred to the second D/A converter 26.
is input.

The output of the second D/A converter 26 is a color signal whose time axis has been expanded by m times and whose original time axis Cζ has been restored. The second
The output of the D/A converter 26 is input to the color signal nonlinear de-emphasis circuit 28, restored to its original level, and outputted from the color signal output terminal 30.

The embodiment of the reproduction circuit described above includes a luminance signal nonlinear emphasis circuit 19 and a color signal nonlinear emphasis circuit 20. Although an example in which the first A/D converter 21 and a second A/D converter 22 are used has been described, an example in which a nonlinear emphasis circuit is shared, or an example in which the A/D converter is also shared is also possible. It is.

The respective circuit diagrams are shown in FIGS. 9 and 10. In these figures, 31 is a non-linear emphasis circuit, 32 is A
A /D converter is shown, and the other symbols are the same as in FIG.

Note that the recording system circuit shown in FIG. 3.6.7 and the recording system circuit shown in FIG.
9. When using in combination with the reproduction circuit shown in Figure 10,
The recording circuits of FIGS. 3, 6, and 7 (respectively 8th
The reproduction circuits shown in FIGS. 9, 9, and 10 are suitable.

Furthermore, as described above, if the luminance signal and color signal that are time-division multiplexed during recording are re-modulated and recorded while being emphasized, the A/D converter in the reproduction circuit 21.22 The non-linear emphasis circuit 19, 20 or 31 provided at the front stage of the circuit can be deleted.

In this way, in the present invention, the luminance signal is sent to the first A/D.
Since non-linear emphasis is applied at the stage before the converters 7 and 21 with the characteristics shown in Figure 4, the video signal portion (excluding the synchronization signal portion) is compared to A/D conversion without emphasis. (part) can be set to a wider dynamic range. Furthermore, it is possible to improve the S/N ratio for visually sensitive low-level signals. This also makes it possible to reduce the number of bits of the A/D converter.

In particular, the reason why the present invention can improve the S/N even when analog memory is used as described above will be explained below.

FIG. 11 is a block diagram illustrating an embodiment of a recording system that performs time axis compression using a semiconductor analog memory. In the figure, 33 is a first semiconductor analog memory, and 34 is a second semiconductor analog memory.

Next, the operation of this circuit will be explained. A luminance signal with a small amplitude component emphasized by the luminance signal non-linear emphasis circuit 5 is written into the first semiconductor analog memory 33. The luminance signal is read out from the first semiconductor analog memory 33 at a frequency that is 0 times the writing frequency. The luminance signal has its time axis compressed by 1/r+l, and is input to the 1V and degree signal nonlinear de-emphasis circuit 13 at the subsequent stage.

The small amplitude component is then de-emphasized in the circuit 13, restored to its original amplitude level, and input to the switch 15.

Further, the color signal whose small amplitude component is emphasized by the color signal non-linear emphasis circuit 6 is written into the second semiconductor analog memory 34 . The color signal read from the second semiconductor analog memory 34 at a frequency m times that of writing is compressed on the time axis to 1/m 2 and is input to the color signal nonlinear de-emphasis circuit 141 at the subsequent stage. The small amplitude component is de-emphasized in the circuit 14,
The signal is restored to its original amplitude level and input to the switch 151.

The luminance signal and chrominance signal input to the switch 15 and subjected to time-base compression are time-division multiplexed and output.

In this way, by providing the non-linear emphasis circuits 5 and 6 at the front stage of the semiconductor analog memory 33 and 34, and the non-linear de-emphasis circuits M13 and 14 at the rear stage, the thermal noise generated at the semiconductor analog memory number ζ0 can be reduced. and other sharp components by the non-linear de-emphasis circuit 13. 141, the amplitude can be suppressed to a small amplitude. This reason Lt.

Thermal noise and other spurious components generated in the semiconductor analog memories 33 and 34 are generally small-amplitude signals, and these small-amplitude signals are further de-emphasized by the nonlinear de-emphasis circuits 13 and 14, resulting in small signals. Therefore, according to the circuit shown in FIG. 11, it is possible to improve the S/N ratio of a screen with low brightness that is visually sensitive.

FIG. 12 shows an example of a reproducing circuit suitable for reproducing signals recorded by the recording system circuit of FIG. 11. At figure number ζ, 35
．． 36 is a semiconductor analog memory, and other symbols indicate the same components as in FIG.

In each of the above embodiments, the characteristics of the nonlinear emphasis circuit 5 provided before the A/D converter or the semiconductor analog memory are selected so as to emphasize the small amplitude component of the luminance signal as shown in FIG. I explained the case. However, the present invention is not limited thereto;
As shown in FIG. 3, a characteristic may be adopted in which not only the small amplitude component of the luminance signal is emphasized, but also the horizontal synchronizing signal portion is de-emphasized. The effects in this case are as follows.

As shown in Figure 13, since the output signal is de-emphasized including the horizontal synchronization signal, the dynamic range of the luminance signal can be set much wider than when the horizontal synchronization signal is not de-emphasized. In addition, an improved S/N ratio can be obtained.

In this case, the S/N ratio can be improved only by de-emphasizing the horizontal synchronizing signal.

Further, in the above embodiment, an example was explained in which the luminance signal is time-division multiplexed with the color signal and recorded. However, the present invention is not limited to this, and can also be applied to the case of recording a video signal that does not have a color signal.

3 and 6 of the present invention in a magnetic recording and reproducing apparatus that time-division multiplexes luminance signals and color signals.

As shown in Figures 7 and 11, the amplitude characteristics of the luminance signal can be returned to the original level by installing the emphasis circuit at the front stage of the circuit that compresses the time axis of the luminance signal and the de-emphasis circuit at the rear stage C. Since the video signal is restored, it is also possible to use a time division multiplexing circuit for the video signal in the form of an adapter, for example, and connect it to a conventional VTR.

In addition, although this time division multiplexing circuit is not shown in the drawings, when it is provided before the angle modulation circuit, it is possible to combine it with an emphasis circuit, which is generally provided before the angle modulation circuit, and a recording mode as in the present invention. This makes it possible to share the emphasis circuit with the emphasis circuit provided before the time-base compression circuit and eliminate the de-emphasis circuit after the time-base compression circuit.Similarly, the de-emphasis circuit provided after the general angle modulation circuit can be used This makes it possible to share the circuit and the de-emphasis circuit provided after the time-base expansion circuit during playback, and to delete the emphasis circuit before the time-base expansion circuit.

In the present invention, the luminance signal to be recorded can be applied to any of the NTSC system, PAL system, and SECAf"i system.Also, although the color signal has been described using a line-sequential color difference signal as an example, it is particularly applicable to It is not limited.

(Effects) According to the present invention, since at least the luminance signal of the video signal is compressed in time by A/D conversion or semiconductor analog memory and recorded, the following effects can be achieved. .

+1) In magnetic recording and reproducing devices that perform time axis compression by A/D conversion, it is possible to improve S/N and improve A/D.
This has the effect of reducing the number of converter bits, reducing circuit scale, and reducing costs.

(2) A magnetic recording/reproducing device that performs time axis compression using a semiconductor analog memory has the effect of improving the S/N.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the frequency allocation of signals recorded in a conventional magnetic recording/reproducing device, and FIG.
3.6 and 7.11 are block diagrams illustrating an embodiment of the recording system circuit according to the present invention;
4 and 13 are diagrams explaining the luminance signal non-linear emphasis characteristics, FIG. 5 is diagrams explaining the color signal non-linear emphasis characteristics, and Figures 8 and 9.10.12 (j,
FIG. 2 is a block diagram illustrating an embodiment of a reproducing circuit according to the present invention. 5.19... Bright IJt (M number non-linear emphasis circuit, 7, 8, 21.22.32 ・A/D converter, 13, 27... Bright IJt' signal non-linear de-emphasis times %, 17...・Non-linear de-emphasis 7 times M, 31...Non-linear emphasis circuit, 15...Switch, 33.35...First semiconductor analog memory, 34.36...Second semiconductor analog memory attorney patent attorney Michi Hiraki Human Output Signal Page 1 Continued 0 Inventor Akira Shiba 29 Akira, Yoshida-cho, Totsuka-ku, Yokohama Hitachi, Ltd. Home Appliance Research Laboratory

Claims (4)

[Claims] (1) In a magnetic recording/reproducing device that compresses and records at least a luminance signal of a video signal in the time domain, a nonlinear circuit that emphasizes the small amplitude component of the luminance signal is provided in the preceding stage of the time domain compression circuit. A magnetic recording and reproducing device characterized by: (2) The magnetic recording and reproducing apparatus according to the first aspect of the patent specification, wherein the nonlinear circuit suppresses a horizontal synchronization signal of the luminance signal. (3) The magnetic recording and reproducing apparatus according to claim 1 or 2, wherein the time axis compression circuit is composed of an A/D converter, a memory, and a D/A converter. . (4) Claim 1, wherein the time base compression circuit is constructed of a semiconductor analog memory.
2. The magnetic recording and reproducing device according to item 1 or 2.