JPH04302868A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve picture quality by lowering the amplitude of a digital sum variation(DSV) value, suppressing the maximum of the absolute value of the DSV value to a prescribed value or below and reducing the components of direct current and low frequency in a recording signal. CONSTITUTION:An input color video signal is converted to the digital signal of (m) bits by an A/D converter 2 and converted to the code signal of (m) bits at one to one by a mapping converter 3. Then, the polarity and the time base of a code data are inverted by one word each by a code polarity inversion circuit 4, after the data is converted to a serial signal by a parallel/serial converter 8, then, the serial signal is outputted to a VTR 11 to record it on a magnetic tape. Further, this is returned to an original code word by a code polarity inversion circuit 13, further, is converted to the digital signal of 8 bits by a reverse mapping converter 15 and converted to an analog video signal by a D/A converter 16 to output the result.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording and reproducing apparatus, and more particularly to an encoding method for converting a digital signal such as a video signal into code words for recording and reproducing.

0002

2. Description of the Related Art After sampling a correlated signal, for example a color video signal, and converting it into digital data of m bits per sample, for example 8 bits (1 word),
A device has been developed that records and reproduces this information on a video tape recorder (VTR). When 8-bit data is recorded as is with such a device, the binary levels of "1" and "0" of the recorded signal do not appear uniformly, so they often contain DC components. Put it away. However, since the magnetic head of a general magnetic recording/reproducing device cannot reproduce the DC component during reproduction, encoding to prevent the recorded signal from including the DC component during recording is performed on the recording signal. It will be done.

[0003] Such encoding during recording is as follows:
DSV (DigitalSum Variation) of the recording signal
ation) value is made as small as possible. Here, DSV is a binary level of “1” and “0”.
This DSV is a value obtained by integrating the values corresponding to +1 and -1, respectively, and this DSV has a value for an arbitrary time point or period. Then, for continuous binary signals, D
When determining the SV, if the DSV increases or decreases without limit, the signal will have a DC component, and if the DSV is bounded, it will not have a DC component.

FIG. 14 is a block diagram showing a conventional example of a magnetic recording and reproducing apparatus that digitizes the color video signal as described above and records and reproduces it on a VTR. The video signal input from the input terminal 1 is converted into an 8-bit parallel digital signal by the A/D converter 2, and then converted to a DSV control encoder.
The signal is supplied to the loading circuit 103. In this encoding circuit 103, as described above, each 8-bit data word is rearranged according to a predetermined rule and replaced with an 8-bit word. In this case, the word to be replaced is stored, for example, in a ROM, and by specifying its address with a corresponding natural binary code, the replacement word is read from said ROM, and the input data is changed into a word. It is now replaced by -. In this way, the word replaced by the encoding circuit 103 is input to the inversion processing circuit 104. The inversion processing circuit 104 replaces each word with a complementary word, for example.

That is, in the inversion processing circuit 104, a certain word is output as is, and the following word is output as "1".
" and "0" are completely inverted. For example, a data word with a CDS value of -2 (DSVC
C) If [00110001] is inverted, it is converted to [11001110]. This data tower
The CDS value of the code is +2. That is, a complementary word to the word inputted from the encoding circuit 103 is a word in which the positive and negative polarities of the CDS are opposite to the original word. In this way, the inversion processing circuit 104 alternately outputs the same word as input and the inverted word. Considering that the input color video signal is a highly correlated signal, , this inversion processing circuit 104
When calculating the DSV of the output data word, the value is ``
It is easily understood that the direction is convergent to 0. The word output from the inversion processing circuit 104 is supplied to a parallel/serial converter 105 and converted into serial data. That is, 8-bit parallel data is converted to serial data, and this is supplied to the VTR 11. In this VTR 11, data for one field of a color video signal is recorded on a tape as a plurality of tracks. Here, the above-mentioned CDS value refers to the value obtained by taking the sum of 1 word of code data, assuming that code data "1" is +1 and "0" is -1. This is called weight. Therefore, the DSV value is the cumulative value of these CDS values.

[0006] Thereafter, the tape recorded in the above manner is played back by the VTR 11, and the obtained playback data is converted into 8-bit parallel data by the serial/parallel converter 107. , this parallel data is input to the inversion processing circuit 108 in word units. The inversion processing circuit 108 is the inversion processing circuit 10 at the time of recording the input word.
The conversion is performed in the opposite manner to the processing in step 4, and the complementary word at the time of recording is returned to the original word. In this way, the word returned to the original word by the inversion processing circuit 108 is DSV
The signal is input to a control decoding circuit 109. This DSV control decoding circuit 109 performs processing on the input word that is completely opposite to that of the recording system encoding circuit 103, and returns the input word to the original digital data. For this reason, the DSV control decoding circuit 109 has a RAM, and the word obtained from this circuit 109 becomes the original natural binary code. This natural binary code is input to the D/A converter 50. D/A converter 5
0 converts the input digital data into an analog color video signal, which is delivered to the output terminal 60.

In the conventional example described above, when the signals input to the input terminal 1 are correlated video signals and the levels between two consecutively input words are almost the same, the inversion processing circuit is used. 4, the DSV can be reduced by making each word a complementary word. However, if there is a difference in the signal level between the two words, that is, if the level of the input signal continues to change,
The amplitude width of the DSV value increases, and in the worst case, ±∞
This has the disadvantage that a direct current component enters the recording signal for the VTR 11 and a low frequency component increases, resulting in an increase in the error rate during recording and reproduction, and a deterioration in the image quality during recording and reproduction.

Therefore, the present invention aims to eliminate the above-mentioned drawbacks by making the amplitude width of the DSV value even smaller than in the conventional example, or by keeping the maximum absolute value of the DSV value below a predetermined value. It is an object of the present invention to provide a magnetic recording and reproducing device that can improve image quality during recording and reproducing by reducing DC components and low frequency components in signals. [Structure of the invention]

[0009]

[Means for Solving the Problems] The present invention provides a magnetic recording and reproducing apparatus that converts an input signal into a digital signal, converts it into a code word, and records and reproduces it on a magnetic tape. The code polarity time axis reversing means comprises a converting means for converting into a code word of bits, and a code polarity time axis reversing means for reversing the polarity and time axis of the code word output from the converting means in units of h words, the code polarity time axis reversing means It has a configuration for recording code words output from the magnetic tape on a magnetic tape.

As another configuration, the present invention provides a magnetic recording and reproducing apparatus that converts an input signal into a digital signal, converts it into a code word, and records and reproduces it on a magnetic tape. converting means for converting the 1-word m-bit digital signal multiplexed by the multiplexing means into a 1-word n-bit code word; and converting means for converting the polarity and time axis of the code word output from the converting means. A code polarity time axis reversing means for inverting the code polarity time axis in units of h words is provided, and the code word outputted from the code polarity time axis reversing means is recorded on a magnetic tape.

[0011] As a configuration added to the above configuration, the present invention provides that when converting an input m-bit digital signal into an n-bit code word, the conversion means converts 2m code words into codes from 1 to 2m −2. It has a configuration to allocate to.

As another configuration, the present invention provides a magnetic recording and reproducing apparatus that converts an input signal into a digital signal, converts it into a code word, and records and reproduces it on a magnetic tape. a conversion means for converting the polarity of the code word outputted from the conversion means, a sign inversion means for inverting the polarity of the code word outputted from the conversion means in units of h words, and a code inversion means for inverting the polarity of the code word outputted from the sign inversion means or a non-inverted polarity. code polarity inversion control means for controlling whether to output the code word as it is; CDS calculation means for calculating a CDS value of the code word output from the code inversion means; and a DSV value of the code word output from the code polarity inversion control means. a DSV calculation means for calculating, and an absolute value of a DSV value to be calculated next by the DSV calculation means is decreased based on the DSV value calculated by the DSV calculation means and the CDS value calculated by the CDS calculation means; control bit generating means for generating a control bit for determining inversion or non-inversion of the code polarity inversion control circuit so that the code polarity inversion control circuit and an insertion means for inserting a control bit generated from the code polarity reversal control means, and has a configuration for recording the code word output from the code polarity reversal control means on the magnetic tape.

As a configuration added to the above configuration, the CDS calculation means of the present invention calculates the CDS value of the code word output from the sign inversion means, and also calculates the change in this CDS value, and transmits this to the control bit generation means. The control bit generation means then calculates the following value by the DSV value calculation means based on the CDS value calculated by the CDS calculation means, the change in this CDS value, and the DSV value calculated by the DSV calculation means. DS to be done
The present invention is configured to generate a control bit that determines whether the sign polarity inversion control circuit is inverted or non-inverted so that the absolute value of the V value decreases.

[0014]

In the magnetic recording/reproducing apparatus of the present invention, the converting means converts a digital signal of m bits per word into a code word of n bits per word. The code polarity time axis inverting means inverts the polarity and time axis of the code word output from the converting means in units of h words. The code word output from the code polarity time axis reversing means is recorded on a magnetic tape.

As another feature of the structure, in the magnetic recording/reproducing apparatus of the present invention, the multiplexing means time-axis multiplexes different types of input signals. The converting means converts the digital signal of one word and m bits multiplexed by the multiplexing means into a code word of one word and n bits. The code polarity time axis inverting means inverts the polarity and time axis of the code word output from the converting means in units of h words. The code word output from the code polarity time axis reversing means is recorded on a magnetic tape.

As an additional effect to the above effect, the converting means converts the input m-bit digital signal into n-bit code words by converting 2m code words from 1 to 2.
Allocate to the sign of m −2.

As another feature of the structure, in the magnetic recording/reproducing apparatus of the present invention, the converting means converts a digital signal of one word and m bits into one word and n bits. The sign inverting means inverts the polarity of the code word output from the converting means in units of h words. The code polarity inversion control means controls whether the polarity of the code word outputted from the code inversion means is inverted or output without being inverted. The CDS calculating means calculates the CD of the code word output from the sign inverting means.
Calculate the S value. The DSV calculation means calculates the DSV value of the code word output from the code polarity inversion control means. The control bit generation means determines the direction in which the absolute value of the DSV value calculated next by the DSV calculation means decreases based on the DSV value calculated by the DSV calculation means and the CDS value calculated by the CDS calculation means. A control bit is generated to determine whether the sign polarity inversion control circuit is inverted or not. The insertion means inserts the control bit generated by the control bit generation means into the code word output from the code polarity inversion control means. The code word output from the code polarity reversal control means is recorded on the magnetic tape.

As an additional effect to the above-mentioned effect, the CDS calculating means of the present invention calculates the CDS value of the code word output from the sign inverting means, and also calculates the change in this CDS value, and uses this as the control bit generating means. Output to
Further, the control bit generation means is configured to generate a D that is next calculated by the DSV value calculation means based on the CDS value calculated by the CDS calculation means, a change in this CDS value, and the DSV value calculated by the DSV calculation means.
A control bit is generated to determine whether or not the sign polarity inversion control circuit is inverted so that the absolute value of the SV value decreases.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of the magnetic recording/reproducing apparatus of the present invention. 1 is an input terminal for inputting an analog recording signal such as a video signal, and 2 is an input terminal A for converting the input analog video signal etc. into an 8-bit digital signal.
/D converter 3 is a mapping conversion circuit that converts an 8-bit digital signal into an 8-bit code word on a one-to-one basis; 4
converts the code word input from the mapping conversion circuit 3 into 1
A code polarity inversion circuit that inverts the polarity and time axis for each word; 8 a parallel/serial conversion circuit that converts the code word output from the mapping conversion circuit 3 into a serial signal; 11 an input from the NRZI modulation circuit 10; a VTR section 1 for recording recorded signals on a magnetic tape (not shown);
2 is a serial/parallel conversion circuit that converts an input serial signal into a parallel signal based on the synchronization signal;
13 is a code polarity inversion circuit that inverts the polarity and time axis of each code word input from the serial/parallel conversion circuit 12; 15 is a mapping conversion circuit for mapping the code word input from the code polarity inversion circuit 13; 16 is a D/A converter that converts a digital signal into an analog signal; and 17 is an output terminal that outputs a reproduced analog video signal. still,
It is assumed that the mapping conversion circuit 3 and the inverse mapping conversion circuit 15 perform conversion using completely opposite processes.

Next, the operation of this embodiment will be explained. A color video signal inputted from an input terminal 1 is converted into an m-bit digital signal by an A/D converter 2, and then inputted to a mapping conversion circuit 3. The mapping conversion circuit 3 converts the input m-bit digital signal into an m-bit code word on a one-to-one basis, and outputs the obtained code word to the code polarity inversion circuit 4. The code polarity inversion circuit 4 inverts the polarity of the input code data word by word, and also inverts the time axis thereof. In this way, the sign polarity inversion circuit 4
The code word whose polarity and time axis are inverted word by word is input to the parallel/serial conversion circuit 8. The parallel/serial conversion circuit 8 converts the code word inputted from the code polarity inversion circuit 4 into a serial signal, and then converts the code word into a serial signal.
It is output to the R section 11. Although not mentioned in the above explanation of the operation, it goes without saying that an error correction code, a synchronization signal, etc. are also added to the recording signal recorded on the magnetic tape by the VTR section 11.

Next, the signal reproduced by the VTR unit 11 is input to the serial/parallel conversion circuit 14 and converted back into a parallel code word, and this code word is input to the code polarity inversion circuit 13. The code polarity inversion circuit 13 inverts the polarity and time axis of each input code word word by word, returns the code word to the original code word, and then outputs the code word to the inverse mapping conversion circuit 15 . The inverse mapping conversion circuit 15 inversely converts the input 8-bit code word into an 8-bit digital signal and outputs this to the D/A converter 16. The D/A converter 16 converts the input digital signal into an analog video signal and outputs it to the output terminal 17.

Next, detailed operation of the sign polarity inversion circuit 4 of this embodiment shown in FIG. 1 will be explained. The code polarity inversion circuit 4 not only inverts the polarity of each input code word word by word, but also inverts the time axis. This time axis reversal is performed by reading out the input word in the opposite direction to the direction in which it was input into the shift register. For example, 1101
When the data of 00 is converted to the time axis, it becomes 001011. Therefore, when the code word 010101 is input to the code polarity inversion circuit 4, first, its polarity is inverted to 101010, and then its time axis is inverted to 0.
The code data is 10101, and this is the parallel/
It will be output to the serial conversion circuit 8. Figure 2 (A
) is the modulation code word output from the code polarity inversion circuit 4. When such modulation is performed, the DSV of the modulation code word recorded in the VTR unit 11 is + as shown in FIG. 2(B).
The range of change is from 2 to -4. However, when the same data as above is subjected to only polarity reversal as in the conventional example, as shown in Figure 2 (
The DSV of the signal recorded in the VTR section 11 at this time varies from +2 to -6 as shown in FIG. 2(D).
The width of the change is larger than that shown in FIG. 2(B) in this example. The reason for this is that when 1 or 0 continues in a code word, the absolute value of the DSV value becomes large in the positive or negative direction, but in this example, the time axis is reversed, so the next code word This is because it acts in the direction of reducing the absolute value of the DSV from the initial dead data.

According to this embodiment, the mapping conversion circuit 3
The polarity of the encoded data is inverted word by word in the code polarity inversion circuit 4, and the modulated data obtained by inverting the time axis is used as the recording signal of the VTR unit 11. The width of the change in value can be kept small, and the direct current component and low frequency component included in the recording signal can be reduced accordingly, making it possible to reduce the error rate and improving the image quality during recording and playback. can. In the above embodiment, the mapping conversion circuit 3 converts m-bit data into m-bit code words, but the same effect can be obtained even if the data is converted into n-bit code words. However, there is a relationship of m≦n.

FIG. 3 is a block diagram showing a second embodiment of the present invention. In this example, in addition to the luminance signal Y, the color difference signal PB
, PR are input, so three A/D converters 2-
1, 2-2, and 2-3 are provided. The luminance signal and color difference signal digitized by these A/D converters are input to a time axis multiplexing encoder circuit 27, where they are subjected to encoding processing for multiplexing the time axis. The signal whose time axis has been multiplexed by the time axis multiplex encoding circuit 27 is output to the mapping conversion circuit 3, and thereafter subjected to the same processing as in the embodiment shown in FIG. 1 and input to the VTR unit 11. . The signal reproduced by the VTR unit 11 is returned to a parallel code word by the serial/parallel conversion circuit 9, similar to the device shown in FIG. The polarity and time axis of the word are reversed for each word,
This is returned to the original time axis multiplexed signal in the inverse mapping conversion circuit 15. Time axis multiple decoding circuit 28
returns the time axis multiplexing of the input signal to the original signal before multiplexing, and each signal is sent to the D/A converter 16-1,
The signal is returned to analog luminance signal Y and color difference signals PB and PR at 16-2 and 16-3.

The operation of the time axis multiplex encoder circuit 27, which is a characteristic feature of this embodiment, will now be explained. The luminance signal after digitization is Y1, Y2, and the color difference signal is P
B1, PB2, PR1, and PR2, and these signals are input to the time axis multiplex encoder circuit 27. However, if one word of the input signal is 6 bits,
For example, Y1=Y2=100000, PB1=PB2=
110000, PR1=PR2=000011, etc. When these signals are input to the time axis multiplex encoder circuit 27, the encoder circuit 27 converts the input signals into Y1→Y2→PB1→PB2→PR1→PR2.
The data are rearranged in this manner and output to the mapping conversion circuit 3. FIG. 4 is a diagram showing the processing results of the time axis multiplex encoding circuit 7, and the line above the symbol in the figure indicates that the polarity and time axis have been inverted.

FIG. 5A shows modulated data time-domain multiplexed by the time-domain multiplex encoding circuit 7, and the data modulated in this way is transmitted to the mapping conversion circuit 3.
When the signal is converted into a recording signal through the code polarity conversion circuit 4, the DSV changes as shown in FIG. 5(B), and the width of the change falls within the range of +2 to -4. Here, if the time axis multiplexing encoder circuit 27 does not perform time axis multiplexing in units of two pixels, the input data is Y1→PB1→PR1.
→ Y2 → PB2 → PR2, and the modulated data is as shown in Figure 5(C), and the DS of the recording signal in this case is
The change in V is as shown in FIG. 5(D), and the change width is in the range of +1 to -10. Therefore, as shown in FIG. 5(B), in this embodiment, the width of change in DSV of the recording signal can be reduced, and the DC component and low frequency component of the recording signal can be reduced. Image quality can be improved by reducing error rate.

Next, a third embodiment of the present invention will be described. In the mapping conversion circuit shown in FIG. 1 or 3 described above, for example, 8-bit digital data is converted into an 8-bit code word. It is a mapping diagram. Looking at this, it can be seen that 00 and FF exist in the modulation code, and if this value continues, the run length may become infinite. Therefore, in this example, as shown in FIG. 7, both 00 and 01 are set to 80, and the FF
, FE are both set to 7F, it is possible to avoid the run length from becoming infinite. As a result, D
Divergence of the SV value can be avoided, and as in the previous embodiment, it is possible to reduce the mixing of DC components into the recording signal and improve the image quality during recording and reproducing. In the above example, 8 bits to 8
Although an example of conversion into bits has been shown, when converting from m bits to m bits, it is sufficient to allocate a code of 1 to 2m-2.

FIG. 8 is a block diagram showing a fourth embodiment of the present invention. 31 is an input terminal for inputting an analog recording signal such as a video signal; 32 is an A/D converter for converting the input analog video signal etc. into an 8-bit digital signal;
33 is a mapping conversion circuit that converts an 8-bit input digital signal into a 1:1 8-bit code word; 34 is 1;
A code polarity inversion circuit that inverts the polarity of an input code word word by word; 35 is a CDS calculation circuit that calculates the CDS values of all code words output from the code polarity inversion circuit 34; 36 is a code polarity inversion circuit; A control bit generation circuit 3 which generates a control bit in the direction of decreasing the DSV value of the code word output from the control circuit 38;
7 is D for calculating the accumulated DSV value from the past of the code word output from the code polarity inversion control circuit 38.
38 is a code polarity inversion control circuit that controls whether or not to invert the polarity of the code word output from the code polarity inversion circuit 34; 39 is a code word control circuit that controls the code word output from the code polarity inversion control circuit 38; 40 is a parallel/serial conversion circuit that converts the code into a serial signal and inserts the control bit output from the control bit generation circuit 36 into the code word input from the code polarity inversion control circuit 38; 41 is a parallel/serial conversion circuit 39;
A VTR unit 42 records recording signals inputted from the VTR unit on a magnetic tape (not shown), and a serial/recording unit 42 converts inputted serial signals into parallel signals based on the synchronization signal.
A parallel conversion circuit 43 detects a synchronization signal from the parallelized playback signal and supplies it to a control bit detection circuit 44; 44 is based on the synchronization signal supplied from the synchronization signal detection circuit 43; hand,
A control bit detection circuit detects the control bit of the reproduction signal parallelized by the serial/parallel conversion circuit 42, and 45 is a code polarity that controls whether or not to invert the polarity of the code word output from the serial/parallel conversion circuit 42. An inversion control circuit 46 is a code polarity inversion circuit that inverts the polarity of the code word inputted from the code polarity inversion control circuit 45 word by word;
47 is an inverse mapping conversion circuit that inversely maps the code word input from the code polarity inversion circuit 46 and converts it into the original digital signal; 48 is a D/A conversion circuit that converts the digital signal into an analog signal; 49 is a reproduction analog This is an output terminal that outputs a video signal. Furthermore, the mapping conversion circuit 3
3 and the inverse mapping conversion circuit 47 are performed by completely opposite processes.

Next, the operation of this embodiment will be explained. Before explaining the operation, the parameters in the apparatus shown in FIG. 8 are set as follows. The number m of bits of data input to the mapping conversion circuit 33 is assumed to be eight, and the number n of bits of the code word converted by the mapping conversion circuit 33 is assumed to be eight. The polarity inversion unit h of the sign polarity inversion circuit 34 is assumed to be 1. Further, it is assumed that the polarity inversion word unit of the sign polarity inversion control circuit 38 is l×h, where l=2 and h=1. Furthermore, the mapping conversion circuit 33 converts the digital data of 8 bits per pixel into
It is converted into an 8-bit code word at , and this is taken as one word.

The video signal input from the input terminal 31 is A
After being converted into an 8-bit digital signal by the /D converter 32, it is input to the mapping conversion circuit 33. The mapping conversion circuit 33 converts the input 8-bit digital data into a code word of 8 bits per word, and outputs this to the code polarity inversion circuit 38 . Sign polarity inversion circuit 3
8 inverts the polarity of the input code word in units of one word, and inverts the polarity of the input code word by a code polarity inversion control circuit 38 and the CDS.
It is output to the calculation circuit 35. The CDS calculation circuit 35 calculates the CDS value of the code word input from the code polarity inversion circuit 34 and sends the result to the control bit generation circuit 36.
give to The code polarity inversion control circuit 38 controls whether the polarity of the input code word is inverted or not in units of two words according to the control bits generated from the control bit generation circuit 36, and if the polarity is not inverted, the polarity of the input word is If it is to be inverted, the polarity of the input code word is inverted and outputted to the parallel/serial conversion circuit 39 and the DSV calculation circuit 37. DS
The V calculation circuit 37 calculates the cumulative DSV value of the code word output from the code polarity inversion control circuit 38 and outputs the result to the control bit generation circuit 36. The parallel/serial conversion circuit 39 serializes the input code word, inserts the control bits output from the control bit generation circuit 36 to create a recording signal, and outputs this recording signal to the VTR section 41. The VTR unit 41 records input recording signals on a magnetic tape (not shown).

Next, during playback, the playback signal output from the VTR section 41 is converted into a parallel code word by the serial/parallel conversion circuit 42, and then sent to the code polarity inversion control circuit 45, the sync signal detection circuit 43, and the control circuit 42. The signal is input to the bit detection circuit 44. The sync signal detection circuit 43 detects a synchronization signal from the code word output from the serial/parallel conversion circuit 42 and passes it to the control bit detection circuit 44. The control bit detection circuit 44 detects the control bit of the code word inputted from the serial/parallel conversion circuit 42 based on the synchronization signal, and passes the detection result to the code polarity inversion control circuit 45. The code polarity inversion control circuit 45 controls whether or not to invert the polarity of the code word inputted from the serial/parallel conversion circuit 42 based on the control bits. has its polarity inverted and outputs it to the sign polarity inversion circuit 46. Sign polarity inversion circuit 46
Inverts the code word input from the code polarity inversion control circuit 45 word by word, and then outputs it to the inverse mapping conversion circuit 47. Inverse mapping conversion circuit 4
7 inversely maps the input code word to return it to the original digital signal, and then outputs this to the D/A converter 48. The D/A converter 48 converts the input digital signal into an analog video signal and outputs it to the output terminal 49. Although not mentioned in the above operation explanation, the VTR section 4
It goes without saying that an error correction code, a synchronization signal, etc. are also added to the recording signal recorded on the magnetic tape in step 1.

Next, the detailed operation of each circuit in the above-mentioned apparatus will be explained in sequence. The mapping circuit 33 maps and converts the 8-bit input digital data into an 8-bit code word as described above, and the conversion mapping diagram at this time is as shown in FIG. In FIG. 9, the code word "1" is considered to be +1 and "0" to be -1, and the sum of the 8-bit codes in one pixel is defined as the code weight, that is, CDS, and the input digital Data levels from 0 to 255 are made to correspond one-to-one to the 8-bit code words arranged in the order of the CDS values. The relationship between the CDS and the image level (the level of digital data input to the mapping conversion circuit 33) is as shown in FIG. 10, and the CDS value can take a value from -8 to +8.

[0033]

[Outside 1] ◆◆

[Outside 2] ◆◆

[Outer 3] ◆◆

According to this embodiment, when control bits are inserted into the recording signal as shown in FIG. 12, the high-frequency components increase by 1/16 in the band of the recording signal, but the band of the recording signal increases by 1/16. -10 conversion M, the high-frequency components are reduced, and furthermore, considering that the video signal input from the input terminal 31 has a high correlation, the C of each word
Since the probability that the DS value is close to 0 can be increased, the final absolute value of the DSV of the recording signal can be suppressed to 16 or less. This makes it possible to reduce the direct current component and low-frequency component of the recording signal recorded on the magnetic tape by the VTR section 42, thereby reducing the error rate and improving the image quality during recording and playback.

FIG. 13 is a block diagram showing a fifth embodiment of the present invention. The configuration of this example is almost the same as the example shown in FIG. 8, but the operations of the CDS calculation circuit and control bit generation circuit are different as described below. That is, in the embodiment shown in FIG. 8, only the final value of the CDS of the two code words is focused, but in this example, the change in the CDS value is also focused, and the DSV calculated by the DSV calculation circuit 37 is It has a configuration in which the sign polarity inversion control circuit 38 is controlled in the direction of further decreasing the value. Here 2
Even if the final value of the CDS value of the word is set to 0, Figure 11
There are cases where the maximum absolute value of DSV becomes large, as shown in (e) of (E), and cases where it does not become large, as shown in (f). Therefore, in this example, the CDS shown in FIG.
Change calculation circuit 60 (corresponding to the CDS calculation circuit 35 in FIG. 8)
is the code word C output from the code polarity inversion circuit 34.
The CDS is calculated including not only the final value of DS but also the change in the CDS value of this CDS, and the result is given to the control bit generation circuit 36. For example, if the DSV changes of the code words Y3 and Y4 input to the CDS change calculation circuit 60 are as shown in FIG. It can be seen that if the control is performed to invert, the change in the DSV calculated by the DSV calculation circuit 37 becomes as shown in (f) of FIG. In this case, the maximum absolute value of DSV including the change in CDS is 20 as shown in (G) of FIG. 11(E). this(
The case shown in (g) is an example in which the maximum absolute value of DSV is the same for both inversion and non-inversion. Therefore, in the control bit generation circuit 38 of this example, the maximum absolute value of DSV is large based on the CDS value given from the CDS change calculation circuit 36, its change, and the previous DSV value given from the DSV calculation circuit 3. A control bit is generated to determine whether the sign polarity inversion control circuit 38 is inverted or not.

According to this embodiment, since the maximum value of the DSV of the recording signal is controlled to be small by taking into consideration not only the final value of CDS but also its change, the recording speed is even greater than that of the embodiment shown in FIG. The DSV value of the signal can be reduced, and the image quality during recording and playback can be further improved.

[0037]

As described above, according to the magnetic recording and reproducing apparatus of the present invention, the amplitude width of the DSV value can be made smaller than that of the conventional example, or the maximum absolute value of the DSV value can be kept below a predetermined value. By doing so, it is possible to reduce the direct current component and low frequency component in the recording signal, thereby improving the image quality during recording and playback.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of a magnetic recording/reproducing apparatus of the present invention.

FIG. 2 is a diagram showing modulation words and DSV values output from the code polarity inversion circuit shown in FIG. 1, and also shows conventional modulation words and DSV values.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing an example of a data string output from the time axis multiplex encoding circuit shown in FIG. 3;

FIG. 5 is a diagram showing modulation words and DSV values output from the code polarity inversion circuit shown in FIG. 3, as well as conventional modulation words and DSV values.

FIG. 6 is an 8-8 conversion mapping diagram using a conventional mapping conversion circuit.

FIG. 7 is a mapping diagram used in the third embodiment of the present invention.

FIG. 8 is a block diagram showing a fourth embodiment of the present invention.

FIG. 9 is a conversion mapping diagram of the mapping conversion circuit shown in FIG. 8;

FIG. 10 is a diagram showing the relationship between the CDS value of an 8-bit code word and the input image level.

FIG. 11 is a diagram illustrating the operation of the apparatus shown in FIG. 8 and the apparatus shown in FIG. 13.

FIG. 12 is a diagram showing an example of a recording signal in which control bits are inserted in the parallel/serial conversion circuit shown in FIG. 8, and an example of a conventional recording signal.

FIG. 13 is a block diagram showing a fifth embodiment of the present invention.

FIG. 14 is a block diagram showing an example of a conventional magnetic recording/reproducing device.

[Explanation of symbols]

2, 32... A/D converter, 3, 33... Mapping conversion circuit, 4, 13, 34, 46... Sign polarity inversion circuit, 8, 39...
Parallel-serial conversion circuit, 9, 42... Serial-parallel conversion circuit, 10... NRZI modulation circuit, 11, 41... VTR section, 12... NRZI demodulation circuit, 15, 47... Inverse mapping conversion circuit, 16, 48... DA converter, 27... Time axis multiple encoder circuit, 28... Time axis multiple decode circuit, 35... CDS calculation circuit, 36... Control bit generation circuit, 37... DSV calculation circuit, 38, 45... Sign polarity inversion control. circuit, 43... sink signal detection circuit, 44... control bit detection circuit

Claims (5)

[Claims] Claim 1: A magnetic recording and reproducing device that converts an input signal into a digital signal, converts it into a code word, and records and reproduces it on a magnetic tape, in which a digital signal of m bits per word is converted into a code word of n bits per word. The code word is provided with a converting means and a code polarity time axis reversing means for inverting the polarity and time axis of the code word outputted from the converting means in units of h words. A magnetic recording/reproducing device characterized by recording on magnetic tape. 2. A magnetic recording and reproducing apparatus that converts an input signal into a digital signal, converts it into a code word, and records and reproduces it on a magnetic tape, a multiplexing means for time-axis multiplexing different types of input signals; 1 multiplexed by
A converting means for converting a digital signal of m bits per word into a code word of n bits per word, and a code polarity time axis inverting means for inverting the polarity and time axis of the code word output from the converting means in units of h words. 1. A magnetic recording and reproducing apparatus comprising: a magnetic recording/reproducing apparatus for recording a code word output from the code polarity time axis reversing means on a magnetic tape. 3. The converting means, when converting an input m-bit digital signal into an n-bit code word, allocates 2m code words to codes from 1 to 2m −2. 2. The magnetic recording and reproducing device according to 1 or 2. 4. A magnetic recording and reproducing apparatus that converts an input signal into a digital signal, converts it into a code word, and records and reproduces it on a magnetic tape, comprising: a conversion means for converting a digital signal of m bits per word into n bits per word; , a sign inverting means for inverting the polarity of the code word output from the converting means in units of h words, and controlling whether to invert the polarity of the code word output from the sign inverting means or output it without inversion. and a CDS for calculating a CDS value of a code word output from the code inverting means.
a calculation means, a DSV calculation means for calculating the DSV value of the code word output from the code polarity inversion control means, and a DSV value calculated by the DSV calculation means and the C
Based on the CDS value calculated by the DS calculation means, inversion or non-inversion of the sign polarity inversion control circuit is determined so that the absolute value of the DSV value next calculated by the DSV calculation means decreases. and inserting means for inserting the control bits generated from the control bit generation means into the code word output from the code polarity inversion control means, A magnetic recording/reproducing device characterized in that a code word output from a control means is recorded on a magnetic tape. 5. The CDS calculating means calculates the CDS value of the code word output from the sign inverting means and calculates the CDS value of the code word output from the sign inverting means.
The change in value is also calculated and outputted to the control bit generation means, and the control bit generation means
CDS value calculated by the DS calculation means, change in this CDS value, and DS calculated by the DSV calculation means
Based on the V value, a control bit is generated for determining whether or not the sign polarity inversion control circuit is inverted so that the absolute value of the DSV value that is next calculated by the DSV value calculation means is in a decreasing direction. 5. The magnetic recording and reproducing apparatus according to claim 4, characterized in that: