JPH0474362A - Digital magnetic recorder - Google Patents

Abstract

PURPOSE:To reduce recording errors by additionally recording adjusting bits for changing a preset data of a precoder to a recording data in front of its data train. CONSTITUTION:The digital magnetic recorder is of a partial response system using the precoder, and its recording is performed by adding the adjusting bits for changing the preset data of the precoder to the recording data in front of its data train. In this case, each of adjusting bit inserting circuits 31, 32, 33 and 34 is the circuit for inserting the adjusting bits of 2 bits into a spot just in front of the data train of the recording data, and the adjusting bits to be inserted are changed by the individual circuits 31, 32, 33 and 34 respective ly. By this method, since the data precoded in order to minimize the errors is recorded, the digital data is recorded under good condition with few errors.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is applicable to, for example, a VTR (VTR) that records digital video signals.
The present invention relates to a digital magnetic recording device suitable for application to a video tape recorder.

[Summary of the invention]

The present invention is directed to a digital magnetic recording device using a precoder based on a partial response method, in which an adjustment bit for changing the preset data of the precoder is added at least before a data string for recording, thereby reducing recording errors. This allows for good recording.

[Conventional technology]

Conventionally, various so-called digital VTRs have been developed that convert video signals into digital signals and record them. According to such a digital VTR, for example, image quality deterioration during dubbing can be minimized.

[Problem to be solved by the invention]

By the way, when recording and reproducing signals on magnetic tape, the third
As shown in the figure, because the electromagnetic conversion system such as a magnetic head has differential characteristics, the CN ratio deteriorates at lower frequencies, whereas as the frequency increases, the CN ratio similarly deteriorates due to the magnetization characteristics of the magnetic tape. The ratio deteriorates.

Therefore, in a magnetic recording/reproducing system, a digitized video signal (hereinafter referred to as a digital video signal) has a characteristic that the frequency band is narrow in order to obtain a good CN ratio.

Therefore, when recording digital video signals,
A recording method is selected in which the signal spectrum concentrates near the area where the CN ratio is maximum, and this reduces the CN of the reproduced signal.
It is necessary to effectively avoid ratio deterioration and efficiently record and reproduce digital video signals.

In this case, a method of recording and reproducing the digital video signal using a class (■) partial response method, which is one of the high-efficiency encoding methods, may be considered.

In other words, in magnetic recording and reproduction, the CN ratio deteriorates at low and high frequencies, so the frequency characteristics are expressed by the class ■ partial response ( 1-D”) can be approximated and expressed as the frequency characteristic H(ω).

By the way, the frequency ω at which the response is minimum.

(that is, the Nyquist frequency) is related to the delay time T expressed by the delay operator D as shown in the following equation (1).

Therefore, select the amount of delay represented by delay operator D,
It is thought that if the signal spectrum is concentrated in the vicinity where the CN ratio is maximum, it is possible to efficiently record and reproduce digital video signals by effectively utilizing the frequency characteristics of the magnetic recording and reproduction system.

That is, during recording, if the arithmetic processing expressed by the following equation is sequentially performed on the digital video signal, the frequency characteristics of the digital video signal are converted into a recording signal that approximates the frequency characteristics of the magnetic recording and reproducing system. be able to.

Therefore, by sequentially recording the recording signals on the magnetic tape, the frequency characteristics of the magnetic recording and reproducing system can be effectively utilized.
It is believed that digital video signals can be recorded efficiently.

By the way, MOD2 represents the remainder of 2.

On the other hand, since the electromagnetic conversion system has differential characteristics, the reproduced signal output from the magnetic head is expressed as (1-D) using the delay operator D, and is indicated by the broken line in Fig. 4. It is expressed by the frequency characteristics shown below.

Therefore, during playback, (1+
By executing the arithmetic processing in D), it is possible to add the following correction to the entire recording and reproducing system as a whole, and thereby set the transfer function to 1 for the entire recording and reproducing system and reproduce the digital video signal. It is considered possible.

Here, we will explain the configuration of the recording circuit of a digital VTR to which the partial response method of
As shown in the figure, (1) in this Figure 5 indicates the input terminal of the video signal to be recorded, and the analog video signal supplied to this input terminal (1) is transferred to the analog-to-digital converter (2).
and is converted into a digital video signal by this analog-to-digital converter (2).

Then, the digital video signal output from the analog-to-digital converter (2) is supplied to a pit reduction circuit (3) and compressed into digital data with a number of bits suitable for the recording rate of this VTR. The digital data output by this pit reduction circuit (3) is then supplied to a parity encoder (4).
) and then supplies it to the scrambling circuit (5). The scrambling circuit (5) performs scrambling by multiplying the recording data by M-series scrambled data (pseudo-random data), and supplies the scrambled digital data to the synchronization insertion circuit (6). Then, a synchronization insertion circuit (6) adds synchronization data to the recording data, and supplies the added recording data to a precoder (10).

This precoder (10) performs the calculation of the above-mentioned equation (2), and is configured as shown in FIG. That is, the recording data supplied from the synchronization insertion circuit (6) to the terminal (11) is supplied to one input of the Ex-OR game (12), and the output of this Ex-OR game (12) is Ex-OR (
12) is configured to feed back to the other input. In this case, each delay circuit (13), (1, 4) is a circuit that delays input data by one clock. Then, the output of the Ex-OR gate (12) is supplied to a terminal (15), and from this terminal (15) is supplied to the subsequent circuit.

By configuring the precoder (10) in this way,
The frequency characteristics of recorded data are approximated to the frequency characteristics of a magnetic recording/reproducing system.

Then, the output of this precoder (10) is converted into a recording amplifier (
7) to a magnetic head device (8) and recorded on a videotape (9).

FIG. 7 shows the configuration of a reproducing circuit that reproduces the signals recorded on the video tape (9) in this way. ) and send the playback signal to the reproducing amplifier (2).
1) to the equalizer circuit (22). Then, the reproduction signal output from the equalizer circuit (22) is supplied to the data reproduction circuit (23).

This data reproducing circuit (23) is a circuit that reproduces binary digital data from the reproduced signal, and supplies the reproduced data to the synchronization detection circuit (24).
Extract the synchronized data inserted during recording. and,
The reproduced data output from the synchronization detection circuit (24) is supplied to a descrambler circuit (25), which multiplies it by an M sequence and descrambles it. Then, the descrambled playback data is supplied to the parity decoder (26), and this parity decoder (
26) performs a parity check. Then, the output of the parity decoder (26) is transferred to the pit reduction circuit (2
7), the compressed data is returned to the original bit number data, and the returned playback data is supplied to the digital-to-analog converter (28) to convert it into an analog video signal, and this analog video signal is converted into an analog video signal. The signal is supplied to the playback signal output terminal (29).

In this way, recording and playback are performed using the class ■ partial response method, but due to the modulation in the precoder (10) during recording, the PA0" signal or the "1PA signal continues for a long time, resulting in a DC component. It may occur. That is, originally, the scrambling circuit (5) multiplies the M-sequence scrambled data to prevent the generation of DC components, but precoating using the partial response method may cause DC components to occur depending on the input data. be.

If a DC component occurs in the recorded data in this way,
There has been an inconvenience that errors occur in the recorded data due to various reasons. For example, the rotary transformer that supplies recording data to the magnetic head device in the rotating head drum does not pass the DC component, so the recorded data does not reach the magnetic head device accurately, making it impossible to record accurately. Even if the recorded data arrives, it will not be possible to completely override the data already recorded on the videotape.

An object of the present invention is to prevent DC components from being generated during precoating in a digital magnetic recording device that performs recording using a partial response method.

[Means to solve the problem]

The present invention is a digital magnetic recording apparatus using a precoder based on a partial response method, in which an adjustment bit for changing the precent data of the precoder is added at least before a data string for recording.

[Effect]

By doing this, the recording data precoated by the precoder is changed by the adjustment bit, and by adding the adjustment bit that generates the least direct current component,
Direct current components are prevented from being included in the recorded data, and errors do not occur in the recorded data.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 and 2. In this Fig. 1 and Fig. 2, Fig. 3~
Portions corresponding to those in FIG. 7 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In this example, the VT converts the video signal into a digital signal and records it using the class ■ partial response method.
This is applied to the recording system of the R apparatus, and is configured as shown in FIG. FIG. 1 shows the configuration after the synchronization insertion circuit (6), and the configuration before the synchronization insertion circuit (6) is constructed in the same manner as the conventional recording circuit shown in FIG.

In this example, after the data string is scrambled and synchronization data is added to the recorded data supplied from the terminal (6a) to the synchronization insertion circuit (6), the synchronization insertion circuit (6) outputs four sets of adjustment bit insertion circuit (31),
Record data is supplied to (32), (33), and (34).

These respective adjustment bit insertion circuits (31), (3
2).

(33) and (34) are circuits that insert 2-bit adjustment bits immediately before the data string of recording data, and each circuit (
The adjustment bits inserted in 31), (32), (33), and (34) are changed. That is, the adjustment bit insertion circuit (31) inserts an adjustment bit of "0.O", the adjustment bit insertion circuit (32) inserts an adjustment bit of "1.0", and the adjustment bit insertion circuit (33) inserts an adjustment bit of "1.0". An adjustment bit of “0.1” is inserted, and the adjustment bit insertion circuit (34)
．． Insert a 1” adjustment bit.

Here, the insertion state of this adjustment bit is shown in Fig. 2.
This figure 2 shows the recorded data structure of one block. The recorded data of each block consists of synchronization data D1 first, identification code (ID) D2, and then video data, etc. A data string D3 is arranged, and finally a parity D4 is arranged. Here, the 2 immediately before data string D3
The bit is an adjustment bit) D5, and each adjustment bit insertion circuit (31), (32), (33), (34)
Then, data such as the above-mentioned "1.0" is inserted into these 2 bits. In this case, the scrambling circuit (5) preceding the synchronization insertion circuit (6) performs scrambling only on the data string D3 and the parity D4.

In this way, each adjustment bit insertion circuit (31)
, (32), (33), and (34) are transferred to precoders (41) and (42) connected to the next stage, respectively.

(43) and (44), and precoating is performed using the partial response method based on the above-mentioned equation (2).

In this case, each precoder (41) to (44) has the same configuration as the precoder (10) shown in FIG.
It consists of a gate (12) and delay circuits (13) and (14).

Then, each precoder (41), (42), (
43) and (44), respectively, to the first switch (50). 2nd ° Third and fourth fixed contacts (51
), (52), (53) and (54) as well as direct current component detection circuits (61), (62)
.

(63) and (64) and continuous length detection circuit (71),
(72), (73) and (74). In this case, each of the DC component detection circuits (61) to (64) detects the difference in the number of "1" data included in the recorded data within a predetermined section and the PON data, and the continuous length detection circuit (
In 71) to (74), “
The maximum continuous length of consecutive data of "1" or "0" is detected.

And each DC component detection circuit (61), (62)
, (63) and (64) and each continuous length detection circuit (71), (72).

The detection data of (73) and (74) are
0). This determination circuit (80) determines the detection data supplied from each circuit and determines which precoder output is most suitable for recording. That is, each precoder (41), (
From the outputs of 42), (43), and (44),
The one that generates the least direct current component and has the shortest maximum continuous length, thus minimizing the occurrence of recording errors, is determined.

Then, based on this determination, the connection of the movable contact (55) of the changeover switch (50) is controlled. That is, the movable contact (55) is connected to the fixed contact (any one of (51) to (54)) to which the output of the precoder that provides optimal recording data is supplied.
Connect. The recording data obtained at the movable contact (55) of this changeover switch (50) is transferred to the recording amplifier (
7) to a rotary head device (8) and recorded on a videotape (9).

Note that the determination by the determination circuit (80) is performed for each block of recording data, and the optimum adjustment bit is set for each block, and the adjustment bit changes for each block.

The other parts are constructed in the same manner as the conventional VTR shown in FIG. 5.

By configuring the VTR of this example in this way, the recording data supplied to the rotary head device (8) has less DC components and continuous data of "°1" or "'0". The continuous length also becomes shorter. That is, each precoder (41
), (42), (43), and (44), a different adjustment pitch D5 is inserted immediately before the data string D3 of each block.

Therefore, each precoder (41), (42), (
When the data string D3 of each block is supplied to 43), (44), the value (preset value) fed back to the Ex-OR game (12) configuring the precoder is different, and each precoder (41), ( 42) , (43
) and (44) handle the same data string, but the output states are different.

Then, from among these different output data, each DC component detection circuit (61), (62), (63)
and (64) detection data and each continuous length detection circuit (71)
, (72), (73), and (74), the determination circuit (80) supplies data determined to be most suitable for recording to the rotating head device (8) side. Therefore, the generation of DC components is small, and
The continuous length of continuous data of "1°" or "0°" also becomes shorter.

Here, to show an example in which the recorded data changes by inserting a different adjustment bit D5, at the timing immediately before this adjustment bit D5 is supplied to each precoder (41) to (44),
Delay circuits (
13) and the delay circuit (14), it is assumed that data of "0" is input to each of them. At this time, for example, adjustment pitch)D
5 is "1, 0" (the value inserted by the adjustment bit insertion circuit (32)), data of "1" is input to the delay circuit (13) at the timing immediately before the data string D3 is supplied. , ``0'' data is input to the delay circuit (14).In this way, the input data of the delay circuits (13) and (14) immediately before the data string D3 is supplied changes, The output changes after precoating.

Table 1 shown below shows the cases when the adjustment bit D5 is set to "0, 0" (the value inserted by the adjustment bit insertion circuit (31)) and when it is set to "o, i" (the value inserted by the adjustment bit insertion circuit (31)). 33)
This figure shows the difference in the output after precoating compared to the value inserted in . In this case, the changes in the data string are sequentially shown in the vertical direction, and the changes from the first 0th bit to the 20th bit of the data string D3 are shown.

Table 1 The judgment circuit (80) makes a judgment on the output data in Table 1. In the example of Table 1, the amount of DC component generated is the same for any adjustment bit, but if the adjustment bit is "0" .0
”, the maximum continuous length is 3 bits, whereas when the adjustment bits are “0, 1”, the maximum continuous length is 4 bits, and the adjustment bits “'o, o” are better. It can be seen that the data will be recorded.Actually, the state in which all the adjustment focuses (four types) have been inserted is detected in the entire interval of the data string D3 and the parity D4, and the optimum one is determined.

In this way, although the VTR of this example is configured to include precoders (41) to (44) based on the partial response method, the generation of DC components is small and the continuous length is not increased, and the rotary transformer Recorded data is supplied to the magnetic head device in a good manner through the video tape, and override for erasing data already recorded on the video tape can also be done well, resulting in the effect that good recording can be performed without errors.

In the above embodiment, the adjustment bit is inserted immediately before the data string, but even if the adjustment bit is inserted at another position before the data string of the recording data of each block, the data This is effective in preventing column recording errors. Further, in the above embodiment, the present invention is applied to a recording system circuit of a digital VTR, but it can also be applied to various other digital devices that record digital data. Furthermore, it goes without saying that the present invention is not limited to the above-mentioned embodiments, and can take various other configurations.

(41), (42), (43), (44)
is the precoder, (50) is the changeover switch, (61),
(62), (63), (64) are DC component detection circuits, (71), (72), (73),
(74) is a continuous length detection circuit, and (80) is a determination circuit.

〔Effect of the invention〕

According to the present invention, in a digital magnetic recording device to which a partial response method is applied, precoated data is recorded so as to minimize recording errors, so that digital data is recorded satisfactorily with few recording errors.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, FIG. 2 is an explanatory diagram showing the recording data structure of one embodiment, FIGS. 3 and 4 are frequency characteristic diagrams for explaining the partial response method, FIG. 5 is a configuration diagram showing an example of a conventional recording device, and FIG.
The figure is a block diagram of a precoder used in the partial response method, and FIG. 7 is a block diagram showing an example of a playback device.

Claims (1)

[Claims] A digital magnetic recording device using a precoder based on a partial response method, wherein an adjustment bit for changing preset data of the precoder is added at least before a data string for recording.