JP2523554B2 - Digital signal recording device - Google Patents

Description

The present invention relates to a digital signal recording device, and more particularly,
The present invention relates to signal processing suitable for a digital signal recording apparatus for converting 1-word n-bit data such as 9 conversion code into m-bit (m> n) data and recording the data.

[Conventional technology]

Conventionally, regarding the modulation code of the digital VTR, as described in the technical report VR58-2 (July, 1983) of the Television Society of Japan, the 8-9 conversion code converts 1 bit 8 bit data into 9 bit data. It is converted into a DC-free modulation code and recorded. The DC-free code is suitable for magnetic recording. With 8-10 conversion, the DC component can be further reduced, and the code is suitable for magnetic recording.

[Problems to be solved by the invention]

The above-mentioned conventional technique converts 1-word n-bit data into m-bits (m> n). Since the 1-word time is constant, the bit interval after conversion is shortened to n / m. Correspondingly, there is a problem that the recording wavelength is shortened by n / m as compared with the case where the n-bit data is directly written.

An object of the present invention is to provide a system capable of recording while keeping the recording wavelength as it is.

[Means for solving problems]

The purpose of the above is to lengthen the track length by the magnetic head, that is, to increase the winding angle of the tape, and to use the buffer memory to read the data converted into 1 word m bit by time expansion to m / n. To be achieved.

[Action]

By increasing the tape wrap angle by approximately m / n, the track length that can be recorded by the magnetic head can be increased by m / n. On the other hand, 1-word n-bit data is converted into 1-word m-bit data in the read-only memory and then time-expanded to m / n using the buffer memory. Therefore, the track length is long, but the recording wavelength is 1 word n.
The same as when writing the bit directly, there is no shortening of the recording wavelength by using n, m conversion. Therefore, a reliable digital VTR can be constructed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.
FIG. 1 is a signal processing block diagram of a recording circuit of a digital VTR according to the present invention. The input video signal is converted by the A / D converter 1 into a digital code of 8 bits per pixel (word), and in order to reduce the influence of dropout generated on the magnetic tape 8, the order of data (shuffling) and the like. Insert an error correction code. These 1-word 8-bit data are converted by the 8-bit-10-bit conversion ROM3 to 1
Converted to word 10 bits. 2 ¹⁰ = 2 ⁸ out of 1024
= 256 will be selected, so out of 1024 data,
The generation of a DC component is suppressed except for data in which a lot of 1s and 0s are continuous, such as data such as 1111111111. The output of conversion ROM3 consists of 10 bits per word.
It is separated into two signal sequences for each field. Each signal string is converted into serial data by the parallel / serial conversion circuits 5-1 and 5-2. At this time, the bit clock B.CK to be read is 1/8 of the word clock cycle. Thank you
Since 10 bits per word are read with the bit clock corresponding to the bits of 1 word, 2 bits per word are read out with a delay.

FIG. 2 shows the switch 4 and the parallel-serial conversion 5-1.
It is a time chart showing the operation of 5-2. Switch 4
It is shown that the signals divided by ... are read out as "" by the parallel-serial conversion circuit. As shown in FIG. 2A, since the switch 4 switches the data for each one field, the parallel-serial conversion circuit 5-1 reads out one field for 5/4 field as shown in B. Therefore, the parallel-serial conversion circuit 5-
1 requires a memory capacity of at least 1/4 field. The parallel / serial conversion circuit 5-2 operates in the same manner. The data read in this way is recorded by the recording amplifier 6-1,
Recording is performed on the magnetic tape 8 by the magnetic heads 7-1 and 7-2 via 6-2.

FIG. 3 shows the head arrangement on the cylinder and the tape winding angle in the above embodiment of the present invention. The cylinder rotates once for one frame and the two magnetic heads 7-
1,7-2 are mounted on the cylinder 9 against each other by 180 °. The magnetic tape 8 has a field of 180 °, so 1
It is wound as much as / 4 fields, at least 225 ° or more. Since it is wound in this way, the parallel-serial conversion circuits 5-1 and 5-
Two signals can be recorded on the magnetic tape.

The reproducing circuit will not be described because it is easy to infer that the original video signal can be obtained by performing signal processing in the reverse process of the recording circuit of FIG.

If one word is encoded with, for example, 6 bits and S / N lowered, 6-8 conversion × 6-9 conversion is used, but it can be easily inferred that the present invention can be applied to this case as well. .

〔The invention's effect〕

According to the present invention, a code mn (m> n) conversion code suitable for magnetic recording can be used without shortening the recording wavelength.
A highly reliable digital VTR can be realized. In addition, the number of bit clocks required for signal processing is one, and the effect that bit clocks having a high frequency interfere with the video signal can be reduced.

[Brief description of drawings]

FIG. 1 shows a digital VTR in one embodiment according to the present invention.
FIG. 2 is a signal processing block diagram of the recording circuit, FIG. 2 is a time chart showing a part of the operation of the recording circuit, and FIG. 3 is an explanatory diagram showing the arrangement of the cylinder, the magnetic tape, the magnetic head and the like in the above embodiment. . 1 ... A / D converter, 3 ... 8-10 conversion circuit, 4 ... switch, 5-1 and 5-2 ... parallel-serial conversion circuit, 6
-1,6-2 ... Recording amplifier.

Claims (1)

(57) [Claims] 1. A digital signal recording apparatus for converting a digital signal into a new word having a number of bits larger than the number of bits in a word unit and recording the digital signal, wherein a bit clock for reading out the new word in serial is converted. A digital signal recording device characterized in that it is equivalent to the bit clock before the operation.