Coded data generation or conversion – Digital code to digital code converters – To or from nrz codes
Patent
1996-07-24
1998-06-09
Gaffin, Jeffrey A.
Coded data generation or conversion
Digital code to digital code converters
To or from nrz codes
341 58, G11B 2014
Patent
active
057641692
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a coding method and apparatus. More specifically, the present invention realtes to a coding method and apparatus used for a VTR, VCR, and etc. adopting a digital pilot signal recording system so as to convert input data to which a control bit is added at a head into an output code.
PRIOR ART
One example of conventional such a kind of coding apparatus is disclosed in, for example, Japanese Patent Application Laying-open No. 4-255969 frequency components of two kinds of codes obtained by inserting a control bit of "0" or "1" at a head of input data of N+1 bits and by subjecting the same to I-NRZ modulation, and an appropriate code is selectively outputted through comparison of processed results, and last two bits of a selected code to a precoder for the I-NRZ modulation of next input data.
Since in such a prior art coding apparatus, the last two bits of the output code are fed-back, it is necessary to process preceding input data within a time that the input data equal to one code is modulated, e.g. a time period of 25 clocks in a case where one code is 25 bits so as to output the appropriate code, it is difficult to put the coding apparatus into practical use. More specifically, since a frequency component extraction circuit performs Fourier transform for a DC component and components of frequencies f1 and f2 in a modulated code, a circuit becomes quite large and a processing time for the extraction of the frequency components becomes long, it is quite difficult to shorten a time period to extract the frequency components for one bit in comparison with a time period for the I-NRZ modulation of one bit data, therefore, and accordngly, it is difficult to put the coding apparatus into practical use.
SUMMARY OF THE INVENTION
Therefore, a principal object of the present invention is to provide a novel coding mathod.
Another object of the present invention is to provide a coding method in which it is unnecessary to feed-back a portion of a preceding code.
A further object of the present invention is to provide a coding apparatus which implements the above described coding method.
According to the present invention, a coding method comprises steps of: (a) inserting a control bit into input data; (b) generating a reference code on the basis of input data into which the control bit is inserted; (c) generating a predetermined number of associate codes on the basis of the reference code; and (d) selectively outputting one of the reference code and the associate codes on the basis of frequency components of the reference code and the associate codes.
According to the present invention, a coding apparatus comprises: insertion means (12) for inserting a control bit into input data; reference code generation means (14) for generating a reference code on the basis of data outputted from the insertion means; associate code generation means (22, 56a, 56b, 56c) for generating a predetermined number of associate codes being in correlation with the reference code on the basis of the reference code; judgment signal output means (18, 20) for outputting a judgment signal on the basis of frequency components of the reference code and the associate codes; and code output means (22, 54) for selectively outputting one of the reference code and the associate codes according to the judgment signal.
In accordance with the present invention, since the associate codes are generated in advance on the basis of the reference code, and one code is selectively outputted on the basis of the frequency components of these codes, it is unnecessary to feed-back last two bits of a preceding output code, and therefore, a time restriction is released, and accordingly, it is possible to certainly convert the input data into the code.
In one embodiment, the judgment signal output means includes first to N-th extraction means for extracting first to N-th (N is an integer) frequency components of each of the reference codes and the associate codes, first to N-th calculation means for calculatin
REFERENCES:
patent: 5432651 (1995-07-01), Maeno et al.
patent: 5579182 (1996-11-01), Hamai et al.
Gaffin Jeffrey A.
Jean-Pierre Peguy
Sanyo Electric Co,. Ltd.
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