Coded data generation or conversion – Digital code to digital code converters – Coding by table look-up techniques
Patent
1996-03-08
1998-10-06
Young, Brian K.
Coded data generation or conversion
Digital code to digital code converters
Coding by table look-up techniques
H03M 742
Patent
active
058183671
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to a signal modulating method, a signal modulating apparatus, a signal demodulating method and a signal demodulating apparatus which are used for recording or reproducing digital signals, such as, digital speech signals, digital video signals and data, in a recording medium, and for example, to the signal modulating method, the signal modulating apparatus, the signal demodulating method and the signal demodulating apparatus which may be adapted for a mastering device for a read-only optical disc or a recording/reproducing device for a re-writable optical disc.
2. Background Art
When recording digital signals, such as digital speech signals, digital video signals or data, error correction code data is first appended to the digital signals, and the resulting data is routed to a modulating circuit where it is converted by channel coding into the code suited to the characteristics of a recording/reproducing system.
An optical disc, such as, a compact disc (CD), is a recording medium having a wide field of application as a package medium for picture information or as a storage device for a computer. The optical disc system reproduces signals recorded on a reflective surface of the disc via a transparent substrate having a thickness of the order of 1.2 mm. On the optical disc, information such as digitized audio signals, video signals or digital data, is recorded. In this case, the error correction code data is appended to the digital signals, and the resulting data is routed to a modulating circuit where it is converted by so-called channel coding into code data suited to the characteristics of the recording/reproducing system.
The signal format of the above-mentioned compact disc (CD) system is summarized as follows:
______________________________________ sampling frequency 44.1 kHz
number of quantizing bits
16 (linear)
modulation system EFM
channel bit rate 4.3218 Mb/s
error correction system
CIRC
data transmitting rate
2.034 Mb/s
______________________________________
With the EFM, an input 8-bit code, referred to hereinafter as a symbol, is converted into a 14 channel bit code, to which a frame synchronization signal of 24 channel bits and a subcode of 14 channel bits are appended and the neighboring codes are interconnected by merging bits of 3 channel bits. The resulting data is recorded by the NRZI modulation system.
FIG. 1 shows a frame structure of the CD system.
Referring to FIG. 1, 24 symbol data (music signals) and 8 symbol parity, entering a modulating circuit from a cross-interleave Reed-Solomon code (CIRC) encoder during a sync frame (6 sample value domains, six samples each of the L and R channels, with each sample being 16-bit data) are transformed into 14 channel bits and connected by merging bits of three channel bits to give 588 channel bits per frame. The resulting data is recorded by the NRZI system at a channel bit rate of 4.3218 Mbps.
The respective symbols entering the modulating circuit are transformed, with reference to a lookup table composed of a ROM, into a channel bit pattern in which the number of "0"s between "1" and "1" is not less than 2 and not more than 10. The channel bit pattern of a frame synchronization signal Sf is "100000000001000000000010" in binary expression. As for the merging bit pattern, one of "000", "001", "010" and "100" is selected. Each sub-coding frame is made up of 98 frames. As the subcode for the 0'th and first frames, the subcode sync signal S0 (="00100000000001") and S1 (="00000000010010") are appended (see FIG. 2).
FIG. 3 shows, for a typical sample value of input data, a channel bit pattern after EFM and a digital sum variation (DSV).
Each 16-bit sample is split into upper 8 bits and lower 8 bits each of which is entered to the modulation circuit via a CIRC encoder for 8-14 conversion to produce 14 channel-bit information bits. Not less than 2 and not more than 10 "0"s are interposed between "1" and "1" of the information bits, as previously described. One of the merging bit
REFERENCES:
patent: 5196848 (1993-03-01), Sakazaki et al.
patent: 5341134 (1994-08-01), Benjauthrit
patent: 5355133 (1994-10-01), Shimpuku et al.
patent: 5365232 (1994-11-01), Ido et al.
patent: 5371771 (1994-12-01), Kim
patent: 5469162 (1995-11-01), Chaki et al.
patent: 5570248 (1996-10-01), Ido et al.
E-mail transmission received by inventors dated Feb. 24, 1994, not published.
Okazaki Toru
Yoshimura Shunji
Sony Corporation
Young Brian K.
LandOfFree
Signal modulating method, signal modulating apparatus, signal de does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Signal modulating method, signal modulating apparatus, signal de, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Signal modulating method, signal modulating apparatus, signal de will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-83079