Error coding for video disc system

• US 4,309,721 A
• Filed: 10/12/1979
• Issued: 01/05/1982
• Est. Priority Date: 10/12/1979
• Status: Expired due to Term

• Current Assignee: RCA Corporation
• Original Assignee: RCA Corporation
• Inventors: Christopher, Todd J.
• Primary Examiner(s): Psitos, Aristotelis M.
• Application Number:
  US06/084,396
• Time in Patent Office: 816 Days
• Field of Search: 358/128.5, 358/128.6, 358/147, 360/72.2, 360/75, 360/77.78, 360/53, 360/40, 360/48, 179/100.3 V, 371/38, 371/40, 369/53, 369/59, 369/54, 369/47
• US Class Current: 386/263
• CPC Class Codes: G11B 20/1813 by adding special bits or symbols to the coded information G11B20/1809 takes precedence

Abstract

An improved error code used for encoding and decoding data in a video disc system of the type wherein the data format comprises a start code followed by an error code and information bits. The error code is chosen so that the error code check register in the video disc player begins with the start code in the register, and, if no errors are detected after the full message is received, also ends with the start code in the register. This unique code simplifies both the control logic and the decoding logic in the video disc player decoder.

Claims

1. An encoding apparatus for encoding an information word on video signal for recording on a video disc, the encoded signal to be subsequently recovered in video disc player having a compatible decoder, said encoding apparatus comprising:

means (49)(47) for generating a start code corresponding to a start sequence;

means (45) responsive to said information word for generating a prescribed error code word;

means (52)(54) for combining said information word and said error code;

means (36) for modulating said video signal in accordance with a data word comprising said start code and said combined information word and error code word; and

wherein said error code word produces in said compatible decoder an error check result over at least a portion of said data word equal to said start code when said portion of the data word is free from errors.

2. An improved video disc recording apparatus for recording video signal including an encoded digital information signal on a video disc, said recorded signals to be recovered in a video disc player having a compatible decoder, said recording apparatus including encoding means for generating a data word including an information word, said encoding means including means for generating a start code word and means for generating an error code word, wherein the improvement comprises:

means for controlling the generation of said error code word so that at least a portion of said data word generates an error check result, in said compatible decoder, that is equal to said start code when said data word is free of errors.

3. An encoding apparatus for encoding an information word I (x) on a video signal, for recording on a video disc, said recorded signal to be recovered in a video disc player having a compatible decoder, said encoding apparatus comprising:

means for generating a start code, B(x), corresponding to a start sequence;

means for generating an error code, C(x), using a generator polynomial g(x), said error code being of the form,

C(x)=[I(x)·

H(x)]+M(x), where H(x) and M(x) are each constant polynomials;

means for modulating said video signal in accordance with a data word T(x), given by

T(x)=B(x)x^m+n +C(x)x^m +I(x) where n equals the number of bits in said error code and m equals the number of bits in said information word; and

wherein H(x) and M(x) are chosen so that said compatible decoder dividing T(x) by g(x) produces a remainder after division equal to B(x) when T(x) is transmitted without errors.

4. In a video disc player for playing a video disc having a video signal recorded thereon, said recorded video signal being modulated in accordance with a data word comprising a start code, and a combined information word and error check code, a video disc decoder apparatus comprising:

receiving means responsive to said video signal for detecting individual bits of a received data word;

an information buffer comprising error check means coupled to said receiving means for generating an error check result; and

said buffer including means responsive to said error check means, for generating a status signal indicating that said received data word is valid if at least a portion of said received data word has an error check result equal to said start code.

5. A video disc decoder apparatus according to claim 4 wherein said status signal is generated when the complete received data word has an error check result equal to said start code.

6. In a video disc player for playing a video disc having a video signal recorded thereon, said video signal being modulated in accordance with a data word containing a start code and a combined information word and error check code, a video disc decoder apparatus comprising:

receiving means responsive to said modulated video signal for detecting individual bits of a received data word;

polynomial divider means coupled to said receiving means for dividing at least a portion of said received data word by a constant polynomial g(x), said polynomial divider means having a remainder output; and

means responsive to said remainder output, for indicating that said received data word is valid if said remainder output after division by g(x) is equal to said start code.

7. In a video disc player for playing a video disc having a video signal recorded thereon, said video signal being modulated in accordance with a data word containing a start code and a combined information word and error check code, a video disc decoder apparatus comprising:

receiving means responsive to said modulated video signal for detecting the individual bits of a received data word; and

further means responsive to said detected data word bits for generating a control signal upon detecting said start code, and wherein said further means, responsive to said control signal and said detected data, generates an error check result over at least a portion of said detected data word and produces a status signal only when the error check result is equal to said start code, said status signal indicating that said portion of said detected data word is free of errors.

8. In a video disc player for playing a video disc having a video signal recorded thereon, said video signal being modulated in accordance with a data word containing a start code and a combined information word and error check code, a video disc decoder apparatus comprising:

receiving means responsive to said modulated video signal for detecting the individual bits of a received data word;

detector means coupled to said receiving means for detecting said start code;

polynomial divider means coupled to said receiving means for dividing, responsive to a divide command signal, at least a portion of said received data word by a constant polynomial g(x), said polynomial divider means including a remainder register; and

means responsive to said decoder means for providing said divide command signal after the detection of said start code;

said means for providing said divide command signal further including means responsive to said remainder register contents for generating a control signal only when the contents of said remainder register after said polynomial division is equal to said start code, the occurrence of said control signal being indicative of said portion of said data word being free of errors.

9. In a video disc player for playing a video disc having a video signal recorded thereon, said video signal being modulated in accordance with a data word containing a start code and a combined information word and error check code, a video disc decoder apparatus comprising:

receiving means responsive to said video signal for detecting the individual bits of a received data word;

shift register means connected to said receiving means, said shift register means including feedback means responsive to an enabling signal for multiplying the output of said shift register means by a constant polynomial, g(x) and subtracting the result thereof from the contents of said shift register;

detector means connected to said shift register for generating said enabling signal upon detecting said start code in said shift register with the shift register feedback means disabled; and

means responsive to said detector means and the contents of the shift register for generating a status control signal when a further start code occurs in said shift register with the feedback means enabled, the occurrence of said status control signal indicating detection of an error-free data word.