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A method of embedding an additional layer of error correction into an error correcting code, wherein information is encoded into code words of said code over a first Galois field and wherein a number of code words are arranged in the columns of a code block comprising a user data sub-block and a par

A method of embedding an additional layer of error correction into an error correcting code, wherein information is encoded into code words of said code over a first Galois field and wherein a number of code words are arranged in the columns of a code block comprising a user data sub-block and a parity data sub-block, provides an additional layer of error correction that can be easily implemented without losing compatibility improving the error correction capabilities. The method includes the steps of: encoding the rows of at least the user data sub-block separately or in groups using a horizontal error correcting code over a second Galois field larger than the first Galois field to obtain horizontal parities, and embedding the horizontal parities as additional layer in the error correcting code.

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The invention claimed is: 1. In a method of encoding multiword information, which includes the steps of encoding information into first code words of an error correcting code over a first Galois field, and arranging a number of the first code words in columns of a code block comprising a user data

The invention claimed is: 1. In a method of encoding multiword information, which includes the steps of encoding information into first code words of an error correcting code over a first Galois field, and arranging a number of the first code words in columns of a code block comprising a user data sub-block and a parity data sub-block, wherein said code block comprises the first code words over the first Galois field arranged in the columns of said code block, a method of embedding an additional layer of error correction into the error correcting code, said method comprising the steps of: adding bits of a predetermined number to the first code words to form second code words over a second Galois field arranged in the columns of said code block, wherein the bits have different bit values and comprise an identical sequence of bits added to each row; encoding rows of at least said user data sub-block separately or in groups using a horizontal error correcting code over the second Galois field larger than said first Galois field to obtain horizontal parities; and embedding said horizontal parities as the additional layer in said error correcting code. 2. The method as claimed in claim 1, wherein the bits having a predetermined value is added to each symbol of said user data sub-block before encoding the rows of said user-data sub-block. 3. The method as claimed in claim 2, wherein one or two the bits having bit value zero are added to each symbol of said user data sub-block. 4. The method as claimed in claim 1, wherein said first Galois field is GF(28), and wherein said code block is a Long Distance Code (LDC) block comprising LDC code words over the first Galois field GF(28), arranged in the columns of said LDC block. 5. The method as claimed in claim 4, wherein in said encoding the rows step, each row of said user data sub-block is encoded separately using a [306, 304, 3] Reed Solomon code over a Galois field GF(29). 6. The method as claimed in claim 4, wherein in said encoding the rows step, each row of said user data sub-block is encoded separately using a subspace subcode of a Reed Solomon code over a Galois field GF(29). 7. The method as claimed in claim 4, wherein in said encoding the rows step, the rows of said user data sub-block are encoded in groups of three consecutive rows using a Reed Solomon code over a Galois field GF(210). 8. The method as claimed in claim 4, wherein in said encoding the rows step, the rows of said user data sub-block are encoded in groups of three consecutive rows using a subspace subcode of a Reed Solomon code over a Galois field GF(210). 9. The method as claimed in claim 1, wherein said horizontal parities are encoded by a Burst Indicator Subcode (BIS) comprising Reed Solomon code words over GF(28). 10. An apparatus for embedding an additional layer of error correction into an error correcting code, wherein information is encoded into first code words of said code over a first Galois field, and wherein a number of the first code words are arranged in the columns of a code block comprising a user data sub-block and a parity data sub-block, wherein said code block comprises the first code words over the first Galois field arranged in the columns of said code block, said apparatus comprising: means for receiving the error correcting code; means for adding bits of a predetermined number to the first code words to form second code words over a second Galois field arranged in the columns of said code block, wherein the bits have different bit values and comprise an identical sequence of bits added to each row; means for encoding the rows of at least said user data sub-block separately or in groups using a horizontal error correcting code over a second Galois field larger than said first Galois field, thereby forming at least horizontal parities; means for embedding said horizontal parities as additional layer in said error correcting code; and means for outputting said modified error correcting code.