14. An apparatus for producing N-bit output words of RLL-encoded data having both a global constraint G o and an interleave constraint I o on bits of a first value, the apparatus comprising: a register configured to receive successive N-bit input words of RLL-encoded data having both a global constraint G i and an interleave constraint I i on bits of like value; and sliding-window encoder logic configured to produce the output words from respective input words by sliding-window encoding of each input word to replace predetermined bit-sequences with respective substitute sequences such that G o <G i ; wherein each substitute sequence is unique and violates a run-length limit associated with the interleave constraint I i such that I o >I i .
14. An apparatus for producing N-bit output words of RLL-encoded data having both a global constraint G o and an interleave constraint I o on bits of a first value, the apparatus comprising: a register configured to receive successive N-bit input words of RLL-encoded data having both a global constraint G i and an interleave constraint I i on bits of like value; and sliding-window encoder logic configured to produce the output words from respective input words by sliding-window encoding of each input word to replace predetermined bit-sequences with respective substitute sequences such that G o <G i ; wherein each substitute sequence is unique and violates a run-length limit associated with the interleave constraint I i such that I o >I i . 16. The apparatus of claim 14 , wherein the sliding-window encoder logic is adapted such that the window slides one bit at a time.