*To*: cdwrite@other.debian.org*Subject*: Re: Announcing cdrskin-0.7.2*From*: "D. Hugh Redelmeier" <hugh@mimosa.com>*Date*: Sun, 18 Oct 2009 02:08:47 -0400 (EDT)*Message-id*: <alpine.LRH.2.00.0910180121320.17323@redclaw.mimosa.com>*Reply-to*: "D. Hugh Redelmeier" <hugh@mimosa.com>*In-reply-to*: <104762433218526@212.46.126.165>*References*: <4ad433a1.LwWU1i7QhBk4CQUG%Joerg.Schilling@fokus.fraunhofer.de> <104762433218526@212.46.126.165>

| From: Thomas Schmitt <scdbackup@gmx.net> | Do you know by chance a smart student who can | contribute an implementation or explanation of | ECMA-130 Annex A ? | | "The RSPC is a product code over GF(28) producing | P- and Q-parity bytes. The GF(28) field is | generated by the primitive polynomial | P(x) = x8 + x4 + x3 + x2 + 1 | The primitive element a of GF(28) is | a = (00000010) where the right-most bit is the | least significant bit. | [...] | " | The words "RSPC" and "P- and Q-parity bytes" | belong to the CD sector format specs. But the | others must be established mathematic terms. | (How is this connected to a Fourier | transformation of the bit sequence on time | domain ? Urgh ! Analysis ! On a finite set !) I am not a mathematician. I'd guess that this is really GF(2^8). GF stands for Gallois Field. Gallois Fields have size p^m where p is a prime (in our case, 2). Ahh. The standard confirms this: http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-130.pdf Thus all elements of GF(2^8) would be polynomials of degree 7 or less. The coefficients are from the integers mod 2 and thus any polynomial in this field can be represented as 8 bits. The primitive polynomial would be: P(x) = x^8 + x^4 + x^3 + x^2 + x^0 See http://en.wikipedia.org/wiki/Finite_field RSPC seems to be Reed-Solomon Product-like Code. See http://en.wikipedia.org/wiki/Finite_field >From that article, it looks as if the discrete Fourier transform you require can be done by a cook book method: http://en.wikipedia.org/wiki/Berlekamp-Massey_algorithm I admit that I'm shooting from the hip here. But it seems as if the internet has enough information to get to a solution.

**Follow-Ups**:**Re: Announcing cdrskin-0.7.2***From:*"Thomas Schmitt" <scdbackup@gmx.net>

**Re: Announcing cdrskin-0.7.2***From:*Joerg.Schilling@fokus.fraunhofer.de (Joerg Schilling)

**References**:**Re: Announcing cdrskin-0.7.2***From:*Joerg.Schilling@fokus.fraunhofer.de (Joerg Schilling)

**Re: Announcing cdrskin-0.7.2***From:*"Thomas Schmitt" <scdbackup@gmx.net>

- Prev by Date:
**Re: solaris cdrecord BH08LS20 drive BD-R problems** - Next by Date:
**Re: Announcing cdrskin-0.7.2** - Previous by thread:
**Re: Announcing cdrskin-0.7.2** - Next by thread:
**Re: Announcing cdrskin-0.7.2** - Index(es):