Hi, > it seems as if the > internet has enough information to get to a solution.
Yes, it has. A new source module ecma130ab was committed to libburn SVN yesterday. I would appreciate if you had a look at the explanations at lines 8 to 115 whether you find any mistakes or gaps. http://libburnia-project.org/browser/libburn/trunk/libburn/ecma130ab.c By help of Norbert Preining i found a document about Reed-Solomon for RAID applications by James S. Plank which provided me with the theoretical background to understand ECMA-130 Annex A. The resulting implementation is unoptimized and needs about 50 % more time than the old one which was labeled "borrowed HEAVILY from cdrdao". ECMA-130 Annex B, the scrambler, was easier to learn. Only obstacle was that the diagram in ECMA-130 shows a 16 bit register in Fibonacci form whereas the text talks of a 15 bit register with a 15 bit polynomial that refers to the Galois form. Well, if one removes the surplus box from the Fibonacci then it is trivial to implement. (Thanks to a company named New Wave Instruments for an overview of Linear Feedback Shift Register nomenclature.) I ran my whole hard disk content through a comparison of old and new output. It matched. Whether the old output exactly complies to ECMA-130 would be subject to a real test case for raw CD writing. I learned that Annex A is needed to encode a data block into an audio-sized sector. Annex B is needed to prepare an audio-sized sector for raw writing. Both tasks are performed by the drive if the MMC defined write modes for data and audio are used. > Gallois Fields have size p^m where p is a prime (in our case, 2). ... and weird arithmentics (at least with p=2). Plus is minus, logarithms are exact, powers of x behave like elements of modulo prime groups. (I seem to have backed out of algebra just before finite fields became topic.) > I admit that I'm shooting from the hip here. Good shot. The only thing that i have to amend is that the road via Fourier turned out to be a diversion. All statements in ECMA-130 Annex A refer already to the finite field aspect of Reed-Solomon. (I did not have to learn how frequencies and finite fields are related. It has to be expected that there is funny arithmetics, too.) Have a nice day :) Thomas -- To UNSUBSCRIBE, email to [email protected] with a subject of "unsubscribe". Trouble? Contact [email protected]
