# Reed solomon question

Started by August 7, 2006
```Hi All,
I want to use the Reed Solomon (255,247) codedec from :
http://www.humanistic.org/~hendrik/reed-solomon/index.html
My question is about the polynomial generator that is used to build the
encoder of RS (255,247) codec.
as the literature says, g(x) is calculated like this :
g(x) = (x- a^b)(x- a^(b +1))(x- a^(b+2)).........(x- a^(b+2t-1 ))
b= 1  : for narrow-sens RS codes, but in this codec there is no way to
know the value of "b". which value can we choose for  (255,247)
codedec?
also:
for calculating the syndrome we have Sj= r(a^i). Which "i" to choose?
the same b+2*j-1 (j=0..t) used to calculate g(x)?
Best regards.

```
```> which value can we choose for  (255,247) codedec?
Choose any integer for 'b' ... though, usually there is a smartest
choice.
For example, a smart 'b' would reduce the hardware implementation.

> for calculating the syndrome we have Sj= r(a^i). Which "i" to choose?
> the same b+2*j-1 (j=0..t) used to calculate g(x)?

You must evaluate the received polynomial at the same roots of the
generator polynomial.

cw

```