How to apply Reed-Solomon algorithm using zxing in C#

Question

I want to transmit binary data over a noisy channel.

I read that a good ECC algorithm to detect errors is Reed-Solomon. The problem is i don't understand the input for this algorithm.

here is my naive failed attempt with zxing.net:

int[] toEncode = { 123,232,432};
var gf = GenericGF.AZTEC_DATA_12;
ReedSolomonEncoder rse = new ReedSolomonEncoder(gf);
rse.encode(toEncode, 2);

ReedSolomonDecoder rsd = new ReedSolomonDecoder(gf);
rse.encode(toEncode, 2);

please explain to me the input for the encoder and decoder.

Answer 1

Is this the implementation you are using here: ReedSolomonEncoder.cs?

If so, to encode N integers with M data correction integers, you need to pass an array of length N+M. Your data should be in the first N indices and the codes look to be added at the end in the final M entries.

Also, note the following restriction in the encoder:

Update: a more recent version is here: http://zxingnet.codeplex.com/. Its most recent version of ReedSolomonEncoder.cs does not have this restriction.

This class implements Reed-Solomon encoding schemes used in processing QR codes. A very brief description of Reed Solomon encoding is here: Reed-Solomon Codes.

An encoding choice of "QR_CODE_FIELD_256" (which is probably a reasonable choice for you) means that error correction codes are being generated on byte-sized chunks ("symbols") of your message, which means your maximum message length (data to encode plus error correction codes) is 255 bytes long. If you are sending more data you will need to break it into chunks.

Update 2: Using QR_CODE_FIELD_256, your integers need to be between 0 and 255 as well, so to encode a general byte stream, you need to put each byte into a separate integer in the integer array, pass the int array (plus space for error correction codes) through the encoder, then reconvert to a (larger) byte array. And the reverse for decoding.