This program encodes numeric data using the ABA standard, typically found on
track 2 of magnetic stripe cards.
For more details, see:
http://en.wikipedia.org/wiki/Magnetic_stripe_card

If interest exists, I can add support for IATA.


Requirements:
 - glib-2.0

To build, simply type "make".

The program takes two command line arguments:
ms_enc <data> [output file]

The "output file" is the name of the output file to save the PCM data.  If no
output file is specified, then no data will be saved.
The content is the numeric content to be encoded.


What content can I encode?
For full details, search Google, but I'll provide a very quick overview.

Only numeric content can be encoded, plus a few instruction characters.
Typically, you will stick to numbers and the instruction characters indicating
the beginning and end of the data, and a field separator.

To follow the standard specifically, the data would be as follows:

<SS><ACCOUNT NUM><FS><EXP><DATA><ES>

SS - Start sentinel, indicating beginning of data.  ASCII character ';'
ACCOUNT NUM - Account number of variable length no longer than 19 numeric digits
FS - Field seperator, indicating the end of the account number
EXP - Four digit expiration date of the format YYMM
DATA - Mmisc data (there is a standard, but I don't recall it entirely)
ES - End sentinel, indicating end of data.  ASCII character '?'
LRC - Checksum character, which will be calculated from the rest of the content

The program will warn you if there is no start or end sentinel.
No other checks are performed to see if you're providing valid data.


What format is the data encoded in?
If you specify an output file, data is saved as a raw PCM stream.
The format is S16 LE.  As time is a very relative aspect, there is no set
sample rate.  However, 48khz would work.