From another thread in this Fascinate General forum (which has a link to the file)
You have to put hwcodec.apk in /system /apps
And also get the system tools you want. For instance for audiotuning you need audiotuning.apk
I couldn't find a link for audiotuning.apk but you can pull it out of a full ROM (not super clean)
That's about all I know about it and that is the only apk I know about for using with hwcodec.