Oops, I hope I didn't fail to respond, Joe!.. Sorry if I did. I try very hard to respond to every detail somebody mentions, because I hate it when people don't answer my questions.
Essentially, I'll use 12 bit conversion, because why not, of course ! I have to use the machine word size anyway, which would be 32 bit, and the SAR converts are fast enough in the ARMs, so there's no reason not to.
Secondly, there's no need for a codec: I'll be converting, buffering, processing, and outputting raw audio, not storing anything, so there's no need to encode anything.
Hope I didn't miss anything. Please feel free to continue to engage on this; the more input, the more encouraged I am to do it, and the better it will be in the end.