[Asterisk-Dev] How to modify data frames?

[MDS]

hi,

I'm a bit new to Asterisk source code, but have successfuly written a 
self-educational app_mytest.c just to get used to Asterisk development.

My new quest is to manipulate raw data frames. Particularly for either 
sound (volume) control, encryption etc..

My question is if I wrote an app_(whatever) how would one grab a channel 
frame, manipulate it's bits and send it off?

I noticed struct ast_frame* ast_read() looked like a candidate. Also the 
variable void*data in ast_frame appears to contain the raw data. How 
would one modify/manipulate this data in the bit level realm?

Am I in the right area? or am I totally off base? 

Thank you for you help.
Mark