How to Write Stereo Codec(ACM DRIVER)?

Hi,
Currently i am involved in a project where i have to write the speech codec.
I took the sample from WDK (mmedia/Gsm610) ,and i am able to create my own
codec which is using different compression algorithm (ACELP). The problem is
,the sample provided in WDK supports MONO playback and i am able to play back
the MONO recording of my own speech recording. now i would like to introduce
stereo play back for my codec and i need a sample code for , How to write
stereo codec?. since i already have a working version of my codec for MONO ,i
just need a sample for how to do the same?
Any guidance on this is greatly appreciated.
Regards
Prakash Samiyappan