Now, does anyone have any pointers on how to convert from mono to stereo?

Erm... Just output the same sample twice .

Each sample is one 16-bit integer for one channel. For stereo, just output the same 16-bit integer twice in a row (for left and right channel).

For the sample rate conversion, from 11KHz to 22KHz or 44KHz is very easy as you only need to output the same sample either two or four times, as they are multiples. 8KHz is more difficulty as you'd need to filter it upwards, thus more expensive.

For instance, converting 11KHz mono sound to 44KHz stereo sound, you just output the same sample 8 times (x 4 for sample rate conversion x 2 for stereo).

Kim