If I want to change some sounds, what process should I follow ?

[jptr]

Do you want me to add them in ogg format or should I convert them before ?
I think it won't work well if we don't use the same converter..

[djbe]

Convert your wav files directly to the AAC codec. Converter doesn't matter as long as the right codec is used; do watch out that you're using the right AAC codec: just AAC, or AAC (LC).

Not the high efficiency version (HE-AAC), or the low delay version (LD). Those other versions are either incompatible or use too much processing power (limiting the amount of simultaneously playing sounds).