This function returns whether or not the current device supports some or all of the EFX features. EFX is fairly new extension to OpenAL that allows advanced DSP (Ditigal signal processing) effects or filters to be performed on sounds. Many older cards (within the last 5 years, or more if your lucky) will generally support EFX reverb and low pass filtering via the generic software device in OpenAL. Older Sound Blaster cards may also support some or all of the EFX features through emulation, if their drivers support it.
Newer Sound cards such as Sound Blaster X-Fi series will support most, if not all of the EFX features.
