Capture or play back audio with the specified sample
format. Specify one of u8, s16le,
s16be, s32le, s32be,
float32le, float32be, ulaw,
alaw, s32le, s32be,
s24le, s24be, s24-32le,
s24-32be. Depending on the endianess of the CPU the
formats s16ne, s16re, s32ne,
s32re, float32ne, float32re,
s32ne, s32re, s24ne,
s24re, s24-32ne, s24-32re (for
native, resp. reverse endian) are available as aliases. Defaults
to s16ne.