Function speex_encode 

pub unsafe extern "C" fn speex_encode(
    state: *mut c_void,
    in_: *mut f32,
    bits: *mut SpeexBits,
) -> c_int

Uses an existing encoder state to encode one frame of speech pointed to by “in”. The encoded bit-stream is saved in “bits”. @param state Encoder state @param in Frame that will be encoded with a +-2^15 range. This data MAY be overwritten by the encoder and should be considered uninitialised after the call. @param bits Bit-stream where the data will be written @return 0 if frame needs not be transmitted (DTX only), 1 otherwise