Set a new pre-amplification value for an equalizer.
    The new equalizer settings are subsequently applied to a media player by invoking
    L{libvlc_media_player_set_equalizer}().
    The supplied amplification value will be clamped to the -20.0 to +20.0 range.
    @param p_equalizer: valid equalizer handle, must not be NULL.
    @param f_preamp: preamp value (-20.0 to 20.0 Hz).
    @return: zero on success, -1 on error.
    @version: LibVLC 2.2.0 or later.

def libvlc_audio_equalizer_set_preamp(p_equalizer, f_preamp):
    '''Set a new pre-amplification value for an equalizer.
    The new equalizer settings are subsequently applied to a media player by invoking
    L{libvlc_media_player_set_equalizer}().
    The supplied amplification value will be clamped to the -20.0 to +20.0 range.
    @param p_equalizer: valid equalizer handle, must not be NULL.
    @param f_preamp: preamp value (-20.0 to 20.0 Hz).
    @return: zero on success, -1 on error.
    @version: LibVLC 2.2.0 or later.
    '''
    f = _Cfunctions.get('libvlc_audio_equalizer_set_preamp', None) or \
        _Cfunction('libvlc_audio_equalizer_set_preamp', ((1,), (1,),), None,
                    ctypes.c_int, ctypes.c_void_p, ctypes.c_float)
    return f(p_equalizer, f_preamp)