Function gstreamer_rtsp_server_sys::gst_rtsp_media_get_rates

pub unsafe extern "C" fn gst_rtsp_media_get_rates(
    media: *mut GstRTSPMedia, 
    rate: *mut c_double, 
    applied_rate: *mut c_double
) -> gboolean

This is supported on crate feature v1_18 only.