Function vaQuerySubpictureFormats 

pub unsafe extern "C" fn vaQuerySubpictureFormats(
    dpy: VADisplay,
    format_list: *mut VAImageFormat,
    flags: *mut c_uint,
    num_formats: *mut c_uint,
) -> VAStatus

Query supported subpicture formats The caller must provide a “format_list” array that can hold at least vaMaxNumSubpictureFormats() entries. The flags arrary holds the flag for each format to indicate additional capabilities for that format. The actual number of formats returned in “format_list” is returned in “num_formats”. flags: returned value to indicate addtional capabilities VA_SUBPICTURE_CHROMA_KEYING - supports chroma-keying VA_SUBPICTURE_GLOBAL_ALPHA - supports global alpha VA_SUBPICTURE_DESTINATION_IS_SCREEN_COORD - supports unscaled screen relative subpictures for On Screen Display