ff_guid_str_buf 158 libavcodec/mf_utils.h char *ff_guid_str_buf(char *buf, size_t buf_size, const GUID *guid); ff_guid_str_buf 159 libavcodec/mf_utils.h #define ff_guid_str(guid) ff_guid_str_buf((char[80]){0}, 80, guid)