static void set_sdp_ext()
{
	u32 i, j;
	for (i=0; i<nb_sdp_ex; i++) {
		if (sdp_lines[i].trackID) {
			u32 track = gf_isom_get_track_by_id(file, sdp_lines[i].trackID);
			if (gf_isom_get_media_type(file, track)!=GF_ISOM_MEDIA_HINT) {
				s32 ref_count;
				u32 k, count = gf_isom_get_track_count(file);
				for (j=0; j<count; j++) {
					if (gf_isom_get_media_type(file, j+1)!=GF_ISOM_MEDIA_HINT) continue;
					ref_count = gf_isom_get_reference_count(file, j+1, GF_ISOM_REF_HINT);
					if (ref_count<0) continue;
					for (k=0; k<(u32) ref_count; k++) {
						u32 refTk;
						if (gf_isom_get_reference(file, j+1, GF_ISOM_REF_HINT, k+1, &refTk)) continue;
						if (refTk==track) {
							track = j+1;
							j=count;
							break;
						}
					}
				}
			}
			gf_isom_sdp_add_track_line(file, track, sdp_lines[i].line);
			do_save = GF_TRUE;
		} else {
			gf_isom_sdp_add_line(file, sdp_lines[i].line);
			do_save = GF_TRUE;
		}
	}
}