MODE_BFF           48 libavfilter/vf_interlace.c         AV_OPT_TYPE_CONST, {.i64 = MODE_BFF }, INT_MIN, INT_MAX, .flags = V, .unit = "scan" },
MODE_BFF           49 libavfilter/vf_setfield.c     {"bff",  "mark as bottom-field-first", 0, AV_OPT_TYPE_CONST, {.i64=MODE_BFF},  INT_MIN, INT_MAX, FLAGS, "mode"},