MODE_DROP_EVEN     43 libavfilter/vf_tinterlace.c     {"drop_even",         "drop even fields",                             0, AV_OPT_TYPE_CONST, {.i64=MODE_DROP_EVEN},         INT_MIN, INT_MAX, FLAGS, "mode"},
MODE_DROP_EVEN    282 libavfilter/vf_tinterlace.c     case MODE_DROP_EVEN: /* only output odd  frames, even frames are dropped; height unchanged, half framerate */
MODE_DROP_EVEN    283 libavfilter/vf_tinterlace.c         out = av_frame_clone(tinterlace->mode == MODE_DROP_EVEN ? cur : next);