DIR_PREV          414 libavfilter/signature_lookup.c         return DIR_PREV;
DIR_PREV          446 libavfilter/signature_lookup.c                         dir = DIR_PREV;
DIR_PREV          471 libavfilter/signature_lookup.c                 dir = iterate_frame(infos->framerateratio, &a, &b, fcount, &bcount, DIR_PREV);