FRAME_TYPE_B       74 libavfilter/vf_codecview.c         CONST("bf", "B-frames", FRAME_TYPE_B, "frame_type"),
FRAME_TYPE_B      252 libavfilter/vf_codecview.c             const int is_bframe = (s->frame_type & FRAME_TYPE_B) && frame->pict_type == AV_PICTURE_TYPE_B;