avfilter_get_class 3256 fftools/ffmpeg_opt.c         show_help_children(avfilter_get_class(), AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_FILTERING_PARAM);
avfilter_get_class 3657 fftools/ffplay.c     show_help_children(avfilter_get_class(), AV_OPT_FLAG_FILTERING_PARAM);
avfilter_get_class  807 libavfilter/avfilter.h const AVClass *avfilter_get_class(void);