av_opt_set_dict_val 1451 libavformat/utils.c         av_opt_set_dict_val(s, "metadata", NULL, AV_OPT_SEARCH_CHILDREN);
av_opt_set_dict_val  735 libavutil/opt.h int av_opt_set_dict_val(void *obj, const char *name, const AVDictionary *val, int search_flags);