-void show_help_options(const OptionDef *options, const char *msg, int mask, int value);
+/**
+ * Print help for all options matching specified flags.
+ *
+ * @param options a list of options
+ * @param msg title of this group. Only printed if at least one option matches.
+ * @param req_flags print only options which have all those flags set.
+ * @param rej_flags don't print options which have any of those flags set.
+ * @param alt_flags print only options that have at least one of those flags set
+ */
+void show_help_options(const OptionDef *options, const char *msg, int req_flags,
+ int rej_flags, int alt_flags);
+
+/**
+ * Show help for all options with given flags in class and all its
+ * children.
+ */
+void show_help_children(const AVClass *class, int flags);
+
+/**
+ * Per-avtool specific help handler. Implemented in each
+ * avtool, called by show_help().
+ */
+void show_help_default(const char *opt, const char *arg);
+
+/**
+ * Generic -h handler common to all avtools.
+ */
+int show_help(void *optctx, const char *opt, const char *arg);