+/**
+ * Check if given option is set to its default value.
+ *
+ * Options o must belong to the obj. This function must not be called to check child's options state.
+ * @see av_opt_is_set_to_default_by_name().
+ *
+ * @param obj AVClass object to check option on
+ * @param o option to be checked
+ * @return >0 when option is set to its default,
+ * 0 when option is not set its default,
+ * <0 on error
+ */
+int av_opt_is_set_to_default(void *obj, const AVOption *o);
+
+/**
+ * Check if given option is set to its default value.
+ *
+ * @param obj AVClass object to check option on
+ * @param name option name
+ * @param search_flags combination of AV_OPT_SEARCH_*
+ * @return >0 when option is set to its default,
+ * 0 when option is not set its default,
+ * <0 on error
+ */
+int av_opt_is_set_to_default_by_name(void *obj, const char *name, int search_flags);
+
+
+#define AV_OPT_SERIALIZE_SKIP_DEFAULTS 0x00000001 ///< Serialize options that are not set to default values only.
+#define AV_OPT_SERIALIZE_OPT_FLAGS_EXACT 0x00000002 ///< Serialize options that exactly match opt_flags only.
+
+/**
+ * Serialize object's options.
+ *
+ * Create a string containing object's serialized options.
+ * Such string may be passed back to av_opt_set_from_string() in order to restore option values.
+ * A key/value or pairs separator occurring in the serialized value or
+ * name string are escaped through the av_escape() function.
+ *
+ * @param[in] obj AVClass object to serialize
+ * @param[in] opt_flags serialize options with all the specified flags set (AV_OPT_FLAG)
+ * @param[in] flags combination of AV_OPT_SERIALIZE_* flags
+ * @param[out] buffer Pointer to buffer that will be allocated with string containg serialized options.
+ * Buffer must be freed by the caller when is no longer needed.
+ * @param[in] key_val_sep character used to separate key from value
+ * @param[in] pairs_sep character used to separate two pairs from each other
+ * @return >= 0 on success, negative on error
+ * @warning Separators cannot be neither '\\' nor '\0'. They also cannot be the same.
+ */
+int av_opt_serialize(void *obj, int opt_flags, int flags, char **buffer,
+ const char key_val_sep, const char pairs_sep);