+/**
+ * Extract a key-value pair from the beginning of a string.
+ *
+ * @param ropts pointer to the options string, will be updated to
+ * point to the rest of the string (one of the pairs_sep
+ * or the final NUL)
+ * @param key_val_sep a 0-terminated list of characters used to separate
+ * key from value, for example '='
+ * @param pairs_sep a 0-terminated list of characters used to separate
+ * two pairs from each other, for example ':' or ','
+ * @param flags flags; see the AV_OPT_FLAG_* values below
+ * @param rkey parsed key; must be freed using av_free()
+ * @param rval parsed value; must be freed using av_free()
+ *
+ * @return >=0 for success, or a negative value corresponding to an
+ * AVERROR code in case of error; in particular:
+ * AVERROR(EINVAL) if no key is present
+ *
+ */
+int av_opt_get_key_value(const char **ropts,
+ const char *key_val_sep, const char *pairs_sep,
+ unsigned flags,
+ char **rkey, char **rval);
+
+enum {
+
+ /**
+ * Accept to parse a value without a key; the key will then be returned
+ * as NULL.
+ */
+ AV_OPT_FLAG_IMPLICIT_KEY = 1,
+};
+