+ * Decode a base64-encoded string.
+ *
+ * @param out buffer for decoded data
+ * @param in null-terminated input string
+ * @param out_size size in bytes of the out buffer, must be at
+ * least 3/4 of the length of in
+ * @return number of bytes written, or a negative value in case of
+ * invalid input
+ */
+int av_base64_decode(uint8_t *out, const char *in, int out_size);
+
+/**
+ * Encode data to base64 and null-terminate.
+ *
+ * @param out buffer for encoded data
+ * @param out_size size in bytes of the output buffer, must be at
+ * least AV_BASE64_SIZE(in_size)
+ * @param in_size size in bytes of the 'in' buffer
+ * @return 'out' or NULL in case of error