* For no string, set to an empty string.
* @return The length in bytes.
*/
-int ff_vorbiscomment_length(AVDictionary *m, const char *vendor_string);
+int64_t ff_vorbiscomment_length(AVDictionary *m, const char *vendor_string);
/**
* Write a VorbisComment into a buffer. The buffer, p, must have enough