* If a and b do not share any common formats, neither is modified, and NULL
* is returned.
*/
-AVFilterFormats *ff_merge_formats(AVFilterFormats *a, AVFilterFormats *b);
+AVFilterFormats *ff_merge_formats(AVFilterFormats *a, AVFilterFormats *b,
+ enum AVMediaType type);
/**
* Add *ref as a new reference to formats.