The stream must be seekable to get the total. A negative value is
returned if the stream is not seekable.
+=item $of->B<current_link>
+
+Retrieve the index of the current link.
+
+This is the link that produced the data most recently read by
+op_read_float() or its associated functions, or, after a seek, the
+link that the seek target landed in. Reading more data may advance the
+link index (even on the first read after a seek).
+
=item $of->B<bitrate>([I<$link_index>])
Computes the bitrate of the stream (with no arguments), or of an