minor comments

include/OggFLAC/stream_encoder.h

@@ -374,6 +374,13 @@ FLAC__bool OggFLAC__stream_encoder_set_total_samples_estimate(OggFLAC__StreamEnc
 FLAC__bool OggFLAC__stream_encoder_set_metadata(OggFLAC__StreamEncoder *encoder, FLAC__StreamMetadata **metadata, unsigned num_blocks);
 
 /** Set the write callback.
+ *
+ * \note
+ * Unlike the FLAC stream encoder write callback, the Ogg stream
+ * encoder write callback will be called twice when writing audio
+ * frames; once for the page header, and once for the page body.
+ * When writing the page header, the \a samples argument to the
+ * write callback will be \c 0.
  *
  * \note
  * The callback is mandatory and must be set before initialization.