Add notes about embedded ast_frame structs holding a format ref.

mod_format.h: Note ast_filestream.fr holds a format ref.

translate.h: Note ast_trans_pvt.f holds a format ref.

Change-Id: I86bda354d725207b41e08920355d7c31b2d7f749

include/asterisk/mod_format.h

@@ -114,7 +114,11 @@ struct ast_filestream {
 	int lasttimeout;
 	struct ast_channel *owner;
 	FILE *f;
-	struct ast_frame fr;	/*!< frame produced by read, typically */
+	/*!
+	 * \brief frame produced by read, typically
+	 * \note This frame holds a fr.subclass.format ref.
+	 */
+	struct ast_frame fr;
 	char *buf;		/*!< buffer pointed to by ast_frame; */
 	void *_private;	/*!< pointer to private buffer */
 	const char *orig_chan_name;

include/asterisk/translate.h

@@ -208,7 +208,7 @@ struct ast_translator {
  */
 struct ast_trans_pvt {
 	struct ast_translator *t;
-	struct ast_frame f;         /*!< used in frameout */
+	struct ast_frame f;         /*!< used in frameout.  This frame holds a f.subclass.format ref. */
 	int samples;                /*!< samples available in outbuf */
 	/*! \brief actual space used in outbuf */
 	int datalen;