add an API so that the number of steps required for a translation path can be acquired

don't transcode via SLINEAR when the option is enabled but there is a direct path from the source to the destination


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@20962 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channel.c

@@ -2744,8 +2744,9 @@ int ast_channel_make_compatible(struct ast_channel *chan, struct ast_channel *pe
 
 	/* if the best path is not 'pass through', then
 	   transcoding is needed; if desired, force transcode path
-	   to use SLINEAR between channels */
-	if ((src != dst) && ast_opt_transcode_via_slin)
+	   to use SLINEAR between channels, but only if there is
+	   no direct conversion available */
+	if ((src != dst) && ast_opt_transcode_via_slin && ast_translate_path_steps(dst, src))
 		dst = AST_FORMAT_SLINEAR;
 	if (ast_set_read_format(chan, dst) < 0) {
 		ast_log(LOG_WARNING, "Unable to set read format on channel %s to %d\n", chan->name, dst);
@@ -2763,10 +2764,12 @@ int ast_channel_make_compatible(struct ast_channel *chan, struct ast_channel *pe
 		ast_log(LOG_WARNING, "No path to translate from %s(%d) to %s(%d)\n", peer->name, src, chan->name, dst);
 		return -1;
 	}
+
 	/* if the best path is not 'pass through', then
 	   transcoding is needed; if desired, force transcode path
-	   to use SLINEAR between channels */
-	if ((src != dst) && ast_opt_transcode_via_slin)
+	   to use SLINEAR between channels, but only if there is
+	   no direct conversion available */
+	if ((src != dst) && ast_opt_transcode_via_slin && ast_translate_path_steps(dst, src))
 		dst = AST_FORMAT_SLINEAR;
 	if (ast_set_read_format(peer, dst) < 0) {
 		ast_log(LOG_WARNING, "Unable to set read format on channel %s to %d\n", peer->name, dst);

include/asterisk/translate.h

@@ -1,7 +1,7 @@
 /*
  * Asterisk -- An open source telephony toolkit.
  *
- * Copyright (C) 1999 - 2005, Digium, Inc.
+ * Copyright (C) 1999 - 2006, Digium, Inc.
  *
  * Mark Spencer <markster@digium.com>
  *
@@ -145,7 +145,7 @@ struct ast_trans_pvt;
  * \brief Register a translator
  * \param t populated ast_translator structure
  * This registers a codec translator with asterisk
- * Returns 0 on success, -1 on failure
+ * \return 0 on success, -1 on failure
  */
 int ast_register_translator(struct ast_translator *t, void *module);
 
@@ -153,7 +153,7 @@ int ast_register_translator(struct ast_translator *t, void *module);
  * \brief Unregister a translator
  * \param t translator to unregister
  * Unregisters the given tranlator
- * Returns 0 on success, -1 on failure
+ * \return 0 on success, -1 on failure
  */
 int ast_unregister_translator(struct ast_translator *t);
 
@@ -171,7 +171,7 @@ int ast_translator_best_choice(int *dsts, int *srcs);
  * \param dest destination format
  * \param source source format
  * Build a path (possibly NULL) from source to dest 
- * Returns ast_trans_pvt on success, NULL on failure
+ * \return ast_trans_pvt on success, NULL on failure
  * */
 struct ast_trans_pvt *ast_translator_build_path(int dest, int source);
 
@@ -189,10 +189,18 @@ void ast_translator_free_path(struct ast_trans_pvt *tr);
  * \param consume Whether or not to free the original frame
  * Apply an input frame into the translator and receive zero or one output frames.  Consume
  * determines whether the original frame should be freed
- * Returns an ast_frame of the new translation format on success, NULL on failure
+ * \return an ast_frame of the new translation format on success, NULL on failure
  */
 struct ast_frame *ast_translate(struct ast_trans_pvt *tr, struct ast_frame *f, int consume);
 
+/*!
+ * \brief Returns the number of steps required to convert from 'src' to 'dest'.
+ * \param dest Destination format
+ * \param src Source format
+ * \return the number of translation steps required, or -1 if no path is available
+ */
+unsigned int ast_translate_path_steps(unsigned int dest, unsigned int src);
+
 #if defined(__cplusplus) || defined(c_plusplus)
 }
 #endif

translate.c

@@ -62,6 +62,8 @@ struct translator_path {
  * indicates the total cost of translation and the first step.
  * The full path can be reconstricted iterating on the matrix
  * until step->dstfmt == desired_format.
+ *
+ * Array indexes are 'src' and 'dest', in that order.
  */
 static struct translator_path tr_matrix[MAX_FORMAT][MAX_FORMAT];
 
@@ -651,3 +653,11 @@ int ast_translator_best_choice(int *dst, int *srcs)
 		return best;
 	}
 }
+
+unsigned int ast_translate_path_steps(unsigned int dest, unsigned int src)
+{
+	if (!tr_matrix[src][dest].step)
+		return -1;
+	else
+		return tr_matrix[src][dest].multistep;
+}