Update support for SILK format.

This commit adds scaffolding in order to support the SILK audio format
on calls. Roughly, this is what is added:

* Cached silk formats. One for each possible sample rate.
* ast_codec structures for each possible sample rate.
* RTP payload mappings for "SILK".

In addition, this change overhauls the res_format_attr_silk file in the
following ways:

* The "samplerate" attribute is scrapped. That's native to the format.
* There are far more checks to ensure that attributes have been
  allocated before attempting to reference them.
* We do not SDP fmtp lines for attributes set to 0.

These changes make way to be able to install a codec_silk module and
have it actually work. It also should allow for passthrough silk calls
in Asterisk.

Change-Id: Ieeb39c95a9fecc9246bcfd3c45a6c9b51c59380e

1 files changed, 20 insertions, 0 deletions

diff --git a/main/format_cache.c b/main/format_cache.c
index def795c9d..b4d426092 100644
--- a/main/format_cache.c
+++ b/main/format_cache.c
@@ -232,6 +232,14 @@ struct ast_format *ast_format_t140_red;
  */
 struct ast_format *ast_format_none;
 
+/*!
+ * \brief Built-in "silk" format
+ */
+struct ast_format *ast_format_silk8;
+struct ast_format *ast_format_silk12;
+struct ast_format *ast_format_silk16;
+struct ast_format *ast_format_silk24;
+
 /*! \brief Number of buckets to use for the media format cache (should be prime for performance reasons) */
 #define CACHE_BUCKETS 53
 
@@ -331,6 +339,10 @@ static void format_cache_shutdown(void)
 	ao2_replace(ast_format_t140_red, NULL);
 	ao2_replace(ast_format_t140, NULL);
 	ao2_replace(ast_format_none, NULL);
+	ao2_replace(ast_format_silk8, NULL);
+	ao2_replace(ast_format_silk12, NULL);
+	ao2_replace(ast_format_silk16, NULL);
+	ao2_replace(ast_format_silk24, NULL);
 }
 
 int ast_format_cache_init(void)
@@ -426,6 +438,14 @@ static void set_cached_format(const char *name, struct ast_format *format)
 		ao2_replace(ast_format_t140, format);
 	} else if (!strcmp(name, "none")) {
 		ao2_replace(ast_format_none, format);
+	} else if (!strcmp(name, "silk8")) {
+		ao2_replace(ast_format_silk8, format);
+	} else if (!strcmp(name, "silk12")) {
+		ao2_replace(ast_format_silk12, format);
+	} else if (!strcmp(name, "silk16")) {
+		ao2_replace(ast_format_silk16, format);
+	} else if (!strcmp(name, "silk24")) {
+		ao2_replace(ast_format_silk24, format);
 	}
 }