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

include/asterisk/format_cache.h

@@ -223,6 +223,14 @@ extern struct ast_format *ast_format_t140_red;
  */
 extern struct ast_format *ast_format_none;
 
+/*!
+ * \brief Built-in SILK format.
+ */
+extern struct ast_format *ast_format_silk8;
+extern struct ast_format *ast_format_silk12;
+extern struct ast_format *ast_format_silk16;
+extern struct ast_format *ast_format_silk24;
+
 /*!
  * \brief Initialize format cache support within the core.
  *

main/codec_builtin.c

@@ -772,6 +772,65 @@ static struct ast_codec t140 = {
 	.type = AST_MEDIA_TYPE_TEXT,
 };
 
+static int silk_samples(struct ast_frame *frame)
+{
+	/* XXX This is likely not at all what's intended from this callback. However,
+	 * since SILK is variable bit rate, I have no idea how to take a frame of data
+	 * and determine the number of samples present. Instead, we base this on the
+	 * sample rate of the codec and the expected number of samples to receive in 20ms.
+	 * In testing, this has worked just fine.
+	 */
+	return ast_format_get_sample_rate(frame->subclass.format) / 50;
+}
+
+static struct ast_codec silk8 = {
+	.name = "silk",
+	.description = "SILK Codec (8 KHz)",
+	.type = AST_MEDIA_TYPE_AUDIO,
+	.sample_rate = 8000,
+	.minimum_ms = 20,
+	.maximum_ms = 100,
+	.default_ms = 20,
+	.minimum_bytes = 160,
+	.samples_count = silk_samples
+};
+
+static struct ast_codec silk12 = {
+	.name = "silk",
+	.description = "SILK Codec (12 KHz)",
+	.type = AST_MEDIA_TYPE_AUDIO,
+	.sample_rate = 12000,
+	.minimum_ms = 20,
+	.maximum_ms = 100,
+	.default_ms = 20,
+	.minimum_bytes = 240,
+	.samples_count = silk_samples
+};
+
+static struct ast_codec silk16 = {
+	.name = "silk",
+	.description = "SILK Codec (16 KHz)",
+	.type = AST_MEDIA_TYPE_AUDIO,
+	.sample_rate = 16000,
+	.minimum_ms = 20,
+	.maximum_ms = 100,
+	.default_ms = 20,
+	.minimum_bytes = 320,
+	.samples_count = silk_samples
+};
+
+static struct ast_codec silk24 = {
+	.name = "silk",
+	.description = "SILK Codec (24 KHz)",
+	.type = AST_MEDIA_TYPE_AUDIO,
+	.sample_rate = 24000,
+	.minimum_ms = 20,
+	.maximum_ms = 100,
+	.default_ms = 20,
+	.minimum_bytes = 480,
+	.samples_count = silk_samples
+};
+
 #define CODEC_REGISTER_AND_CACHE(codec) \
 	({ \
 		int __res_ ## __LINE__ = 0; \
@@ -843,6 +902,10 @@ int ast_codec_builtin_init(void)
 	res |= CODEC_REGISTER_AND_CACHE(t140red);
 	res |= CODEC_REGISTER_AND_CACHE(t140);
 	res |= CODEC_REGISTER_AND_CACHE(none);
+	res |= CODEC_REGISTER_AND_CACHE_NAMED("silk8", silk8);
+	res |= CODEC_REGISTER_AND_CACHE_NAMED("silk12", silk12);
+	res |= CODEC_REGISTER_AND_CACHE_NAMED("silk16", silk16);
+	res |= CODEC_REGISTER_AND_CACHE_NAMED("silk24", silk24);
 
 	return res;
 }

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);
 	}
 }
 

main/rtp_engine.c

@@ -2690,6 +2690,11 @@ int ast_rtp_engine_init(void)
 	/* Opus and VP8 */
 	set_next_mime_type(ast_format_opus, 0,  "audio", "opus", 48000);
 	set_next_mime_type(ast_format_vp8, 0,  "video", "VP8", 90000);
+	/* DA SILK */
+	set_next_mime_type(ast_format_silk8, 0, "audio", "silk", 8000);
+	set_next_mime_type(ast_format_silk12, 0, "audio", "silk", 12000);
+	set_next_mime_type(ast_format_silk16, 0, "audio", "silk", 16000);
+	set_next_mime_type(ast_format_silk24, 0, "audio", "silk", 24000);
 
 	/* Define the static rtp payload mappings */
 	add_static_payload(0, ast_format_ulaw, 0);
@@ -2743,6 +2748,11 @@ int ast_rtp_engine_init(void)
 	add_static_payload(100, ast_format_vp8, 0);
 	add_static_payload(107, ast_format_opus, 0);
 
+	add_static_payload(108, ast_format_silk8, 0);
+	add_static_payload(109, ast_format_silk12, 0);
+	add_static_payload(113, ast_format_silk16, 0);
+	add_static_payload(114, ast_format_silk24, 0);
+
 	return 0;
 }
 

res/res_format_attr_silk.c

@@ -40,7 +40,6 @@ ASTERISK_REGISTER_FILE()
  * \note The only attribute that affects compatibility here is the sample rate.
  */
 struct silk_attr {
-	unsigned int samplerate;
 	unsigned int maxbitrate;
 	unsigned int dtx;
 	unsigned int fec;
@@ -54,10 +53,15 @@ static void silk_destroy(struct ast_format *format)
 	ast_free(attr);
 }
 
+static void attr_init(struct silk_attr *attr)
+{
+	memset(attr, 0, sizeof(*attr));
+}
+
 static int silk_clone(const struct ast_format *src, struct ast_format *dst)
 {
 	struct silk_attr *original = ast_format_get_attribute_data(src);
-	struct silk_attr *attr = ast_calloc(1, sizeof(*attr));
+	struct silk_attr *attr = ast_malloc(sizeof(*attr));
 
 	if (!attr) {
 		return -1;
@@ -65,6 +69,8 @@ static int silk_clone(const struct ast_format *src, struct ast_format *dst)
 
 	if (original) {
 		*attr = *original;
+	} else {
+		attr_init(attr);
 	}
 
 	ast_format_set_attribute_data(dst, attr);
@@ -109,17 +115,17 @@ static void silk_generate_sdp_fmtp(const struct ast_format *format, unsigned int
 		ast_str_append(str, 0, "a=fmtp:%u maxaveragebitrate=%u\r\n", payload, attr->maxbitrate);
 	}
 
+	if (attr->dtx) {
 		ast_str_append(str, 0, "a=fmtp:%u usedtx=%u\r\n", payload, attr->dtx);
+	}
+	if (attr->fec) {
 		ast_str_append(str, 0, "a=fmtp:%u useinbandfec=%u\r\n", payload, attr->fec);
 	}
+}
 
 static enum ast_format_cmp_res silk_cmp(const struct ast_format *format1, const struct ast_format *format2)
 {
-	struct silk_attr *attr1 = ast_format_get_attribute_data(format1);
-	struct silk_attr *attr2 = ast_format_get_attribute_data(format2);
-
-	if (((!attr1 || !attr1->samplerate) && (!attr2 || !attr2->samplerate)) ||
-		(attr1->samplerate == attr2->samplerate)) {
+	if (ast_format_get_sample_rate(format1) == ast_format_get_sample_rate(format2)) {
 		return AST_FORMAT_CMP_EQUAL;
 	}
 
@@ -130,13 +136,10 @@ static struct ast_format *silk_getjoint(const struct ast_format *format1, const
 {
 	struct silk_attr *attr1 = ast_format_get_attribute_data(format1);
 	struct silk_attr *attr2 = ast_format_get_attribute_data(format2);
-	unsigned int samplerate;
 	struct ast_format *jointformat;
 	struct silk_attr *attr_res;
 
-	samplerate = attr1->samplerate & attr2->samplerate;
-	/* sample rate is the only attribute that has any bearing on if joint capabilities exist or not */
-	if (samplerate) {
+	if (ast_format_get_sample_rate(format1) != ast_format_get_sample_rate(format2)) {
 		return NULL;
 	}
 
@@ -145,8 +148,10 @@ static struct ast_format *silk_getjoint(const struct ast_format *format1, const
 		return NULL;
 	}
 	attr_res = ast_format_get_attribute_data(jointformat);
-	attr_res->samplerate = samplerate;
 
+	if (!attr1 || !attr2) {
+		attr_init(attr_res);
+	} else {
 		/* Take the lowest max bitrate */
 		attr_res->maxbitrate = MIN(attr1->maxbitrate, attr2->maxbitrate);
 
@@ -161,6 +166,7 @@ static struct ast_format *silk_getjoint(const struct ast_format *format1, const
 		/* Use the maximum packetloss percentage between the two attributes. This affects how
 		 * much redundancy is used in the FEC. */
 		attr_res->packetloss_percentage = MAX(attr1->packetloss_percentage, attr2->packetloss_percentage);
+	}
 
 	return jointformat;
 }
@@ -183,9 +189,7 @@ static struct ast_format *silk_set(const struct ast_format *format, const char *
 	}
 	attr = ast_format_get_attribute_data(cloned);
 
-	if (!strcasecmp(name, "sample_rate")) {
-		attr->samplerate = val;
-	} else if (!strcasecmp(name, "max_bitrate")) {
+	if (!strcasecmp(name, "max_bitrate")) {
 		attr->maxbitrate = val;
 	} else if (!strcasecmp(name, "dtx")) {
 		attr->dtx = val;
@@ -205,9 +209,7 @@ static const void *silk_get(const struct ast_format *format, const char *name)
 	struct silk_attr *attr = ast_format_get_attribute_data(format);
 	unsigned int *val;
 
-	if (!strcasecmp(name, "sample_rate")) {
-		val = &attr->samplerate;
-	} else if (!strcasecmp(name, "max_bitrate")) {
+	if (!strcasecmp(name, "max_bitrate")) {
 		val = &attr->maxbitrate;
 	} else if (!strcasecmp(name, "dtx")) {
 		val = &attr->dtx;