AMR: Add function to convert between bw-effient and octet aligned mode
RFC3267 specifies two framing modes for AMR packets. An octet aligned
mode is specified where all fields of the AMR packets are aligned to
octet boundaries. The second framing mode is the bandwith efficient mode
where the fields are directly packed one after another.
- add paring/generation functions for related SDP fmtp parameters
- add conversion function to convert AMR payload
Depends: libosmo-netif I5b5a0fa644d8dbb1f04f9d7e35312683c7b3d196
Change-Id: I622c01874b25f5049d4f59eb8157e0ea3cbe16ba
Related: OS#3807
diff --git a/src/libosmo-mgcp/mgcp_network.c b/src/libosmo-mgcp/mgcp_network.c
index e4fd7c0..2c6c571 100644
--- a/src/libosmo-mgcp/mgcp_network.c
+++ b/src/libosmo-mgcp/mgcp_network.c
@@ -34,6 +34,7 @@
#include <osmocom/core/socket.h>
#include <osmocom/core/byteswap.h>
#include <osmocom/netif/rtp.h>
+#include <osmocom/netif/amr.h>
#include <osmocom/mgcp/mgcp.h>
#include <osmocom/mgcp/mgcp_common.h>
#include <osmocom/mgcp/mgcp_internal.h>
@@ -684,6 +685,86 @@
}
}
+/* For AMR RTP two framing modes are defined RFC3267. There is a bandwith
+ * efficient encoding scheme where all fields are packed together one after
+ * another and an octet aligned mode where all fields are aligned to octet
+ * boundaries. This function is used to convert between the two modes */
+static int amr_oa_bwe_convert(struct mgcp_endpoint *endp, char *data, int *len,
+ bool target_is_oa)
+{
+ /* NOTE: *data has an overall length of RTP_BUF_SIZE, so there is
+ * plenty of space available to store the slightly larger, converted
+ * data */
+
+ struct rtp_hdr *rtp_hdr;
+ unsigned int payload_len;
+ int rc;
+
+ OSMO_ASSERT(*len >= sizeof(struct rtp_hdr));
+ rtp_hdr = (struct rtp_hdr *)data;
+
+ payload_len = *len - sizeof(struct rtp_hdr);
+
+ if (osmo_amr_is_oa(rtp_hdr->data, payload_len)) {
+ if (!target_is_oa)
+ /* Input data is oa an target format is bwe
+ * ==> convert */
+ rc = osmo_amr_oa_to_bwe(rtp_hdr->data, payload_len);
+ else
+ /* Input data is already bew, but we accept it anyway
+ * ==> no conversion needed */
+ rc = payload_len;
+ } else {
+ if (target_is_oa)
+ /* Input data is bwe an target format is oa
+ * ==> convert */
+ rc = osmo_amr_bwe_to_oa(rtp_hdr->data, payload_len,
+ RTP_BUF_SIZE);
+ else
+ /* Input data is already oa, but we accept it anyway
+ * ==> no conversion needed */
+ rc = payload_len;
+ }
+ if (rc < 0) {
+ LOGP(DRTP, LOGL_ERROR,
+ "endpoint:0x%x AMR RTP packet conversion failed\n",
+ ENDPOINT_NUMBER(endp));
+ return -EINVAL;
+ }
+
+ *len = rc + sizeof(struct rtp_hdr);
+
+ return 0;
+}
+
+/* Check if a conversion between octet-aligned and bandwith-efficient mode is
+ * indicated. */
+static bool amr_oa_bwe_convert_indicated(struct mgcp_rtp_codec *codec)
+{
+ if (codec->param_present == false)
+ return false;
+ if (!codec->param.amr_octet_aligned_present)
+ return false;
+ if (strcmp(codec->subtype_name, "AMR") != 0)
+ return false;
+ return true;
+}
+
+
+/* Check if a given RTP with AMR payload for octet-aligned mode */
+static bool amr_oa_check(char *data, int len)
+{
+ struct rtp_hdr *rtp_hdr;
+ unsigned int payload_len;
+
+ OSMO_ASSERT(len >= sizeof(struct rtp_hdr));
+ rtp_hdr = (struct rtp_hdr *)data;
+
+ payload_len = len - sizeof(struct rtp_hdr);
+
+ return osmo_amr_is_oa(rtp_hdr->data, payload_len);
+}
+
/* Forward data to a debug tap. This is debug function that is intended for
* debugging the voice traffic with tools like gstreamer */
static void forward_data(int fd, struct mgcp_rtp_tap *tap, const char *buf,
@@ -792,7 +873,11 @@
mgcp_patch_and_count(endp, rtp_state, rtp_end,
addr, buf, buflen);
- if (rtp_end->rfc5993_hr_convert
+ if (amr_oa_bwe_convert_indicated(conn_dst->end.codec)) {
+ amr_oa_bwe_convert(endp, buf, &buflen,
+ conn_dst->end.codec->param.amr_octet_aligned);
+ }
+ else if (rtp_end->rfc5993_hr_convert
&& strcmp(conn_src->end.codec->subtype_name,
"GSM-HR-08") == 0)
rfc5993_hr_convert(endp, buf, &buflen);
@@ -1302,6 +1387,15 @@
len, conn_src, conn_src);
}
+ /* If AMR is configured for the ingress connection a conversion of the
+ * framing mode (octet-aligned vs. bandwith-efficient is explicitly
+ * define, then we check if the incoming payload matches that
+ * expectation. */
+ if (amr_oa_bwe_convert_indicated(conn_src->end.codec)) {
+ if (amr_oa_check(buf, len) != conn_src->end.codec->param.amr_octet_aligned)
+ return -1;
+ }
+
/* Execute endpoint specific implementation that handles the
* dispatching of the RTP data */
return endp->type->dispatch_rtp_cb(proto, &addr, buf, len,