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osmux: Make sure RTP AMR feed to osmux is in octet-aligned mode

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The Osmux implementation in libosmo-netif expects to work with RTP AMR
in octet-aligned mode. Therefore, if the peer connection received RTP
AMR in bandwidth-efficient mode, we need to convert it to octet-aligned
before feeding the packets to the osmux layer.

Related: SYS#6161
Change-Id: Ifeec44241079f7a31da12745c92bfdc4fb222f3a
This commit is contained in:
Pau Espin Pedrol
2022-10-25 13:52:19 +02:00
parent d1e94c7ac3
commit 377d39122d
3 changed files with 18 additions and 3 deletions
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2
include/osmocom/mgcp/mgcp_network.h
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@@ -183,3 +183,5 @@ void rtpconn_rate_ctr_inc(struct mgcp_conn_rtp *conn_rtp, struct mgcp_endpoint *
int id);
void forward_data_tap(int fd, struct mgcp_rtp_tap *tap, struct msgb *msg);
uint32_t mgcp_get_current_ts(unsigned codec_rate);
int amr_oa_bwe_convert(struct mgcp_endpoint *endp, struct msgb *msg, bool target_is_oa);

13
src/libosmo-mgcp/mgcp_network.c
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@@ -717,11 +717,18 @@ static int rfc5993_hr_convert(struct mgcp_endpoint *endp, struct msgb *msg)
return 0;
}
/* For AMR RTP two framing modes are defined RFC3267. There is a bandwith
/*! Convert msg to AMR RTP framing mode specified by target_is_oa.
* \param[in] endp MGCP Endpoint where this message belongs to (used for logging purposes)
* \param[in] msg Message containing an AMR RTP payload (in octet-aligned or bandwidth-efficient format).
* \param[in] target_is_oa the target framing mode that msg will contain after this function succeeds.
* \returns The size of the new RTP AMR content on success, negative on error.
*
* For AMR RTP two framing modes are defined RFC3267. There is a bandwidth
* 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, struct msgb *msg,
* boundaries. This function is used to convert between the two modes.
*/
int amr_oa_bwe_convert(struct mgcp_endpoint *endp, struct msgb *msg,
bool target_is_oa)
{
/* NOTE: the msgb has an allocated length of RTP_BUF_SIZE, so there is

6
src/libosmo-mgcp/mgcp_osmux.c
View File

@@ -226,6 +226,12 @@ int conn_osmux_send_rtp(struct mgcp_conn_rtp *conn, struct msgb *msg)
if (!msg2)
return -1;
/* Osmux implementation works with AMR OA only, make sure we convert to it if needed: */
if (amr_oa_bwe_convert(conn->conn->endp, msg2, true) < 0) {
LOGPCONN(conn->conn, DOSMUX, LOGL_ERROR,
"Error converting to AMR octet-aligned mode\n");
return -1;
}
while ((ret = osmux_xfrm_input(conn->osmux.in, msg2, conn->osmux.remote_cid)) > 0) {
/* batch full, build and deliver it */