laforge submitted this change.
E1: add support for AMR in TW-TS-006 enhanced RTP format
AMR speech codec on E1 BTS is currently possible at all only with
tw-e1abis-mgw and not with classic osmo-mgw. This new E1 AMR MGW
support includes all 3 possible RTP formats from the beginning:
RFC 4867 BWE, RFC 4867 OA and TW-TS-006 OAX.
Because TW-TS-006 is non-standard outside of GSM networks
specifically built with Osmocom+ThemWi hybrid stack, use of this
RTP format has to be explicitly requested by the CN via BSSMAP
extension of TW-TS-003, which OsmoBSC already understands.
Add TW-TS-006 to the set of supported RTP extensions with E1 BTS,
joining already supported TW-TS-001 and TW-TS-002.
Change-Id: Icf859ca4975079c91a2f41190da0ce94aa686365
---
M src/osmo-bsc/assignment_fsm.c
M src/osmo-bsc/lchan_rtp_fsm.c
2 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/src/osmo-bsc/assignment_fsm.c b/src/osmo-bsc/assignment_fsm.c
index 4c54632..c5363b8 100644
--- a/src/osmo-bsc/assignment_fsm.c
+++ b/src/osmo-bsc/assignment_fsm.c
@@ -545,7 +545,10 @@
* Note that specific BTS features are needed only for IP-based BTS;
* for E1 BTS no special support is needed from the BTS itself in order
* to enable these RTP extensions, as they are implemented entirely
- * in the BSC-controlled MGW in this case.
+ * in the BSC-controlled MGW in this case. Furthermore, in the case of
+ * E1 BTS with either AMR or CSD, the MGW can be assumed to be tw-e1abis-mgw
+ * or a potential future Osmo-branded copy or derivative thereof,
+ * since classic osmo-mgw supports neither AMR nor CSD with E1 Abis.
*/
static void handle_rtp_extensions(struct gsm_subscriber_connection *conn,
struct gsm_bts *bts)
@@ -562,6 +565,9 @@
(osmo_bts_has_feature(&bts->features, BTS_FEAT_TWTS002) || is_e1_bts(bts)))
accepted_ext |= OSMO_RTP_EXT_TWTS002;
+ if ((requested_ext & OSMO_RTP_EXT_TWTS006) && is_e1_bts(bts))
+ accepted_ext |= OSMO_RTP_EXT_TWTS006;
+
conn->user_plane.rtp_extensions = accepted_ext;
}
diff --git a/src/osmo-bsc/lchan_rtp_fsm.c b/src/osmo-bsc/lchan_rtp_fsm.c
index 8095378..7d80a73 100644
--- a/src/osmo-bsc/lchan_rtp_fsm.c
+++ b/src/osmo-bsc/lchan_rtp_fsm.c
@@ -987,6 +987,18 @@
*/
switch (codec) {
case CODEC_AMR_8000_1:
+ /* Right now AMR with TW-TS-006 is supported only on E1 BTS,
+ * in which case there is no BSS side, only AoIP side.
+ * However, if TW-TS-006 support gets added to IP-native
+ * OsmoBTS in the future, it will strictly require no-alteration
+ * pass-through from the BSC-associated MGW. Therefore,
+ * indicate this format on both sides when it is enabled. */
+ if (lchan->conn->user_plane.rtp_extensions & OSMO_RTP_EXT_TWTS006) {
+ OSMO_STRLCPY_ARRAY(verb_info->ptmap[0].fmtp,
+ "octet-align=1;tw-ts-006=1");
+ break;
+ }
+ /* standard 3GPP/Osmocom/etc operation with RFC 4867 format */
if (bss_side)
amr_oa = 1;
else
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