falconia has uploaded this change for review. (
https://gerrit.osmocom.org/c/libosmo-abis/+/41536?usp=email )
Change subject: amr_trau: add osmo_amrt_fill_with_dhf() function
......................................................................
amr_trau: add osmo_amrt_fill_with_dhf() function
It is useful to have a function that fills struct osmo_amrt_if
with constant DHF bits. In an E1 Abis MGW this function is needed
in order to emit DHFs on Abis DL during initial or prolonged absence
of RTP input; it can also be used in a transcoding CN MGW to emit
DHFs in RTP on AoIP interface during similar conditions of no G.711
input being transcoded or TFO-handled.
Change-Id: Ie085e593d6326072295a8cedf2c2c103883f93d5
---
M include/osmocom/trau/amr_trau.h
M src/Makefile.am
A src/trau/amr_misc.c
3 files changed, 96 insertions(+), 1 deletion(-)
git pull ssh://gerrit.osmocom.org:29418/libosmo-abis refs/changes/36/41536/1
diff --git a/include/osmocom/trau/amr_trau.h b/include/osmocom/trau/amr_trau.h
index 83780e6..9ae0f65 100644
--- a/include/osmocom/trau/amr_trau.h
+++ b/include/osmocom/trau/amr_trau.h
@@ -344,4 +344,6 @@
const struct osmo_amrt_if *fr,
enum osmo_amrt_rtp_format fmt);
+int osmo_amrt_fill_with_dhf(struct osmo_amrt_if *fr, enum osmo_amr_type mode);
+
/*! @} */
diff --git a/src/Makefile.am b/src/Makefile.am
index c3e39b5..6b1fccc 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -52,7 +52,8 @@
-no-undefined \
$(NULL)
libosmotrau_la_LIBADD = $(COMMONLIBS) $(LIBOSMOCODEC_LIBS) $(ORTP_LIBS)
-libosmotrau_la_SOURCES = trau/amr_rtp.c \
+libosmotrau_la_SOURCES = trau/amr_misc.c \
+ trau/amr_rtp.c \
trau/amr_trau.c \
trau/csd_ra2.c \
trau/csd_v110.c \
diff --git a/src/trau/amr_misc.c b/src/trau/amr_misc.c
new file mode 100644
index 0000000..47db8fc
--- /dev/null
+++ b/src/trau/amr_misc.c
@@ -0,0 +1,92 @@
+/*
+ * AMR TRAU interworking facility: miscellaneous functions.
+ *
+ * This code was contributed to Osmocom Cellular Network Infrastructure
+ * project by Mother Mychaela N. Falconia of Themyscira Wireless.
+ * Mother Mychaela's contributions are NOT subject to copyright:
+ * no rights reserved, all rights relinquished.
+ */
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+#include <errno.h>
+
+#include <osmocom/core/bits.h>
+#include <osmocom/core/utils.h>
+#include <osmocom/codec/codec.h>
+#include <osmocom/trau/amr_trau.h>
+
+/*! \addgroup amr_trau
+ * @{
+ */
+
+/*! Fill AMR frame buffer with constant DHF
+ *
+ * \param[out] fr AMR frame buffer in intermediate format of the present
+ * library.
+ * \param[in] mode One of 8 AMR codec modes, AMR_4_75 through AMR_12_2.
+ * \returns 0 if successful, or negative if \ref mode is invalid.
+ *
+ * IMPORTANT NOTE: unlike osmo_amrt_decode_trau_frame() and
+ * osmo_amrt_decode_rtp(), this function does NOT fully fill out
+ * struct osmo_amrt_if - instead it operates as follows:
+ *
+ * - frame_class, cmi, cmi_valid and s_bits are set by this function.
+ *
+ * - Fields related to CMR, RIF, TA+DTXd+TFOE and 3GPP Rel4 TFO configuration
+ * protocol are the responsibility of the application. If they were
+ * already filled before calling this function, they will not be overwritten;
+ * alternatively the application may fill them after calling this function.
+ *
+ * This function is needed for implementation of an MGW that interfaces to
+ * E1 Abis in the place of a TRAU: during prolonged absence of RTP input
+ * (not yet connected through, call on hold etc), the BTS needs to be
+ * supplied with valid traffic other than endless No_Data frames; filling
+ * with constant DHFs, with mode selected per CMR from the BTS/CCU, is
+ * the simplest solution. The resulting effect is also indistinguishable
+ * from a real TRAU operating with G.711 A-law (although not mu-law)
+ * when that G.711 A-law input is pure 0xD5 silence.
+ */
+int osmo_amrt_fill_with_dhf(struct osmo_amrt_if *fr, enum osmo_amr_type mode)
+{
+ const uint16_t *param;
+
+ switch (mode) {
+ case AMR_4_75:
+ param = osmo_amr_dhf_4_75;
+ break;
+ case AMR_5_15:
+ param = osmo_amr_dhf_5_15;
+ break;
+ case AMR_5_90:
+ param = osmo_amr_dhf_5_90;
+ break;
+ case AMR_6_70:
+ param = osmo_amr_dhf_6_70;
+ break;
+ case AMR_7_40:
+ param = osmo_amr_dhf_7_40;
+ break;
+ case AMR_7_95:
+ param = osmo_amr_dhf_7_95;
+ break;
+ case AMR_10_2:
+ param = osmo_amr_dhf_10_2;
+ break;
+ case AMR_12_2:
+ param = osmo_amr_dhf_12_2;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ fr->frame_class = OSMO_AMRT_FC_SPEECH_GOOD;
+ fr->cmi = mode;
+ fr->cmi_valid = true;
+ osmo_amr_param_to_sbits(fr->s_bits, param, mode);
+
+ return 0;
+}
+
+/*! @} */
--
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Gerrit-MessageType: newchange
Gerrit-Project: libosmo-abis
Gerrit-Branch: master
Gerrit-Change-Id: Ie085e593d6326072295a8cedf2c2c103883f93d5
Gerrit-Change-Number: 41536
Gerrit-PatchSet: 1
Gerrit-Owner: falconia <[email protected]>
