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; +} + +/*! @} */