falconia has uploaded this change for review. ( https://gerrit.osmocom.org/c/libosmo-abis/+/38326?usp=email )

Change subject: rtp2trau: add support for EDATA ......................................................................

rtp2trau: add support for EDATA

Change-Id: I538567ac208c89b3fc8f4dc408dc15a813a1272a --- M src/trau/trau_rtp_conv.c 1 file changed, 49 insertions(+), 0 deletions(-)

git pull ssh://gerrit.osmocom.org:29418/libosmo-abis refs/changes/26/38326/1

diff --git a/src/trau/trau_rtp_conv.c b/src/trau/trau_rtp_conv.c index b0bde7d..9bee640 100644 --- a/src/trau/trau_rtp_conv.c +++ b/src/trau/trau_rtp_conv.c @@ -1393,6 +1393,53 @@ return 0; }

+/* + * For 14.4 kbit/s data, we do _not_ forward A-TRAU bit C5 to E-TRAU bit C6 + * like TS 48.020 section 11.1 Note 1 suggests. That spec note says: + * "Bit C5 corresponds to bit C6 of the E-TRAU frame as defined in 3GPP + * TS 48.060." However, while the note says (effectively) that the two + * bits are logically equivalent, it does not prescribe specific forwarding + * rules for implementations. When the BTS looks at bit C6 in TRAU-DL, + * it will want to know whether its TRAU-UL frames were received correctly + * by the TRAU, hence the TRAU-emulating Abis MGW will need to set this bit + * based on UL reception status - but it has nothing to do with the incoming + * RTP stream. Hence we don't forward this "logically equivalent" bit. + */ + +static int rtp2trau_edata(struct osmo_trau_frame *tf, const uint8_t *data, + size_t data_len) +{ + ubit_t atrau_c4; + + tf->type = OSMO_TRAU16_FT_EDATA; + + /* set all C bits to 1s: covers frame type, initial C6 & C7, + * and the remaining unused bits. */ + memset(tf->c_bits, 1, 13); + /* set C6=0: indicate good reception of TRAU-UL frames */ + tf->c_bits[5] = 0; + + if (data_len == RFC4040_RTP_PLEN && + osmo_csd144_from_atrau_ra2(tf->m_bits, tf->d_bits, &atrau_c4, NULL, + data) >= 0) { + /* We got good A-TRAU input. 3GPP specs define the following + * mapping for DL direction only: + * + * E-TRAU bit C7 is set if idle, inverse of A-TRAU bit C4. + * Spec references: TS 48.020 section 11.1, TS 48.060 + * section 6.5.1. */ + tf->c_bits[6] = !atrau_c4; + } else { + /* We did not get good A-TRAU input: generate idle fill. */ + memset(tf->m_bits, 1, 2); + memset(tf->d_bits, 1, 288); + /* C7=1 means idle */ + tf->c_bits[6] = 1; + } + + return 0; +} + static inline bool check_twts001(struct osmo_trau2rtp_state *st) { if (st->rtp_extensions & OSMO_RTP_EXT_TWTS001) @@ -1448,6 +1495,8 @@ return rtp2trau_data_fr(tf, rtp, rtp_len, st->interm_rate_16k); case OSMO_TRAU16_FT_DATA_HR: return rtp2trau_data_hr16(tf, rtp, rtp_len); + case OSMO_TRAU16_FT_EDATA: + return rtp2trau_edata(tf, rtp, rtp_len); case OSMO_TRAU8_SPEECH: return rtp2trau_hr8(tf, rtp, rtp_len); case OSMO_TRAU8_DATA: