[S] Change in libosmocore[master]: codec: new function osmo_hr_sid_reset()

falconia has uploaded this change for review. ( https://gerrit.osmocom.org/c/libosmocore/+/33060 ) Change subject: codec: new function osmo_hr_sid_reset() ...................................................................... codec: new function osmo_hr_sid_reset() If a network element that receives call leg A UL and is responsible for preparing leg B DL receives a GSM-HR SID frame whose SID field is not all 1s but which is marked as valid SID by out-of-band means (TRAU-UL frame control bits or the FT field in RFC 5993 ToC octet), this SID frame should be rejuvenated (SID field reset to all 1s) prior to retransmission on call leg B DL. Provide a function that performs this operation. Related: OS#6036 Change-Id: Iebc0863ffcc3f8f25aeb54d4b14fac0487bc2bbb --- M include/osmocom/codec/codec.h M src/codec/gsm620.c 2 files changed, 48 insertions(+), 0 deletions(-) git pull ssh://gerrit.osmocom.org:29418/libosmocore refs/changes/60/33060/1 diff --git a/include/osmocom/codec/codec.h b/include/osmocom/codec/codec.h index 4dbe129..c5981f8 100644 --- a/include/osmocom/codec/codec.h +++ b/include/osmocom/codec/codec.h @@ -131,6 +131,7 @@ bool osmo_efr_sid_preen(uint8_t *rtp_payload); void osmo_fr_sid_reset(uint8_t *rtp_payload); +void osmo_hr_sid_reset(uint8_t *rtp_payload); void osmo_efr_sid_reset(uint8_t *rtp_payload); int osmo_amr_rtp_enc(uint8_t *payload, uint8_t cmr, enum osmo_amr_type ft, diff --git a/src/codec/gsm620.c b/src/codec/gsm620.c index 4eae514..ef1d3b9 100644 --- a/src/codec/gsm620.c +++ b/src/codec/gsm620.c @@ -21,6 +21,7 @@ #include <stdint.h> #include <stdbool.h> +#include <string.h> #include <osmocom/core/bitvec.h> #include <osmocom/core/utils.h> @@ -285,3 +286,31 @@ return true; } + +/*! Reset the SID field of a potentially corrupted, but still valid GSM-HR + * SID frame in TS 101 318 format to its pristine state (full SID codeword). + * \param[in] rtp_payload Buffer with RTP payload - must be writable! + * + * Per GSM 06.22 section 5.3, a freshly minted SID frame consists of 33 bits + * of comfort noise parameters and 79 bits of SID codeword (all 1s). Network + * elements that receive SID frames from call leg A uplink and need to + * retransmit them on leg B downlink should "rejuvenate" received SID frames + * prior to retransmission by resetting the SID field to its pristine state + * of all 1s; this function does the job. + * + * Important note: because of HR-specific quirks (lack of exact bit counting + * rules in GSM 06.41 spec compared to 06.31 & 06.81, plus the fact that such + * bit counting can only be done efficiently in the GSM 05.03 channel decoder + * prior to bit reordering based on voiced or unvoiced mode), a generic + * (usable from any network element) SID classification function similar to + * osmo_{fr,efr}_sid_classify() unfortunately cannot exist for HR. Therefore, + * the triggering condition for invoking this SID rejuvenation/reset function + * can only be an out-of-band SID indication, as in GSM 08.61 TRAU frames + * or RFC 5993 ToC octet. + */ +void osmo_hr_sid_reset(uint8_t *rtp_payload) +{ + /* set all 79 SID codeword bits to 1 */ + rtp_payload[4] |= 0x7F; + memset(rtp_payload + 5, 0xFF, 9); +} -- To view, visit https://gerrit.osmocom.org/c/libosmocore/+/33060 To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings Gerrit-Project: libosmocore Gerrit-Branch: master Gerrit-Change-Id: Iebc0863ffcc3f8f25aeb54d4b14fac0487bc2bbb Gerrit-Change-Number: 33060 Gerrit-PatchSet: 1 Gerrit-Owner: falconia &lt;falcon(a)freecalypso.org&gt; Gerrit-MessageType: newchange