fixeria has submitted this change. ( https://gerrit.osmocom.org/c/osmo-bts/+/27430 )

Change subject: osmo-bts-trx: rx_tchh_fn(): fix HR SID detection (wrong offset) ......................................................................

osmo-bts-trx: rx_tchh_fn(): fix HR SID detection (wrong offset)

According to RFC5993, which is referenced by 3GPP TS 48.103, the complete RTP HR payload consists of a Table-of-Contents (ToC) byte followed by the 14 bytes of the HR codec frame. See section 5.2.

gsm0503_tch_hr_decode() outputs frames in the RTP format with length of 15 bytes (120 bits): 1 (ToC) + 14 (HR frame):

+-------------+------------------------- | ToC section | HR codec frame ... +-------------+-------------------------

osmo_hr_check_sid() expects a HR codec frame of 14 bytes (112 bits) as the input, so we should skip the ToC section when calling it.

Change-Id: Ie5fa776dcb2b2203a97aed56ecbf2450af7d87c1 Related: SYS#5853 --- M src/osmo-bts-trx/sched_lchan_tchh.c 1 file changed, 4 insertions(+), 2 deletions(-)

Approvals: pespin: Looks good to me, but someone else must approve laforge: Looks good to me, approved Jenkins Builder: Verified

diff --git a/src/osmo-bts-trx/sched_lchan_tchh.c b/src/osmo-bts-trx/sched_lchan_tchh.c index b6d83d0..d2ee4f0 100644 --- a/src/osmo-bts-trx/sched_lchan_tchh.c +++ b/src/osmo-bts-trx/sched_lchan_tchh.c @@ -147,8 +147,10 @@ */ rc = gsm0503_tch_hr_decode(tch_data, *bursts_p, fn_is_odd, &n_errors, &n_bits_total); - if (rc == (GSM_HR_BYTES + 1)) /* only for valid *speech* frames */ - lchan_set_marker(osmo_hr_check_sid(tch_data, rc), lchan); /* DTXu */ + if (rc == (GSM_HR_BYTES + 1)) { /* only for valid *speech* frames */ + /* gsm0503_tch_hr_decode() prepends a ToC octet (see RFC5993), skip it */ + lchan_set_marker(osmo_hr_check_sid(&tch_data[1], GSM_HR_BYTES), lchan); /* DTXu */ + } break; case GSM48_CMODE_SPEECH_AMR: /* AMR */ /* the first FN 0,8,17 or 1,9,18 defines that CMI is included