falconia has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-bts/+/32128 )

Change subject: rtp continuous-streaming: fix BFI in the quality-suppressed case ......................................................................

rtp continuous-streaming: fix BFI in the quality-suppressed case

The check for (tch_ind->lqual_cb >= bts->min_qual_norm) in l1sap_tch_ind() has the intent of suppressing valid-seeming speech frame output from lower layers when the link quality is too low; this check is particularly important for FR1 codec where the intrinsic validity check is only a 3-bit CRC which has 1/8 probability of indicating "correct" when decoding radio noise during DTXu silence.

However, this check is effectively defeated in the current implementation of rtp continuous-streaming, at least when themyscira-bfi extension is not used or when it doesn't apply because the codec is not FR or EFR: the RTP packet being output is the presumed-bogus speech frame from lower layers, rather than the intended zero-length payload. Fix this bug.

Related: OS#5975 Change-Id: Icee0f57be289a0592a0197469432a012d15f224c --- M src/common/l1sap.c 1 file changed, 27 insertions(+), 2 deletions(-)

git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/28/32128/1

diff --git a/src/common/l1sap.c b/src/common/l1sap.c index bb19524..0664816 100644 --- a/src/common/l1sap.c +++ b/src/common/l1sap.c @@ -1645,7 +1645,7 @@ return 1; } } else { - /* Are we in rtp continuous-stream special mode? If so, send + /* Are we in rtp continuous-streaming special mode? If so, send * out a BFI packet as zero-length RTP payload, or in Themyscira * BFI format if that option is also enabled and the codec is * FR or EFR. */ @@ -1658,7 +1658,7 @@ bfi[1] = (fn % 104 == 52); /* TAF */ send_ul_rtp_packet(lchan, fn, bfi, 2); } else - send_ul_rtp_packet(lchan, fn, msg->data, msg->len); + send_ul_rtp_packet(lchan, fn, bfi, 0); } else { DEBUGPGT(DRTP, &g_time, "Skipping RTP frame with lost payload (chan_nr=0x%02x)\n", chan_nr);