29 May
2023
29 May
'23
2:10 p.m.
Attention is currently required from: falconia.
fixeria has posted comments on this change. (
https://gerrit.osmocom.org/c/osmo-bts/+/33069 )
Change subject: trx TCH DL: transmit invalid speech frames instead of dummy FACCH
......................................................................
Patch Set 1:
(2 comments)
File src/osmo-bts-trx/sched_lchan_tchf.c:
https://gerrit.osmocom.org/c/osmo-bts/+/33069/comment/0096fad3_a0351a92
PS1, Line 500: what is the correct BTS Tx behavior for frame
: * gaps in TCH/AFS
I guess we could indicate a bad frame via AMR's in-band signalling? Just an idea.
IIRC, this is what ip.access nanoBTS does in the absence of RTP frames.
See also: https://osmocom.org/issues/4823.
https://gerrit.osmocom.org/c/osmo-bts/+/33069/comment/db2c9660_e3ed2799
PS1, Line 505: gsm0503_tch_fr_encode
I suggest using a switch here:
```
switch (tch_mode) {
case GSM48_CMODE_SPEECH_V1:
case GSM48_CMODE_SPEECH_EFR:
rc = gsm0503_tch_fr_encode(*bursts_p, NULL, 0, 1);
if (rc == 0)
break;
/* fall-through */
default:
gsm0503_tch_fr_encode(*bursts_p, dummy, sizeof(dummy), 1);
chan_state->dl_facch_bursts = 8;
}
```
The reason why I am suggesting this, specifically the fall-through if `rc != 0`, is that
the user may be running an older version of libosmocore, predating your patch
`Iade3310e16b906efb6892d28f474a0d15204e861`. In this case `gsm0503_tch_fr_encode()` would
return -1 and we will fall-back to FACCH rather than sending garbage.
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Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: I78106802a0aa4af39859c75d29fe0e77037899fe
Gerrit-Change-Number: 33069
Gerrit-PatchSet: 1
Gerrit-Owner: falconia <falcon(a)freecalypso.org>
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Gerrit-Reviewer: pespin <pespin(a)sysmocom.de>
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