Bug #5474: osmo-bts-trx: DTXd support not implemented - OsmoBTS - Open Source Mobile Communications

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Bug #5474

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osmo-bts-trx: DTXd support not implemented

Added by pespin about 2 years ago.

Status:

New

Priority:

Normal

Assignee:

Category:

osmo-bts-trx

Target version:

Start date:

03/02/2022

Due date:

% Done:

Spec Reference:

Description

Other osmo-bts implementations (sysmo, lc15, oc2g) seem to be implementing DTXd (DTX downlink) support, but from what I can tell by looking at the code, osmo-bts-trx doesn't implement it.

Other osmo-bts types seem to use dl_amr_fsm (dtx_dl_amr_fsm.h, msg_utils.c/.h), but I don't see any reference to it under src/osmo-bts-trx/

Reference on how it should look like can be found here: https://downloads.osmocom.org/docs/latest/rtp-amr.pdf

This was discovered because for instance osmo-bts-trx is dropping AMR SID frames (FT=8) being sent to it over RTP from the MGW:

sched_lchan_tchf.c:462 036361/27/13/49/09 (bts=0,trx=0,ts=4) TCH/F: Codec (FT = 8) of RTP frame not in list

I started writing a patch to solve it, but the whole translation of AMR seems to be missing in osmo-bts-trx, so I stopped:
https://gerrit.osmocom.org/c/osmo-bts/+/27361

Furthermore, almost no TTCN3 tests exist to validate it (see related tickets to this one).

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