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Hello Jenkins Builder,

I'd like you to reexamine a change. Please visit

https://gerrit.osmocom.org/c/osmo-bts/+/32099

to look at the new patch set (#3).

Change subject: rtp continuous-streaming: add themyscira-bfi option ......................................................................

rtp continuous-streaming: add themyscira-bfi option

The just-added rtp continuous-streaming mode solves the principal problem of OS#5975, but there is still room for improvement, particularly in the case of FR and EFR codecs. The BFI packet format sent in our rtp continuous-streaming mode (without additional qualifiers) is zero-length RTP payload, which has the benefit of being universal, applicable to any codec type and any encoding variant. However, this most generic BFI packet format lacks the ability to represent the Time Alignment Flag (TAF) of GSM 06.31 and 06.81, traditionally carried in TRAU UL frames of GSM 08.60 in the classic GSM RAN architecture.

There exist published-source implementations of FR and EFR decoders that implement Rx DTX handler functions exactly to the letter of GSM 06.31 and 06.81 specs, they take BFI and TAF flags as inputs along with received frame payloads, and they rely on the TAF bit being correct (reflecting the frame position relative to SACCH) when BFI=1. A need is thus created for an RTP transport mechanism for FR&EFR that includes BFI marker packets that contain this TAF bit.

An ad hoc extension to the standard RTP transport format for FR&EFR that does exactly what has just been described has been implemented by Themyscira Wireless, a retronetworking intentional community (RNIC) that operates an Osmocom-based GSM network. The present change adds OsmoBTS support for this Themyscira RTP BFI extension, and it does so by extending the rtp continuous-streaming vty option added just previously; the new option becomes:

rtp continuous-streaming [themyscira-bfi]

If the last qualifier is included, the special Themyscira extension mode is enabled. In this mode, which only affects FR and EFR codecs, RTP packets emitted when there is no speech or SID frame to be sent change from zero-length RTP payload to Themyscira BFI marker format, including TAF.

Related: OS#5975 Change-Id: Ib935efb1f7c9c8d919a4a0ea2bef244a47e5fb24 --- M include/osmo-bts/bts.h M src/common/l1sap.c M src/common/vty.c M src/osmo-bts-trx/sched_lchan_tchf.c M tests/osmo-bts.vty 5 files changed, 96 insertions(+), 13 deletions(-)

git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/99/32099/3