Attention is currently required from: jolly, pespin.

fixeria has posted comments on this change. ( https://gerrit.osmocom.org/c/osmo-bts/+/35132?usp=email )

Change subject: Transmit invalid AMR speech blocks instead of dummy FACCH ......................................................................

Patch Set 2:

(2 comments)

File src/osmo-bts-trx/sched_lchan_tchf.c:

https://gerrit.osmocom.org/c/osmo-bts/+/35132/comment/c1f9471e_0c017d04 PS2, Line 541: * - If the channel mode is AMR, transmit a dummy with speech

I'd document here the rationale about "FACCH displaces two speech frames rather than one".

This is not specific to TCH/AHS at all, and is already briefly mentioned in the existing code. It's also just one of the reasons; another reason is that some Qualcomm basebands don't seem to like dummy FACCH and report bad RxQual.

So I would be fine with the current state of this patch.

https://gerrit.osmocom.org/c/osmo-bts/+/35132/comment/2cc61db2_e210eeb4 PS2, Line 578: dummy_facch:

Maybe moving the GSM48_CMODE_SPEECH_AMR case inside the default with an "if" block is cleaner than a […]

Alternatively, we can move generation of dummy FACCH into a `static inline` function (`src/osmo-bts-trx/sched_utils.h` would be a good place for it) and just call it, hoping that the compiler would inline it properly for us.