Attention is currently required from: pespin.
neels has posted comments on this change. (
https://gerrit.osmocom.org/c/osmo-msc/+/31697
)
Change subject: [codecs filter] use filter result in MT DTAP CC Setup
......................................................................
Patch Set 3:
(2 comments)
File src/libmsc/gsm_04_08_cc.c:
https://gerrit.osmocom.org/c/osmo-msc/+/31697/comment/9ea88aca_87fc01c2
PS3, Line 711: .speech_ver = { -1 },
everything is starting to be full of magic values
(-1). some UNSET defines would be great.
this is still speech_ver = -1, it is
definitely not "everything full of", maybe you can dial back your wording a
little
https://gerrit.osmocom.org/c/osmo-msc/+/31697/comment/d89bd1ed_859e5e12
PS3, Line 727: * finding a matching codec. */
but we can actually do some transoding already, like
AMR BWE<->OA and AMR<->IuUP. […]
no, not yet.
Intelligently selecting conversions between codecs is a bit more complex, let's tackle
that a bit later. So far the codecs filter is all about: what codec shall we use on the
MGW <-> CN RTP leg. (And so far it needs to match the RAN <-> MGW leg)
The main open point is: should osmo-msc really have knowledge about what can be converted
to what. Because then we need to update the osmo-msc config (or hardcoded) prior knowlede
about what the MGW is able to do. What would be really good: if the MGW can *tell us
dynamically* which codecs translations it is able to do. Maybe in the CRCX or MDCX we can
send codecs, and in the OK response the MGW lists all compatible codecs?? Not sure yet.
Also i haven't finished figuring out the AMR OA vs BE modes really. IIRC I always
force to OA=1 in SDP sent out, but accept BE in SDP coming in from SIP... I tried to make
sense of it but time is running out. So far osmo_mgcp_client can't even send OA and BE
at the same time in one MGCP message, so there's a whole other construction site
there.
Also i haven't finished figuring out the SDP AMR mode-set picking AMR rates, and how
to marry that up to the GSM representation of allowed modes (S0-S15 bits).
So far we just plug any AMR into any other AMR and hope for the best, and we also just
override 3G RAN with IUFP and handwavy magic hopefully happens in osmo-mgw.
I guess we still need a quite complex code compatibility/translatability section. This
patch series has the aim to match up identical codecs, only (plus sneak in
IuUP<->AMR somehow). Even that basic 1:1 codec matching ability is still completely
missing from osmo-msc master, so that is the first step. Proper translation shall follow
later, haven't written anything for that yet.
For 3G I have this way with ran_msg returning AMR because we urgently need the translation
for 3G<->2G now, but it's not really how i want to do it for everything else in
the future.
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Gerrit-Project: osmo-msc
Gerrit-Branch: master
Gerrit-Change-Id: I9586221ef56352b7ce4b2604ae0dc04554145a78
Gerrit-Change-Number: 31697
Gerrit-PatchSet: 3
Gerrit-Owner: neels <nhofmeyr(a)sysmocom.de>
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