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. -- To view, visit https://gerrit.osmocom.org/c/osmo-msc/+/31697 To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings Gerrit-Project: osmo-msc Gerrit-Branch: master Gerrit-Change-Id: I9586221ef56352b7ce4b2604ae0dc04554145a78 Gerrit-Change-Number: 31697 Gerrit-PatchSet: 3 Gerrit-Owner: neels <nhofmeyr@sysmocom.de> Gerrit-Reviewer: Jenkins Builder Gerrit-CC: pespin <pespin@sysmocom.de> Gerrit-Attention: pespin <pespin@sysmocom.de> Gerrit-Comment-Date: Tue, 07 Mar 2023 16:45:42 +0000 Gerrit-HasComments: Yes Gerrit-Has-Labels: No Comment-In-Reply-To: pespin <pespin@sysmocom.de> Gerrit-MessageType: comment