On 07/12/2022 15:21, Neels Hofmeyr wrote:
So far I always have two physical phones camped on a physical BTS to test voice. Speak into each handset and hear if the other plays it back. It involves a lot of plugging and SIM card and android settings / flight mode.
I used some setup a long time ago with the various virtual components, but it was mainly for SMS, I remember I had some problems with paging that was a show stopper, and I never looked at it again.
It would be great to have a simple echo service. Adding osmo-sip-connector and kamailio to osmo-msc is fairly easy, we have example config in osmo-dev.git. But I don't know how to do an actual echo with a delay of two seconds.
Well, You can add some delay with rtp jitter-buffer on the bts.
It accepts up to 10 seconds, but stops working for me with smaller values than that, I start to get:
DLMIB DEBUG <0014> ../../git/src/trau/osmo_ortp.c:205 osmo_rtp_socket_poll(209920): No message received DLMIB NOTICE <0014> ../../git/src/trau/osmo_ortp.c:0 rtp_putq: Queue is full. Discarding message with ts=2870320
but 1500 works and gives you enough delay to be able to say something and hear it back.
I also find basically all of the PBX config daunting and near impossible to understand. Maybe someone who knows which PBX provides an echo service can write up a wiki page on osmocom.org to describe it?
What did you think of https://osmocom.org/projects/cellular-infrastructure/wiki/Simple_Echo_Server ?
I don't see that the SEMS echo app has a param for buffer size, unfortunately, I don't think the delay time is variable. If I find a way, I'll add it to the wiki page.
K/