We don't really know if the HR encoding is compatible with other
equipment, but it _should_ follow Chapter 5.2 of ETSI TS 101 318.
Please note that RFC5993 also specifies a way to encode GSM-HR into RTP,
we do not try to be compatible with that. The only difference seems to
be one additional TOC octet at the beginning of the payload field.
Using osmo-bts-sysmo and this code, it is now possible to do FR and AMR
based voice calls on TCH/F.
A lot of CPU is wasted in the conversion between the RTP formats and the
L1 specific formats for the codec frames. All data needs to be shifted
by four bits, and the order of bits needs to be reversed in every byte.
This only implements creating, binding, connecting and free'ing RTP
sockets, not yet anything regarding receiving or transmitting codec
frames on them.
You will need the rtp branch of libosmocore for libosmotrau
We didn't correctly format the RSLms message that went into LAPDm,
causing LAPDm to drop the message.
Also, disable the fake CIPH MODE COMPLETE generation hack for now
When seinding the fake CIPH MOD COMPL, we should wait a bit, as otherwise it
will reach the MSC _before_ we ever get the (still unencrypted) CLASSMARK
update from the MS.
This is not full encrpytion support, the bts-model part still
needs to detect the ENCR CMD when de-queueing from LAPDm and enable
the de-ciphering, detect the arrival of the first encrypted frame,
etc, enable en-ciphering, ...
when we activate the SCH in the DSP, we start a 5-second timer. If
we ever do not receive any MPH-TIME.ind primitives from L1 within
that time frame, we stop the process (and will be re-spawned)
The BTS IP address can now be specified by the L1FWD_BTS_HOST env
variable.
Option parsing would not have been that easy to integrate without
touching the main program...
The sequence is as follows:
0) start osmo-bts
1) start connection attempts to BTS
2) issue L1-RESET.req
3) receive L1-RESET.conf
4) issue RF-ACTIVATE.req
5) receive RF-ACTIVATE.conf
6) receive attributes for TRX
7) receive opstart for TRX
8) issue MPH-INIT.req
[...]
The important point here is: We don't want the BSC to set TRX attributes or do
TRX opstart before our RF related hardware is initialized.
Harald Welte