* parse AMR multirate config form 04.08 IE into easier format
* CMR, CMC and CMI on the L1 side are an _index_ into the current
mode array
* Fix conversion of AMR SID frames from RTP -> L1
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.
Harald Welte