gsm-codec-lib-r4 release

[Mychaela Falconia]

Hello FreeCalypso and Themyscira community,

I am pleased to announce a new release of Themyscira Wireless GSM codec
libraries and utilities package:

https://www.freecalypso.org/pub/GSM/codecs/gsm-codec-lib-r4.tar.bz2
https://www.freecalypso.org/pub/GSM/codecs/gsm-codec-lib-latest.tar.bz2
(symlink)

Two principal libraries inside the package (libgsmfr2 and libgsmefr)
got new Semantic Version numbers as detailed inside, reflecting
additions to their public API.  As far as library functions go, not
including command line utilities, there are only 3 areas of changes:

* Decoder engines in libgsmfr2 and libgsmefr got new wrapper functions
  that directly accept RTP input as in a const uint8_t pointer to the
  payload plus an explicit payload length; all logic to handle both the
  basic RTP format of RFC 3551 and the extended RTP format of TW-TS-001
  is inside these wrappers.

* A new goal has been set to provide implementations of TFO transform
  (to be covered in an OsmoDevCall or RetroNetCall soon) for all three
  classic GSM codecs.  As a quick preview, this transform is absolutely
  necessary in order to implement a *proper* path from TrFO RTP input
  to TRAU-DL frames going to an E1 BTS such as Ericsson RBS 6000.  The
  present release includes implementation of TFO transform for FRv1.

* const "variables" are provided that give sizes of internal state
  structures, thereby allowing applications to allocate these state
  structs using libosmocore talloc or whatever other fancy scheme is
  desired, beyond plain malloc-based functions built into the libraries.

The set of additions to command line utilities is also fairly small:

* There are several new utilities that support recently defined
  TW-TS-005 hexadecimal file format:

  https://www.freecalypso.org/specs/tw-ts-005-v010003.txt

* There is a new utility that exercises TFO transform for FRv1 - the
  actual transform implementation is in the library, but the command
  line utility serves as a kind of unit test tool.

That's it for the present release.  Future work on gsm-codec-lib suite
will consist of:

1) I need to finish integrating GSM-HR codec.  There is WIP code in
   the Hg repository that has been excluded from the just-made official
   release - this work needs to be finished.

2) I will need to implement TFO transform for EFR.  This one will be
   challenging, but seeing that Nokia TCSM2 implements it, we shall
   implement it too.  I currently plan on doing it after GSM-HR work
   so the repository will be in a cleaner state, without dangling WIP
   bits.

However, I will probably work on some other ThemWi components before
going back to those gsm-codec-lib tasks.

Hasta la Victoria, Siempre,
Mychaela aka The Mother