FreeCalypso > hg > gsm-codec-lib
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libgsmfrp: new refined implementation
The previous implementation exhibited the following defects,
which are now fixed:
1) The last received valid SID was cached forever for the purpose of
handling future invalid SIDs - we could have received some valid
SID ages ago, then lots of speech or NO_DATA, and if we then get
an invalid SID, we would resurrect the last valid SID from ancient
history - a bad design. In our new design, we handle invalid SID
based on the current state, much like BFI.
2) GSM 06.11 spec says clearly that after the second lost SID
(received BFI=1 && TAF=1 in CN state) we need to gradually decrease
the output level, rather than jump directly to emitting silence
frames - we previously failed to implement such logic.
3) Per GSM 06.12 section 5.2, Xmaxc should be the same in all 4 subframes
in a SID frame. What should we do if we receive an otherwise valid
SID frame with different Xmaxc? Our previous approach would
replicate this Xmaxc oddity in every subsequent generated CN frame,
which is rather bad. In our new design, the very first CN frame
(which can be seen as a transformation of the SID frame itself)
retains the original 4 distinct Xmaxc, but all subsequent CN frames
are based on the Xmaxc from the last subframe of the most recent SID.
| author | Mychaela Falconia <falcon@freecalypso.org> |
|---|---|
| date | Tue, 09 May 2023 05:16:31 +0000 |
| parents | 34f8549ff0b1 |
| children | 4c458145e793 |
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The present document is intended to be a guide for any parties who are going to turn the present upstream gsm-codec-lib source package into user-friendly binary packages for specific distributions. The Mother's primary recommendation with regard to downstream packaging of the present software is that end-user binary packages should be divided more finely than the present source package. At the present source level the two principal libraries (libgsmefr and libgsmfrp) are combined together with a bunch of command line utilities for reasons of compile-time dependency (utilities depend on libraries), and also for the purposes of library development and testing - but the same combination does not make much sense from a user's perspective. Therefore, it is our recommendation that the present source package be split as follows at the level of end-user distro packages: libgsmefr package: just libgsmefr.a and its associated gsm_efr.h header file. libgsmfrp package: just libgsmfrp.a and its associated gsm_fr_preproc.h header file. Given that <gsm_fr_preproc.h> depends on <gsm.h> from classic libgsm, the latter library (libgsm) should probably be officially declared as a dependency for libgsmfrp. gsm-codec-utils (or themwi-gsm-codec-utils or themwi-codec-utils) package: all command line utilities built and installed in amrconv, efrtest, frtest and miscutil subdirectories. This package will depend on libgsmefr, libgsmfrp and classic libgsm - the latter is pre-existing software, not provided by Themyscira. With the division recommended above, the set of end-user packages will exhibit a sensible functional division from the user's perspective, and a clean and sensible dependency graph. Package versions ================ The two library packages (libgsmefr and libgsmfrp) should be versioned with their own proper semantic versions listed in the Library-versions document, as opposed to the larger gsm-codec-lib tarball release version. If a later gsm-codec-lib tarball release exhibits no changes in the libraries (the only changes are in the command line utilities) or if only one of the two libraries exhibits changes (as indicated with a new semantic version), then NO new downstream packages should be made for unchanged libraries - instead already made binary packages for that library version (SemVer) should be retained. Downstream package version numbers for command line utilities packages are up to the discretion of packaging maintainers; using gsm-codec-lib tarball release numbers is acceptable. Patience, please ================ Please make downstream package releases *only* from officially published tarball releases of gsm-codec-lib - please do *not* make packaged builds or "releases" from our Mercurial repository. Any time we have a new development that is expected to be useful to downstream end users, we shall make a proper tarball release, and if there are any changes in the libraries, we shall assign new semantic versions as appropriate.