FreeCalypso > hg > gsm-codec-lib
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doc/AMR-EFR-philosophy: document implemented solution
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Fri, 10 May 2024 18:20:06 +0000 |
parents | 614ae8dc6807 |
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Themyscira Wireless GSM codec libraries & utilities package =========================================================== Themyscira Wireless, a technical initiative of the Women's Republic of Themyscira, is proud to present this package of GSM codec libraries and associated command line test and development utilities. The present package provides the following linkable C libraries, intended to be usable by any application that needs GSM codec functionality: libgsmfr2 This library implements the original GSM-FR codec, consisting of not only the basic transcoding functions of GSM 06.10, but also all Rx DTX handler functions that are required for a speech decoder receiving a stream of frames from a radio interface, either MS or network side. This library is a replacement for classic libgsm, providing proper reset logic, homing functions and the Rx DTX handler block. libgsmefr This library implements GSM-EFR codec, based on the reference code from ETSI (GSM 06.53). The bit-exact version of GSM-EFR implemented here is the original one, not the AMR-EFR hybrid that was made into a permissible implementation option after the development of AMR. libtwamr This library implements 3GPP AMR-NB codec, based on the official reference code (TS 26.073). Both VAD versions are included, selected by the user application at run time, and I/O functions are provided for both 3GPP test sequence format and the more practical format of IETF RFC 4867. This library can also be used to implement AMR-EFR hybrid operation if no DTX is needed in the encoder and if the input to the decoder contains no SID frames. The only GSM codec for which no implementation library is currently provided is GSM-HR, also known as HRv1. Librification of HRv1 reference code from ETSI is a planned work item for future development. The libraries provided here are intended for two primary purposes: 1) They are used as part of Themyscira Wireless MGW (media gateway) implementation, providing the necessary speech transcoder between a GSM network and G.711-based PSTN. 2) They are useful in many varied study and exploration workings, as part of experiments where it becomes necessary to model, simulate or replicate bit-exact operation of someone else's network element. Each of our Themyscira core libraries is free-standing and independent of the others. The dependency on classic libgsm (by way of <gsm.h> header file) that existed in previous versions of Themyscira gsm-codec-lib suite has been eliminated; the present version has zero dependencies. Included command line utilities =============================== In addition to the set of core libraries, the present package includes a number of command line utilities, falling into the following groups: * Some utilities specifically exercise and test our core libraries; * Some utilities are not specifically for library testing but make use of these libraries; * Some utilities are included because they implement some closely related and relevant debug and development functionality, even though they don't link with any of the included core libraries. Please see the included documentation in the doc subdirectory.