FreeCalypso > hg > gsm-codec-lib

annotate README @ 477:4c9222d95647

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libtwamr encoder: always emit frame->mode = mode; In the original implementation of amr_encode_frame(), the 'mode' member of the output struct was set to 0xFF if the output frame type is TX_NO_DATA. This design was made to mimic the mode field (16-bit word) being set to 0xFFFF (or -1) in 3GPP test sequence format - but nothing actually depends on this struct member being set in any way, and amr_frame_to_tseq() generates the needed 0xFFFF on its own, based on frame->type being equal to TX_NO_DATA. It is simpler and more efficient to always set frame->mode to the actual encoding mode in amr_encode_frame(), and this new behavior has already been documented in doc/AMR-library-API description in anticipation of the present change.
author Mychaela Falconia <falcon@freecalypso.org>
date Sat, 18 May 2024 22:30:42 +0000
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1 Themyscira Wireless GSM codec libraries & utilities package
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2 ===========================================================
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4 Themyscira Wireless, a technical initiative of the Women's Republic of
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5 Themyscira, is proud to present this package of GSM codec libraries and
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6 associated command line test and development utilities. The present package
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7 provides the following linkable C libraries, intended to be usable by any
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8 application that needs GSM codec functionality:
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10 libgsmfr2 This library implements the original GSM-FR codec, consisting
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11 of not only the basic transcoding functions of GSM 06.10, but
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12 also all Rx DTX handler functions that are required for a speech
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13 decoder receiving a stream of frames from a radio interface,
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14 either MS or network side. This library is a replacement for
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15 classic libgsm, providing proper reset logic, homing functions
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16 and the Rx DTX handler block.
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18 libgsmefr This library implements GSM-EFR codec, based on the reference
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19 code from ETSI (GSM 06.53). The bit-exact version of GSM-EFR
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20 implemented here is the original one, not the AMR-EFR hybrid
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21 that was made into a permissible implementation option after
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22 the development of AMR.
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24 libtwamr This library implements 3GPP AMR-NB codec, based on the official
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25 reference code (TS 26.073). Both VAD versions are included,
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26 selected by the user application at run time, and I/O functions
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27 are provided for both 3GPP test sequence format and the more
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28 practical format of IETF RFC 4867. This library can also be
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29 used to implement AMR-EFR hybrid operation if no DTX is needed
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30 in the encoder and if the input to the decoder contains no SID
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31 frames.
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33 The only GSM codec for which no implementation library is currently provided is
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34 GSM-HR, also known as HRv1. Librification of HRv1 reference code from ETSI is
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35 a planned work item for future development.
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37 The libraries provided here are intended for two primary purposes:
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39 1) They are used as part of Themyscira Wireless MGW (media gateway)
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40 implementation, providing the necessary speech transcoder between a GSM
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41 network and G.711-based PSTN.
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43 2) They are useful in many varied study and exploration workings, as part of
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44 experiments where it becomes necessary to model, simulate or replicate
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45 bit-exact operation of someone else's network element.
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47 Each of our Themyscira core libraries is free-standing and independent of the
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48 others. The dependency on classic libgsm (by way of <gsm.h> header file) that
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49 existed in previous versions of Themyscira gsm-codec-lib suite has been
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50 eliminated; the present version has zero dependencies.
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52 Included command line utilities
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53 ===============================
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55 In addition to the set of core libraries, the present package includes a number
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56 of command line utilities, falling into the following groups:
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58 * Some utilities specifically exercise and test our core libraries;
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60 * Some utilities are not specifically for library testing but make use of
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61 these libraries;
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63 * Some utilities are included because they implement some closely related and
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64 relevant debug and development functionality, even though they don't link
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65 with any of the included core libraries.
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67 Please see the included documentation in the doc subdirectory.