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document tw5b-dump and tw5c-dump
author Mychaela Falconia <falcon@freecalypso.org>
date Fri, 20 Mar 2026 06:43:50 +0000
parents 7fc57e2a6784
children
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Mychaela Falconia <falcon@freecalypso.org>
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1 GSM-HR speech codec is currently deemed by us to have no practical utility:
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Mychaela Falconia <falcon@freecalypso.org>
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2
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Mychaela Falconia <falcon@freecalypso.org>
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3 * GSM networks that need to use half-rate channels for capacity reasons will
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Mychaela Falconia <falcon@freecalypso.org>
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4 preferentially use AMR-HR (superior speech quality to HRv1), and may even
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Mychaela Falconia <falcon@freecalypso.org>
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5 have to reject GSM MS that don't support it;
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6
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7 * GSM networks that aren't so constrained in capacity will use one of AMR-FR,
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Mychaela Falconia <falcon@freecalypso.org>
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8 EFR or FRv1, all of which provide better speech quality than HRv1.
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9
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Mychaela Falconia <falcon@freecalypso.org>
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10 Because of this lack of practical utility, some important limits have been
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Mychaela Falconia <falcon@freecalypso.org>
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11 placed on the scope of work to support this codec in the present Themyscira
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Mychaela Falconia <falcon@freecalypso.org>
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12 Wireless GSM codec libraries and utilities suite:
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13
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14 * Between speech encoder & decoder functions on the one hand and the TFO
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Mychaela Falconia <falcon@freecalypso.org>
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15 transform function (TS 28.062 section C.3.2.1.1) on the other hand, the
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Mychaela Falconia <falcon@freecalypso.org>
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16 latter received more development attention. For completeness, TFO transform
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Mychaela Falconia <falcon@freecalypso.org>
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17 implementations need to be provided for all 3 codecs for which this transform
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Mychaela Falconia <falcon@freecalypso.org>
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18 is defined, and the implementation of TFO transform for GSM-HR serves as a
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Mychaela Falconia <falcon@freecalypso.org>
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19 stepping stone toward the much more important one for EFR.
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20
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Mychaela Falconia <falcon@freecalypso.org>
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21 * Librified forms of speech encoder and decoder engines from GSM 06.06 GSM-HR
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Mychaela Falconia <falcon@freecalypso.org>
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22 reference code have been included in libgsmhr1 for the sake of completeness,
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Mychaela Falconia <falcon@freecalypso.org>
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23 as well as command line utilities built on top of these library engines.
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24 However, unlike the situation with EFR and AMR codecs, no effort is being
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25 expended to make these operations fast or computationally efficient - the
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Mychaela Falconia <falcon@freecalypso.org>
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26 slow and grossly inefficient code from ETSI remains mostly unchanged except
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Mychaela Falconia <falcon@freecalypso.org>
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27 for elimination of global variables and introduction of state structures.