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annotate libgsmefr/preemph.c @ 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
parents 9aef9e54b19d
children
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1 /*---------------------------------------------------------------------*
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2 * routine preemphasis() *
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3 * ~~~~~~~~~~~~~~~~~~~~~ *
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4 * Preemphasis: filtering through 1 - g z^-1 *
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5 *---------------------------------------------------------------------*/
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7 #include "gsm_efr.h"
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8 #include "typedef.h"
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9 #include "namespace.h"
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10 #include "basic_op.h"
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11 #include "no_count.h"
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12 #include "sig_proc.h"
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13 #include "cnst.h"
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14 #include "dec_state.h"
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16 void preemphasis (
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17 struct EFR_decoder_state *st,
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18 Word16 *signal, /* (i/o) : input signal overwritten by the output */
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19 Word16 g, /* (i) : preemphasis coefficient */
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20 Word16 L /* (i) : size of filtering */
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21 )
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22 {
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23 Word16 *p1, *p2, temp, i;
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25 p1 = signal + L - 1;
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26 p2 = p1 - 1;
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27 temp = *p1;
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29 for (i = 0; i <= L - 2; i++)
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30 {
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31 *p1 = sub (*p1, mult (g, *p2--));
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32 p1--;
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33 }
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35 *p1 = sub (*p1, mult (g, st->mem_pre));
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37 st->mem_pre = temp;
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39 return;
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40 }