FreeCalypso > hg > gsm-codec-lib
view libtwamr/preemph.c @ 417:f17e42c63058
libtwamr: integrate ol_ltp.c
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Tue, 07 May 2024 03:21:14 +0000 |
parents | 3618b5cf25a6 |
children |
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/* ******************************************************************************** * * GSM AMR-NB speech codec R98 Version 7.6.0 December 12, 2001 * R99 Version 3.3.0 * REL-4 Version 4.1.0 * ******************************************************************************** * * File : preemph.c * Purpose : Preemphasis filtering * Description : Filtering through 1 - g z^-1 * ******************************************************************************** */ /* ******************************************************************************** * MODULE INCLUDE FILE AND VERSION ID ******************************************************************************** */ #include "namespace.h" #include "preemph.h" /* ******************************************************************************** * INCLUDE FILES ******************************************************************************** */ #include "typedef.h" #include "basic_op.h" #include "no_count.h" /* ******************************************************************************** * LOCAL VARIABLES AND TABLES ******************************************************************************** */ /* ******************************************************************************** * PUBLIC PROGRAM CODE ******************************************************************************** */ /************************************************************************* * * Function: preemphasis_reset * Purpose: Initializes state memory to zero * ************************************************************************** */ void preemphasis_reset (preemphasisState *state) { state->mem_pre = 0; } /* ************************************************************************** * Function: preemphasis * Purpose: Filtering through 1 - g z^-1 * ************************************************************************** */ int preemphasis ( preemphasisState *st, /* (i/o) : preemphasis filter state */ Word16 *signal, /* (i/o) : input signal overwritten by the output */ Word16 g, /* (i) : preemphasis coefficient */ Word16 L /* (i) : size of filtering */ ) { Word16 *p1, *p2, temp, i; p1 = signal + L - 1; move16 (); p2 = p1 - 1; move16 (); temp = *p1; move16 (); for (i = 0; i <= L - 2; i++) { *p1 = sub (*p1, mult (g, *p2--)); move16 (); p1--; } *p1 = sub (*p1, mult (g, st->mem_pre)); move16 (); st->mem_pre = temp; move16 (); return 0; }