FreeCalypso > hg > gsm-codec-lib
view libtwamr/preemph.c @ 477:4c9222d95647
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 | 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; }