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f210c27f43
git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@3761 d0543943-73ff-0310-b7d9-9358b9ac24b2
98 lines
2.5 KiB
C
98 lines
2.5 KiB
C
/*
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* Copyright 1992 by Jutta Degener and Carsten Bormann, Technische
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* Universitaet Berlin. See the accompanying file "COPYRIGHT" for
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* details. THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE.
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*/
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#include <stdlib.h>
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#include <string.h>
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#include "config.h"
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#include "gsm610_priv.h"
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#include "gsm.h"
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/*
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* 4.2 FIXED POINT IMPLEMENTATION OF THE RPE-LTP CODER
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*/
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void Gsm_Coder (
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struct gsm_state * State,
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word * s, /* [0..159] samples IN */
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/*
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* The RPE-LTD coder works on a frame by frame basis. The length of
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* the frame is equal to 160 samples. Some computations are done
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* once per frame to produce at the output of the coder the
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* LARc[1..8] parameters which are the coded LAR coefficients and
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* also to realize the inverse filtering operation for the entire
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* frame (160 samples of signal d[0..159]). These parts produce at
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* the output of the coder:
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*/
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word * LARc, /* [0..7] LAR coefficients OUT */
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/*
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* Procedure 4.2.11 to 4.2.18 are to be executed four times per
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* frame. That means once for each sub-segment RPE-LTP analysis of
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* 40 samples. These parts produce at the output of the coder:
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*/
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word * Nc, /* [0..3] LTP lag OUT */
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word * bc, /* [0..3] coded LTP gain OUT */
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word * Mc, /* [0..3] RPE grid selection OUT */
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word * xmaxc,/* [0..3] Coded maximum amplitude OUT */
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word * xMc /* [13*4] normalized RPE samples OUT */
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)
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{
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int k;
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word * dp = State->dp0 + 120; /* [ -120...-1 ] */
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word * dpp = dp; /* [ 0...39 ] */
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word so[160];
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Gsm_Preprocess (State, s, so);
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Gsm_LPC_Analysis (State, so, LARc);
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Gsm_Short_Term_Analysis_Filter (State, LARc, so);
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for (k = 0; k <= 3; k++, xMc += 13) {
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Gsm_Long_Term_Predictor ( State,
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so+k*40, /* d [0..39] IN */
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dp, /* dp [-120..-1] IN */
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State->e + 5, /* e [0..39] OUT */
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dpp, /* dpp [0..39] OUT */
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Nc++,
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bc++);
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Gsm_RPE_Encoding ( /*-S,-*/
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State->e + 5, /* e ][0..39][ IN/OUT */
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xmaxc++, Mc++, xMc );
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/*
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* Gsm_Update_of_reconstructed_short_time_residual_signal
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* ( dpp, e + 5, dp );
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*/
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{ register int i;
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for (i = 0; i <= 39; i++)
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dp[ i ] = GSM_ADD( State->e[5 + i], dpp[i] );
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}
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dp += 40;
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dpp += 40;
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}
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(void)memcpy( (char *)State->dp0, (char *)(State->dp0 + 160),
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120 * sizeof(*State->dp0) );
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}
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/*
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** Do not edit or modify anything in this comment block.
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** The arch-tag line is a file identity tag for the GNU Arch
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** revision control system.
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**
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** arch-tag: ae8ef1b2-5a1e-4263-94cd-42b15dca81a3
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*/
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