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123 lines
3.4 KiB
C
123 lines
3.4 KiB
C
/*---------------------------------------------------------------------------*\
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FILE........: interp.c
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AUTHOR......: David Rowe
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DATE CREATED: 9/10/09
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Interpolation of 20ms frames to 10ms frames.
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\*---------------------------------------------------------------------------*/
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/*
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Copyright (C) 2009 David Rowe
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All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License version 2.1, as
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published by the Free Software Foundation. This program is
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distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <assert.h>
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#include <math.h>
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#include <string.h>
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#include "defines.h"
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#include "interp.h"
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float sample_log_amp(MODEL *model, float w);
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/*---------------------------------------------------------------------------*\
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FUNCTION....: interp()
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AUTHOR......: David Rowe
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DATE CREATED: 22/8/10
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Given two frames decribed by model parameters 20ms apart, determines
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the model parameters of the 10ms frame between them. Assumes
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voicing is available for middle (interpolated) frame. Outputs are
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amplitudes and Wo for the interpolated frame.
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This version can interpolate the amplitudes between two frames of
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different Wo and L.
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\*---------------------------------------------------------------------------*/
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void interpolate(
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MODEL *interp, /* interpolated model params */
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MODEL *prev, /* previous frames model params */
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MODEL *next /* next frames model params */
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)
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{
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int l;
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float w,log_amp;
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/* Wo depends on voicing of this and adjacent frames */
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if (interp->voiced) {
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if (prev->voiced && next->voiced)
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interp->Wo = (prev->Wo + next->Wo)/2.0;
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if (!prev->voiced && next->voiced)
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interp->Wo = next->Wo;
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if (prev->voiced && !next->voiced)
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interp->Wo = prev->Wo;
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}
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else {
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interp->Wo = TWO_PI/P_MAX;
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}
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interp->L = PI/interp->Wo;
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/* Interpolate amplitudes using linear interpolation in log domain */
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for(l=1; l<=interp->L; l++) {
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w = l*interp->Wo;
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log_amp = (sample_log_amp(prev, w) + sample_log_amp(next, w))/2.0;
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interp->A[l] = pow(10.0, log_amp);
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}
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}
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/*---------------------------------------------------------------------------*\
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FUNCTION....: sample_log_amp()
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AUTHOR......: David Rowe
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DATE CREATED: 22/8/10
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Samples the amplitude envelope at an arbitrary frequency w. Uses
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linear interpolation in the log domain to sample between harmonic
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amplitudes.
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\*---------------------------------------------------------------------------*/
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float sample_log_amp(MODEL *model, float w)
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{
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int m;
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float f, log_amp;
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assert(w > 0.0); assert (w <= PI);
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m = floor(w/model->Wo + 0.5);
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f = (w - m*model->Wo)/w;
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assert(f <= 1.0);
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if (m < 1) {
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log_amp = f*log10(model->A[1]);
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}
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else if ((m+1) > model->L) {
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log_amp = (1.0-f)*log10(model->A[model->L]);
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}
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else {
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log_amp = (1.0-f)*log10(model->A[m]) + f*log10(model->A[m+1]);
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}
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return log_amp;
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}
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