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458 lines
12 KiB
C
458 lines
12 KiB
C
/* G.721 decoder, from Sun's public domain CCITT-ADPCM sources,
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* retrieved from ftp://ftp.cwi.nl/pub/audio/ccitt-adpcm.tar.gz
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*
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* For reference, here's the original license:
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*
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* This source code is a product of Sun Microsystems, Inc. and is provided
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* for unrestricted use. Users may copy or modify this source code without
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* charge.
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*
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* SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
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* THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
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*
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* Sun source code is provided with no support and without any obligation on
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* the part of Sun Microsystems, Inc. to assist in its use, correction,
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* modification or enhancement.
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*
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* SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
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* INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
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* OR ANY PART THEREOF.
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*
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* In no event will Sun Microsystems, Inc. be liable for any lost revenue
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* or profits or other special, indirect and consequential damages, even if
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* Sun has been advised of the possibility of such damages.
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*
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* Sun Microsystems, Inc.
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* 2550 Garcia Avenue
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* Mountain View, California 94043
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*
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*/
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#include <stdlib.h>
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#include "g721.h"
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static short power2[15] = {1, 2, 4, 8, 0x10, 0x20, 0x40, 0x80,
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0x100, 0x200, 0x400, 0x800, 0x1000, 0x2000, 0x4000};
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/*
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* quan()
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*
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* quantizes the input val against the table of size short integers.
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* It returns i if table[i - 1] <= val < table[i].
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*
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* Using linear search for simple coding.
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*/
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static int
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quan(
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int val,
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short *table,
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int size)
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{
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int i;
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for (i = 0; i < size; i++)
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if (val < *table++)
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break;
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return (i);
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}
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/*
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* fmult()
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*
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* returns the integer product of the 14-bit integer "an" and
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* "floating point" representation (4-bit exponent, 6-bit mantessa) "srn".
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*/
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static int
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fmult(
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int an,
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int srn)
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{
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short anmag, anexp, anmant;
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short wanexp, wanmant;
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short retval;
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anmag = (an > 0) ? an : ((-an) & 0x1FFF);
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anexp = quan(anmag, power2, 15) - 6;
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anmant = (anmag == 0) ? 32 :
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(anexp >= 0) ? anmag >> anexp : anmag << -anexp;
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wanexp = anexp + ((srn >> 6) & 0xF) - 13;
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wanmant = (anmant * (srn & 077) + 0x30) >> 4;
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retval = (wanexp >= 0) ? ((wanmant << wanexp) & 0x7FFF) :
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(wanmant >> -wanexp);
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return (((an ^ srn) < 0) ? -retval : retval);
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}
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/*
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* g72x_init_state()
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*
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* This routine initializes and/or resets the g72x_state structure
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* pointed to by 'state_ptr'.
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* All the initial state values are specified in the CCITT G.721 document.
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*/
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void
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g72x_init_state(struct g72x_state *state_ptr)
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{
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int cnta;
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state_ptr->yl = 34816;
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state_ptr->yu = 544;
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state_ptr->dms = 0;
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state_ptr->dml = 0;
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state_ptr->ap = 0;
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for (cnta = 0; cnta < 2; cnta++) {
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state_ptr->a[cnta] = 0;
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state_ptr->pk[cnta] = 0;
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state_ptr->sr[cnta] = 32;
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}
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for (cnta = 0; cnta < 6; cnta++) {
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state_ptr->b[cnta] = 0;
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state_ptr->dq[cnta] = 32;
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}
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state_ptr->td = 0;
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}
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/*
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* predictor_zero()
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*
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* computes the estimated signal from 6-zero predictor.
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*
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*/
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static int
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predictor_zero(
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struct g72x_state *state_ptr)
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{
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int i;
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int sezi;
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sezi = fmult(state_ptr->b[0] >> 2, state_ptr->dq[0]);
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for (i = 1; i < 6; i++) /* ACCUM */
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sezi += fmult(state_ptr->b[i] >> 2, state_ptr->dq[i]);
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return (sezi);
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}
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/*
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* predictor_pole()
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*
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* computes the estimated signal from 2-pole predictor.
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*
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*/
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static int
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predictor_pole(
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struct g72x_state *state_ptr)
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{
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return (fmult(state_ptr->a[1] >> 2, state_ptr->sr[1]) +
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fmult(state_ptr->a[0] >> 2, state_ptr->sr[0]));
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}
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/*
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* step_size()
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*
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* computes the quantization step size of the adaptive quantizer.
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*
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*/
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static long
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step_size(
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struct g72x_state *state_ptr)
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{
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long y;
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long dif;
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long al;
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if (state_ptr->ap >= 256)
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return (state_ptr->yu);
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else {
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y = state_ptr->yl >> 6;
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dif = state_ptr->yu - y;
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al = state_ptr->ap >> 2;
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if (dif > 0)
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y += (dif * al) >> 6;
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else if (dif < 0)
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y += (dif * al + 0x3F) >> 6;
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return (y);
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}
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}
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/*
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* reconstruct()
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*
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* Returns reconstructed difference signal 'dq' obtained from
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* codeword 'i' and quantization step size scale factor 'y'.
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* Multiplication is performed in log base 2 domain as addition.
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*/
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static int
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reconstruct(
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int sign, /* 0 for non-negative value */
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int dqln, /* G.72x codeword */
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int y) /* Step size multiplier */
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{
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short dql; /* Log of 'dq' magnitude */
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short dex; /* Integer part of log */
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short dqt;
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short dq; /* Reconstructed difference signal sample */
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dql = dqln + (y >> 2); /* ADDA */
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if (dql < 0) {
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return ((sign) ? -0x8000 : 0);
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} else { /* ANTILOG */
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dex = (dql >> 7) & 15;
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dqt = 128 + (dql & 127);
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dq = (dqt << 7) >> (14 - dex);
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return ((sign) ? (dq - 0x8000) : dq);
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}
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}
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/*
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* update()
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*
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* updates the state variables for each output code
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*/
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static void
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update(
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/*int code_size,*/ /* distinguish 723_40 with others */
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int y, /* quantizer step size */
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int wi, /* scale factor multiplier */
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int fi, /* for long/short term energies */
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int dq, /* quantized prediction difference */
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int sr, /* reconstructed signal */
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int dqsez, /* difference from 2-pole predictor */
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struct g72x_state *state_ptr) /* coder state pointer */
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{
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int cnt;
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short mag, exp; /* Adaptive predictor, FLOAT A */
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short a2p; /* LIMC */
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short a1ul; /* UPA1 */
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short pks1; /* UPA2 */
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short fa1;
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char tr; /* tone/transition detector */
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short ylint, thr2, dqthr;
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short ylfrac, thr1;
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short pk0;
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pk0 = (dqsez < 0) ? 1 : 0; /* needed in updating predictor poles */
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mag = dq & 0x7FFF; /* prediction difference magnitude */
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/* TRANS */
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ylint = state_ptr->yl >> 15; /* exponent part of yl */
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ylfrac = (state_ptr->yl >> 10) & 0x1F; /* fractional part of yl */
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thr1 = (32 + ylfrac) << ylint; /* threshold */
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thr2 = (ylint > 9) ? 31 << 10 : thr1; /* limit thr2 to 31 << 10 */
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dqthr = (thr2 + (thr2 >> 1)) >> 1; /* dqthr = 0.75 * thr2 */
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if (state_ptr->td == 0) /* signal supposed voice */
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tr = 0;
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else if (mag <= dqthr) /* supposed data, but small mag */
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tr = 0; /* treated as voice */
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else /* signal is data (modem) */
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tr = 1;
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/*
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* Quantizer scale factor adaptation.
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*/
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/* FUNCTW & FILTD & DELAY */
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/* update non-steady state step size multiplier */
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state_ptr->yu = y + ((wi - y) >> 5);
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/* LIMB */
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if (state_ptr->yu < 544) /* 544 <= yu <= 5120 */
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state_ptr->yu = 544;
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else if (state_ptr->yu > 5120)
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state_ptr->yu = 5120;
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/* FILTE & DELAY */
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/* update steady state step size multiplier */
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state_ptr->yl += state_ptr->yu + ((-state_ptr->yl) >> 6);
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/*
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* Adaptive predictor coefficients.
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*/
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if (tr == 1) { /* reset a's and b's for modem signal */
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state_ptr->a[0] = 0;
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state_ptr->a[1] = 0;
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state_ptr->b[0] = 0;
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state_ptr->b[1] = 0;
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state_ptr->b[2] = 0;
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state_ptr->b[3] = 0;
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state_ptr->b[4] = 0;
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state_ptr->b[5] = 0;
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a2p=0; /* won't be used, clear warning */
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} else { /* update a's and b's */
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pks1 = pk0 ^ state_ptr->pk[0]; /* UPA2 */
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/* update predictor pole a[1] */
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a2p = state_ptr->a[1] - (state_ptr->a[1] >> 7);
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if (dqsez != 0) {
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fa1 = (pks1) ? state_ptr->a[0] : -state_ptr->a[0];
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if (fa1 < -8191) /* a2p = function of fa1 */
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a2p -= 0x100;
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else if (fa1 > 8191)
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a2p += 0xFF;
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else
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a2p += fa1 >> 5;
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if (pk0 ^ state_ptr->pk[1])
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/* LIMC */
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if (a2p <= -12160)
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a2p = -12288;
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else if (a2p >= 12416)
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a2p = 12288;
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else
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a2p -= 0x80;
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else if (a2p <= -12416)
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a2p = -12288;
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else if (a2p >= 12160)
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a2p = 12288;
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else
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a2p += 0x80;
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}
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/* TRIGB & DELAY */
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state_ptr->a[1] = a2p;
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/* UPA1 */
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/* update predictor pole a[0] */
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state_ptr->a[0] -= state_ptr->a[0] >> 8;
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if (dqsez != 0) {
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if (pks1 == 0)
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state_ptr->a[0] += 192;
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else
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state_ptr->a[0] -= 192;
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}
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/* LIMD */
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a1ul = 15360 - a2p;
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if (state_ptr->a[0] < -a1ul)
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state_ptr->a[0] = -a1ul;
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else if (state_ptr->a[0] > a1ul)
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state_ptr->a[0] = a1ul;
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/* UPB : update predictor zeros b[6] */
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for (cnt = 0; cnt < 6; cnt++) {
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/*if (code_size == 5)*/ /* for 40Kbps G.723 */
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/* state_ptr->b[cnt] -= state_ptr->b[cnt] >> 9;*/
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/*else*/ /* for G.721 and 24Kbps G.723 */
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state_ptr->b[cnt] -= state_ptr->b[cnt] >> 8;
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if (dq & 0x7FFF) { /* XOR */
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if ((dq ^ state_ptr->dq[cnt]) >= 0)
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state_ptr->b[cnt] += 128;
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else
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state_ptr->b[cnt] -= 128;
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}
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}
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}
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for (cnt = 5; cnt > 0; cnt--)
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state_ptr->dq[cnt] = state_ptr->dq[cnt-1];
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/* FLOAT A : convert dq[0] to 4-bit exp, 6-bit mantissa f.p. */
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if (mag == 0) {
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state_ptr->dq[0] = (dq >= 0) ? 0x20 : 0xFC20;
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} else {
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exp = quan(mag, power2, 15);
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state_ptr->dq[0] = (dq >= 0) ?
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(exp << 6) + ((mag << 6) >> exp) :
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(exp << 6) + ((mag << 6) >> exp) - 0x400;
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}
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state_ptr->sr[1] = state_ptr->sr[0];
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/* FLOAT B : convert sr to 4-bit exp., 6-bit mantissa f.p. */
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if (sr == 0) {
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state_ptr->sr[0] = 0x20;
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} else if (sr > 0) {
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exp = quan(sr, power2, 15);
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state_ptr->sr[0] = (exp << 6) + ((sr << 6) >> exp);
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} else if (sr > -32768) {
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mag = -sr;
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exp = quan(mag, power2, 15);
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state_ptr->sr[0] = (exp << 6) + ((mag << 6) >> exp) - 0x400;
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} else
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state_ptr->sr[0] = 0xFC20;
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/* DELAY A */
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state_ptr->pk[1] = state_ptr->pk[0];
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state_ptr->pk[0] = pk0;
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/* TONE */
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if (tr == 1) /* this sample has been treated as data */
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state_ptr->td = 0; /* next one will be treated as voice */
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else if (a2p < -11776) /* small sample-to-sample correlation */
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state_ptr->td = 1; /* signal may be data */
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else /* signal is voice */
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state_ptr->td = 0;
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/*
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* Adaptation speed control.
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*/
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state_ptr->dms += (fi - state_ptr->dms) >> 5; /* FILTA */
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state_ptr->dml += (((fi << 2) - state_ptr->dml) >> 7); /* FILTB */
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if (tr == 1)
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state_ptr->ap = 256;
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else if (y < 1536) /* SUBTC */
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state_ptr->ap += (0x200 - state_ptr->ap) >> 4;
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else if (state_ptr->td == 1)
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state_ptr->ap += (0x200 - state_ptr->ap) >> 4;
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else if (abs((state_ptr->dms << 2) - state_ptr->dml) >=
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(state_ptr->dml >> 3))
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state_ptr->ap += (0x200 - state_ptr->ap) >> 4;
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else
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state_ptr->ap += (-state_ptr->ap) >> 4;
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}
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/*
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* Maps G.721 code word to reconstructed scale factor normalized log
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* magnitude values.
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*/
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static short _dqlntab[16] = {-2048, 4, 135, 213, 273, 323, 373, 425,
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425, 373, 323, 273, 213, 135, 4, -2048};
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/* Maps G.721 code word to log of scale factor multiplier. */
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static short _witab[16] = {-12, 18, 41, 64, 112, 198, 355, 1122,
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1122, 355, 198, 112, 64, 41, 18, -12};
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/*
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* Maps G.721 code words to a set of values whose long and short
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* term averages are computed and then compared to give an indication
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* how stationary (steady state) the signal is.
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*/
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static short _fitab[16] = {0, 0, 0, 0x200, 0x200, 0x200, 0x600, 0xE00,
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0xE00, 0x600, 0x200, 0x200, 0x200, 0, 0, 0};
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/*
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* g721_decoder()
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*
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* Description:
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*
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* Decodes a 4-bit code of G.721 encoded data of i and
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* returns the resulting linear PCM, A-law or u-law value.
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* return -1 for unknown out_coding value.
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*/
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int
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g721_decoder(int i,
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struct g72x_state *state_ptr)
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{
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short sezi, sei, sez, se; /* ACCUM */
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short y; /* MIX */
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short sr; /* ADDB */
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short dq;
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short dqsez;
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i &= 0x0f; /* mask to get proper bits */
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sezi = predictor_zero(state_ptr);
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sez = sezi >> 1;
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sei = sezi + predictor_pole(state_ptr);
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se = sei >> 1; /* se = estimated signal */
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y = step_size(state_ptr); /* dynamic quantizer step size */
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dq = reconstruct(i & 0x08, _dqlntab[i], y); /* quantized diff. */
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sr = (dq < 0) ? (se - (dq & 0x3FFF)) : se + dq; /* reconst. signal */
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dqsez = sr - se + sez; /* pole prediction diff. */
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update(y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);
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return (sr << 2); /* sr was 14-bit dynamic range */
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}
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