281 lines
7.9 KiB
C++
Executable file
281 lines
7.9 KiB
C++
Executable file
/******************************************************************************\
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* Copyright (c) 2004-2006
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*
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* Author(s):
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* Volker Fischer, Erik de Castro Lopo
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*
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* This code is based on the Open-Source implementation of IMA-ADPCM written
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* by Erik de Castro Lopo <erikd[at-#]mega-nerd[dot*]com> in 1999-2004
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*
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* Changes:
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* - only support for one channel
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* - put 2 audio samples in header to get even number of audio samples encoded
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*
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******************************************************************************
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*
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* This program is free software; you can redistribute it and/or modify it under
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* the terms of the GNU General Public License as published by the Free Software
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* Foundation; either version 2 of the License, or (at your option) any later
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* version.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc.,
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* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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\******************************************************************************/
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#include "audiocompr.h"
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/* Implementation *************************************************************/
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int CAudioCompression::Init ( const int iNewAudioLen,
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const EAudComprType eNewAuCoTy )
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{
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eAudComprType = eNewAuCoTy;
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switch ( eNewAuCoTy )
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{
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case CT_NONE:
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return iCodeSize = 2 * iNewAudioLen; /* short = 2 * byte */
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case CT_IMAADPCM:
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return ImaAdpcm.Init ( iNewAudioLen );
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default: return 0;
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}
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}
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CVector<unsigned char> CAudioCompression::Encode ( const CVector<short>& vecsAudio )
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{
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if ( eAudComprType == CT_NONE )
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{
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/* no compression, simply ship pure samples */
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CVector<unsigned char> vecbyOut ( iCodeSize );
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const int iAudSize = iCodeSize / 2;
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for ( int i = 0; i < iAudSize; i++ )
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{
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vecbyOut[2 * i] = vecsAudio[i] & 0xFF;
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vecbyOut[2 * i + 1] = ( vecsAudio[i] >> 8 ) & 0xFF;
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}
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return vecbyOut;
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}
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else
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{
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switch ( eAudComprType )
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{
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case CT_IMAADPCM:
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return ImaAdpcm.Encode ( vecsAudio ); /* IMA-ADPCM */
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default:
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return CVector<unsigned char> ( 0 );
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}
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}
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}
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CVector<short> CAudioCompression::Decode ( const CVector<unsigned char>& vecbyAdpcm )
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{
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if ( eAudComprType == CT_NONE )
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{
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/* no compression, reassemble pure samples */
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const int iAudSize = iCodeSize / 2;
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CVector<short> vecsOut ( iAudSize );
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for ( int i = 0; i < iAudSize; i++ )
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{
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int current = vecbyAdpcm[2 * i] | ( vecbyAdpcm[2 * i + 1] << 8 );
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if ( current & 0x8000 )
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{
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current -= 0x10000;
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}
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vecsOut[i] = (short) current;
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}
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return vecsOut;
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}
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else
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{
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switch ( eAudComprType )
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{
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case CT_IMAADPCM:
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return ImaAdpcm.Decode ( vecbyAdpcm ); /* IMA-ADPCM */
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default:
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return CVector<short> ( 0 );
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}
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}
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}
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/* IMA-ADPCM implementation ------------------------------------------------- */
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int CImaAdpcm::Init ( const int iNewAudioLen )
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{
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/* set lengths for audio and compressed data */
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iAudSize = iNewAudioLen;
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iAdpcmSize = 4 /* bytes header */ + (int) ceil (
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(double) ( iAudSize - 2 /* first two samples are in header */ ) / 2 );
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iStepindEnc = 0;
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return iAdpcmSize;
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}
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CVector<unsigned char> CImaAdpcm::Encode ( const CVector<short>& vecsAudio )
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{
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int i;
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CVector<unsigned char> vecbyAdpcm;
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CVector<unsigned char> vecbyAdpcmTemp;
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/* init size */
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vecbyAdpcm.Init ( iAdpcmSize );
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vecbyAdpcmTemp.Init ( iAudSize );
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/* encode the block header ----------------------------------------------- */
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vecbyAdpcm[0] = vecsAudio[0] & 0xFF;
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vecbyAdpcm[1] = ( vecsAudio[0] >> 8 ) & 0xFF;
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vecbyAdpcm[2] = iStepindEnc;
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int iPrevAudio = vecsAudio[0];
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/* encode the samples as 4 bit ------------------------------------------- */
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for ( i = 1; i < iAudSize; i++ )
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{
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/* init diff and step */
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int diff = vecsAudio[i] - iPrevAudio;
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int step = ima_step_size[iStepindEnc];
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short bytecode = 0;
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int vpdiff = step >> 3;
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if ( diff < 0 )
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{
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bytecode = 8;
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diff = -diff;
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}
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short mask = 4;
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while ( mask )
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{
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if ( diff >= step )
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{
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bytecode |= mask;
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diff -= step;
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vpdiff += step;
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}
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step >>= 1;
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mask >>= 1;
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}
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if ( bytecode & 8 )
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{
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iPrevAudio -= vpdiff;
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}
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else
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{
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iPrevAudio += vpdiff;
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}
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/* adjust step size */
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iStepindEnc += ima_indx_adjust[bytecode];
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/* check that values do not exceed the bounds */
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iPrevAudio = CheckBounds ( iPrevAudio, _MINSHORT, _MAXSHORT );
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iStepindEnc = CheckBounds ( iStepindEnc, 0, IMA_STEP_SIZE_TAB_LEN - 1 );
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/* use the input buffer as an intermediate result buffer */
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vecbyAdpcmTemp[i] = bytecode;
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}
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/* pack the 4 bit encoded samples ---------------------------------------- */
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/* The first encoded audio sample is in header */
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vecbyAdpcm[3] = vecbyAdpcmTemp[1] & 0x0F;
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for ( i = 4; i < iAdpcmSize; i++ )
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{
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vecbyAdpcm[i] = vecbyAdpcmTemp[2 * i - 6] & 0x0F;
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vecbyAdpcm[i] |= ( vecbyAdpcmTemp[2 * i - 5] << 4 ) & 0xF0;
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}
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return vecbyAdpcm;
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}
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CVector<short> CImaAdpcm::Decode ( const CVector<unsigned char>& vecbyAdpcm )
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{
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int i;
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CVector<short> vecsAudio;
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vecsAudio.Init ( iAudSize );
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/* read and check the block header --------------------------------------- */
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int current = vecbyAdpcm[0] | ( vecbyAdpcm[1] << 8 );
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if ( current & 0x8000 )
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{
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current -= 0x10000;
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}
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/* get and bound step index */
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int iStepindDec = CheckBounds ( vecbyAdpcm[2], 0, IMA_STEP_SIZE_TAB_LEN - 1 );
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/* set first sample which was delivered in the header */
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vecsAudio[0] = current;
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/* --------------------------------------------------------------------------
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pull apart the packed 4 bit samples and store them in their correct sample
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positions */
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/* The first encoded audio sample is in header */
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vecsAudio[1] = vecbyAdpcm[3] & 0x0F;
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for ( i = 4; i < iAdpcmSize; i++ )
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{
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const short bytecode = vecbyAdpcm[i];
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vecsAudio[2 * i - 6] = bytecode & 0x0F;
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vecsAudio[2 * i - 5] = ( bytecode >> 4 ) & 0x0F;
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}
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/* decode the encoded 4 bit samples -------------------------------------- */
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for ( i = 1; i < iAudSize; i++ )
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{
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const short bytecode = vecsAudio[i] & 0xF ;
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short step = ima_step_size[iStepindDec];
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int current = vecsAudio[i - 1];
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int diff = step >> 3;
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if ( bytecode & 1 )
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{
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diff += step >> 2;
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}
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if ( bytecode & 2 )
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{
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diff += step >> 1;
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}
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if ( bytecode & 4 )
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{
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diff += step;
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}
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if ( bytecode & 8 )
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{
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diff = -diff;
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}
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current += diff;
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iStepindDec += ima_indx_adjust[bytecode];
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/* check that values do not exceed the bounds */
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current = CheckBounds ( current, _MINSHORT, _MAXSHORT );
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iStepindDec = CheckBounds ( iStepindDec, 0, IMA_STEP_SIZE_TAB_LEN - 1 );
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vecsAudio[i] = current;
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}
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return vecsAudio;
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}
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