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adpcm.cpp

/* ScummVM - Scumm Interpreter
 * Copyright (C) 2005 The ScummVM project
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.

 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.

 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * $Header: /cvsroot/scummvm/scummvm/sound/adpcm.cpp,v 1.8.2.2 2005/10/21 02:25:20 sev Exp $
 *
 */

#include "common/stdafx.h"

#include "sound/adpcm.h"


// Routines to convert 12 bit linear samples to the
// Dialogic or Oki ADPCM coding format aka VOX.
// See also <http://www.comptek.ru/telephony/tnotes/tt1-13.html>
//
// In addition, also IMA ADPCM is supported.

ADPCMInputStream::ADPCMInputStream(Common::SeekableReadStream *stream, uint32 size, typesADPCM type, int channels, uint32 blockAlign)
      : _stream(stream), _channels(channels), _type(type), _blockAlign(blockAlign) {

      _status.last = 0;
      _status.stepIndex = 0;
      _endpos = stream->pos() + size;

      if (type == kADPCMIma && blockAlign == 0)
            error("ADPCMInputStream(): blockAlign isn't specifiled for MS ADPCM IMA");
}

int ADPCMInputStream::readBuffer(int16 *buffer, const int numSamples) {
      switch (_type) {
      case kADPCMOki:
            return readBufferOKI(buffer, numSamples);
            break;
      case kADPCMIma:
            if (_channels == 1)
                  return readBufferMSIMA1(buffer, numSamples);
            else
                  return readBufferMSIMA2(buffer, numSamples);
            break;
      default:
            error("Unsupported ADPCM encoding");
            break;
      }
      return 0;
}

int ADPCMInputStream::readBufferOKI(int16 *buffer, const int numSamples) {
      int samples;
      byte data;

      assert(numSamples % 2 == 0);

      for (samples = 0; samples < numSamples && !_stream->eos() && _stream->pos() < _endpos; samples += 2) {
            data = _stream->readByte();
            buffer[samples] = TO_LE_16(decodeOKI((data >> 4) & 0x0f));
            buffer[samples + 1] = TO_LE_16(decodeOKI(data & 0x0f));
      }
      return samples;
}


int ADPCMInputStream::readBufferMSIMA1(int16 *buffer, const int numSamples) {
      int samples;
      byte data;
      int blockLen;
      int i;

      assert(numSamples % 2 == 0);

      samples = 0;

      while (samples < numSamples && !_stream->eos() && _stream->pos() < _endpos) {
            // read block header
            _status.last = _stream->readSint16LE();
            _status.stepIndex = _stream->readSint16LE();

            blockLen = MIN(_endpos - _stream->pos(), _blockAlign - 4);

            for (i = 0; i < blockLen && !_stream->eos() && _stream->pos() < _endpos; i++, samples += 2) {
                  data = _stream->readByte();
                  buffer[samples] = TO_LE_16(decodeMSIMA(data & 0x0f));
                  buffer[samples + 1] = TO_LE_16(decodeMSIMA((data >> 4) & 0x0f));
            }
      }
      return samples;
}


// Microsoft as usual tries to implement it differently. This method
// is used for stereo data.
int ADPCMInputStream::readBufferMSIMA2(int16 *buffer, const int numSamples) {
      int samples;
      uint32 data;
      int nibble;

      for (samples = 0; samples < numSamples && !_stream->eos() && _stream->pos() < _endpos;) {
            for (int channel = 0; channel < 2; channel++) {
                  data = _stream->readUint32LE();
                  
                  for (nibble = 0; nibble < 8; nibble++) {
                        byte k = ((data & 0xf0000000) >> 28);
                        buffer[samples + channel + nibble * 2] = TO_LE_16(decodeMSIMA(k));
                        data <<= 4;
                  }
            }
            samples += 16;
      }
      return samples;
}

// adjust the step for use on the next sample.
int16 ADPCMInputStream::stepAdjust(byte code) {
      static const int16 adjusts[] = {-1, -1, -1, -1, 2, 4, 6, 8};

      return adjusts[code & 0x07];
}

static const int16 okiStepSize[49] = {
        16,   17,   19,   21,   23,   25,   28,   31,
        34,   37,   41,   45,   50,   55,   60,   66,
        73,   80,   88,   97,  107,  118,  130,  143,
       157,  173,  190,  209,  230,  253,  279,  307,
       337,  371,  408,  449,  494,  544,  598,  658,
       724,  796,  876,  963, 1060, 1166, 1282, 1411,
      1552
};

// Decode Linear to ADPCM
int16 ADPCMInputStream::decodeOKI(byte code) {
      int16 diff, E, SS, samp;

      SS = okiStepSize[_status.stepIndex];
      E = SS/8;
      if (code & 0x01)
            E += SS/4;
      if (code & 0x02)
            E += SS/2;
      if (code & 0x04)
            E += SS;
      diff = (code & 0x08) ? -E : E;
      samp = _status.last + diff;

    // Clip the values to +/- 2^11 (supposed to be 12 bits)
      if (samp > 2048)
            samp = 2048;
      if (samp < -2048)
            samp = -2048;

      _status.last = samp;
      _status.stepIndex += stepAdjust(code);
      if (_status.stepIndex < 0)
            _status.stepIndex = 0;
      if (_status.stepIndex > 48)
            _status.stepIndex = 48;

      // * 16 effectively converts 12-bit input to 16-bit output
      return samp * 16;
}


static const uint16 imaStepTable[89] = {
            7,      8,  9,     10,   11,   12,   13,   14,
         16,       17,   19,   21,   23,   25,   28,   31,
         34,       37,   41,   45,   50,   55,   60,   66,
         73,       80,   88,   97,  107,  118,  130,  143,
        157,      173,  190,  209,  230,  253,  279,  307,
        337,      371,  408,  449,  494,  544,  598,  658,
        724,      796,  876,  963, 1060, 1166, 1282, 1411,
       1552, 1707, 1878, 2066, 2272, 2499, 2749, 3024,
       3327, 3660, 4026, 4428, 4871, 5358, 5894, 6484,
       7132, 7845, 8630, 9493,10442,11487,12635,13899,
      15289,16818,18500,20350,22385,24623,27086,29794,
      32767
};

int16 ADPCMInputStream::decodeMSIMA(byte code) {
      int32 diff, E, SS, samp;

      SS = imaStepTable[_status.stepIndex];
      E = SS >> 3;
      if (code & 0x04)
            E += SS;
      if (code & 0x02)
            E += SS >> 1;
      if (code & 0x01)
            E += SS >> 2;
      diff = (code & 0x08) ? -E : E;
      samp = _status.last + diff;

      if (samp < -0x8000)
            samp = -0x8000;
      else if (samp > 0x7fff)
            samp = 0x7fff;

      _status.last = samp;

      _status.stepIndex += stepAdjust(code);
      if (_status.stepIndex < 0)
            _status.stepIndex = 0;
      if (_status.stepIndex > 88)
            _status.stepIndex = 88;

      return samp;
}

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