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/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* 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 3 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, see <http://www.gnu.org/licenses/>.
*
*/
#include "common/stream.h"
#include "common/util.h"
#include "common/textconsole.h"
#include "audio/audiostream.h"
#include "audio/decoders/xan_dpcm.h"
namespace Audio {
/**
* Implements the Xan DPCM decoder used in Crusader: No Regret and Wing
* Commander IV movies. Implementation based on the description on the
* MultiMedia Wiki:
* https://wiki.multimedia.cx/index.php/Xan_DPCM
*/
class Xan_DPCMStream : public Audio::AudioStream {
public:
Xan_DPCMStream(int rate, int channels, Common::SeekableReadStream *data) : _rate(rate), _channels(channels), _data(data) {
assert(channels == 1 || channels == 2);
_pred[0] = data->readSint16LE();
if (channels == 2)
_pred[1] = data->readSint16LE();
_shift[0] = 4;
_shift[1] = 4;
};
int readBuffer(int16 *buffer, const int numSamples) override {
int i = 0;
for (; i < numSamples; i++) {
int32 *pshift = ((_channels == 2 && (i % 2)) ? _shift + 1 : _shift);
int32 *ppred = ((_channels == 2 && (i % 2)) ? _pred + 1 : _pred);
const uint8 b = _data->readByte();
const int diff = static_cast<int8>(b & 0xFC) * 256;
if ((b & 3) == 3)
*pshift += 1;
else
*pshift -= (2 * (b & 3));
if (*pshift < 0)
*pshift = 0;
if (*pshift > 15) {
warning("Xan DPCM shift should not go over 15, corrupt data?");
*pshift = 15;
}
*ppred += (diff >> *pshift);
*ppred = CLIP(*ppred, (int32)-32768, (int32)32767);
*buffer = *ppred;
buffer++;
if (_data->eos())
break;
}
return i;
}
bool isStereo() const override {
return _channels == 2;
}
int getRate() const override {
return _rate;
}
bool endOfData() const override {
return _data->eos();
}
private:
int _channels;
int _rate;
Common::SeekableReadStream *_data;
int32 _pred[2];
int32 _shift[2];
};
XanDPCMStream::XanDPCMStream(int rate, int channels) :
Audio::StatelessPacketizedAudioStream(rate, channels) {
}
AudioStream *XanDPCMStream::makeStream(Common::SeekableReadStream *data) {
return new Xan_DPCMStream(getRate(), getChannels(), data);
}
} // End of namespace Audio
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