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105 lines
2.9 KiB
C++
105 lines
2.9 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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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 General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include "common/stream.h"
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#include "common/util.h"
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#include "common/textconsole.h"
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#include "audio/audiostream.h"
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#include "audio/decoders/xan_dpcm.h"
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namespace Audio {
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/**
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* Implements the Xan DPCM decoder used in Crusader: No Regret and Wing
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* Commander IV movies. Implementation based on the description on the
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* MultiMedia Wiki:
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* https://wiki.multimedia.cx/index.php/Xan_DPCM
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*/
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class Xan_DPCMStream : public Audio::AudioStream {
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public:
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Xan_DPCMStream(int rate, int channels, Common::SeekableReadStream *data) : _rate(rate), _channels(channels), _data(data) {
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assert(channels == 1 || channels == 2);
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_pred[0] = data->readSint16LE();
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if (channels == 2)
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_pred[1] = data->readSint16LE();
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_shift[0] = 4;
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_shift[1] = 4;
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};
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int readBuffer(int16 *buffer, const int numSamples) override {
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int i = 0;
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for (; i < numSamples; i++) {
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int32 *pshift = ((_channels == 2 && (i % 2)) ? _shift + 1 : _shift);
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int32 *ppred = ((_channels == 2 && (i % 2)) ? _pred + 1 : _pred);
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const uint8 b = _data->readByte();
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const int diff = static_cast<int8>(b & 0xFC) * 256;
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if ((b & 3) == 3)
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*pshift += 1;
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else
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*pshift -= (2 * (b & 3));
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if (*pshift < 0)
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*pshift = 0;
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if (*pshift > 15) {
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warning("Xan DPCM shift should not go over 15, corrupt data?");
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*pshift = 15;
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}
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*ppred += (diff >> *pshift);
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*ppred = CLIP(*ppred, (int32)-32768, (int32)32767);
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*buffer = *ppred;
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buffer++;
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if (_data->eos())
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break;
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}
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return i;
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}
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bool isStereo() const override {
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return _channels == 2;
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}
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int getRate() const override {
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return _rate;
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}
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bool endOfData() const override {
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return _data->eos();
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}
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private:
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int _channels;
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int _rate;
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Common::SeekableReadStream *_data;
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int32 _pred[2];
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int32 _shift[2];
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};
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XanDPCMStream::XanDPCMStream(int rate, int channels) :
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Audio::StatelessPacketizedAudioStream(rate, channels) {
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}
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AudioStream *XanDPCMStream::makeStream(Common::SeekableReadStream *data) {
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return new Xan_DPCMStream(getRate(), getChannels(), data);
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}
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} // End of namespace Audio
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