Initial commit

audio/decoders/xan_dpcm.cpp

@@ -0,0 +1,104 @@
+/* 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