mirror of
https://github.com/libretro/scummvm.git
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128 lines
4.0 KiB
C++
128 lines
4.0 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 "audio/decoders/g711.h"
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#include "audio/audiostream.h"
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#include "common/stream.h"
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#include "common/util.h"
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/* from g711.c by SUN microsystems (unrestricted use) */
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#define SIGN_BIT (0x80) /* Sign bit for a A-law byte. */
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#define QUANT_MASK (0xf) /* Quantization field mask. */
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#define SEG_SHIFT (4) /* Left shift for segment number. */
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#define SEG_MASK (0x70) /* Segment field mask. */
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#define BIAS (0x84) /* Bias for linear code. */
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namespace Audio {
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/**
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* Logarithmic PCM (G.711)
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* https://en.wikipedia.org/wiki/G.711
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* https://wiki.multimedia.cx/index.php/PCM#Logarithmic_PCM
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*/
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class G711AudioStream : public SeekableAudioStream {
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Common::DisposablePtr<Common::SeekableReadStream> _stream;
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const int _rate;
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const int _channels;
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protected:
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virtual int16 decodeSample(uint8 val) = 0;
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public:
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G711AudioStream(Common::SeekableReadStream *stream, DisposeAfterUse::Flag disposeAfterUse, int rate, int channels) :
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_stream(stream, disposeAfterUse),
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_rate(rate),
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_channels(channels) {
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}
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int readBuffer(int16 *buffer, const int numSamples) override {
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int samples;
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for (samples = 0; samples < numSamples; samples++) {
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uint8 val = _stream->readByte();
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if (endOfData())
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break;
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buffer[samples] = decodeSample(val);
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}
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return samples;
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}
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bool isStereo() const override { return (_channels == 2); }
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int getRate() const override { return _rate; }
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bool endOfData() const override { return _stream->eos(); }
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bool seek(const Timestamp &where) override {
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const uint32 seekSample = convertTimeToStreamPos(where, getRate(), isStereo()).totalNumberOfFrames();
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return _stream->seek(seekSample, SEEK_SET);
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}
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Timestamp getLength() const override {
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return Timestamp(0, _stream->size() / _channels, _rate);
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}
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};
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class G711ALawStream : public G711AudioStream {
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int16 decodeSample(uint8 val) override {
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val ^= 0x55;
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int t = val & QUANT_MASK;
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int seg = ((unsigned)val & SEG_MASK) >> SEG_SHIFT;
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if (seg)
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t = (t + t + 1 + 32) << (seg + 2);
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else
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t = (t + t + 1) << 3;
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return (val & SIGN_BIT) ? t : -t;
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}
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public:
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G711ALawStream(Common::SeekableReadStream *stream, DisposeAfterUse::Flag disposeAfterUse, int rate, int channels) :
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G711AudioStream(stream, disposeAfterUse, rate, channels) {
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}
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};
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SeekableAudioStream *makeALawStream(Common::SeekableReadStream *stream, DisposeAfterUse::Flag disposeAfterUse, int rate, int channels) {
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return new G711ALawStream(stream, disposeAfterUse, rate, channels);
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}
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class G711MuLawStream : public G711AudioStream {
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int16 decodeSample(uint8 val) override {
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val = ~val;
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int t = ((val & QUANT_MASK) << 3) + BIAS;
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t <<= ((unsigned)val & SEG_MASK) >> SEG_SHIFT;
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return (val & SIGN_BIT) ? (BIAS - t) : (t - BIAS);
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}
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public:
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G711MuLawStream(Common::SeekableReadStream *stream, DisposeAfterUse::Flag disposeAfterUse, int rate, int channels) :
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G711AudioStream(stream, disposeAfterUse, rate, channels) {
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}
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};
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SeekableAudioStream *makeMuLawStream(Common::SeekableReadStream *stream, DisposeAfterUse::Flag disposeAfterUse, int rate, int channels) {
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return new G711MuLawStream(stream, disposeAfterUse, rate, channels);
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}
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} // End of namespace Audio
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