macmixer.h

/* 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 "audio/audiostream.h"
#include "audio/mixer.h"
#include "common/frac.h"
#include "common/mutex.h"
#include "common/system.h"

#ifndef DGDS_SOUND_DRIVERS_MACMIXER_H
#define DGDS_SOUND_DRIVERS_MACMIXER_H

namespace Dgds {

// Unsigned version of frac_t
typedef uint32 ufrac_t;
static inline ufrac_t uintToUfrac(uint16 value) { return value << FRAC_BITS; }
static inline uint16 ufracToUint(ufrac_t value) { return value >> FRAC_BITS; }

template <typename T>
class Mixer_Mac : public Audio::AudioStream {
public:
    enum {
        kChannels = 4,
        kInterruptFreq = 60
    };

    enum Mode {
        kModeAuthentic,
        kModeHq,
        kModeHqStereo
    };

    Mixer_Mac(Mode mode);
    void startMixer();
    void stopMixer();
    void setMixerVolume(byte volume) { _mixVolume = volume; }
    void resetChannel(uint channel);
    void resetChannels();
    // NOTE: Last sample accessed is data[endOffset + 1] in kModeHq(Stereo)
    void setChannelData(uint channel, const byte *data, uint16 startOffset, uint16 endOffset, uint16 loopLength = 0);
    void setChannelStep(uint channel, ufrac_t step);
    void setChannelVolume(uint channel, byte volume);
    void setChannelPan(uint channel, byte pan);

    // AudioStream
    bool isStereo() const override { return _mode == kModeHqStereo; }
    int getRate() const override { return (_mode == kModeAuthentic ? 11127 : g_system->getMixer()->getOutputRate()); }
    int readBuffer(int16 *data, const int numSamples) override;
    bool endOfData() const override { return false; }

    Common::Mutex _mutex;

private:
    template <Mode mode>
    void generateSamples(int16 *buf, int len);

    struct Channel {
        ufrac_t pos;
        ufrac_t step;
        const byte *data;
        uint16 endOffset;
        uint16 loopLength;
        byte volume;
        int8 pan;
    };

    ufrac_t _nextTick;
    ufrac_t _samplesPerTick;
    bool _isPlaying;
    const Mode _mode;
    Channel _mixChannels[kChannels];
    byte _mixVolume;
};

template <typename T>
Mixer_Mac<T>::Mixer_Mac(Mode mode) :
    _nextTick(0),
    _samplesPerTick(0),
    _mode(mode),
    _isPlaying(false),
    _mixChannels(),
    _mixVolume(8) {}

template <typename T>
void Mixer_Mac<T>::startMixer() {
    _nextTick = _samplesPerTick = uintToUfrac(getRate() / kInterruptFreq) + uintToUfrac(getRate() % kInterruptFreq) / kInterruptFreq;

    resetChannels();
    _isPlaying = true;
}

template <typename T>
void Mixer_Mac<T>::stopMixer() {
    resetChannels();
    _isPlaying = false;
}

template <typename T>
void Mixer_Mac<T>::setChannelData(uint channel, const byte *data, uint16 startOffset, uint16 endOffset, uint16 loopLength) {
    assert(channel < kChannels);

    Channel &ch = _mixChannels[channel];

    ch.data = data;
    ch.pos = uintToUfrac(startOffset);
    ch.endOffset = endOffset;
    ch.loopLength = loopLength;
}

template <typename T>
void Mixer_Mac<T>::setChannelStep(uint channel, ufrac_t step) {
    assert(channel < kChannels);

    if (_mode == kModeAuthentic) {
        _mixChannels[channel].step = step;
    } else {
        // We could take 11127Hz here, but it appears the original steps were
        // computed for 11000Hz
        // FIXME: One or two more bits of step precision might be nice here
        _mixChannels[channel].step = (ufrac_t)(step * 11000ULL / getRate());
    }
}

template <typename T>
void Mixer_Mac<T>::setChannelVolume(uint channel, byte volume) {
    assert(channel < kChannels);
    _mixChannels[channel].volume = volume;
}

template <typename T>
void Mixer_Mac<T>::setChannelPan(uint channel, byte pan) {
    assert(channel < kChannels);
    _mixChannels[channel].pan = pan;
}

template <typename T>
template <typename Mixer_Mac<T>::Mode mode>
void Mixer_Mac<T>::generateSamples(int16 *data, int len) {
    for (int i = 0; i < len; ++i) {
        int32 mixL = 0;
        int32 mixR = 0;

        for (int ci = 0; ci < kChannels; ++ci) {
            Channel &ch = _mixChannels[ci];

            if (!ch.data)
                continue;

            const uint16 curOffset = ufracToUint(ch.pos);

            if (mode == kModeHq || mode == kModeHqStereo) {
                int32 sample = (ch.data[curOffset] - 0x80) << 8;
                // Since _extraSamples > 0, we can safely access this sample
                const int32 sample2 = (ch.data[curOffset + 1] - 0x80) << 8;
                sample += fracToInt((sample2 - sample) * (ch.pos & FRAC_LO_MASK));
                sample *= ch.volume;

                if (mode == kModeHqStereo) {
                    mixL += sample * (127 - ch.pan) / (63 * 64);
                    mixR += sample * ch.pan / (63 * 64);
                } else {
                    mixL += sample / 63;
                }
            } else {
                mixL += static_cast<T *>(this)->applyChannelVolume(ch.volume, ch.data[curOffset]) << 8;
            }

            ch.pos += ch.step;

            if (ufracToUint(ch.pos) > ch.endOffset) {
                if (ch.loopLength > 0) {
                    do {
                        ch.pos -= uintToUfrac(ch.loopLength);
                    } while (ufracToUint(ch.pos) > ch.endOffset);
                } else {
                    static_cast<T *>(this)->onChannelFinished(ci);
                    ch.data = nullptr;
                }
            }
        }

        *data++ = (int16)CLIP<int32>(mixL, -32768, 32767) * _mixVolume / 8;
        if (mode == kModeHqStereo)
            *data++ = (int16)CLIP<int32>(mixR, -32768, 32767) * _mixVolume / 8;
    }
}

template <typename T>
int Mixer_Mac<T>::readBuffer(int16 *data, const int numSamples) {
    // Would probably be better inside generateSamples, but let's follow Audio::Paula
    Common::StackLock lock(_mutex);

    if (!_isPlaying) {
        memset(data, 0, numSamples * 2);
        return numSamples;
    }

    const int stereoFactor = isStereo() ? 2 : 1;
    int len = numSamples / stereoFactor;

    do {
        int step = len;
        if (step > ufracToUint(_nextTick))
            step = ufracToUint(_nextTick);

        switch (_mode) {
        case kModeAuthentic:
            generateSamples<kModeAuthentic>(data, step);
            break;
        case kModeHq:
            generateSamples<kModeHq>(data, step);
            break;
        case kModeHqStereo:
            generateSamples<kModeHqStereo>(data, step);
        }

        _nextTick -= uintToUfrac(step);
        if (ufracToUint(_nextTick) == 0) {
            static_cast<T *>(this)->interrupt();
            _nextTick += _samplesPerTick;
        }

        data += step * stereoFactor;
        len -= step;
    } while (len);

    return numSamples;
}

template <typename T>
void Mixer_Mac<T>::resetChannel(uint channel) {
    assert(channel < kChannels);

    Channel &ch = _mixChannels[channel];

    ch.pos = 0;
    ch.step = 0;
    ch.data = nullptr;
    ch.endOffset = 0;
    ch.loopLength = 0;
    ch.volume = 0;
    ch.pan = 64;
}

template <typename T>
void Mixer_Mac<T>::resetChannels() {
    for (uint ci = 0; ci < kChannels; ++ci)
        resetChannel(ci);
}

} // End of namespace Dgds

#endif // DGDS_SOUND_DRIVERS_MACMIXER_H