rate.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/>.
 *
 */

#ifndef AUDIO_RATE_H
#define AUDIO_RATE_H

#include "common/frac.h"

namespace Audio {
class AudioStream;

typedef uint16 st_volume_t;
typedef uint32 st_size_t;
typedef uint32 st_rate_t;

enum MixMode {
    MIX_ADD,
    MIX_CLAMPED_ADD
};

// This assumes that 'a' and 'b' are 24-bit samples at most
template <MixMode Mode, typename T>
static inline void processSample(T& a, int b) {
    constexpr unsigned long long highestBit = 1ULL << (sizeof(T) * 8 - 1);
    constexpr int maxVal = (int)(highestBit - 1);
    constexpr int minVal = ~maxVal;

#ifdef OUTPUT_UNSIGNED_AUDIO
    constexpr int signMask = (int)highestBit;
#endif

    if (Mode == MIX_ADD) {
        a += b;
    } else if (Mode == MIX_CLAMPED_ADD) {
        int val;
#ifdef OUTPUT_UNSIGNED_AUDIO
        val = ((int)a ^ signMask) + b;
#else
        val = (int)a + b;
#endif

        if (val > maxVal)
            val = maxVal;
        else if (val < minVal)
            val = minVal;

#ifdef OUTPUT_UNSIGNED_AUDIO
        a = (T)(val ^ signMask);
#else
        a = (T)val;
#endif
    }
}

// Fallback for engine code
template <typename T>
static inline void clampedAdd(T& a, int b) {
    processSample<MIX_CLAMPED_ADD>(a, b);
}

class RateConverter {
public:
    RateConverter() {}
    virtual ~RateConverter() {}

    virtual int convert(AudioStream &input, byte *outBuffer, uint outBytesPerSample, st_size_t numSamples, st_volume_t vol_l, st_volume_t vol_r, MixMode mixMode) = 0;

    virtual void setInputRate(st_rate_t inputRate) = 0;
    virtual void setOutputRate(st_rate_t outputRate) = 0;

    virtual st_rate_t getInputRate() const = 0;
    virtual st_rate_t getOutputRate() const = 0;

    virtual bool needsDraining() const = 0;
};

RateConverter *makeRateConverter(st_rate_t inRate, st_rate_t outRate, bool inStereo, bool outStereo, bool reverseStereo);

} // End of namespace Audio

#endif