qt-everywhere-src-5.15.1/qtmultimedia/src/multimedia/audio/qaudiohelpers.cpp

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#include "qaudiohelpers_p.h"

#include <QDebug>

QT_BEGIN_NAMESPACE

// Base implementation of 24 bits number.
// Used to adjust 3 bytes values by a factor.
// TODO: Uses little-endian only.
class Int24
{
public:
    quint8 data[3];
    Int24(qint32 v) {
        data[0] = v & 0xFF;
        data[1] = (v & 0xFF00) >> 8;
        data[2] = (v & 0xFF0000) >> 16;
    }
    template<class T>
    T multiply(qreal factor, T v = 0) const {
        v |= data[0];
        v |= data[1] << 8;
        v |= data[2] << 16;
        v *= factor;
        return v;
    }
};

class qint24: public Int24
{
public:
    qint24(qint32 v): Int24(v) {}
    qint24 operator*(qreal factor) const {
        // Checks if it is a signed value.
        qint32 v = (data[2] & 0x80) ? 0xFF000000 : 0;
        return multiply(factor, v);
    }
};

class quint24: public Int24
{
public:
    quint24(quint32 v): Int24(v) {}
    quint24 operator*(qreal factor) const {
        return multiply<quint32>(factor);
    }
};


namespace QAudioHelperInternal
{

template<class T> void adjustSamples(qreal factor, const void *src, void *dst, int samples)
{
    const T *pSrc = (const T *)src;
    T *pDst = (T*)dst;
    for ( int i = 0; i < samples; i++ )
        pDst[i] = pSrc[i] * factor;
}

// Unsigned samples are biased around 0x80/0x8000 :/
// This makes a pure template solution a bit unwieldy but possible
template<class T> struct signedVersion {};
template<> struct signedVersion<quint8>
{
    typedef qint8 TS;
    enum {offset = 0x80};
};

template<> struct signedVersion<quint16>
{
    typedef qint16 TS;
    enum {offset = 0x8000};
};

template<> struct signedVersion<quint32>
{
    typedef qint32 TS;
    enum {offset = 0x80000000};
};

template<class T> void adjustUnsignedSamples(qreal factor, const void *src, void *dst, int samples)
{
    const T *pSrc = (const T *)src;
    T *pDst = (T*)dst;
    for ( int i = 0; i < samples; i++ ) {
        pDst[i] = signedVersion<T>::offset + ((typename signedVersion<T>::TS)(pSrc[i] - signedVersion<T>::offset) * factor);
    }
}

void qMultiplySamples(qreal factor, const QAudioFormat &format, const void* src, void* dest, int len)
{
    int samplesCount = len / (format.sampleSize()/8);

    switch ( format.sampleSize() ) {
    case 8:
        if (format.sampleType() == QAudioFormat::SignedInt)
            QAudioHelperInternal::adjustSamples<qint8>(factor,src,dest,samplesCount);
        else if (format.sampleType() == QAudioFormat::UnSignedInt)
            QAudioHelperInternal::adjustUnsignedSamples<quint8>(factor,src,dest,samplesCount);
        break;
    case 16:
        if (format.sampleType() == QAudioFormat::SignedInt)
            QAudioHelperInternal::adjustSamples<qint16>(factor,src,dest,samplesCount);
        else if (format.sampleType() == QAudioFormat::UnSignedInt)
            QAudioHelperInternal::adjustUnsignedSamples<quint16>(factor,src,dest,samplesCount);
        break;
    case 24:
        if (format.sampleType() == QAudioFormat::SignedInt)
            QAudioHelperInternal::adjustSamples<qint24>(factor,src,dest,samplesCount);
        else if (format.sampleType() == QAudioFormat::UnSignedInt)
            QAudioHelperInternal::adjustSamples<quint24>(factor,src,dest,samplesCount);
        break;
    default:
        if (format.sampleType() == QAudioFormat::SignedInt)
            QAudioHelperInternal::adjustSamples<qint32>(factor,src,dest,samplesCount);
        else if (format.sampleType() == QAudioFormat::UnSignedInt)
            QAudioHelperInternal::adjustUnsignedSamples<quint32>(factor,src,dest,samplesCount);
        else if (format.sampleType() == QAudioFormat::Float)
            QAudioHelperInternal::adjustSamples<float>(factor,src,dest,samplesCount);
    }
}
}

QT_END_NAMESPACE