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# voicegenerator.cpp Example File

demos/mobile/guitartuner/src/voicegenerator.cpp

     /****************************************************************************
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     ** This file is part of the QtDeclarative module of the Qt Toolkit.
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     #include "voicegenerator.h"

     const int BufferSizeMilliseconds = 100;

     VoiceGenerator::VoiceGenerator(const QAudioFormat &format,
                                    qreal frequency, qreal amplitude,
                                    QObject *parent) :
         QIODevice(parent),
         m_format(format),
         m_amplitude(0.5)
     {
         Q_ASSERT(m_format.sampleSize() % 8 == 0);
         int sampleBytes = m_format.channels() * (m_format.sampleSize() / 8);
         // + 1 to round up, just to be sure that all samples fit.
         qint64 samplesInBuffer = m_format.sampleRate()
                                  * BufferSizeMilliseconds / 1000 + 1;
         qint64 length = samplesInBuffer * sampleBytes;
         m_buffer.resize(length);
         m_max_position = 0;
         m_position = 0;
         m_amplitude = amplitude;
         setFrequency(frequency);
     }

     VoiceGenerator::~VoiceGenerator()
     {
     }

     /**
       * Opens the parent QIODevice.
       */
     void VoiceGenerator::start()
     {
         open(QIODevice::ReadOnly);
     }

     /**
       * Closes the parent QIODevice. Resets the m_position to zero.
       */
     void VoiceGenerator::stop()
     {
         close();
         m_position = 0;
     }

     /**
       * Sets the frequency to new frequency.
       */
     void VoiceGenerator::setFrequency(qreal frequency)
     {
         Q_ASSERT(1 / frequency < BufferSizeMilliseconds);
         this->m_frequency = frequency;
         refreshData();
     }

     /**
       * Sets the amplitude for the voice.
       */
     void VoiceGenerator::setAmplitude(qreal amplitude)
     {
         Q_ASSERT(amplitude >= 0);
         m_amplitude = amplitude;
         refreshData();
     }

     /**
       * Returns the current frequency.
       */
     qreal VoiceGenerator::frequency()
     {
         return m_frequency;
     }

     /**
       * Generates voice data corresponding a sine voice with target frequency.
       * The number of data generated is calculated
       * and stored to m_max_position.
       */
     void VoiceGenerator::refreshData()
     {
         const int channelBytes = m_format.sampleSize() / 8;
         const int sampleSize = m_format.channels() * channelBytes;
         const qint64 voiceOscillationsInBuffer = BufferSizeMilliseconds
                                              * m_frequency / 1000;
         const qint64 voiceSamplesInBuffer = voiceOscillationsInBuffer
                                        * m_format.sampleRate() / m_frequency;
         m_max_position = voiceSamplesInBuffer * sampleSize;
         qint64 dataGenerationLength = m_buffer.size();

         Q_ASSERT(m_max_position % (sampleSize) == 0);
         Q_ASSERT(dataGenerationLength <= m_buffer.size());

         short *t = (short*)m_buffer.data();

     /*
         int te ;
         static float fpos = 0.0f;
         //dataGenerationLength>>=1;           // in words
         for (int f=0; f<dataGenerationLength; f++) {
           te = (short)((sinf(fpos))* (65536.0f/2.0f));
           fpos += m_frequency/2000.0f;
           t[f]= te;
         };

         m_amplitude = 1.0f; */
         uchar *ptr = reinterpret_cast<uchar *>(m_buffer.data());
         int sampleIndex = 0;
         while (dataGenerationLength > 0) {
             qreal realValue = 0;
             if (sampleIndex < voiceSamplesInBuffer) {
                 realValue = m_amplitude
                            *qSin(2.0f * M_PI * m_frequency
                                  * qreal(sampleIndex % m_format.sampleRate())
                                    / m_format.sampleRate());
             }
             for (int i=0; i<m_format.channels(); ++i) {
                 setValue(ptr, realValue);
                 ptr += channelBytes;
                 dataGenerationLength -= channelBytes;
             }
             ++sampleIndex;
         }
     }

     /**
       * Stores the realValue into bytes pointed by ptr as an int value.
       * Align-safe.
       */
     void VoiceGenerator::setValue(uchar *ptr, qreal realValue) {
         if (m_format.sampleSize() == 8)
         {
             quint8 value = 0;
             if (m_format.sampleType() == QAudioFormat::UnSignedInt) {
                 value = static_cast<quint8>(
                             qRound((1.0 + realValue) / 2
                                    * M_MAX_AMPLITUDE_8BIT_UNSIGNED));
             } else if (m_format.sampleType() == QAudioFormat::SignedInt) {
                 value = static_cast<qint8>(
                             qRound(realValue
                                    * M_MAX_AMPLITUDE_8BIT_SIGNED));
             }
             *reinterpret_cast<quint8*>(ptr) = value;
         } else if (m_format.sampleSize() == 16) {
             quint16 value = 0;
             if (m_format.sampleType() == QAudioFormat::UnSignedInt) {
                 value = static_cast<quint16>(
                             qRound((1.0 + realValue) / 2
                                    * M_MAX_AMPLITUDE_16BIT_UNSIGNED));
             } else if (m_format.sampleType() == QAudioFormat::SignedInt) {
                 value = static_cast<qint16>(
                             qRound(realValue
                                    * M_MAX_AMPLITUDE_16BIT_SIGNED));
             }
             if (m_format.byteOrder() == QAudioFormat::LittleEndian)
                 qToLittleEndian<qint16>(value, ptr);
             else
                 qToBigEndian<qint16>(value, ptr);
         }
     }

     qint64 VoiceGenerator::bytesAvailable() const
     {
         return m_max_position + QIODevice::bytesAvailable();
     }

     /**
       * Called by the QIODevice. Puts maxlen amount of voice
       * samples into the data array.
       */
     qint64 VoiceGenerator::readData(char *data, qint64 maxlen)
     {
         qint64 total = 0;
         qint64 chunk = 0;
         while (total < maxlen) {
             if (maxlen - total >= m_max_position - m_position) {
                 // the needed buffer is longer than the currently
                 // available buffer from m_position to the m_max_position
                 chunk = m_max_position - m_position;
                 memcpy(data, m_buffer.constData() + m_position, chunk);
                 m_position = 0;
             }
             else {
                 // we can copy the needed data directly, and the loop will end
                 chunk = maxlen - total;
                 memcpy(data, m_buffer.constData() + m_position, chunk);
                 m_position = (m_position + chunk) % m_max_position;
             }
             data += chunk;
             total += chunk;
         }
         return total;
     }

     /**
       * Empty implementation for writeData, since no data is provided
       * for the VoiceGenerator class.
       */
     qint64 VoiceGenerator::writeData(const char *data, qint64 maxlen)
     {
         Q_UNUSED(data);
         Q_UNUSED(maxlen);

         return 0;
     }