Playing a sound with QtMultimedia

   1 from math import pi, sin
   2 import struct, sys
   3 
   4 from PyQt4.QtCore import QBuffer, QByteArray, QIODevice, Qt
   5 from PyQt4.QtGui import QApplication, QFormLayout, QLineEdit, QHBoxLayout, \
   6                         QPushButton, QSlider, QVBoxLayout, QWidget
   7 from PyQt4.QtMultimedia import QAudio, QAudioDeviceInfo, QAudioFormat, QAudioOutput
   8 
   9 class Window(QWidget):
  10 
  11     def __init__(self, parent = None):
  12     
  13         QWidget.__init__(self, parent)
  14         
  15         format = QAudioFormat()
  16         format.setChannels(1)
  17         format.setFrequency(22050)
  18         format.setSampleSize(16)
  19         format.setCodec("audio/pcm")
  20         format.setByteOrder(QAudioFormat.LittleEndian)
  21         format.setSampleType(QAudioFormat.SignedInt)
  22         self.output = QAudioOutput(format, self)
  23         
  24         self.frequency = 440
  25         self.volume = 0
  26         self.buffer = QBuffer()
  27         self.data = QByteArray()
  28         
  29         self.deviceLineEdit = QLineEdit()
  30         self.deviceLineEdit.setReadOnly(True)
  31         self.deviceLineEdit.setText(QAudioDeviceInfo.defaultOutputDevice().deviceName())
  32         
  33         self.pitchSlider = QSlider(Qt.Horizontal)
  34         self.pitchSlider.setMaximum(100)
  35         self.volumeSlider = QSlider(Qt.Horizontal)
  36         self.volumeSlider.setMaximum(32767)
  37         self.volumeSlider.setPageStep(1024)
  38         
  39         self.playButton = QPushButton(self.tr("&Play"))
  40         
  41         self.pitchSlider.valueChanged.connect(self.changeFrequency)
  42         self.volumeSlider.valueChanged.connect(self.changeVolume)
  43         self.playButton.clicked.connect(self.play)
  44         
  45         formLayout = QFormLayout()
  46         formLayout.addRow(self.tr("Device:"), self.deviceLineEdit)
  47         formLayout.addRow(self.tr("P&itch:"), self.pitchSlider)
  48         formLayout.addRow(self.tr("&Volume:"), self.volumeSlider)
  49         
  50         buttonLayout = QVBoxLayout()
  51         buttonLayout.addWidget(self.playButton)
  52         buttonLayout.addStretch()
  53         
  54         horizontalLayout = QHBoxLayout(self)
  55         horizontalLayout.addLayout(formLayout)
  56         horizontalLayout.addLayout(buttonLayout)
  57     
  58     def changeFrequency(self, value):
  59     
  60         self.frequency = 440 + (value * 2)
  61     
  62     def play(self):
  63     
  64         if self.output.state() == QAudio.ActiveState:
  65             self.output.stop()
  66         
  67         if self.buffer.isOpen():
  68             self.buffer.close()
  69         
  70         self.createData()
  71         
  72         self.buffer.setData(self.data)
  73         self.buffer.open(QIODevice.ReadOnly)
  74         self.buffer.seek(0)
  75         
  76         self.output.start(self.buffer)
  77     
  78     def changeVolume(self, value):
  79     
  80         self.volume = value
  81     
  82     def createData(self):
  83     
  84         # Create 2 seconds of data with 22050 samples per second, each sample
  85         # being 16 bits (2 bytes).
  86         
  87         self.data.clear()
  88         for i in xrange(2 * 22050):
  89             t = i / 22050.0
  90             value = int(self.volume * sin(2 * pi * self.frequency * t))
  91             self.data.append(struct.pack("<h", value))
  92 
  93 
  94 if __name__ == "__main__":
  95 
  96     app = QApplication(sys.argv)
  97     window = Window()
  98     window.show()
  99     sys.exit(app.exec_())