How to use QFile with Python VLC MediaPlayer

Question

I can simply play a wav file from a file with the code below:

media = vlc.MediaPlayer('c.wav')
media.audio_set_volume(50)
media.play()

How can I do the same with qrc resource file? I tried this code but doesn't seem to work:

mediafile = QFile(':/sounds/c.wav')
media = vlc.Instance().media_player_new()
media.set_media(mediafile)
media.audio_set_volume(50)
media.play()

Answer 1

You need to use vlc.media_new_callbacks for this so that you can wrap the QFile and use its methods. Below is a demo script that shows how to implement that:

import sys, vlc
from PyQt5.QtCore import QFile, QCoreApplication

@vlc.CallbackDecorators.MediaOpenCb
def open_cb(opaque, data, size):
    data.contents.value = opaque
    size.value = sys.maxsize
    return 0

@vlc.CallbackDecorators.MediaReadCb
def read_cb(opaque, buffer, length):
    data = qfile.read(length)
    for index, char in enumerate(data):
        buffer[index] = char
    return len(data)

@vlc.CallbackDecorators.MediaSeekCb
def seek_cb(opaque, offset):
    qfile.seek(offset)
    return 0

@vlc.CallbackDecorators.MediaCloseCb
def close_cb(opaque):
    qfile.close()

if __name__ == '__main__':

    import time, signal
    signal.signal(signal.SIGINT, signal.SIG_DFL)

    print('Press Ctrl+C to Quit')

    player = vlc.Instance().media_player_new()

    qfile = QFile(sys.argv[1])
    qfile.open(QFile.ReadOnly)

    player.set_media(vlc.Instance().media_new_callbacks(
        open_cb, read_cb, seek_cb, close_cb, None))

    player.play()

    app = QCoreApplication(sys.argv)
    app.exec_()

---

UPDATE:

It's somewhat tricky to get this working correctly in a more typical PyQt application, because the callbacks have to be static functions. Here is an extended example that shows how it can be done:

import sys, ctypes, vlc
from PyQt5 import QtCore, QtWidgets

class VLCPlayer(QtCore.QObject):
    def __init__(self, parent=None):
        super().__init__()
        self._player = vlc.Instance().media_player_new()

    @staticmethod
    @vlc.CallbackDecorators.MediaOpenCb
    def _open_cb(voidptr, data, size):
        data.contents.value = voidptr
        size.value = sys.maxsize
        return 0

    @staticmethod
    @vlc.CallbackDecorators.MediaReadCb
    def _read_cb(voidptr, buffer, length):
        stream = ctypes.cast(
            voidptr, ctypes.POINTER(ctypes.py_object)).contents.value
        data = stream.read(length)
        for index, char in enumerate(data):
            buffer[index] = char
        return len(data)

    @staticmethod
    @vlc.CallbackDecorators.MediaSeekCb
    def _seek_cb(voidptr, offset):
        stream = ctypes.cast(
            voidptr, ctypes.POINTER(ctypes.py_object)).contents.value
        stream.seek(offset)
        return 0

    @staticmethod
    @vlc.CallbackDecorators.MediaCloseCb
    def _close_cb(voidptr):
        stream = ctypes.cast(
            voidptr, ctypes.POINTER(ctypes.py_object)).contents.value
        stream.close()

    def play(self):
        self._player.play()

    def stop(self):
        self._player.stop()

    def load(self, path):
        file = QtCore.QFile(path)
        file.open(QtCore.QIODevice.ReadOnly)
        voidptr = ctypes.cast(ctypes.pointer(
            ctypes.py_object(file)), ctypes.c_void_p)
        self._player.set_media(vlc.Instance().media_new_callbacks(
            self._open_cb, self._read_cb,
            self._seek_cb, self._close_cb, voidptr))


class Window(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()
        self.buttonPlay = QtWidgets.QPushButton('Play')
        self.buttonPlay.clicked.connect(self.handlePlay)
        self.buttonStop = QtWidgets.QPushButton('Stop')
        self.buttonStop.clicked.connect(self.handleStop)
        self.buttonOpen = QtWidgets.QPushButton('Open')
        self.buttonOpen.clicked.connect(self.handleOpen)
        layout = QtWidgets.QHBoxLayout(self)
        layout.addWidget(self.buttonOpen)
        layout.addWidget(self.buttonPlay)
        layout.addWidget(self.buttonStop)
        self.player = VLCPlayer(self)

    def handlePlay(self):
        self.player.play()

    def handleStop(self):
        self.player.stop()

    def handleOpen(self):
        path, ok = QtWidgets.QFileDialog.getOpenFileName(
            self, filter='Audio Files (*.wav)')
        if ok:
            self.player.load(path)

if __name__ == '__main__':

    app = QtWidgets.QApplication(sys.argv)
    window = Window()
    window.setWindowTitle('VLC Player')
    window.setGeometry(600, 100, 200, 80)
    window.show()
    sys.exit(app.exec_())