(PySide6) How can I run QMediaPlayer in separate thread? - multithreading

Question

I am trying to process every QVideoFrame from QMediaPlayer and display it on QLabel.
Here is the sample code.
QMediaPlayer sends QVideoFrame to QVideoSink
Video sink sends the frame to MyWorker.
MyWorker converts QVideoFrame to QPixmap, does some processing and sends the pixmap to QLabel.
from PySide6.QtCore import QObject, QUrl, Signal, Slot
from PySide6.QtGui import QPixmap
from PySide6.QtWidgets import QLabel, QApplication
from PySide6.QtMultimedia import QMediaPlayer, QVideoSink, QVideoFrame
import sys
import time
class MyWorker(QObject):
pixmapChanged = Signal(QPixmap)
#Slot(QVideoFrame)
def setVideoFrame(self, frame: QVideoFrame):
qimg = frame.toImage()
pixmap = QPixmap.fromImage(qimg)
time.sleep(0.5) # represents time-consuming work
self.pixmapChanged.emit(pixmap)
app = QApplication(sys.argv)
player = QMediaPlayer()
sink = QVideoSink()
worker = MyWorker()
widget = QLabel()
player.setVideoSink(sink)
sink.videoFrameChanged.connect(worker.setVideoFrame)
worker.pixmapChanged.connect(widget.setPixmap)
player.setSource(QUrl.fromLocalFile("my-video.mp4"))
widget.show()
player.play()
app.exec()
app.quit()
Processing takes some time, so the label is updating slower than the original video FPS. This is fine, but the problem is that my current code without QThread is blocking the GUI.
Using player.moveToThread(...) didn't work. How can I run QMediaPlayer in separate thread?

Answer 1

Thanks to #musicamente, I fixed it by moving the worker to separate thread.
Note that the window sends the frame to worker only when the worker is ready. If not, blocked signals are queued with QVideoFrame instance and quickly consume all the memory.
Media player
from PySide6.QtCore import QObject, Signal, Slot, QThread, QUrl
from PySide6.QtGui import QPixmap
from PySide6.QtMultimedia import QMediaPlayer, QVideoSink, QVideoFrame
from PySide6.QtWidgets import QMainWindow, QLabel
import time
class FrameWorker(QObject):
pixmapChanged = Signal(QPixmap)
def __init__(self, parent=None):
super().__init__(parent)
self.ready = True
#Slot(QVideoFrame)
def setVideoFrame(self, frame: QVideoFrame):
self.ready = False
time.sleep(1) # represents time-consuming work
self.pixmapChanged.emit(QPixmap.fromImage(frame.toImage()))
self.ready = True
class FrameSender(QObject):
frameChanged = Signal(QVideoFrame)
class Window(QMainWindow):
def __init__(self, parent=None):
super().__init__(parent)
self.workerThread = QThread()
self.player = QMediaPlayer()
self.frameSender = FrameSender()
self.frameWorker = FrameWorker()
self.displayLabel = QLabel()
self.frameWorker.moveToThread(self.workerThread)
self.workerThread.start()
self.player.setVideoSink(QVideoSink(self))
self.player.videoSink().videoFrameChanged.connect(self.onFramePassedFromPlayer)
self.frameSender.frameChanged.connect(self.frameWorker.setVideoFrame)
self.frameWorker.pixmapChanged.connect(self.displayLabel.setPixmap)
self.setCentralWidget(self.displayLabel)
#Slot(QVideoFrame)
def onFramePassedFromPlayer(self, frame: QVideoFrame):
if self.frameWorker.ready:
self.frameSender.frameChanged.emit(frame)
def closeEvent(self, event):
self.workerThread.quit()
self.workerThread.wait()
super().closeEvent(event)
if __name__ == "__main__":
from PySide6.QtWidgets import QApplication
import sys
app = QApplication(sys.argv)
window = Window()
window.player.setSource(QUrl.fromLocalFile("my-video.mp4"))
window.show()
window.player.play()
app.exec()
app.quit()
Camera
from PySide6.QtCore import QObject, Signal, Slot, QThread
from PySide6.QtGui import QPixmap
from PySide6.QtMultimedia import QMediaCaptureSession, QVideoSink, QVideoFrame, QCamera
from PySide6.QtWidgets import QMainWindow, QLabel
import time
class FrameWorker(QObject):
pixmapChanged = Signal(QPixmap)
def __init__(self, parent=None):
super().__init__(parent)
self.ready = True
#Slot(QVideoFrame)
def setVideoFrame(self, frame: QVideoFrame):
self.ready = False
time.sleep(1) # represents time-consuming work
self.pixmapChanged.emit(QPixmap.fromImage(frame.toImage()))
self.ready = True
class FrameSender(QObject):
frameChanged = Signal(QVideoFrame)
class Window(QMainWindow):
def __init__(self, parent=None):
super().__init__(parent)
self.workerThread = QThread()
self.captureSession = QMediaCaptureSession()
self.frameSender = FrameSender()
self.frameWorker = FrameWorker()
self.displayLabel = QLabel()
self.frameWorker.moveToThread(self.workerThread)
self.workerThread.start()
self.captureSession.setVideoSink(QVideoSink(self))
self.captureSession.videoSink().videoFrameChanged.connect(
self.onFramePassedFromCamera
)
self.frameSender.frameChanged.connect(self.frameWorker.setVideoFrame)
self.frameWorker.pixmapChanged.connect(self.displayLabel.setPixmap)
self.setCentralWidget(self.displayLabel)
camera = QCamera(self)
self.captureSession.setCamera(camera)
camera.start()
#Slot(QVideoFrame)
def onFramePassedFromCamera(self, frame: QVideoFrame):
if self.frameWorker.ready:
self.frameSender.frameChanged.emit(frame)
def closeEvent(self, event):
self.workerThread.quit()
self.workerThread.wait()
super().closeEvent(event)
if __name__ == "__main__":
from PySide6.QtWidgets import QApplication
import sys
app = QApplication(sys.argv)
window = Window()
window.show()
app.exec()
app.quit()