Merge Two Videos with Python3

How can I merge two video with Python3? I tried ffmpeg but i couldn't. Then I tried install moviepy but i couldn't too. Can you help me?

(One of videos has only sound)

I am using PyQt5. The application closes when I run. and this is the exit code:

Process finished with exit code -1073740791 (0xC0000409)

But if I delete ffmpeg lines it works fine.

First way I tried:

video = ffmpeg.input('videoo.mp4')
audio = ffmpeg.input('voicee.mp4')
ffmpeg.output(video, audio, 'out.mp4').run()

Second way I tried:

ffmpeg.concat(ffmpeg.input('videoo.mp4'), ffmpeg.input('voicee.mp4'), v=1, a=1).output('vdeo.mp4').run()

Third way I tried:

subprocess.run("ffmpeg -i videoo.mp4 -i voicee.webm -c:v copy -c:a copy output.mp4")

Since the OP does not provide an MRE, it is difficult to know where the problem is, so my answer focuses on providing a code that only implements the functionality.

In this case, the conversion is very time consuming, so it must be executed in a secondary thread:

import sys
import threading

import ffmpeg

from PyQt5 import QtCore, QtWidgets


class Converter(QtCore.QObject):
    started = QtCore.pyqtSignal()
    finished = QtCore.pyqtSignal()

    def concatenate(self, inputs, output):
        threading.Thread(
            target=self._concatenate, args=(inputs, output), daemon=True
        ).start()

    def _concatenate(self, inputs, output):
        self.started.emit()
        ffmpeg.concat(*[ffmpeg.input(i) for i in inputs]).output(output).run()
        self.finished.emit()


class Widget(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)

        self.input_1_le = QtWidgets.QLineEdit()
        self.input_2_le = QtWidgets.QLineEdit()
        self.output_le = QtWidgets.QLineEdit()

        self.load_1_btn = QtWidgets.QPushButton("Select 1 input")
        self.load_2_btn = QtWidgets.QPushButton("Select 2 input")
        self.load_3_btn = QtWidgets.QPushButton("Select output")

        self.start_btn = QtWidgets.QPushButton("Start")

        lay = QtWidgets.QGridLayout(self)

        lay.addWidget(QtWidgets.QLabel("Input 1"), 0, 0)
        lay.addWidget(self.input_1_le, 0, 1)
        lay.addWidget(self.load_1_btn, 0, 2)

        lay.addWidget(QtWidgets.QLabel("Input 2"), 1, 0)
        lay.addWidget(self.input_2_le, 1, 1)
        lay.addWidget(self.load_2_btn, 1, 2)

        lay.addWidget(QtWidgets.QLabel("Output"), 2, 0)
        lay.addWidget(self.output_le, 2, 1)
        lay.addWidget(self.load_3_btn, 2, 2)

        lay.addWidget(self.start_btn, 3, 0, 1, 3)

        self.converter = Converter()

        self.load_1_btn.clicked.connect(self.load_input_1)
        self.load_2_btn.clicked.connect(self.load_input_2)
        self.load_3_btn.clicked.connect(self.load_output)

        self.start_btn.clicked.connect(self.start)
        self.converter.started.connect(lambda: self.start_btn.setEnabled(False))
        self.converter.finished.connect(lambda: self.start_btn.setEnabled(True))

    @QtCore.pyqtSlot()
    def load_input_1(self):
        filename, _ = QtWidgets.QFileDialog.getOpenFileName(
            self,
            self.tr("Select Video"),
            QtCore.QDir.homePath(),
            self.tr("Video Files (*.mp4)"),
        )
        if filename:
            self.input_1_le.setText(filename)

    @QtCore.pyqtSlot()
    def load_input_2(self):
        filename, _ = QtWidgets.QFileDialog.getOpenFileName(
            self,
            self.tr("Select Video"),
            QtCore.QDir.homePath(),
            self.tr("Video Files (*.mp4)"),
        )
        if filename:
            self.input_2_le.setText(filename)

    @QtCore.pyqtSlot()
    def load_output(self):
        filename, _ = QtWidgets.QFileDialog.getSaveFileName(
            self,
            self.tr("Select Video"),
            QtCore.QDir.homePath(),
            self.tr("Video Files (*.mp4)"),
        )
        if filename:
            self.output_le.setText(filename)

    @QtCore.pyqtSlot()
    def start(self):
        self.converter.concatenate(
            [self.input_1_le.text(), self.input_2_le.text()], self.output_le.text()
        )


def main():
    app = QtWidgets.QApplication(sys.argv)
    w = Widget()
    w.show()
    sys.exit(app.exec_())


if __name__ == "__main__":
    main()