Why qt webengine can't play youtube live video streams - qt

Question

I was creating a simple webbrowser using webengine. I went to youtube and tried to play a live stream but failed. Same thing happens with every video which requires HTML5 video support in browsers. I didn't saw any recent problems which are identical to this. Qt says that webengine has HTML5 support from they released Qt5. Some old answers to same questions suggest them to compile qtwebengine your own. I tried several attempts and failed(may be my computer can't do the job). Some other say to enable proprietary plugins from the code. But in my case it too didn't work.
Running the code also logs an error WebEngineContext used before QtWebEngine::initialize() or OpenGL context creation failed.
So this is my simple qml code.
import QtQuick 2.12
import QtQuick.Window 2.12
import QtWebEngine 1.0
Window {
width: 640
height: 480
visible: true
title: qsTr("Hello World")
WebEngineView{
anchors.fill:parent
url:"https://www.youtube.com/watch?v=iL53Y28Rp84"
}
}
Qt version: 5.15.1(GNU Public License )
Installed using qt online installer.

Answer 1

Your problem is likely that - as the error in the console said - you haven't initialized the web engine. In your main(), you must call QtWebEngine::initialize() before you do any rendering. So your main function should look like this:
#include <QtWebEngine>
int main(int argc, char* argv[])
{
QGuiApplication a(argc, argv);
QtWebEngine::initialize();
(...)
}
As per the Qt documentation, the initialize() function makes sure that the OpenGL context can be shared between the GUI and the renderer process.
Link to the Qt documentation.

Answer 2

The error message you get is trivial and they already gave you the solution in the other answer, instead my answer is to solve the underlying problem. Can't play youtube videos because chromium (and Qt WebEngine) was not compiled by enabling proprietary codecs. The solution is to recompile Qt WebEngine with that flag enabled.
From the comments it can be seen that the OP is using Qt 5.15.1 so he must follow the following steps:
sudo apt-get install '^libxcb.*-dev' libx11-xcb-dev libglu1-mesa-dev libxrender-dev libxi-dev libxkbcommon-dev libxkbcommon-x11-dev
sudo apt-get install -y libxcursor-dev libxcomposite-dev libxdamage-dev libxrandr-dev libxtst-dev libxss-dev libdbus-1-dev libevent-dev libfontconfig1-dev libcap-dev libpulse-dev libudev-dev libpci-dev libnss3-dev libasound2-dev libegl1-mesa-dev gperf bison nodejs
git clone -b 5.15.1 git://code.qt.io/qt/qtwebengine.git
cd qtwebengine
git submodule update --init
/path/of/Qt/5.15.1/gcc_64/bin/qmake . -- -webengine-proprietary-codecs
make
make install
Note: According to the logs shown in the comments /path/of/Qt/5.15.1/gcc_64/bin/qmake in your case is /mnt/volume1/main_file_folder/Home/Qt/5.15.1/gcc_64/bin/qmake