I need to achieve low-latency real-time video streaming playback. In my software, I use the win11 system, qt6.6.3 or 6.7.2, VideoOutput+QVideoSink to play the existing YUV420 video data, and I find that the rendering speed is slow, but

Set at the beginning of main

QQuickWindow::setGraphicsApi(QSGRendererInterface::OpenGL); 

Then the rendering is very fast, 80~100ms faster. The decoding layer will not affect this delay, because I use ffmpeg to implement decoding alone, and Qt only participates in rendering.

This can be tested simply using the QML Video Recorder in the case.

The following picture is on a dual-screen PC. The left side shows the timing on the other screen in real time.

1. Enable OpenGL globally

2. not use OpenGL

Enabling OpenGL will make the rendering faster. I know that Qt6 uses d3d11 for rendering globally in win11, which can be known by using QQuickWindow::graphicsApi();. But why is d3d11 not as fast as opengl in rendering videos? Is there any problem when QRHI uses d3d11 to render videos?