A QML application using QWebEngineView to play a local video  (with QTWEBENGINE_DISABLE_SANDBOX=1) shows a significant mismatch between the time the video visibly begins and the time reported by backend trace logs. The video takes about 3 seconds to render its first frame, while instrumentation reports the operation completing in roughly 1.5 seconds. This suggests that the first frame is rendered later than the logical start of playback, and the delay is not consistent across runs.
 
Steps to reproduce
 Build and run the attached sample project Linux (amd64) machine with Qt 6.8.1.
 Before launching, set the environment variable QTWEBENGINE_DISABLE_SANDBOX=1.
 The sample loads a local video file into a QWebEngineView and begins playback automatically.
 Measure the elapsed time from playback start until the first frame is visibly rendered (3 seconds).
 Independently measure the same operation using backend instrumentation/trace logs (1.5 seconds).
 Repeat across multiple runs to observe that the discrepancy persists and can vary slightly.