Wrong QMediaPlayer::position when QMediaPlayer::videoOutput==NULL

Create a QMediaPlayer and connect it to a QAudioOutput. Do not connect it to a video output. The QMediaPlayer can still play a video file set with QMediaPlayer::setSource. However, QMediaPlayer::position reports wrong values.

QMediaPlayer::position increases much faster than the real position until it reaches the video duration and remains constant.

This problem occurs only when playing video files (mp4, webm, mov) without connecting the media player to a video output. When playing audio files (.wav, .flac) no such problem arises. The problem does not occur in Qt 5.15.2. Minimal code for reproducing the problem is attached.